CHAPTER 39. GRAMINEAE

The Gramineae comprise roughly 10000 species of herbaceous and sometimes woody plants within more than 600 genera. It is the most important of the plant families for man providing cereals, forage and fodders, sugar, construction materials, oils, and many other useful products. Consequently this chapter is substantially longer than other chapters.

In Gramineae the term seed is applied to a wide range of fruiting bodies. The basic component is the caryopsis, the single-seeded fruit: this may be naked (e.g. Triticum aestivum L.) or, more commonly, enclosed within other flower structures. The number and type of other structures which may enclose the caryopses are dependent upon how they become detached from the parent plant and the point of abscission. In many grasses abscission occurs in the spikelet-axis beneath the glumes: thus the caryopses are enclosed within the glumes. The following types of dispersal units may be observed in different species.

1. The caryopsis only.

2. The caryopsis loosely or tightly enclosed within the lemma and palea (a floret).

3. One or more florets enclosed within several glumes and bracts (a spikelet).

4. A cluster of spikelets.

See Chapter 3 (Volume I) for more information on seed development and morphology. In gene banks, the most important morphological feature is to confirm that dispersal units tested for germination do in fact contain a seed (see Chapter 8, Volume I).

Almost all Gramineae are known to exhibit orthodox seed storage characteristics. Two possible exceptions have been reported, viz: Glyceria striata Hitche (manna grass) and Zizania aquatica L. (wild rice). Whilst these species must be treated as recalcitrant seeds for the present, both species are known to exhibit considerable seed dormancy and it is possible that the species may, in fact, possess orthodox seeds and that dormancy and viability have been confused in the past. Some support for this assertion is provided in this chapter for the genus Zizania.

SEED DORMANCY AND GERMINATION

The seeds are endospermic and can show considerable dormancy. Part, but not all, of the problem of germinating the seeds may be associated with the seed covering structures. Typical treatments to overcome dormancy include pre-chilling, alternating temperatures, potassium nitrate and removal of the seed covering structures. Detailed information on seed germination and dormancy-breaking treatments is provided in this chapter for the 42 genera listed in Table 39.1. The table of genera is divided into their respective tribes since there may be some advantage to consult the information provided for closely related genera as well as for the genus of immediate concern. In addition Table 39.1 indicates whether the information on each genus includes information for species with synonyms in other genera. Table 39.2 provides a summary of recommendations for germination test procedures and dormancy-breaking treatments for other species. In addition the algorithm below may be useful in developing suitable germination test procedures for other species for which no information is provided here and for difficult accessions of all graminaceous species.

RBG Kew Wakehurst Place algorithm

Comment on, and an explanation of, the Gramineae algorithm have been provided in Chapter 17. Since that comment includes several alternative suggestions the reader is urged to read the appropriate section of Chapter 17 before attempting to follow this algorithm.

The first and second steps of the algorithm are dependent upon each accession's origin. In the first step of the algorithm accessions of temperate origin are tested at constant temperatures of 16°C and 21°C, whilst those of tropical origin are tested at constant temperatures of 21°C and 26°C. If an accession's origin is unknown or doubtful, test at all three constant temperatures, viz: 16°C, 21°C and 26°C. In all cases light is applied for 12h/d. If the results of these initial tests show a trend in the response of germination to constant temperatures (but full germination has not been achieved) then carry out further tests at more extreme constant temperatures. For example, if the germination of a temperate accession is greater at 16°C than at 21°C, then test further samples of seeds at constant temperatures of 6°C and 11°C with light applied for 12h/d.

If the first step of the algorithm has not resulted in full germination then the second step is to test a further sample of seeds in an alternating temperature regime: 23°/9° (12h/12h) for accessions of temperate origin; 33°/19°C (12h/12h) for accessions of tropical origin; in each case light is applied for 12h/d during the period spent at the upper temperature of each cycle. If an accessions' origin is unknown or doubtful then test a sample of seeds in each alternating temperature regime.

If the second step of the algorithm has not resulted in full germination then the third step is to co-apply 10^-3 M potassium nitrate to the germination test substrate and test in the most successful temperature regime determined from the results of steps one and two.

If the third step of the algorithm has not resulted in full germination then the fourth step is to remove - in part or all - the seed covering structures from a fresh sample of seeds and then test in the most successful regime determined from the results of steps one to three. The actual treatment to the seed covering structures will be dependent upon the morphology of the dispersal units. Where possible extract each caryopsis from the floret (where this is the dispersal unit) and the lemma and palea (if present). This may not be easy for very small seeds, in which case the end of the dispersal unit opposite to the embryo can be chipped or cut away to expose the endosperm. In some cases the lemma and palea adhere very tightly to the caryopsis and their removal can be difficult - and possibly damaging. If this is the case then puncture the seed covering structures and the endosperm in the vicinity of the embryo. The removal of the lemma and palea, in particular, may be easier once the seeds have imbibed.

If the fourth step of the algorithm has not resulted in full germination then the fifth step of the algorithm is to pre-chill the seeds at 2° to 6°C for 8w and then test for germination in the most successful regime determined from the results of steps one to four. If this includes a requirement to remove the seed covering structures this may be easier to accomplish after the pre-chill treatment, but may be more effective in promoting germination if carried out before the pre-chill treatment.

If full germination has still not been promoted, the sixth step of the algorithm is to estimate viability using a tetrazolium test (see Chapter 11, Volume 1).

If the result of the tetrazolium test indicates that the failure to achieve full germination is due to the presence of dead seeds and that one of the above regimes promoted the germination of all, or almost all, the viable seeds, then this regime is used for all subsequent germination tests. If, however, the result of the tetrazolium test indicates that dormancy has not been broken by the regimes applied so far in the algorithm, then experiment with modifications to the above regimes. Clues to possible satisfactory dormancy-breaking treatments and promotory germination test environments can be obtained from the information provided for 42 genera in this chapter. A glance at Table 39.2, however, will provide an initial indication of likely suitable treatments.

TABLE 39.1 List of genera by tribe within the Gramineae for which detailed information on seed germination procedures and dormancy-breaking treatments is provided in this chapter.

TRIBE and Genus		Synonyms
ANDROPOGONEAE
	- Andropogon
	- Bothriochloa
	- Cymbopogon
	- Saccharum
	- Sorghastrum
	- Sorghum	Andropogon, Holcus
	- Themeda
	- Zea	Euchlaena
ARISTIDEAE
	- Aristida
ARUNDINARIEAE
	- Sasa	Bambusa
AVENEAE
	- Agrostis
	- Avena
	- Phleum
BROMEAE
	- Bromus
CHLORIDEAE
	- Bouteloua
	- Chloris
	- Cynodon	Panicum
ERAGROSTIDEAE
	- Eleusine	Cynosurus
	- Eragrostis	Poa
ORYZEAE
	- Oryza
	- Zizania
PANICEAE
	- Brachiaria	Panicum
	- Digitaria
	- Echinochloa	Panicum
	- Panicum
	- Paspalum
	- Pennisetum	Panicum
	- Setaria	Chaetochloa, Panicum
PHALARIDEAE
	- Phalaris
POEAE
	- Dactylis
	- Festuca	Vulpia
	- Lolium
	- Poa
STIPEAE
	- Oryzopsis
	- Stipa
TRITICEAE
	- Aegilops	Triticum
	- Agropyron
	- Hordeum
	- Secale
	- Triticale
	- Triticum
ZOYSIEAE
	- Zoysia	Agrostis

TABLE 39.2 Summary of germination test recommendations for species within the Gramineae

Species and Authority	Substrate	Temperature	Duration	Additional directions	Source
Alopecurus pratensis L.	TP	20°/30°C; 15°/25°C; 10°/30°C	14d	pre-chill, potassium nitrate	ISTA
	TP	20°/30°C	14d	light	AOSA
Alysicarpus vaginalis (L.) DC.	BP	35°C	21d	pierce the seed coats and continue test for a further 5d if (reversible) hard seeds have begun to imbibe, or test swollen seeds at 20°C, 48h, then 35°C, 3d	AOSA
Anthoxanthum odoratum L.	TP	20°/30°C	14d		ISTA
	TP	20°/30°C	14d	light	AOSA
Arrhenatherum elatius (L.) Beauv.	TP	20°/30°C	14d	pre-chill	ISTA
	TP	20°/30°C	14d	light	AOSA
Axonopus affinis Chase	TP	20°/35°C	21d	potassium nitrate, light	ISTA/AOSA
Axonopus compressus (Sw.) Beauv.	TP	20°/35°C	21d	potassium nitrate, light	ISTA
Beckmannia eruciformis (L.) Host	TP	20°/30°C	21d		ISTA
Briza maxima L.	TP	20°/30°C	21d	pre-chill	ISTA
Buchloe dactyloides (Nutt.) Engelm. (burs)	TP; S	20°/35°C	28d	light, potassium nitrate, pre-chill, 5°C, 6w, then test for 14d	AOSA
(caryopses)	TP	20°/35°C	14d	light, potassium nitrate	AOSA
Calamagrostis canadensis (Michx.) Nutt.	TP	15°/25°C	21d	light, potassium nitrate, pre-chill, 5°C, 5d	AOSA
Cenchrus ciliaris L.	TP; S	20°/35°C; 20°/30°C; 30°C	28d	pre-dry, pre-chill, potassium nitrate	ISTA
	S	30°C	28d	light, press fascicles into well packed soil, then pre-chill, 5°C, 7d	AOSA
(caryopses)	TP	30°C	21d	pre-chill, 5°C, 7d, after test scratch firm seeds and continue test, 7d	AOSA
Cenchrus setigerus Vahl	TP	20°/35°C	14d	pre-dry (40°C), potassium nitrate	ISTA
Cynosurus cristatus L.	TP	20°/30°C	21d	pre-chill, potassium nitrate	ISTA
	TP	20°/30°C	21d	light, pre-chill, 5°C or 10°C, 3d	AOSA
Coix lacrima-jobi L.	BP	20°/30°C	21d		ISTA
	BP	20°/30°C	16d	very sensitive to low temperatures	AOSA
Deschampsia caespitosa (L.) Beauv.	TP	20°/30°C; 20°C	16d	pre-chill, potassium nitrate	ISTA
Deschampsia flexuosa (L.) Trin.	TP	20°/30°C; 20°C	16d	pre-chill, potassium nitrate	ISTA
Dichanthium aristatum (Poir.) C.E. Hubbard	TP	20°/35°C	21d	potassium nitrate	ISTA
Ehrharta calycina Smith	TP	20°C	21d	pre-chill	ISTA
	TP	10°/30°C	28d	light	AOSA
Elymus canadensis L.	TP	15°/30°C	21d	light, pre-chill, 5°C, 2w	AOSA
Elymus junceus Fisch.	TP	20°/30°C	14d	pre-chill	ISTA
	TP	20°/30°C	14d	light, pre-chill, 5°C or 10°C, 5d	AOSA
Holcus lanatus L.	TP	20°/30°C	14d	pre-chill, potassium nitrate	ISTA
	TP	20°/30°C	14d	light	AOSA
Melinis minutiflora Beauv.	TP	20°/30°C	21d	pre-chill, potassium nitrate	ISTA
	TP	20°/30°C	21d	light	AOSA
Schizachyrium scoparium (Michx.) Nash	TP; S	20°/30°C	28d	light, potassium nitrate, pre-chill, 5°C, 2w	AOSA
Sporobolus cryptandrus (Torr.) Gray	TP	5°/35°C; 15°/35°C	28d	light, potassium nitrate, pre-chill, 5°C, 4w	AOSA
Trisetum flavescens (L.) Beauv.	TP	20°/30°C	21d	pre-chill, potassium nitrate	ISTA
Urochloa mosambicensis (Hack.) Dandy	TP	20°/35°C	21d		ISTA

AEGILOPS

A. cylindrica Host [Triticum cylindricum Ces., Pass. & Gib.]
A. Kotschyi Boiss.
A. ovata L.
A. triuncialis	barb goatgrass

I. Evidence of dormancy

Freshly harvested seeds of Aegilops spp. show considerable dormancy (1-10, 12). Seeds of A. triuncialis require 3 to 4 months after-ripening for full germination (3), whereas after-ripening seeds of A. ovata for 1 year did not entirely remove dormancy (2).

II. Germination regimes for non-dormant seeds

A. cylindrica

Constant temperatures: 20°C, dark (4)

A. Kotschyi

Constant temperatures: 20°C, dark (6,7,8,12)

A. ovata

Constant temperatures: 20°C in light, 150-250 fc (1)

III. Unsuccessful dormancy-breaking treatments

A. cylindrica

Constant temperatures: 30°C, 35°C (4)

Potassium nitrate: co-applied, 0.1, 1 g/1, at 10°C, 15°C, 20°C (4)

GA₃: co-applied, 1000 ppm, at 10°C, 15°C (4)

A. kotschyi

Constant temperatures: 30°C (5)

Pre-dry: (6)

Auxin: co-applied, 50 ppm, at 20°C (8)

Cytokinin: co-applied, 50 ppm, at 20°C (8)

A. ovata

Constant temperatures: 35°C, 40°C, in light or dark (1)

IV. Partly-successful dormancy-breaking treatments

A. cylindrica

Constant temperatures: 10°C, 28d (4)

A. kotschyi

Constant temperatures: 5°C (5)

GA₃: co-applied, 50 ppm, at 20°C (8); co-applied, 10-100 ppm (11)

Removal of seed covering structures: dehull (5,6,8,11)

A. ovata

Constant temperatures: 5°C in light or dark (1); 10°C, dark (1); 15°C, 20°C, 25°C, light, 16d (1,2)

V. Successful dormancy-breaking treatments

A. cylindrica

Constant temperatures: 15°C, 20°C, 28d (4)

GA₃: co-applied, 1000 ppm, at 20°C (4)

A. kotschyi

Removal of seed covering structures: dehull, germinate at 5°C (5); dehull, plus GA₃, co-applied, 10-100 ppm (11)

GA₃: co-applied, 50 ppm (10); co-applied, 50 ppm, plus RNAase, 10g/ml, co-applied (10)

A. ovata

Constant temperatures: 10°C in light, 150-250 fc (1)

Removal of seed covering structures: dehull (1)

VI. Comment

We suggest that a constant temperature of between 5° and 10°C combined, where necessary, with removal of the seed covering structures should be satisfactory for testing accessions of Aegilops spp. for germination.

VII. References

1. Datta, S.C., Evenari, M. and Gutterman, Y. (1970). The heteroblasty of Aegilops ovata L. Israel Journal of Botany, 19, 463-483.

2. Datta, S.C., Gutterman, Y. and Evenari, M. (1972). The influence of the origin of the mother plants on yield and germination of their caryopses in Aegilops ovata. Planta, 105, 155-164.

3. Laude, H.M. (1956). Germination of freshly harvested seeds of some western range species. Journal of Range Management, 9, 126-129.

4. Morrow, L.A., Young, F.L. and Flom, D.G. (1982). Seed germination and seedling emergence of jointed goatgrass (Aegilops cylindrica). Weed Science, 30, 395-398.

5. Waisel, Y. and Adler, Y. (1959). Germination behavior of Aegilops Kotschyi Boiss. Canadian Journal of Botany, 37, 741-742.

6. Wurzburger, J. and Koller, D. (1973). Onset of seed dormancy in Aegilops Kotschyi Boiss. and its experimental modification. New Phytologist, 72, 1057-1061.

7. Wurzburger, J. and Koller, D. (1976). Differential effects of the parental photothermal environment on development of dormancy in caryopses of Aegilops Kotschyi. Journal of Experimental Botany, 27, 43-48.

8. Wurzburger, J. and Leshem, Y. (1967). Gibberellin and hull controlled inhibition of germination in Aegilops Kotschyi Boiss. Israel Journal of Botany, 16, 181-186.

9. Wurzburger, J. and Leshem, Y. (1969). Physiological action of the germination inhibitor in the husk of Aegilops Kotschyi Boiss. New Phytologist, 68, 337-341.

10. Wurzburger, J. and Leshem, Y. (1971). Ribonucleic acid as an inducer of germination inhibition in Aegilops Kotschyi. Plant and Cell Physiology, 12, 211-215.

11. Wurzburger, J. and Leshem, Y. (1974). The role of gibberellin and the hulls in the control of germination in Aegilops Kotschyi caryopses. Canadian Journal of Botany, 52, 1597-1601.

12. Wurzburger, J., Leshem, Y. and Koller, D. (1976). Correlative aspects of imposition of dormancy in caryopses of Aegilops Kotschyi. Plant Physiology, 57, 670-671.

AGROPYRON

A. cristatum (L.) Gaertn.	fairway crested
A. dasystachyum (Host) Scribn.	thickspike wheatgrass wheatgrass
A. desertorum Fisch. ex Link	standard crested wheatgrass
A. elongatum (Host) Beauv.	tall wheatgrass
A. intermedium (Host) Baumg.	intermediate wheatgrass
A. repens (L.) Beauv.	quackgrass
A. riparium Scribn. & Smith	streambank wheatgrass
A. semicostatum
A. siberian Willd.	Siberian wheatgrass
A. smithii Rydb.	Western wheatgrass
A. spicatum (Pursh) Scribn. & Smith	bluebunch or beardless wheatgrass
A. trachycaulum (Link) H.F. Lewis	slender wheatgrass
A. trichophorum Link	pubescent wheatgrass

I. Evidence of dormancy

Severe dormancy has been reported in seed lots of A. repens (6, 7, 16), A. semicostatum (13), A. trachycaulum (13), A. interm edium (20), A. cristatum (1,8,9,20), A. siberian (20), A. trichophorum (20), A. smithii (2-4,10,12,15,18,20) and A. spicatum (2 0). Secondary dormancy has been induced: in A. elongatum where moist seeds experienced sub-zero temperatures before harvest (17); in A. smithii where seeds wer e pre-chilled at 10°C for 5 days (3); and in A. smithii where imbibed seeds were exposed to high constant temperatures (18).

II. Germination regimes for non-dormant seeds

A. cristatum, A. desertorum

TP: 15°/25°C; 20°/30°C (16h/8h): 14d (AOSA, ISTA)

A. elongatum

TP: 15°/25°C; 20°/30°C (16h/8h): 21d (ISTA)

TP: 15°/25°C (16h/8h): 21d (AOSA)

A. intermedium

TP: 15°/25°C; 20°/30°C (16h/8h): 28d (AOSA, ISTA)

A. repens

TP: 10°/30°C; 20°/30°C (16h/8h): 21d (ISTA)

A. smithii

TP; BP: 15°/25°C; 20°/30°C (16h/8h): 28d (ISTA)

TP; BP: 15°/30°C (16h/8h): 28d (AOSA)

A. spicatum

TP; BP: 15°/25°C (16h/8h): 14d (AOSA)

A. trachycaulum

TP: 15°/25°C; 20°/30°C (16h/8h): 14d (ISTA)

TP: 20°/30°C (16h/8h): 14d (AOSA)

A. trichophorum

TP: 15°/25°C; 20°/30°C (16h/8h): 28d (AOSA,ISTA)

III. Unsuccessful dormancy-breaking treatments

A. desertorum

Potassium nitrate: co-applied, 0.2% (13)

A. smithii

Potassium nitrate: co-applied, 0.2% (13)

Thiourea: co-applied, 0.2% (13)

GA₃: co-applied, 100 ppm (13)

Light: white (10); white, 9h/d (3,4,15); incandescent, 22 lux, continuous (18); red, 15 min (15); far red, 1300 lux, intermittent (18)

A. trachycaulum

Potassium nitrate: co-applied, 0.2% (13)

Thiourea: co-applied, 0.2% (13)

GA₃: co-applied, 100 ppm (13,14)

IV. Partly-successful dormancy-breaking treatments

A. cristatum

Alternating temperatures: 15°/25°C, 10°/20°C, 10°/25°C, 10°/30°C, 15°/20°C, 15°/30°C, 20°/25°C, 20°/30°C (16h/8h) (20); 20°/30°C (16h/8h) (8); 20°/30°C (18h/6h) (9)

Pre-chill: 6°-8°C, 4d, germinate at 20°C (8); 10°C, 7d, germinate at 20°/30°C (16h/8h) in light (1)

A. desertorum

Constant temperatures: 20°C (14)

Light: (13,14)

GA₃: co-applied, 100 ppm (14)

A. elongatum

Pre-chill: 5°C, 5d, plus potassium nitrate, co-applied, germinate at 20°/30°C (16h/8h) in light (17)

A. intermedium

Alternating temperatures: 10°/25°C, 15°/25°C, 20°/25°C, 15°/20°C (16h/8h) (20)

A. repens

Alternating temperatures: (16); 15°/30°C (15h/9h) (6); 25°/30°C (16h/8h) in light (20)

Removal of seed covering structures: dehull (19)

A. semicostatum

Pre-chill: (13)

A. siberian

Alternating temperatures: 15°/25°C, 5°/20°C, 5°/25°C, 10°/20°C, 10°/25°C, 15°/20°C (16h/8h) (20)

A. smithii

Alternating temperatures: 15°/25°C, 15°/30°C (20h/4h) (18); 15°/40°C, 20°/40°C, 25°/40°C (16h/8h) (20); 15°/30°C (16h/8h) (12, 15); 20°/30°C, 20°/35°C (18h/6h) (10)

Pre-chill: (13); 8°-10°C, 14°-17°C, 6d, germinate at 20°/30°C (16h/8h) (10)

Light: dark, continuous (3); red, 4,8 min (15); red, 13000 lux, 3,5 min (18)

Potassium nitrate: co-applied, 0.2%, at 15°/30°C (16h/8h) (2,4,12); pre-applied, 24h, 0.2% (15)

Ethylene chlorohydrin: pre-applied, 24h, 750, 1250 ppm (3,4)

GA₃: co-applied, 10^-3 M, plus kinetin, co-applied, 0.5 M (18); pre-applied, 24h, 100 ppm (15)

Kinetin: pre-applied, 24h, 100 ppm (15)

A. spicatum

Alternating temperatures: 15°/20°C, 20°/25°C (16h/8h) (20)

A. trachycaulum

Constant temperatures: 0°-40°C (20)

Alternating temperatures: 15°/25°C, 15°/30°C, 20°/30°C, 20°/35°C (16h/8h) (20)

Pre-chill: (13)

Light: (13)

A. trichophorum

Alternating temperatures: 15°/25°C, 15°/30°C (16h/8h) (20)

V. Successful dormancy-breaking treatments

A. cristatum

Pre-chill, Potassium nitrate (ISTA)

Light, Pre-chill, Potassium nitrate (AOSA)

Pre-chill: 8°-10°C, 4-6d (9); 10°C, 7d, plus potassium nitrate, co-applied, 0.2% (1)

A. dasystachyum

Alternating temperatures: 15°/25°C, 15°/30°C, 20°/30°C (16h/8h) (20)

A. desertorum

Pre-chill, Potassium nitrate (ISTA)

Light, Pre-chill, Potassium nitrate (AOSA)

Alternating temperatures: 15°/30°C (13); 15°/25°C, 10°/25°C (16h/8h) (20)

Pre-chill: (13)

Potassium nitrate: co-applied, 0.2% (13)

Thiourea: co-applied, 0.2% (13)

GA₃: co-applied, 100 ppm (13,14)

A. elongatum

Pre-chill, Potassium nitrate (ISTA)

Light, Pre-chill, Potassium nitrate (AOSA)

Constant temperatures: 8°C, 14°C (11)

Alternating temperatures: 15°/25°C, 15°/30°C (16h/8h) (20)

Pre-chill: 5°C, 5d, plus potassium nitrate, co-applied, 0.2%, germinate at 20°/30°C (16h/8h) in light, then pierce ungerminated seeds which remain (17)

Potassium nitrate: co-applied, 0.2%, germinate at 15°/30°C (16h/8h) and pierce ungerminated seeds which remain (17)

A. intermedium

Pre-chill, Potassium nitrate (ISTA)

Light (AOSA)

A. repens

Pre-chill, Potassium nitrate (ISTA)

Alternating temperatures: 20°/30°C in light, 25°/20°C (16h/8h) (19)

A. semicostatum

Alternating temperatures: 15°/30°C (16h/8h) (13)

Pre-chill: (13)

A. smithii

Pre-chill, Potassium nitrate (ISTA)

Potassium nitrate, test in soil (AOSA)

Alternating temperatures: 15°/30°C (13)

Removal of seed covering structures: expose embryo, germinate at 15°/30°C (16h/8h) in dark (2,3,4)

GA₃: co-applied, 10^-3 M, plus kinetin, 0.5 M, germinate at 15°/25°C (20h/4h) in light, 13000 lux, 4h/d (18)

A. spicatum

Light, Pre-chill, Potassium nitrate (AOSA)

Constant temperatures: 20°C (5)

A. trachycaulum

Pre-chill, Potassium nitrate (ISTA)

Pre-chill, repeat Pre-chill, then test at 20°/30°C, 4d (AOSA)

Alternating temperatures: 15°/30°C (16h/8h) (13); 15°/25°C, 15°/30°C, 20°/30°C, 20°/35°C (16h/8h) (20)

A. trichophorum

Pre-chill, Potassium nitrate (ISTA)

Light (AOSA)

VI. Comment

It is essential that seeds of Agropyron spp. be provided with alternating temperature regimes for germination (13,15,16,18-20). In general alternating temperature regimes of 15°/25°C or 20°/25°C (16h/8h) appear to be suitable for accessions of Agropyron spp. with the possible exception of A. smithii where the temperature during the 8h cycle may have to be as high as 40°C (20), but the use of alternating temperature regimes alone is unlikely to be sufficient to promote full germination in all Agropyron accessions. For most Agropyron spp. the ISTA and AOSA recommendations for breaking dormancy suggest that potassium nitrate and pre-chilling treatments also be applied. For A. smithii treatment with potassium nitrate, only, is recommended in an alternating temperature regime of 15°/30°C (16h/8h). This regime, however, is not completely successful in promoting germination (2,4,12,15), but full germination can be promoted by careful removal of the seed covering structures, pricking and testing in alternating temperature regimes (2-4,12,17,19). Some labour can be avoided by removing the seed covering structures and/or pricking only those seeds which have failed to germinate after between 10 and 28 days in an alternating temperature germination test regime. Attention is drawn to the multifactor procedure outlined above for A. elongatum (17) - combining pre-chilling (5°C, 5 days), potassium nitrate (co-applied, 0.2%), pricking and testing at 20°/30°C (16h/8h) - which may be more widely applicable. Care is required with the light environment since light can inhibit the germination of some seed lots of A. repens, A. semicostatum, and A. smithii (2-4,10,13-16,18).

VII. References

1. Andersen, A.L. and Drake, V.C. (1944). Preliminary study of seed of crested wheatgrass exhibiting delayed germination. Proceedings of the Association of Official Seed Analysts, 35, 146-152.

2. Bass, L.N. (1955). Determining the viability of Western wheatgrass seed lots. Proceedings of the Association of Official Seed Analysts, 45, 102-104.

3. Delouche, J.C. (1956). Dormancy in seeds of Agropyron smithii, Digitaria sanguinalis and Poa pratensis. Iowa State Colle Journal of Science, 30, 348-349.

4. Delouche, J.C. and Bass, L.N. (1954). Effect of light and darkness upon the germination of seeds of western wheatgrass Agropyron smithii L. Proceedings of the Association of Official Seed Analysts, 44, 104-113.

5. Evans, G.R. and Tisdale, E.W. (1972). Ecological characteristics of Aristida longiseta and Agropyron spicatum in West-Central Ida Ecology, 53, 137-142.

6. Everson, L.E. (1954). The germination of mature and immature seeds of quackgrass (Agropyron repens). Proceedings of the Association of Official Seed Analysts, 44, 127-128.

7. Grime, J.P., Mason, G., Curtis, A.V., Redman, J., Band, S.R., Mowforth, M.A.G., Neal, A.M. and Shaw, S. (1981). A comparative study of germination characteristics in a local flora. Journal of Ecology, 69, 1017-1059.

8. Hay, W.D. (1936). Germination of crested wheatgrass (Agropyron cristatum): preliminary studies. Proceedings of the Association of Official Seed Analysts, 28, 66-70.

9. Hay, W.D. (1936). Further studies with the germination of crested wheatgrass. Proceedings of the Association of Official Seed Analysts, 28, 86-88.

10. Hay, W.D. (1939). Laboratory germination studies with Agropyron smithii. Preliminary results. Proceedings of the Association of Official Seed Analysts, 30, 244-245.

11. Hunt, O.J. (1961). Low-temperature germination, a possible strain response of tall wheatgrass, Agropyron elongatum (Host.) Beauv. Agronomy Journal, 53, 277.

12. Kinch, R.C. (1963). A method of inducing rapid germination of Western wheatgrass. Proceedings of the Association of Official Seed Analysts, 53, 55-57.

13. Nakamura, S. (1962). Germination of grass seeds. Proceedings of the International Seed Testing Association, 27, 710-729.

14. Nakamura, S., Watanabe, S. and Ichihara, J. (1960). Effect of gibberellin on the germination of agricultural seeds. Proceedings of the International Seed Testing Association, 25, 433-439.

15. Schultz, Q.E. and Kinch, R.C. (1976). The effect of temperature and growth promoters on seed dormancy in Western wheatgrass seed. Journal of Seed Technology, 1, 79-85.

16. Thompson, K., Grime, J.P. and Mason, G. (1977). Seed germination in response to diurnal fluctuations of temperature. Nature, 267, 147-149.

17. Thornton, M.L. (1966). Seed dormancy in tall wheatgrass (Agropyron elongatum). Proceedings of the Association of Official Seed Analysts, 56, 116-119.

18. Toole, V.K. (1976). Light and temperature control of germination in Agropyron smithii seeds. Plant and Cell Physiology, 17 1263-1272.

19. Williams, E.D. (1968). Preliminary studies of germination and seedling behaviour in Agropyron repens (L.) Beavu. and Agrostis gigantea Roth. Proceedings of the 9th British Weed Control Conference, Vol.1, 119-124.

20. Young, J.A. and Evans, R.A. (1982). Temperature profiles for germination of cool season range grasses. USDA, Agriculture Research Service, Agriculture Research Results, Western Series, No. 27.

AGROSTIS

A. canina L.	velvet bentgrass
A. capillaris
A. gigantea Roth.	redtop
A. stolonifera L. [A. alba Auth.; A. maritima Lam.; A. palustris Huds.]	creeping bentgrass
A. tenuis Sibth. [A. capillaris Huds.; A. vulgaris With.]	colonial bentgrass

I. Evidence of dormancy

Freshly harvested seeds of Agrostis spp. can be very dormant (1-3,5,6,8,9,11,13-17). Between 6 and 8 months after-ripening may be required to remove dormancy (8,16), whilst seeds of A. capillaris stored for 41-44 weeks at 10°C remained dormant (17). Secondary dormancy was induced in imbibed seeds of A. capillaris exposed to an alternating temperature regime of 10°/20°C (12h/12h) in the dark (17).

II. Germination regimes for non-dormant seeds

A. canina

TP: 15°/25°C; 20°/30°C; 10°/30°C (16h/8h): 21d (ISTA)

TP: 20°/30°C (16h/8h): 21d (AOSA)

A. gigantea

TP: 15°/25°C; 20°/30°C; 10°/30°C (16h/8h): 10d (ISTA)

TP: 20°/30°C (16h/8h): 10d (AOSA)

A. stolonifera

TP: 15°/25°C; 20°/30°C; 10°/30°C (16h/8h): 28d (ISTA)

TP: 15°/30°C; 10°/30°C; 15°/25°C (16h/8h): 28d (AOSA)

A. tenuis

TP: 15°/25°C; 20°/30°C; 10°/30°C (16h/8h): 28d (ISTA)

TP: 15°/25°C; 15°/30°C; 10°/30°C (16h/8h): 28d (AOSA)

III. Unsuccessful dormancy-breaking treatments

A. capillaris

Constant temperatures: 19°-22°C in dark or light, far red, 1.7 x 10^-6 mol m^-2 s^-1, 10 min (17)

A. gigantea

Constant temperatures: 20°C, dark (16)

Potassium nitrate: co-applied, 0.2% (9)

GA₃: co-applied, 100 ppm (9,10)

A. stolonifera

Constant temperatures: 20°C, dark (8)

A. tenuis

Constant temperatures: 20°C, dark (8); 5°-30°C (13)

Alternating temperatures: 10°/30°C (16h/8h), dark (2); 20°/30°C (16h/8h), dark (8)

IV. Partly-successful dormancy-breaking treatments

A. canina

Alternating temperatures: 15°/20°C (9h/15h) in light, 15h/d (6); 20°/30°C (16h/8h) in light, 5 lux (8)

A. capillaris

Alternating temperatures: 5°-16°/20°C, 23°-30°/20°C (12h/12h) in dark (17)

A. gigantea

Alternating temperatures: 15°/20°C (9h/15h) (6); 20°/30°C (16h/8h) (15); 20°/30°C (16h/8h) in light (9,10); 25°/30°C (16h/8h) in light (16)

Light: at 15°/20°C (9h/15h) (6)

Thiourea: co-applied, 0.2% (9)

A. stolonifera

Alternating temperatures: 15°/20°C (9h/15h) in light (6); 20°/30°C (16h/8h) in light, 50, 200 fc (8): 30°/40°C, 28°/34°C (12h/12h) (4) Light: red (14)

A. tenuis

Alternating temperatures: 10°/30°C, 15°/30°C, 20°/30°C (16h/8h) in light (2,5,8,9,11,14); 10°/30°C, 15°/30°C, 20°/30°C (18h/6h) in light (1,3); 15°/25°C (18h/6h), dark (1,11); 20°/30°C, 10°/26°C, 10°/30°C (18h/6h) (5); 20°/30°C, 5°/15°C (16h/8h) (12)

Pre-chill: 4°C, 2,7d (1); 5°C, 10°C, 33d, germinate at 10°/25°C (12h/12h) (13); 4°C, 10°C, 7d, plus potassium nitrate, co-applied, 0.2%, germinate at 20°/30°C (16h/8h) in light (2)

Warm stratification: 15°C, 20°C, 25°C, 30°C, 33d, germinate at 10°/25°C (12h/12h) (13)

Potassium nitrate: co-applied, 0.2%, at 15°/25°C (18h/6h) in dark (1); co-applied, 0.2%, at 10°/30°C, 20°/30°C (16h/8h) in light (2); co-applied, 0.2%, at 15°/25°C, 15°/30°C (15h/9h) in light (3)

V. Successful dormancy-breaking treatments

A. canina

Pre-chill, Potassium nitrate (ISTA)

Light, Potassium nitrate (AOSA)

Alternating temperatures: 20°/30°C (16h/8h) in light, 50, 200 fc (8)

Potassium nitrate: co-applied, 0.2%, at 20°/30°C (16h/8h) in light (8)

A. capillaris

Alternating temperatures: 5°-16°/20°C (12h/12h) in light, red, 1.4x10^-6 mol m^-2 s^-1, 10 min (17)

Potassium nitrate: co-applied, 2x10^-2, 2x10^-3 M, at 5°-16°/20°C (12h/12h) dark (17)

GA₃: co-applied, 0.144 M, at 5°-16°/20°C in light, red, 1.4x10^-6 mol m^-2 s^-1, 10 min (17)

A. gigantea

Pre-chill, Potassium nitrate (ISTA)

Light, Potassium nitrate (AOSA)

Alternating temperatures: 20°/30°C (16h/8h) in light (15, 16)

Pre-chill: 5°C, 10d (9)

A. stolonifera

Pre-chill, Potassium nitrate (ISTA)

Light, Pre-chill, Potassium nitrate (AOSA)

Alternating temperatures: 20°/30°C, 25°/35°C (16h/8h) (7); 25°/18°C (12h/12h) (4); 15°/25°C (16h/8h) in light (14)

Potassium nitrate: co-applied, 0.2%, at 20°/30°C (16h/8h) in light (8)

A. tenuis

Pre-chill, Potassium nitrate (ISTA)

Light, Pre-chill, Potassium nitrate (AOSA)

Alternating temperatures: 15°/30°C, 15°/35°C, 15°/40°C (16h/8h) (14); 10°/20°C (16h/8h) in light (12); 5°/19°-26°C, 9°-16°/25°C (12h/12h) (13)

Pre-chill: 5°C, 10°C, 33d, plus GA₃, co-applied, 500 ppm, germinate at 10°/25°C (12h/12h) (13); 4°C, 2-7d, plus potassium nitrate, co-applied, 0.2% (1)

Warm stratification: 15°-30°C, 33d, plus GA₃, co-applied, 500 ppm, germinate at 10°/25°C (12h/12h) (13)

Potassium nitrate:co-applied, 0.2%, germinate at 15°/25°C, 15°/30°C, 10°/30°C (16-18h/6-8h) in light (1,2,3,5,8,11)

VI. Comment

Dormant seed accessions of Agrostis spp. require light and alternating temperatures for germination (1-3,6,8,9,11,14-17): additionally potassium nitrate in the germination test medium may be of further benefit (1,8) or avoid the requirement for light (17). A brief, low intensity exposure of the seeds to light can promote germination considerably (2,8,11,17), but higher intensities can reduce the proportion of seeds germinating, e.g. 200 fc, 7.5 hours per day (8). The above tends to suggest that AOSA/ISTA prescriptions and recommendations are satisfactory, but in A. capillaris 10°/20°C (12h/12h) with a brief light treatment has been suggested (17).

VII. References

1. Andersen, A.M. (1944). Germination of freshly harvested seed of Western grown Astoria bentgrass. Proceedings of the Association of Official Seed Analysts, 35, 138-146.

2. Andersen, A.M. (1946). The effect of light, temperature and potassium nitrate on the germination of Agrostis tenuis Sibth. and A. tenu is var. Highland seed. Procedures of the Association of Official Seed Analysts, 36, 112-125.

3. Bass, L.N. (1959). Comparison of germination percentages obtained for highland bentgrass seed tested at different temperature alternations. Proceedings of the Association of Official Seed Analysts, 49, 73-76.

4. Eggens, J.L. and Ormrod, D.P. (1982). Creeping bentgrass, Kentucky bluegrass and annual bluegrass seed germination response to elevated temperature. HortScience, 17, 624-625.

5. Gadd, I. (1955). Germination of seed of New Zealand browntop, Agrostis tenuis Sibth. Proceedings of the International Seed Testing Association, 20, 29-45.

6. Grime, J.P., Mason, G., Curtis, A.V., Rodman, J, Band, S.R., Mowforth, M.A.G., Neal, A.M. and Shaw, S. (1981). A comparative study of germination characteristics in a local flora. Journal of Ecology, 69, 1017-1059.

7. Harrington, G.T. (1923). Use of alternating temperatures in the germination of seeds. Journal of Agricultural Research, 23, 295-33 2.

8. Leggatt, C.W. (1946). Germination of seeds of three species of Agrostis. Canadian Journal of Research, C, 24, 7-21.

9. Nakamura, S. (1962). Germination of grass seeds. Proceedings of the International Seed Testing Association, 27, 710-729.

10. Nakamura, S., Watanabe, S. and Ichihara, J. (1960). Effect of gibberellin on the germination of agricultural seeds. Proceedings of the International Seed Testing Association, 25, 433-439.

11. Pierpoint, M. and Jensen, L. (1958). Activation of germination of Highland bentgrass by infra-red lamp. Proceedings of the Association of Official Seed Analysts, 48, 75-80.

12. Schmidt, B. (1969). [On the influence of temperature at the course of germination of some important lawn grasses.] Saatgut Wirtschaft, 21, 584-589.

13. Schonfeld, M.A. and Chancellor, R.J. (1983). Factors influencing seed movement and dormancy in grass seeds. Grass and Forage Science, 38, 243-250.

14. Toole, V.K. and Koch, E.J. (1977). Light and temperature control of dormancy and germination in bentgrass seeds. Crop Science, 17, 806-811.

15. Williams, E.D. (1968). Preliminary studies of germination and seedling behaviour in Agropyron repens (L.) Beauv. and Agrostis gigante ea Roth. Proceedings of the 9th British Weed Control Conference, Vol. 1, 119-124.

16. Williams, E.D. (1973). Seed germination of Agrostis gigantea Roth. Weed Research, 13, 310-324.

17. Williams, E.D. (1983). Effects of temperature fluctuation, red and far-red light and nitrate on seed germination of five grasses. Journal of Applied Ecology, 20, 923-935.

ANDROPOGON

A. gayanus Kunth	gamba grass
A. furcatus Muhl.	big bluestem
A. gerardii Vitm.	big bluestem
A. gerardii Vitm. x A. hallii Hack.	champ bluestem
A. hallii Hack.	sand bluestem
A. ischaemum L.	bluestem
A. scoparius Michx.	little bluestem

I. Evidence of dormancy

A. furcatus (2), A. gerardii (1,4,8), A. hallii (7) and A. scoparius (2,8) show considerable seed dormancy. For example, seeds of A. hallii and A. gerardii after-ripened for 1 (7) and 4 years (4) respectively remained dormant. Reports of dormancy in A. gayanus conflict: seeds have been reported to show both considerable dormancy (10) and no dormancy (12).

II. Germination regimes for non-dormant seeds

A. gayanus

Alternating temperatures: 25°/35°C (12h/12h) in light, 3.2x10^-6 W cm^-2 (12)

A. gerardii, A. hallii

TP; S: 20°/30°C (16h/8h): 28d (AOSA)

Alternating temperatures: 20°/30°C (16h/8h) in light, fluorescent, 16h/d (5)

III. Unsuccessful dormancy-breaking treatments

A. gayanus

Hydrogen peroxide: co-applied, 1, 1.5 M (10)

A. gerardii

Phosphine: fumigation, 120h, 3920-4720 ppm (9)

A. hallii

Light: 15000 lux, 8,12,16h/d (7) pH: 2.5 (6)

A. ischaemum, A. scoparius

Phosphine: fumigation, 120h, 3920-4720 ppm (9)

IV. Partly-successful dormancy-breaking treatments

A. gayanus

Pre-chill: 5°C, 2w (10)

Potassium nitrate: co-applied, 0.1-0.3% (10)

Hydrogen peroxide: co-applied, 0.5 M (10)

GA₃: co-applied, 250-1000 ppm (10)

Removal of seed covering structures: (10)

A. gerardii

Alternating temperatures: 15°/30°C, 20°/30°C (16h/8h) (1); 10°/20°C (6h/18h) in dark or light, 400-500 fc, 6h/d in 20°C cycle (4);20°/30°C (16h/8h) in light (11)

Pre-chill: 5°-8°C, 2w (1); 5°C, 10°C, 14d (11); then germinate at 20°/30°C (16h/8h) in light, 14d (14); 5°C, 10°C, 14d, plus potassium nitrate, co-applied, 0.2% (11)

GA₃: pre-applied, 24h, 100 ppm (4); pre-applied, 10-500 ppm (8)

Potassium nitrate: co-applied, 0.2% (11)

A. hallii

Constant temperatures: 25°C, 30°C, 35°C (7)

Alternating temperatures: 15°/25°C, 20°/30°C, 25°/35°C (16h/8h) in light or dark (7)

Pre-chill: then germinate at 20°/30°C (16h/8h) in light, 14d (14)

pH: 4-11.5 (6)

Phosphine: fumigation, 120h, 3920-4720 ppm (9)

A. scoparius

GA₃: pre-applied, 10-500 ppm (8)

V. Successful dormancy-breaking treatments

A. gerardii, A. hallii

Light, Pre-chill, Potassium nitrate (AOSA)

VI. Comment

Seeds of A. gayanus are likely to cause the greatest problems of dormancy, but it is important to ensure that the problem of lack of germination is not caused by empty seeds. The following germination test procedures have been recommended as at least partly effective in promoting the germination of dormant seeds of this species: germinate on top of filter papers - moistened optionally with potassium nitrate (probably 0.2%) - at 20°/35°C (presumably 16h/8h) with light for 21 days (3); germinate on top of filter papers moistened with potassium nitrate at 20°/30°C (16h/8h) with light applied for 8 hours per day for 28 days (3).

In a comparison of germination test results from different laboratories with seeds of A. gerardii x A. hallii at 15°/30°C or 20°/30°C (16h/8h) with no pre-chill or a 2 week pre-chill treatment at 5°C, 7°C or 8°C, the regime 20°/30°C after pre-chill at 7°C gave significantly greater germination (1), but the difference was only marginal. The pre-chill treatments were, however, beneficial (1).

Although most of the results for A. hallii were from tests where light was applied for 8 hours per day during the high temperature phase of the alternating temperature cycle (e.g. 6), there is one report of light being applied for 16 hours per day during the low temperature phase of the alternating temperature cycle (5). This is unlikely to be of any particular benefit (7). For this species a constant germination test temperature of 35°C or an alternating temperature regime of 25°/35°C (16h/8h) have been recommended (7).

It is suggested that seeds of Andropogon spp. be tested for germination at 20°/35°C (16h/8h) for at least 28 days with potassium nitrate co-applied at 0.2% and the light regime described in Chapter 6 after a 2-week pre-chill treatment at 5°-7°C. Alternatively removal of the seed covering structures - with subsequent testing at 20°/35°C (16h/8h) in light, 8h/d - can avoid the need to pre-chill and co-apply potassium nitrate (13).

References

1. Atkins, B.A. (1977). Variations on purities, germination and PLS (pure live seed) on champ bluestem. Journal of Seed Technology, 2 40-47.

2. Coukos, C.J. (1944). Seed dormancy and germination in some native grasses. Journal of American Society of Agronomy, 36, 337-345.

3. Ferguson, J.E. (1982). C.I.A.T. (Personal communication).

4. Kucera, C.L. (1966). Some effects of gibberellic acid on grass seed germination. Iowa State Journal of Science, 41, 137-143.

5. Shaidaee, G., Dahl, B.E. and Hansen, R.M. (1969). Germination and emergence of different age seed of six grasses. Journal of Range Management, 22, 240-243.

6. Stubbendieck, J. (1974). Effect of pH on germination of three grass species. Journal of Range Management, 27, 78-79.

7. Stubbendieck, J. and McCully, W.G. (1976). Effect of temperature and photoperiod on germination and survival of sand bluestem. Journal of Range Management, 29, 206-208.

8. Svedarsky, D. and Kucera, C.L. (1970). Effects of gibberellic acid and post-harvest age on germination of prafrie grasses. Iowa State Journal of Science, 44, 513-518.

9. White, G.D. and Jacobson, E.T. (1972). Phosphine fumigation: effects on the germination of grass seed. Journal of Economic Entomology, 65, 1523-1524.

10. Eira, M.T.S. (1983). [Comparison of methods for overcoming seed dormancy in Andropogon grass.] Revista Brasileira de Sementes, 5, 37-49.

11. Faroua, H., Ahring, R.M., Powell, J. and Rommann, L.M. (1976). Increasing seed germination of rangeland species. Oklahoma Agricultural Experiment Station, Research Report No. P.735, pp. 27-30.

12. Felippe, G.M., Silva, J.C.S. and Cardoso, V.J.M. (1983). Germination studies in Andropogon gayanus Kunth. Revista Brasileira de Botanica, 6, 41-48.

13. Goedert, C. (1984). Seed dormancy of tropical forage grasses and implications for the conservation of genetic resources. Ph.D. Thesis, University of Reading.

14. Prentice, L.J. (1981). Observations on the germination time on rangegrasses. Newsletter of the Association of Official Seed Analysts, 55, 59.

ARISTIDA

A. armata

A. contorta F. Muell.

A. longespica Poir.

A. longiseta

A. murina Cay.

A. purpurea

A. ramosa R. Br.

I. Evidence of dormancy

Seed lots of A. armata, A. ramosa, A. contorta and A. longespica have shown considerable dormancy requiring after-ripening periods of between 4 and 18 months for dormancy to be removed (1,2,6-8).

II. Germination regimes for non-dormant seeds

-

III. Unsuccessful dormancy-breaking treatments

A. contorta

Pre-chill: 5°C, 8w (7)

A. longespica

Constant temperatures: 10°C, 20°C, 30°C in light, 12h/d, or dark (1)

Potassium nitrate: co-applied, 200 ppm (1)

GA₃: co-applied, 200 ppm (1)

Thiourea: co-applied, 200 ppm (1)

A. longiseta

Constant temperatures: 20°C, 25°C, 35°C (3,5)

Pre-chill: 0°C (3)

A. murina

Light: fluorescent, 2.2 W m^-2, 12h/d, at 20°C, (4); red, 0.37 W m^-2, 5,25 min, at 20°C (4)

IV. Partly-successful dormancy-breaking treatments

A. armata

Alternating temperatures: 25°/30°C (12h/12h) in light (2)

Pre-chill: 4°C, 6w (2)

Pre-dry: 70°C (2)

A. contorta

Constant temperatures: 30°C in light (8)

Alternating temperatures: 25°/30°C (12h/12h) (7)

Scarification: sand paper (7)

Pre-soak: 48h (7)

GA₃: co-applied, 10^-5g/ml, with or without seed covering structures (8)

Thiourea: co-applied, 10^-2 M, with or without seed covering structures (8)

Removal of seed covering structures: seed coat (8)

Hydrogen peroxide: pre-applied, 48h, 1 M (8)

Potassium cyanide: pre-applied, 24h, 10^-2 M (8)

Sodium azide: pre-applied, 24h, 10^-3 M (8)

A. ramosa

Constant temperatures: 20°-30°C (6)

Light: (6)

Removal of seed covering structures: seed coat (6)

V. Successful dormancy-breaking treatments

A. armata

Alternating temperatures: 25°/30°C (12h/12h), in light, dehulled seed (2)

A. contorta

Alternating temperatures: 25°/30°C (night/day), dehulled seed (7)

A. longespica

Pre-chill: 5°C, 12-24w, germinate at 30°C in light, 12h/d (1)

Removal of seed covering structures: excise embryo, germinate at 30°C in light, 12h/d (1)

A. longiseta

Alternating temperatures: 20°-24°/41°C (night/day) (3)

VI. Comment

Successful germination test regimes for accessions of Aristida spp. are likely to include alternating temperatures, seed coat removal, and probably light (low intensity). The amplitude of temperature alternation required to promote full germination does not appear to be particularly great - 5°C (2,7) - although greater amplitudes may also be satisfactory - 17°C (3). For the present it is suggested that the regime 25°/30°C (12h/12h) be used after the seed coats have first been removed.

VII. References

1. Baskin, J.M. and Caudle, C. (1967). Germination and dormancy in cedar glade plants. I. Aristida longespica and Sporobolus vaginiflorus. Journal of the Tennessee Academy of Science, 42, 132-133.

2. Brown, R.F. (1982). Seed dormancy in Aristida armata. Australian Journal of Botany, 30, 67-73.

3. Evans, G.R. and Tisdale, E.W. (1972). Ecological characteristics of Aristida longiseta and Agropyron spicatum in West-Central Idah o. Ecology, 53, 137-142.

4. Ginzo, H.D. (1978). Red and far red inhibition of germination in Aristida murina Cav. Zeitschrift fur Pflanzenphysiologie, 90, 303-307.

5. Jackson, C.V. (1928). Seed germination in certain New Mexico range grasses. Botanical Gazette, 86, 270-294.

6. Lodge, G.M. and Whalley, R.D.B. (1982). Establishment of warm- and cool-season native perennial grasses on the north-west slopes of New South Wales. I. Dormancy and germination. Australian Journal of Botany, 29, 111-119.

7. Mott, J.J. (1972). Germination studies on some annual species from an arid region of Western Australia. Journal of Ecology, 60, 293-304.

8. Mott, J.J. (1974). Mechanisms controlling dormancy in the arid zone grass Aristida contorta. I. Physiology and mechanisms of dormancy. Australian Journal of Botany, 22, 635-645.

AVENA

A. barbata Brot.	slender wild oat
A. byzantina K. Koch	red oat
A. fatua L.	spring or common wild oat
A. ludoviciana Durieu	winter wild oat
A. nuda L.	naked oat
A. sativa L.	common oat
A. sativa L. x A. fatua L.	dormoat
A. sterilis L.	animated oat
A. strigosa Schreber	bristle or small oat

I. Evidence of dormancy

Dormancy is common in the cultivated oat A. sativa (2,10,16,50,53), and pronounced in the wild oat species A. barbata (35,37), A. byzantina (13,48), A. fatua (1,5,6,9,21,30,31,42,51,52), A. ludoviciana (44,45,54), A. nuda (10), A. sterilis (13), and the hybrid dormoat A. sativa x A. fatua (3,18).

II. Germination regimes for non-dormant seeds

A. byzantina, A. sativa

BP; S: 20°C; 15°C: 10d (AOSA)

BP; S: 20°C: 10d (ISTA)

III. Unsuccessful dormancy-breaking treatments

A. byzantina

Pre-soak: 20h (48)

A. fatua

Constant temperatures: 5°-30°C (8); 5°-15°C (17); above 25°C (17,39,41,43,49)

Alternating temperatures: 10°-40°/40°-10°C (39)

Light: (5,23,28,31,39); 6x10³ erg cm^-2 s^-1 (21); white, blue, infra-red, red (14)

Oxygen: below 20% (5,21)

Carbon dioxide: 0-20% (21)

Pre-soak: 10°C, 48h (22); 25°C, 16-112h (23); 15 min-8h (26)

Aluminium phosphide: 48,72h fumigation (11)

Sodium azide: co-applied, 2x10^-3 M (15); co-applied, 1-2x10^-4 M (52); co-applied, 2, 4x10^-3 M (52); co-applied, 10^-3 M, plus 2-chloroethyl trimethylammonium chloride, co-applied, 5x10^-2 M (52); co-applied, 10^-3 M, plus salicylhydroxamic acid, co-applied, 3x10^-3 M (52)

GA₃: co-applied, 1, 1000 ppm, in light (28); co-applied, 10^-8-10^-5 M, intact or dehulled seeds (26)

Thiourea: co-applied, 10^-2-10^-4 M (25)

Kinetin: co-applied, 10^-4-10^-5 M (25)

Ethrel: co-applied, 10-500 ppm (25)

Naphthylacetic acid: co-applied, 10^-6 M (25)

Abscisic acid: co-applied, 10^-3, 10^-4 M (25)

Ethylene chlorohydrin: pre-applied, 1 min, 1, 3, 6% (31)

Dichloroethylene: pre-applied, 1 min, 0.1-1% (31)

Sodium thiocyanate: pre-applied, 1h, 2, 3% (31)

Potassium nitrite; co-applied, 1 M (39)

Methylene blue:pre-applied, 24h, 10^-3 M (47)

Reduced nitrogenous compounds: pre-applied, 24h (47)

Sodium fluoride: pre-applied, 24h, 10^-2, 10^-3 M (47)

2-4 Dinitrophenol: pre-applied, 24h, 10^-3-10^-6 M (47)

Sodium arsenate: pre-applied, 24h, 10^-2, 10^-3 M (47)

Sodium hypochlorite: pre-applied, 1 min-6h, 6% (26); pre-applied, 0.25-2h, 8x10^-1 M (29); co-applied, dehulled seed, 1.3-135x10^-3 M (29)

Sucrose: (22)

Hydrogen peroxide: co-applied, 0.375-3x10^-1 M (29); co-applied, 1.5x10^-1 M, dehulled seeds (29)

Removal of seed covering structures: (26,29,31); pierce, germinate in excess water (29)

Pre-dry: (25)

A. ludoviciana

Light: (54)

A. sativa

Vacuum: partial, 10,30 min (16)

Carbon dioxide: 30-38.7%, plus 12.8-14.7% oxygen (16)

Pre-soak: 1-5h (20); 12,24h (23,34)

Potassium cyanide: pre-applied, 24h, 10^-4 M (36)

Sodium azide: pre-applied, 24h, 10^-2 M (36)

Sodium sulphide: pre-applied, 24h, 10^-3, 10^-4 M (36)

Hydroxylamine: pre-applied, 24h, 10^-1, 10^-3, 10^-4 M (36)

Dimercaptol: pre-applied, 24h, 10^-3, 10^-4 M (36)

Diethyldithiocarbamate: pre-applied, 24h, 10^-3M (36)

Iodoacetate: pre-applied, 24h, 10^-3, 10^-4 M (36)

Sodium monofluoroacetate: pre-applied, 24h, 10^-3 M (36)

2,4 Dinitrophenol: pre-applied, 24h, 10^-2-10^-6 M (36)

A. sativa x A. fatua

Removal of seed covering structures: (3)

Warm stratification: 20°C, 1-4d, germinate at 3°C, 7°C (3)

GA₃: co-applied, 0.1, 1 ppm, dehulled seeds (3)

IV. Partly-successful dormancy-breaking treatments

A. barbata

Removal of seed covering structures: pricking (37)

A. byzantina

Pre-chill: 7°C, 5d (48)

Pre-dry: (48)

Scarification: sulphuric acid, 10%, 5 min, then pre-dry, 2h, then

GA₃, pre-applied, 20h, 100, 250, 500 ppm (48); sulphuric acid, 10%, 5 min, then pre-dry, 2h, then potassium nitrate, pre-applied, 20h, 0.1, 0.2, 0.5% (48)

A. fatua

Constant temperatures: 10°C (39,54); 10°-25°C (17,43); 15°C (1,44); 3°C, 10°C (40); 8°-16°C (42)

Alternating temperatures: 11°/14°-23°C (12h/12h) (43); 17°/20°-30°C (12h/12h) (43)

Light: dark (14,21,23,28,31,39)

Removal of seed covering structures: (5,6,9,21); cut, pierce or prick (6,27,28,29,37,54,58)

Ethrel: co-applied, 100-5000 ppm (1)

Potassium nitrate: pre-applied, 24, 48h, 0.2-2% (31); pre-applied, 1-6h, 1% (31); co-applied, 10^-2M (39,40); co-applied, 0.2% (23); co-applied, 0.2%, plus pre-chill, 5°-7°C, 10-14d (6)

Potassium nitrite: co-applied, 10^-4 -10^-1 M (39)

Potassium cyanide: pre-applied, 24h, 10^-2 -10^-4 M (47)

Sodium nitrate: co-applied, 0.2% (23)

Sodium nitrite: pre-applied, 24h, 10^-2 M (47)

Sodium azide: pre-applied, 3,6h, 0.5-2x10^-3, M (15); pre-applied, 24h, 10^-3, 10^-4 M (47); co-applied, 0.5x10^-3, 10^-3 M (15); co-applied, 0.2-2x10^-3 M (52)

Sodium hypochlorite: pre-applied, 1.5h, 0.8 M (29); pre-applied, 0.5-2h, 0.8 M, then GA₃, co-applied, 10^-8 -10^-3 M (26); pre-applied, 15,30 min, 0.8 M, dehulled seeds or naked caryopses (29); pre-applied, 1-30s, 0.8 M, dehulled seeds, then GA₃, co-applied, 5x10^-4 M (29); pre-applied, 3h, 0.8 M, dehulled seeds (29); pre-applied, 6h, 0.54-0.8 M, dehulled seeds (29); pre-applied, 1h, 0.8 M, then hydrogen peroxide, co-applied, 0.15 M (29); co-applied, 5.4x10^-3 M - 0.1 M, dehulled seeds (29)

Sodium thiocyanate: pre-applied, 1h, 1% (31)

GA₃: pre-applied, 30 min, 1,10,100 ppm (6); pre-applied, 24h, 400 ppm (55); co-applied, 10 ppm (6); co-applied, 25,50 ppm (19); co-applied, 10^-2 M (25,39); co-applied, 50-500 ppm, light (28); co-applied, 1-500 ppm, dark (28); co-applied, 10^-4 -10^-3 M, intact or dehulled seeds (26,29); co-applied, 500, 1000, 2500 ppm (46); co-applied, 1500 ppm (51); co-applied, 1.44x10^-3 M (58)

Hydrogen peroxide: co-applied, 0.1 M (22); co-applied, 0.15 M, intact, pierced, or dehulled seeds (29); co-applied, 37.5x10^-3 -1.5x10^-1 M, dehulled seeds (29); co-applied, 10^-2 M, dehulled seeds (23)

Oxygen: above 20% (5); 20-80% (6,21); 60, 100% (31)

Pre-chill: 0°C, 90d (31)

Pre-soak: 48h (22,31)

Ether: (31)

Aluminium phosphide: 6-18h fumigation (11)

Removal of seed covering structures: pierce, plus GA₃, co-applied, 10^-8 -10^-3 M (27); dehull, pierce, plus GA₃, co-applied, 10^-8 M (26); dehull, scarify (6,31)

A. ludoviciana

Removal of seed covering structures: (54)

A. sativa

Pre-chill: 5°C, 3d (2)

Potassium cyanide: pre-applied, 24h, 10^-2, 10^-3 M (36)

Sodium azide: pre-applied, 24h, 10^-3, 10^-4 M (36)

Hydrogen sulphide: pre-applied, 24h, 10^-1, 10^-2 M (36)

Hydroxylamine: pre-applied, 24h, 10^-2, M (36)

Diethyldithiocarbamate: pre-applied, 24h, 10^-4, M (36)

Malonate: pre-applied, 24h, 10^-1, 10^-2 M (36)

Sodium monofluoroacetate: pre-applied, 24h, 10^-2 M (36)

Sodium sulphide: pre-applied, 24h, 10^-1, 10^-2 M (36)

GA₃: co-applied, 20 ppm (32,33); co-applied, 400-800 ppm (34); pre-applied, 15-18h, 150 ppm (2)

Pre-dry: 2d (2); 50°C, 2d plus 70°C, 5h (2); 40°C, 12h (16); 40°C, 5d (20); 50°C, 2d, then pre-chill, 5°C, 3d (2)

Removal of seed covering structures: (16,32,50)

Vacuum: partial, 1h (16)

A. sativa x A. fatua

Pre-chill: 3°-7°C, 1-4d (3)

GA₃: co-applied, 10, 100 ppm, dehulled seeds (3); co-applied, 0.1-10 ppm, peeled caryopses (3)

A. sterilis

Removal of seed covering structures: dehull (59)

V. Successful dormancy-breaking treatments

A. barbata

Constant temperatures: 10°C (56)

Alternating temperatures: 5°/20°C, 5°/15°C (16h/8h) (56)

A. byzantina

Pre-dry, Pre-chill, GA₃ (ISTA)

Pre-chill, Pre-dry (AOSA)

A. fatua

Constant temperatures: 4°C (41,49)

Warm stratification: 20°C, 21d, plus GA₃, co-applied, 1.4x10^-4 M (52)

GA₃: co-applied, 1000 ppm (6,28); co-applied, 100 ppm (19); co-applied, 100 ppm, dehulled seeds (23)

Sodium azide: pre-applied, 6h, 10^-3 M (15); pre-applied, 21d, dark, 0.8x10^-3, 10^-3 M, then GA₃, co-applied, 1.4x10^-4 M (52); co-applied, 0.8x10^-3, 10^-3 M, plus GA₃, 1.4x10^-4, 2.8x10^-4 M (52)

Potassium nitrate: pre-applied, 12,24h, 1% (31); pre-applied, 1-24h, 2% (31); co-applied, 2x10^-4 -2x10^-2 M, in light (57)

Removal of seed covering structures: (22,28); plus oxygen, 100% (9); dehull and prick (5,14,23,29); dehull, prick and re-prick (39); dehull, prick, plus GA₃, co-applied, 10 ppm (42); dehull, prick, plus GA₃, co-applied, 10^-7 -10^-3 M (27); prick, plus GA₃, co-applied, 1.44x10^-3 M, at 15°C in light, 10.7x10^-6 mol m^-2 s^-1, 8h/d (58); dehull, prick, plus hydrogen peroxide, co-applied, 0.15 M (26); dehull, plus sodium hypochlorite, pre-applied, 1h, 0.8 M (26,29); dehull, plus sodium hypochlorite, pre-applied, 1h, 0.8 M, then GA₃, co-applied, 10^-8 -10^-3 M (26,29); dehull, plus sodium hypochlorite, pre-applied, 1h, 0.8 M, then hydrogen peroxide, co-applied, 0.15 M (29); dehull, plus sodium hypochlorite, pre-applied, 1h, 0.8 M, then GA₃, co-applied, 5x10^-4 M (29)

Sodium hypochlorite: pre-applied, 2h, 0.8 M, then GA₃, co-applied, 10^-4 M (26); pre-applied, 2h, 0.8 M, then dehull (29)

Hydrogen peroxide: co-applied, 0.3 M, dehulled seeds (29); co-applied, 0.15 M, dehulled seeds in excess moisture (29)

Aluminium phosphide: 18-24h fumigation (11)

A. sativa

Pre-dry, Pre-chill, GA₃ (ISTA)

Pre-chill, Pre-dry (AOSA)

Constant temperatures: 12°-15°C (2); 7°-17°C (4); 4°-24°C (41); 5°-12°C (20); 6°-14°C (38); 4°-12°C (50); 2°C, 10°C (10); 7.5°C (12); 12°C, 7d, then 20°C, 3d (33,34); 15°C (13,24)

Pre-chill: 4°C, 4d (50); 10°C, 5d (16); 5°C, 6d (53); 5°C, 7d (32)

GA₃: co-applied, 200 ppm (32,33); co-applied, 400 ppm (32,34); co-applied, 500 ppm (7)

Potassium nitrate: co-applied, 0.2% (24,50); pre-applied 1h, 2% (50); co-applied, 0.2%, plus pre-chill, 10°C, 5d (32); co-applied, 0.2%, dehull (24)

Calcium nitrate: co-applied, 0.2% (50); pre-applied, 1h, 2% (50)

Ammonium nitrate: co-applied, 0.2% (50); pre-applied, 1h, 2% (50)

Removal of seed covering structures: (53); dehull, pre-chill, 10°C, 5d (16); dehull, prick (16,20)

Oxygen: 51, 59, 100% (16)

A. sativa x A. fatua

Constant temperatures: 7°C (3)

GA₃: co-applied, 100 ppm, naked caryopses (3)

Removal of seed covering structures: excise embryo (3)

VI. Comment

A low constant temperature is an essential component of suitable germination test regimes for accessions of Avena spp. The range 7° to 10°C is suggested as being the most suitable.

A. byzantina The ISTA and AOSA recommendations for breaking dormancy (pre-chill, pre-dry, potassium nitrate) are not completely effective in promoting the germination of dormant seeds of A. byzantina (48).

A. fatua Procedures which combine the action of several dormancy-breaking agents are more likely to be successful (e.g. 29). The following procedure has been found to be satisfactory. Test at 7.5° to 10°C for 28 days with removal of the seed covering structures once the seed has imbibed, pricking in the area of the embryo, and subsequent repricking of ungerminated seeds after 28 days and continue test for a further period (39,A). An alternative procedure (which is equally effective but delays the time at which the onerous task of removing seed coats and pricking is performed and reduces the number of seeds pricked) is to test intact seeds at 7.5° to 10°C for 21 days, then remove seed covering structures and prick ungerminated seeds in the area of the embryo and test for a further 21 days at 7.5° to 10°C (A). Another alternative is to prick the seeds and test in light with gibberellic acid co-applied at 1.44x10^-3 M (58). Note that light tends to promote the germination of partly-dormant seed lots but is ineffective with strongly dormant seed lots (58) - unless combined with several other dormancy-breaking agents.

A. sativa Testing at low temperatures is the most satisfactory method of promoting germination in the cultivated oat (2,4,10,12,13,16,20,24,32,34,37,38,42). Testing at between 7.5° and 10°C for 28 days is recommended (A). Not only does this promote full germination of the dormant seeds but it is also safe for non-dormant and aged seeds (A).

VII. References

1. Adkins, S.W. and Ross, J.D. (1981). Studies in wild oat seed dormancy. I. The role of ethylene in dormancy breakage and germination of wild oat seeds (Avena fatua L.). Plant Physiology, 67, 358-362.

2. Andersen, S. (1965). The germination of freshly harvested seed of ripe and unripe barley and oats. Euphytica, 14, 91-96.

3. Andrews, C.J. and Burrows, V.D. (1972). Germination response of dormoat seeds to low temperature and gibberellin. Canadian Journal of Plant Science, 52, 295-303.

4. Atterberg, A. (1907). Die Nachreife des Getreides. Landwirtsch Versuch Stat, 67, 129-143.

5. Atwood, W.M. (1914). A physiological study of the germination of Avena fatua. Botanical Gazette, 57, 386-414.

6. Baker, L.O. and Leighty, D.H. (1958). Germination studies with wild oat seeds. Proceedings 16th West Weed Control Conference, 69-74.

7. Bekendam, J. (1975). Report of the working group on the application of gibberellic acid in routine germination testing to break dormancy of cereal seed. Seed Science and Technology, 3, 92-93.

8. Bewley, J.D. and Black, M. (1982). Physiology and biochemistry of seeds in relation to germination. Volume 2. Viability, dormancy and environmental control. Springer-Verlag, Berlin.

9. Black, M. (1959). Dormancy studies in seed of Avena fatua. I. The possible role of germination inhibitors. Canadian Journal of Botany, 37, 393-402.

10. Brown, E., Stanton, T.R., Wiebe, G.A. and Martin, J.H. (1948). Dormancy and the effect of storage on oats, barley, and sorghum. USDA Technical Bulletin, No. 953.

11. Cairns, A.L.P. and Villiers, O.T. de (1980). Effect of aluminium phosphide fumigation on the dormancy and viability of Avena fatua seed. South African Journal of Science, 76, 323.

12. Chippindale, H.G. (1934). The effect of soaking in water on the "seeds" of some gramineae. Annals of Applied Biology, 21, 225-232

13. Coffman, F.A. and Stanton, T.R. (1938). Variability in germination of freshly harvested Avena. Journal of Agricultural Research, 57-72.

14. Cumming, B.G. and Hay, J.R. (1958). Light and dormancy in wild oats (Avena fatua L.). Nature, 182, 609-610.

15. Fay, P.K. and Gorecki, R.S. (1978). Stimulating germination of dormant wild oat (Avena fatua) seed with sodium azide. Weed Science, 26, 323-326.

16. Forward, B.F. (1958). Studies of germination in oats. Proceedings of the International Seed Testing Association, 23, 5-37.

17. Friesen, G. and Shebeski, L.H. (1961). The influence of temperature on the germination of wild oat seeds. Weeds, 9, 634-638.

18. Garber, R.J. and Quisenberry, K.S. (1923). Delayed germination and the origin of false wild oats. The Journal of Heredity, 14, 267-274.

19. Green, J.G. and Helgeson, E.A. (1957). The effect of gibberellic acid on dormant seeds of wild oats. Proceedings 14th North Central Weed Control Conference, USA, 39.

20. Harrington, G.T. (1923). Forcing the germination of freshly harvested wheat and other cereals. Journal of Agricultural Research, 23, 79-100.

21. Hart, J.W. and Berrie, A.M.M. (1966). The germination of Avena fatua under different gaseous environments. Physiologia Plantarum, 19, 1020-1025.

22. Hay, J.R. (1962). Experiments on the mechanism of induced dormancy in wild oats, Avena fatua L. Canadian Journal of Botany, 40, 191-202.

23. Hay, J.R. and Cumming, B.G. (1959). A method for inducing dormancy in wild oats (Avena fatua L.). Weeds, 7, 34-40.

24. Heit, C.E. (1948). Thirty-eighth annual meeting. Report of subcommittee on dormancy of seeds. Proceedings of the Association of Official Seed Analysts, 38, 25-26.

25. Holm, R.E. and Miller, M.R. (1972). Weed seed germination responses to chemical and physical treatments. Weed Science, 20, 150-15

26. Hsiao, A.I. (1979). The effect of sodium hypochlorite and gibberellic acid on seed dormancy and germination of wild oats (Avena fatua). Canadian Journal of Botany, 57, 1729-1734.

27. Hsiao, A.I., McIntyre, G.I. and Hanes, J.A. (1983). Seed dormancy in Avena fatua. 1. Induction of germination by mechanical injury. Botanical Gazette, 144, 217-222.

28. Hsiao, A.I. and Simpson, G.M. (1971). Dormancy studies in seed of Avena fatua. 7. The effects of light and variation in water regime on germination. Canadian Journal of Botany, 49, 1347-1357.

29. Hsiao, A.I. and Quick, W.A. (1984). Actions of sodium hypochlorite and hydrogen peroxide on seed dormancy and germination of wild oats (Avena fatua). Weed Research, 24, 411-419.

30. Jana, S., Acharya, S.N. and Naylor, J.M. (1979). Dormancy studies in seed of Avena fatua. 10. On the inheritance of germination behaviour. Canadian Journal of Botany, 57, 1663-1667.

31. Johnson, L.P.V. (1935). General preliminary studies on the physiology of delayed germination in Avena fatua. Canadian Journal of Research, Section C, 13, 283-300.

32. Kahre, L. (1969). Comparisons of methods for germination. Report from the working group on cereal seed. Proceedings of the International Seed Testing Association, 34, 585-598.

33. Kahre, L., Kolk, N. and Fridz, T. (1965). Gibberellic acid for breaking of dormancy in cereal seed. Proceedings of the International Seed Testing Association, 30, 887-891.

34. Kahre, L., Kolk, H. and Wiberg, H. (1962). Note on dormancy-breaking in seeds. (Cereals and Timothy). Proceedings of the International Seed Testing Association, 27, 679-683.

35. Laude, H.M. (1956). Germination of freshly harvested seed of some western range species. Journal of Range Management, 9, 126-129.

36. Major, W. and Roberts, E.H. (1968). Dormancy in cereal seeds. I. The effects of oxygen and respiratory inhibitors. Journal of Experimental Botany, 58, 77-89.

37. Marshall, D.R. and Jain, S.K. (1970). Seed predation and dormancy in the population dynamics of Avena fatua and A. barbata. Ecology, 51, 886-891.

38. Munerati, M.O. (1926). Possibilité de déterminer l'âge des graines de blé par la temperature de leur germination. Comptes Rendus de l'Académie des Sciences, Paris, 182, 535-537.

39. Murdoch, A.J. (1982). Factors influencing the depletion of annual weed seeds in the soil. Ph.D. Thesis, University of Reading, UK.

40. Murdoch, A.J. and Roberts, E.H. (1982). Biological and financial criteria of long-term control strategies for annual weeds. Proceedings 1982 British Crop Protection Conference Weeds. 741-748.

41. Naylor, J.M. and Fedec, P. (1978). Dormancy studies in seed of Avena fatua. 8. Genetic diversity affecting reponse to temperature. Canadian Journal of Botany, 56, 2224-2229.

42. Naylor, J.M. and Jana, S. (1976). Genetic adaptation for seed dormancy in Avena fatua. Canadian Journal of Botany, 54, 306-312.

43. Paterson, J.G., Boyd, W.J.R. and Goodchild, N.A. (1976). Effect of temperature and depth of burial on the persistence of seed of Avena fatua L. in western Australia. Journal of Applied Ecology, 13, 841-847.

44. Quail, P.H. and Carter, O.G. (1968). Survival and seasonal germination of seeds of Avena fatua and A. ludoviciana. Australian Journal of Agricultural Research, 19, 721-729.

45. Quail, P.H. and Carter, O.G. (1969). Dormancy in seeds of Avena ludoviciana and A. fatua. Australian Journal of Agricultural Research, 20, 1-11.

46. Richardson, S.G. (1979). Factors influencing the development of primary dormancy in wild oat seeds. Canadian Journal of Plant Science, 59, 777-784.

47. Roberts, E.H. and Madden, D. Cited by Roberts, E.H. (1972). Oxidative processes and the control of seed germination. In Seed Ecology (ed. W. Heydecker), pp. 189-218, Butterworths, London.

48. Santacruz, R.F. (1981). [Response of oats to seed dormancy breaking treatment.] ICA. Information Colombia, 15, 6-9. (From Seed Abstracts, 1983, 6, 2205.)

49. Sawhney, R. and Naylor. J.M. (1980). Dormancy studies in seed of Avena fatua. 12. Influence of temperature on germination behavior of non-dormant families. Canadian Journal of Botany, 58, 578-581.

50. Schwendiman, A. and Shands, H.L. (1943). Delayed germination on seed dormancy in vicland oats. Journal of American Society of Agronomy, 35, 681-688.

51. Somody, C.N., Nalewaja, J.D. and Miller, S.D. (1981). Morphology characteristics and dormancy of 1200 wild oat selections. Proceedings of North Central Weed Control Conference, 36, 34.

52. Upadhyaya, M.K., Naylor, J.M. and Simpson, G.M. (1982). The physiological basis of seed dormancy in Avena fatua L. I. Action of the respiratory inhibitors sodium azide and salicylhydroxamic acid. Physiologia Plantarum, 54, 419-424.

53. Whitcomb, W.O. (1923). Germination of newly threshed grains. Proceedings of the Association of Official Seed Analysts, 14, 84-88.

54. Whittington, W.J., Hillman, J., Gatenby, S.M., Hooper, B.E. and White, J.C. (1970). Light and temperature effects of the germination of wild oats. Heredity, 25, 641-650.

55. Wiberg, H. and Kolk, H. (1960). Effect of gibberellin on germination of seeds. Proceedings of the International Seed Testing Association, 25, 440-445.

56. Young, J.A., Evans, R.A. and Kay, B.L. (1973). Temperature requirements for seed germination in an annual-type rangeland community. Agronomy Journal, 65, 656-659.

57. Hilton, J.R. (1984). The influence of light and potassium nitrate on the dormancy and germination of Avena fatua L. (wild oat) seed and its ecological significance. New Phytologist, 96, 31-34.

58. Hilton, J.R. and Bitterli, C.J. (1983). The influence of light on the germination of Avena fatua L. (wild oat) seed and its ecological significance. New Phytologist, 95, 325-333.

59. Tal, M. (1977). Abscisic acid and germination in Avena sterilis L. Israel Journal of Botany, 26, 100-103.

BOTHRIOCHLOA

B. intermedia (R. Br.) A. Camus
B. ischaemum (L.) Keng	yellow bluestem
B. macra (Steud.) Blake	red grass

I. Evidence of dormancy

Dormancy is often present in seeds of Bothriochloa spp. (2-4). After-ripening for 8 months or so is reported to result in loss in dormancy (4).

II. Germination regimes for non-dormant seeds

B. ischaemum

TP; S: 20°/30°C (16h/8h): 21d (AOSA)

B. macra

Constant temperatures: 25°C (4)

Alternating temperatures: 15°/25°C, 20°/30°C (16h/8h) in light (3); 20°/30°C (16h/8h) in light (2)

III. Unsuccessful dormancy-breaking treatments

-

IV. Partly-successful dormancy-breaking treatments

B. intermedia

Removal of seed covering structures: (1)

B. ischaemum

Alternating temperatures: 20°/30°C (16h/8h) in light (2)

Pre-chill: 5°-10°C, 5d (2); 5°-10°C, 5d, plus potassium nitrate, co-applied, 0.2% (2)

Potassium nitrate: co-applied, 0.2% (2)

Removal of seed covering structures: (1)

B. macra

Removal of seed covering structures: (3,4)

GA₃: co-applied, 100 ppm (3)

Light: 6.5-7.5 W m^-2 (3)

V. Successful dormancy-breaking treatments

B. ischaemum

Light, Potassium nitrate, Pre-chill (AOSA)

B. macra

Removal of seed covering structures: lemma and palea, germinate at 20°/30°C (16h/8h) in light, plus GA₃, co-applied, 100 ppm (3); lemma and palea, germinate at 30°C (5)

VI. Comment

The literature cited (1-5) suggests light (8h/d), alternating temperatures and the removal of the lemma and palea to be the most stimulatory factors in promoting the germination of dormant seeds of Bothriochloa spp. It is suggested that the AOSA germination test procedure be followed but with the additional treatment of lemma and palea removal. AOSA recommend that seeds be pre-chilled at 5°C for 14 days. A 5-day pre-chill at 5°C is only partly-promotory (2), but treatment with gibberellic acid - co-applied, 100 ppm - can be effective when combined with seed coat removal (3). Consequently this treatment may be a worthwhile alternative to pre-chilling - particularly if a more rapid test procedure is required.

VII. References

1. Ahring, R.M., Eastin, J.D. and Garrison, C.S. (1975). Seed appendages and germination of two Asiatic bluestems. Agronomy Journal, 67,

2. Ahring, R.M. and Harlan, J.R. (1961). Germination characteristics of some accessions of Bothriochloa ischaemum (L.) Keng. Oklahoma Agricultural Experiment Station, Technical Bulletin T-89, 19pp.

3. Hagon, M.W. (1976). Germination and dormancy of Themeda australis, Danthonia spp., Stipa bigeniculata, and Bothriochloa macra. Australian Journal of Botany, 24, 319-327.

4. Lodge, G.M. and Whalley, R.D.B. (1981). Establishment of warm- and cool-season native perennial grasses on the North-west slopes of New South Wales. I. Dormancy and Germination. Australian Journal of Botany, 29, 111-119.

5. Watt, L.A. and Whalley, R.D.B. (1982). Establishment of small-seeded perennial grasses on black clay soils in North-western New South Wales. Australian Journal of Botany, 30, 611-623.

BOUTELOUA

B. chrondrosioides (HBK) Benth.
B. curtipendula (Michx.) Torr.	coronada side-oats grama
B. eriopoda Torr.	black grama
B. filiformis (Fowen) Griff.	slender grama
B. gracilis (HBK) Lag.	blue grama
B. parryi (Fowen) Griff.	parry grama
B. rothrockii Vasey	Roth rock grama

I. Evidence of dormancy

Dormancy may be exhibited by seeds of Bouteloua spp. (1,2,4,8-11) and may persist after 5 years dry storage at room temperature (3). Seeds of B. parryi and B. rothrockii are particularly dormant and very difficult to germinate (7).

II. Germination regimes for non-dormant seeds

B. curtipendula

TP: 15°/30°C (16h/8h): 28d (AOSA)

Alternating temperatures: 20°/30°C (16h/8h) in light (4)

B. filiformis

Constant temperatures: 20°C, 30°C, 35°C (7)

Alternating temperatures: 35°/10°C, 10°/35°C, 20°/40°C, 20°/35°C, 20°/30°C, 10°/30°C, 15°/25°C, 25°/40°C (18h/6h) (7); 25°/40°C, 20°/40°C (21h/3h) (7)

B. gracilis

TP: 20°/30°C (16h/8h): 28d (AOSA)

III. Unsuccessful dormancy-breaking treatments

B. curtipendula

Alternating temperatures: 10°-20°/20°-10°C (12h/12h) (8)

Potassium nitrate: co-applied, 0.2% (7)

B. eriopoda

Light: red, far red, 30 min (11); fluorescent, 8h/d (11)

Calcium nitrate: co-applied, 0.1, 0.2% (11)

Potassium nitrate: co-applied, 0.1-0.5% (11)

B. gracilis

Potassium nitrate: co-applied, 0.2% (7)

B. parryi, B. rothrockii

Constant temperatures: 20°-35°C (7)

Alternating temperatures: 20°/40°C, 25°/40°C, 35°/10°C, 10°/35°C, 20°/35°C, 20°/30°C in light (18h/6h) (7); 15°/25°C (18h/6h) (7)

Pre-chill: 3°-5°C, 7,14d (7)

Potassium nitrate: co-applied, 0.2%, alone or at the above alternating temperatures in the presence or absence of light (7)

Light: (7)

IV. Partly-successful dormancy-breaking treatments

B. chrondrosioides

Alternating temperatures: 20°/35°C, 25°/40°C (18h/6h) (7)

Potassium nitrate: co-applied, 0.2% (7)

B. curtipendula

Constant temperatures: 20°-35°C (7); 10°-40°C in light (8)

Alternating temperatures: 20°/30°C (16h/8h) in light (4,6,9); 10°/30°C, 15°/25°C, 20°/35°C, 25°/40°C, 20°/40°C, 35°/10°C (18h/6h) (7); 20°-40°/40°-20°C (12h/12h, 16h/8h, 20h/4h) (8)

Pre-chill: (3); 3°-5°C, 7, 14d (7); 3°-5°C, 7, 14d, plus potassium nitrate, co-applied, 0.2% (7)

Light: (3,5,6,7); 100 fc, 12h/d (8)

Sodium hypochlorite: pre-applied, 0.5h, 5.2% (3,4,5,6,9)

Removal of seed covering structures: (4); clip (9)

Alternating moisture: wet/dry/rewet (3)

Oxygen: 100% (3,9)

Pre-wash: (3); 0.5-3h (4)

Sodium carbonate: (3)

Hydrogen peroxide: (3)

B. eriopoda

Alternating temperatures: 20°-25°/35°C (18h/6h) (7); 20°/35°C, 15°/30°C, 20°/30°C (16h/8h) (11)

Potassium nitrate: co-applied, 0.2% (7)

GA₃: co-applied, 50 ppm (11)

Removal of seed covering structures: (11)

B. gracilis

Alternating temperatures: 20°/30°C, 15°/25°C (18h/6h) (7)

Potassium nitrate: co-applied, 0.2%, at 20°/30°C (16h/8h) in light (10)

V. Successful dormancy-breaking treatments

B. chrondrosioides

Potassium nitrate: co-applied, 0.2%, germinate at 20°/35°C or 25°/40°C (18h/6h) (7)

B. curtipendula

Light, Potassium nitrate (AOSA)

Alternating temperatures: 20°/30°C in light (18h/6h) (7); 10°/30°C, 15°/25°C, 10°/35°C (18h/6h) (7)

Removal of seed covering structures: lemma and palea (3,9)

Sodium hypochlorite: pre-applied, 0.5h, 5.2%, germinate in 100% oxygen atmosphere (9)

B. eriopoda

Potassium nitrate: co-applied, 0.2%, germinate at 20°-25°/35°C (18h/6h) (7)

B. gracilis

Light, Potassium nitrate (AOSA)

Alternating temperatures: 20°/30°C, 15°/25°C (18h/6h) (7)

VI. Comment

With the exception of those of B. parryi and B. rothrockii, the seed lots tested for germination in reference (7) were not particularly dormant. Consequently the dormancy-breaking treatments listed as successful by reference (7) may not promote full germination in more dormant accessions of B. chrondrosioides, B. curtipendula, B. eriopoda and B. gracilis. According to the AOSA dormant seed s of B. curtipendula require light or potassium nitrate for germination. In contrast to this recommendation light has been reported as inessential for germination (4-6,8,11) and potassium nitrate (co-applied, 0.2%) has been reported to reduce germination (7,11). Treatment with gibberellic acid, however, has been reported to be a very effective dormancy-breaking treatment (11).

Alternating temperature regimes are essential to promote the germination of dormant seeds of Bouteloua accessions (3,7,8,11). However, the AOSA prescription for B. curtipendula, 15°/30°C (16h/8h), appears to be less promotory than either 20°/30°C (16h/8h) or 15°/30°C (12h/12h) (8), whilst 35°/30°C (4h/20h) or 35°/15°C (8h/16h) are even more beneficial (8). Consequently it is suggested that the alternating temperature regime 20°/30°C (16h/8h) be adopted as a general germination test procedure for accessions of Bouteloua spp. with additional treatments of dehulling and GA₃ co-applied at 50 ppm where necessary, with a further suggestion that tests also be carried out at 35°/15°C (4-8h/20-16h) to determine whether this might provide a more suitable environment for germination.

References

1. Coukos, C.J. (1944). Seed dormancy and germination in some native grasses. Journal of American Society of Agronomy, 36, 337-345.

2. Jackson, C.V. (1928). Seed germination in certain New Mexico range grasses. Botanical Gazette, 86, 270-294.

3. Major, R.L. (1972). Seed dormancy of side-oats gramagrass Bouteloua curtipendula (Michx.). Dissertation Abstracts, 33B, 531

4. Sumner, D.C. and Cobb, R.D. (1962). Post harvest dormancy of coronado side-oats grama Bouteloua curtipendula (Michx.) Torr. as affected by storage temperature and germination inhibitors. Crop Science, 2, 321-325.

5. Sumner, D.C., Cobb, R.D. and Jones, L.G. (1959). Modification of standard germination procedure for coronado side-oats grama (Bouteloua curtipendula). Newsletter of the Association of Official Seed Analysts, 33, 7-9 and 27.

6. Sumner, D.C., Cobb, R.D. and Jones, L.G. (1960). The effect of temperature and light on the germination of coronado side-oats grama. Newsletter of the Association of Official Seed Analysts, 34, 12.

7. Toole, V.K. (1939). Germination requirements of the seed of some introduced and native range grasses. Proceedings of the Association of Official Seed Analysts, 30, 227-243.

8. Cole, D.F., Major, R.L. and Wright, L.N. (1974). Effects of light and temperature on germination of sideoats grama. Journal of Range Management, 27, 41-44.

9. Major, R.L. and Wright, L.N. (1974). Seed dormancy characteristics of sideoats gramagrass, Bouteloua curtipendula (Michx.) Torr. Crop Science, 14, 37-40.

10. Thornton, M.L. and Thornton, B.J. (1962). Firm seed and longevity of blue grama (Bouteloua gracilis). Proceedings of the Association of Official Seed Analysts, 52, 112-115.

11. Wright, L.N. and Baltensperger, A.A. (1964). Influence of temperature, light radiation, and chemical treatment on laboratory germination of black gramagrass, Bouteloua eriopoda Torr. Crop Science, 4, 168-171.

BRACHIARIA

B. brizantha (Hochst.) Stapf	palisade grass, signal grass
B. decumbens Stapf	signal grass, Surinam grass
B. dictyoneura (Fig. & De Not.) Stapf
B. dura Stapf
B. humidicola (Rendle) Schweickt	creeping signal grass, coronivia grass
B. miliiformis (Presl) Chase
B. mutica (Forsk.) Stapf [Panicum muticum Forsk.; P. purppurascens Raddi; P. barbinode Trin.]	para grass, Mauritius grass, malohillo, Angola grass, capim angola, egipto, penhalonga grass, mirable
B. plantaginea (Link) Hitchc. [Panicum plantagineum Link]	marmalade grass
B. radicans Napper [B. arrecta (Hack. ex Th. Dur. & Schinz) Stent.]	tanner grass
B. ramosa	brown top millet
B. ruziziensis Germain & Evrard	ruzi grass, Congo grass, Congo signal grass, kennedy ruzi

I. Evidence of dormancy

Dormancy in Brachiaria species can be particularly persistent and pronounced resulting in considerable problems for seed testing (7,10) and germplasm evaluation (1).

II. Germination regimes for non-dormant seeds

B. decumbens

TP: 20°/35°C (16h/8h): 21d (ISTA)

Alternating temperatures: 20°/35°C (16h/8h) in light, 21d (7)

B. humidicola, B. mutica

TP: 20°/35°C (16h/8h): 21d (ISTA)

B. ramosa

BP; TP: 20°/30°C (16h/8h); 30°C: 14d (AOSA)

III. Unsuccessful dormancy-breaking treatments

B. decumbens

Potassium nitrate: co-applied, 0.2% (11)

Pre-dry: 40°-80°C, 14h (11); 40°C, 12d (11)

Pre-soak: 70°C, 10 min (11)

Scarification: concentrated sulphuric acid, 5-20 min (11)

Light: (3)

B. dictyoneura

Pre-dry: (1)

Scarification: concentrated sulphuric acid, 15 min, plus thiourea, co-applied (1)

B. mutica

Pre-dry: 55°C, 4d (8)

Scarification: concentrated sulphuric acid, 15 min (8); sandpaper (8)

B. ruziziensis

Constant temperatures: 20°C, 25°C (9)

Light: (9)

Pre-dry: 50°C, 3d (8)

Removal of seed covering structures: excision of spikelet top (9)

IV. Partly-successful dormancy-breaking treatments

B. decumbens

Pre-chill: 5°C, 7d (11)

Potassium nitrate: co-applied, 0.2% (2,3)

Scarification: concentrated sulphuric acid (2); concentrated sulphuric acid, 5-20 min (11); concentrated sulphuric acid, 15 min (5,6); concentrated sulphuric acid, 13 min (3); concentrated sulphuric acid, 13 min, plus potassium nitrate, co-applied, 0.2%, germinate at 20°/35°C (16h/8h) in light (3); mechanical (11)

Pre-dry: 40°-80°C, 14h (11)

Pre-soak: 24h (11)

Hydrogen peroxide: pre-applied, 24,48h, 1 M (11)

Removal of seed covering structures: lemma and palea (5,11)

Light: 15000 lux (3)

B. dictyoneura

Removal of seed covering structures: lemma and palea (1)

Scarification: concentrated sulphuric acid, 20-25 min (1); concentrated sulphuric acid, 20-25 min, plus thiourea, co-applied (1)

B. humidicola

Potassium nitrate: co-applied, 0.2% (2)

Scarification: concentrated sulphuric acid, with or without potassium nitrate, co-applied, 0.2% (2)

B. ruziziensis

Alternating temperatures: 25°/15°C (12h/12h) (9)

Scarification: concentrated sulphuric acid, 15 min (4,8); mechanical (8)

V. Successful dormancy-breaking treatments

B. decumbens

Scarification, Light, Potassium nitrate (ISTA)

Potassium nitrate: co-applied, 0.2% (7)

Scarification: concentrated sulphuric acid, 13 min (7); concentrated sulphuric acid, 13 min, wash, then potassium nitrate, co-applied, 0.2% (10)

B. humidicola

Potassium nitrate (ISTA)

B. mutica

Scarification, Potassium nitrate (ISTA)

B. ramosa

Light, Potassium nitrate, Pre-dry, test at 30°C (AOSA)

B. ruziziensis

Scarification, Potassium nitrate (ISTA)

Removal of seed covering structures: dehull (9)

Hydrogen peroxide: pre-applied, 24h, 1 M (9)

Brachiaria spp.

Scarification: concentrated sulphuric acid, 13 min, wash, then potassium nitrate, co-applied, 0.2%, at 20°/35°C (16h/8h) in light (10)

VI. Comment

The apparently satisfactory procedure for Brachiaria (10) - described above - has been found elsewhere to fail to promote the germination of all viable seeds (3), at least over a 21 day germination test period. An alternating temperature regime of 15°/30°C or 10°/30°C (16h/8h) can be extremely promotory for B. humidicola but not promotory for B. decumbens (A). More recent work with B. humidicola has shown that al