In this handbook the Liliaceae is deemed to include the Alliaceae. It should also be noted that some authorities have classified the Alliaceae as the Amaryllidaceae. From the point of view of seed germination and dormancy, however, it is convenient to adopt the widest classification of the Liliaceae.
The Liliaceae, by this definition, comprise roughly 2500 species of herbaceous plants within about 200 genera. The most important genus for crop production is Allium. The fruits of Liliaceae are small capsules or berries and, mostly, many-seeded. Seed storage behaviour is orthodox.
SEED DORMANCY AND GERMINATION
Seed dormancy is common in the Liliaceae, but unfortunately often not detected. The seeds are endospermic, the endosperm surrounding the embryo. Low germination test temperatures and/or pre-chill treatments generally promote the germination of the dormant seeds. Detailed information on seed dormancy and germination is provided for the genera Allium and Asparagus in this chapter. A brief summary of additional recommended germination test procedures is provided in Table 44.1. In addition the algorithm below may be helpful in developing suitable germination test-procedures for some accessions.
RBG Kew Wakehurst Place algorithm
The first step of the algorithm is to test seeds at constant temperatures of 11°C and 26°C with light applied for 12/d. If full germination has not been achieved and the results of the tests at 11°C and 26°C indicate a trend of the response of germination to constant temperatures then test a further sample of seeds at a more extreme constant temperature. For example, if a greater proportion of seeds germinate at 11°C than at 26°C then test a further sample of seeds at 6°C with light applied for 12h/d. If no trend is apparent test a further sample of seeds at a constant temperature of 31°C with light applied for 12h/d.
If the first step has not resulted in full germination then the second step of the algorithm is to pre-chill a further sample of seeds at 2° to 6°C for 8w and then test for germination in the most suitable constant temperature regime determined from the results of step one.
If the second step has not resulted in full germination then the third step of the algorithm is to chip a fresh sample of seeds so that the embryo is exposed and then test for germination in the most suitable regime determined from the results of steps one and two. This may include a pre-chill treatment if the proportion of seeds germinating in step two was significantly greater than that in step one.
If full germination has not been promoted, the fourth step of the algorithm is to estimate viability using a tetrazolium test (see Chapter 11, Volume I).
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 in this chapter for the genera Allium and Asparagus.
TABLE 44.1 Summary of germination test recommendations for species within the Liliaceae
|
Species and Authority |
Substrate |
Temperature |
Duration |
Additional directions |
Source |
|
Kniphofia uvaria (L.) Hook. |
TP |
20°/30°C |
21d |
|
ISTA |
|
Kniphofia spp. |
TP |
20°/30°C |
18d |
|
AOSA |
|
Lilium regale Wils. |
TP; S |
20°/30°C; 20°C |
28d |
|
ISTA |
|
|
TP |
20°C |
21d |
|
AOSA |
ALLIUM
|
A. albo-pilosum W. Right |
|
|
A. ampeloprasum L. |
great-headed garlic, wild leek |
|
A. ampeloprasum L. var porrum (L.) Gray [A.
porrum L.] |
leek |
|
A. angulosum L. |
|
|
A. asclepiadeum Bornm. |
|
|
A. atropurpureum W. & K. |
|
|
A. cepa L. |
onion |
|
A. curtum Boiss. & Gaill |
|
|
A. cyanthophorum var farreri Stearn |
|
|
A. fistulosum L. |
Welsh onion, spring onion, Japanese bunching onion |
|
A. flavum L. |
|
|
A. giganteum Regel |
|
|
A. heldreichii Boiss. |
|
|
A. hirstum Zucc. |
|
|
A. ledebourianum Schult. |
|
|
A. neapolitanum Cyr. |
|
|
A. pulchellum G. Don |
|
|
A. rosenbachianum Regel |
|
|
A. sativum L. |
garlic |
|
A. schoenoprasum L. |
chive |
|
A. schubertii Zucc. |
|
|
A. senescens L. |
|
|
A. tanguticum Regel |
|
|
A. tel-avivense Eig. |
|
|
A. ursinum L. |
|
|
A. victorialis L. var platyphylum Mak. |
|
I. Evidence of dormancy
Freshly harvested seeds of the above Allium spp. may be dormant (1,5,7,11,14,15,17,18,22,27,29). Within the above, seeds of A. albo-pilosum, A. ampeloprasum, A. curtum, A. flavum, A. giganteum, A. hirstum, A. neapolitanum, A. pulchellum, A. rosenbachianum, A. schubertii and A. tel-avivense are likely to be the more dormant (1). In A. cepa seed dormancy is comparatively weak requiring, for example, between 2 weeks (14) and 2 months (18) after-ripening at room temperature to remove dormancy. Seed dormancy in A. ampeloprasum var porrum can be more pronounced (18) and the seeds may require, for example, 3 years after-ripening at room temperature to remove dormancy (5). Seeds of A. ursinum are reported to be very dormant, failing to germinate within 14 months of harvest (29).
II. Germination regimes for non-dormant seeds
A. ampeloprasum var porrum
BP: TP: 20°C; 15°C: 14d (ISTA)
BP: 20°C: 14d (AOSA)
Alternating temperatures: 10°/20°C (16h/8h) (7)
A. cepa
BP; TP: 20°C; 15°C: 12d (ISTA)
BP: 20°C: 10d (AOSA)
S: 20°C: 12d (AOSA)
Constant temperatures: 15°-22°C (10); 20°-25°C (21); 18°C (16)
Alternating temperatures: 20°/30°C (15h/9h) (12)
A. fistulosum
BP; TP: 20°C; 15°C: 12d (ISTA)
A. schoenoprasum
BP; TP: 20°C; 15°C: 14d (ISTA)
BP: 20°C: 14d (AOSA)
Constant temperatures: 20°C (13)
III. Unsuccessful dormancy-breaking treatments
A. albo-pilosum
Constant temperatures: 13°C, 20°C, 50d (1)
A. ampeloprasum var porrum
Constant temperatures: above 27°C (5)
Pre-chill: 3°-4°C, 7-28d, germinate at 20°C, 20°/30°C (16h/8h) (9); -1°C, 7-28d, germinate at 30°C (9)
Light: continuous, 1000 lux (18)
A. atropurpureum
Constant temperatures: 5°C, 50d (1)
A. cepa
Constant temperatures: above 28°C (19)
Alternating temperatures: 28°/33°C (8h/16h) (19)
Light: (19); continuous, 1000 lux (18)
GA3: pre-applied, 6h, 50 ppm (20)
Naphthaleneacetic acid: pre-applied, 6h, 50 ppm (20)
A. curtum
Constant temperatures: 20°C, 30d (1)
A. fistulosum
Constant temperatures: above 28°C (19)
Alternating temperatures: 28°/33°C (8h/16h) (19)
Light: (19)
A. giganteum
Constant temperatures: 20°C, 50d (1)
A. hirstum
Constant temperatures: 5°C, 20°C, 50d (1)
A. neapolitanum
Constant temperatures: 20°C, 30d (1)
A. rosenbachianum
Constant temperatures: 13°C, 50d (1)
A. sativum
B-Naphthoxyacetic acid: pre-applied, 6h, 75 ppm (22)
A. senescens
Constant temperatures: 13°C, 30d (1)
A. victorialis var platyphylum
Constant temperatures: 10°C, 50d (1)
A. ursinum
Constant temperatures: 20°C in light or dark (29)
Pre-chill: 2d (29)
IV. Partly-successful dormancy-breaking treatments
A. albo-pilosum
Constant temperatures: 5°C, 50d (1)
A. ampeloprasum
Constant temperatures: 20°C, 30d (1)
A. ampeloprasum var porrum
Constant temperatures: 7°C, 15°C, 23°C (3); 12°-24°C (5); 15°C, 20°C (15, 18)
Alternating temperatures: 20°/25°C, 15°/28°C (16h/8h) (18)
Pre-chill: 3°-4°C, 14-28d, germinate at 25°C, 30°C (9); 5°C, 1d (17); 12°C, 3d (17); 5°C, 4d, germinate at 15°/28°C (18); 10°C, 5d, germinate at 10°/30°C (16h/8h) (7)
Warm stratification: 18°C, 3d (5); 12°C, 5d (5); 30°C, 14d (9)
Light: dark (18)
A. angulosum
Constant temperatures: 5°C, 13°C, 30d (1)
A. atropurpureum
Constant temperatures: 10°C, 20°C, 50d (1)
A. cepa
Constant temperatures: 12°C, 20°C (14); 15°C, 20°C (18); 20°C in light (28)
Alternating temperatures: 20°/25°C, 15°/28°C (16h/8h) (18); 12°/20°C (15h/9h) (14); 25°/33°C (8h/16h) (19)
Pre-chill: 12°C, 3d (17); 5°C, 1d (17); 5°C, 4d (18); 1.5°C, 6w, germinate at 7.5°C (27)
Light: dark (18)
GA3: pre-applied, 6h, 30-75 ppm (22)
3-Indolepropionic acid: pre-applied, 6h, 30-75 ppm (22)
B-Naphthoxyacetic acid: pre-applied, 6h, 30-75 ppm (22)
Calcium peroxide: seed coating, 125-375 g/kg, germinate at 10°C, 20°C, light (28)
A. cyathophorum
Constant temperatures: 5°C, 13°C, 20°C, 50d (1)
A. fistulosum
Alternating temperatures: 25°/33°C (8h/16h) (19)
A. flavum
Constant temperatures: 5°C, 13°C, 20°C, 50d (1)
A. giganteum
Constant temperatures: 5°C, 110d (1)
A. heldreichii
Constant temperatures: 5°C, 10°C, 15°C, 30d (1)
A. ledebourianum
Constant temperatures: 15°C, 20°C, 25°C, 50d (1)
A. neapolitanum
Constant temperatures: 5°C, 13°C, 30d (1)
A. pulchellum
Constant temperatures: 5°C, 13°C, 20°C, 15d (1)
A. sativum
GA3: pre-applied, 6h, 30, 75 ppm (22)
3-Indolepropionic acid: pre-applied, 6h, 30, 75 ppm (22)
B-Naphthoxyacetic acid: pre-applied, 6h, 30, 50 ppm (22)
A. schoenoprasum
Constant temperatures: 5°C, 110d (1)
A. schubertii
Constant temperatures: 20°C, 30d (1)
A. senescens
Constant temperatures: 5°C, 30d (1)
A. tanguticum
Constant temperatures: 20°C, 25°C, 50d (1)
A. tel-avivense
Constant temperatures: 5°C, 110d (1); 13°C, 20°C, 50d (1)
A. victorialis var platyphyllum
Constant temperatures: 15°C, 20°C, 50d (1)
V. Successful dormancy-breaking treatments
A. ampeloprasum
Constant temperatures: 5°C, 30d (1); 6°-15°C (24); 13°C, 15d (1)
A. ampeloprasum var porrum
Pre-chill (ISTA)
Constant temperatures: 5°C, 13°C, 20°C, 15d (1); 3°-17°C (2); 6°-15°C (24); 8°-22°C (10); 15°C (11); 7.5°-15°C (23,24); 12°-18°C (5)
Warm stratification: 27°C, 7d, germinate at 15°C (5); 20°C, 2d, then pre-chill, 1°C, 12d, germinate at 20°C (6)
A. angulosum
Constant temperatures: 20°C, 10d (1)
A. asclepiadeum
Constant temperatures: 10°C, 26d (26)
A. atropurpureum
Constant temperatures: 15°C, 10d (1)
A. cepa
Pre-chill (ISTA)
Constant temperatures: 3°-17°C (2); 4°-15°C (4); 10°C (27); 10°C in light (28); 18°C in dark (8, 16); 8°-22°C (10, 11, 25)
Pre-chill: 5°C, 4d, germinate at 20°/25°C (16h/8h) (18)
A. curtum
Constant temperatures: 5°C, 50d (1); 13°C, 20d (1)
A. fistulosum
Pre-chill (ISTA)
A. hirstum
Constant temperatures: 13°C, 15d (1)
A. rosenbachianum
Constant temperatures: 5°C, 110d (1)
A. sativum
GA3: pre-applied, 6h, 50 ppm (22)
3-Indolepropionic acid: pre-applied, 6h, 50 ppm (22)
A. schoenoprasum
Pre-chill (ISTA)
Constant temperatures: 13°C, 20°C, 15d (1)
A. schubertii
Constant temperatures: 5°C, 30d (1); 10°C (26); 13°C, 30d (1)
A. senescens
Constant temperatures: 20°C, 25°C, 10d (1)
A. tanguticum
Constant temperatures: 15°C, 50d (1)
VI. Comment
The following constant temperatures or range of constant temperatures have been described as optimum for germinating seeds of Allium spp.: 2°-7°C for A. albo-pilosum, A. giganteum and A. rosenbachianum (1); 5°-13°C for A. ampeloprasum, A. curtum, A. heldreichii, A. pulchellum, A. neapolitanum, and A. schubertii (1); 5°-20°C for A. ampeloprasum var porrum, A. flavum and A. schoenoprasum (1,3); 10°-20°C for A. atropurpureum (1); 13°C for A. hirstum and A. tel-avivense (1); 13°-20°C for A. cyathophorum (1); 15°-20°C for A. ledebourianum and A. victorialis var platyphyllum (1); 20°C for A. angulosum (1); and finally 20°-25°C for A. senescens and A. tanguticum (1). However, for the more dormant seeds of the above species a constant temperature germination test regime alone may be insufficient to promote the germination of all dormant seeds.
When compared with certain constant temperatures there may be an advantage in testing the seeds for germination in alternating temperature regimes, or at least no disadvantage: with seeds of A. ampeloprasum var porrum and A. cepa alternating temperature regimes of 15°/28°C (16h/8h) (18) or 10°/20°C (16h/8h) (7) were reported to provide greater promotion of germination than constant temperatures of 15°C or 20°C; in other investigations with A. cepa there was no difference between germination at a constant temperature of 20°C and at alternating temperature regimes of 20°/30°C (16h/8h) (12,13) or 12°/20°C (15h/9h) (14). However, it is suggested here that lower constant temperatures - combined with an extended test period - may be preferable.
Seed dormancy in Allium spp. tends to delay germination, rather than completely preventing it. For dormant seeds of most Allium species cultivated as vegetables, 49-day - or more - germination tests at 10°C in the dark are likely to be successful (4,27). In some accessions only a minority of seeds may germinate during a 63-day test at 10°C (A). Should full germination not be observed in this regime then it is suggested that the seeds then be transferred to 20°C for a further 14 days: in other words the original test regime is treated as a pre-chill treatment, during which some germination may occur. In A. schoenoprasum such transfers have been extremely promotory (A). As an alternative to this somewhat lengthy test, combining potassium nitrate (0.2%, co-applied) and pre-chilling treatments (3°-5°C, 7 days) enables the subsequent germination test period at 15°C for seeds of A. schoenoprasum to be reduced from 77 days to between 14 and 21 days (A). Consequently we suggest this regime as an alternative procedure to shorten overall germination test periods. Where dormancy is not a problem - as may often be the case in A. cepa for example - testing at 15°C for a much shorter period with no additional treatments is adequate.
VII. References
1. Aoba, T. (1967). [Effects of different temperatures on seed germination of garden ornamentals in Allium.] Journal of the Japanese Society for Horticultural Science, 36, 333-338.
2. Bierhuizen, J.F. and Wagenvoort, W.A. (1974). Some aspects of seed germination in vegetables. 1. The determination and application of heat sums and minimum temperature for germination. Scientia Horticultures, 2, 213-219.
3. Bremer, A.H. (1927). Oppspiring av hagefro under unlike temperaturer. Nord. Jordbr. Forsk., 9, 377-390.
4. Dowker, B.D., Winarno, J.F. and Fennell, J.F.M. (1981). Germination studies on onion seed lots. Horticultural Research, 21, 41-48.
5. Dragland, S. (1972). Germination of leek seed at different temperatures. Meldinger fra Norges Landbrukshogskole, 51, 1-9.
6. Finch-Savage, W.E. and Cox, C.J. (1982). A cold-treatment technique to improve the germination of vegetable seeds prior to fluid drilling. Scientia Horticulturae, 16, 301-311.
7. Fornerod, C. (1975). Remarques sur la germination des semences potageres en laboratoire. Revue Horticole Suisse, 48, 6-9.
8. Gadd, I. (1939). On methods for the elimination of seed dormancy in seed control work. Proceedings of the International Seed Testing Association, 11, 96-118.
9. Gelmond, H. (1965). Pre-treatment of leek seed as a means of overcoming superoptimal temperatures of germination. Proceedings of the International Seed Testing Association, 30, 737-742.
10. Guy, R. (1980). Quelques exemples des effets de la temperature sur la germination des plantes potagères. Revue Suisse de Viticulture, d'Arboriculture et d'Horticulture, 12, 35-37.
11. Guy, R. (1981). Influence de la tempèrature sur la durèe de germination des semences de dix espèces potagères. Revue Suisse de Viticulture, d'Arboriculture et d'Horticulture, 13, 219-225.
12. Harrington, G.T. (1923). Use of alternating temperatures in the germination of seeds. Journal of Agricultural Research, 23, 295-332.
13. Heit, C.E. (1948). Laboratory germination results with herb and drug seed. Proceedings of the Association of Official Seed Analysts, 38, 58-62.
14. Ingold, M. (1960). Contribution à l'ètude de la germination des semences d'Allium cepa L. et Cucurbita pepo L. Proceedings of the International Seed Testing Association, 25, 787-799.
15. Klitgård, K. (1969). Report of the working group on the germination of Beta, Brassica and Allium. Proceedings of the International Seed Testing Association, 34, 609-612.
16. Kotowski, F. (1926). Temperature relations to germination of vegetable seed. Proceedings of the American Society for Horticultural Science, 23, 176-184.
17. Lovato, A. and Amaducci, M.T. (1964). Examination of the problem of whether dormancy exists in seeds of onion (Allium cepa L.) and leek (Allium porrum L.). I. A comparative test of different tetrazolium test techniques. Proceedings of the International Seed Testing Association, 29, 17-26.
18. Lovato, A. and Amaducci, M.T. (1965). Examination of the problem of whether dormancy exists in seeds of onion (Allium cepa L.) and leek (Allium porrum L.). II. Effect of temperature, prechilling and light on germination. Proceedings of the International Seed Testing Association, 30, 803-820.
19. Nakamura, S., Okasako, Y. and Yamada, E. (1955). [Effect of light on the germination of vegetable seeds.] Journal of the Horticultural Association of Japan, 24, 17-28.
20. Sandhu, J.S., Nandpuri, K.S. and Thakur, J.C. (1972). Studies on the germination of freshly harvested mature and immature onion seeds. Indian Journal of Horticulture, 29, 339-341.
21. Singh, H. and Kumar, A. (1979). Germination studies on vegetable crops onion, pea and spinach. Journal of Research, India, 16, 164-168. (From Horticultural Abstracts, 1982, 52, 2137.)
22. Srivastava, R.P. and Adhikari, B.S. (1968). Influence of growth substances on the germination of onion and garlic. Allahabad Farmer, 42, 103-104.
23. Thompson, P.A. (1972). Geographical adaptation of seeds. In Seed Ecology (ed. W. Heydecker), pp. 31-58, Butterworths, London.
24. Thompson, P.A. and Cox, D.J.C. (1976). The germination responses of vegetable seeds in relation to their history of cultivation by man. Scientia Horticulturae, 4, 1-14.
25. Wagenvoort, W.A., Boot, A. and Bierhuizen, J.F. (1981). Optimum temperature range for germination of vegetable seeds. Gartenbauwissenschaft, 46, 97-101.
26. Wallerstein, I. (1981). [Propagation of Allium asclepiadeum and Allium schubertii from seeds.] Hassadeh, 61, 1678-1681. (From Seed Abstracts, 1982, 5, 1266.)
27. Whitwell, J.D. and Davies, A.C.W. (1976). Some effects of temperature on the emergence of bulb onion seed stocks. Experimental Horticulture, 28, 41-46.
28. Brocklehurst, P.A. and Dearman, J. (1983). Effects of calcium peroxide as a supplier of oxygen for seed germination and seedling emergence in carrot and onion. Seed Science and Technology, 11, 293-299.
29. Tutin, T.G. (1957). Biological flora of the British Isles. Allium ursinum L. Journal of Ecology, 45, 1003-1010.
ASPARAGUS
|
A. densiflorus (Kunth) Jessop [A. Sprengeri
Regel] |
sprenger asparagus |
|
A. officinalis L. |
garden asparagus |
|
A. setaceus (Kunth) Jessop [A. plumosus
Baker] |
fern asparagus |
I. Evidence of dormancy
Seeds of A. officinalis may show slight dormancy at harvest (3,4,7), which can be removed by 3 weeks storage (3). However, secondary dormancy may be induced during drying, or in germination tests where the medium is allowed to dry out, or where the concentration of carbon dioxide is increased (4). Problems of hardseededness may arise in A. densiflorus (5) and A. setaceus.
II. Germination regimes for non-dormant seeds
A. densiflorus
BP; TP; S: 20°/30°C (16h/8h); 20°C: 35d (ISTA)
BP; TP: 20°/30°C (16h/8h): 30d (AOSA)
A. officinalis
BP; TP; S: 20°/30°C (16h/8h): 28d (ISTA)
BP; S: 20°/30°C (16h/8h): 21d (AOSA)
A. setaceus
BP; TP; S: 20°/30°C (16h/8h); 20°C: 35d (ISTA)
TP; BP: 20°/30°C (16h/8h): 30d (AOSA)
III. Unsuccessful dormancy-breaking treatments
A. densiflorus
Pre-soak: 12h (5)
Ultrasonics: 0-1000 kHz, 30s-5 min, with or without pre-soak, 12h (5)
A. officinalis
Pre-chill: -10°C, -10°/4°C (7d/7d), 4°C, -10°/4°/21°C (7d/7d/7d), moist sand, 2m, germinate at 26°C ± 4°C in light, 12000 lux, 14h/d (8)
Pre-soak: 6-110h, 22°-38°C (2); 6-86h, 45°C (2); 6-40h, 50°C (2); 110h, 45°C (2); 12h, 20°C, 30°C (2); 12-48h, 30°C, germinate at 30°C (3); 2m, -10°C, -10°/4°C (7d/7d), 4°C, germinate at 26°C ± 4°C in light, 12000 lux, 14h/d (8)
IV. Partly-successful dormancy-breaking treatments
A. densiflorus
Constant temperatures: 30°C (6)
Ultrasonics: 0-1000 kHz, 5s, then pre-soak, 12h (5) pH: 5.6 (6)
A. officinalis
Constant temperatures: 15°C, 30°C (3,4); 26°C ± 4°C in light, 12000 lux, 14h/d (8)
Pre-chill: 0°-5°C, 10-40d, germinate at 15°C (3); 0°-5°C, 10-60d, germinate at 10°C (4); 0°-5°C, 30d, germinate at 15°C, 20°C (4); 10°-12°C, 10-30d, germinate at 15°C (3); 10°-12°C, 10,20d, germinate at 30°C (3)
Pre-soak: 1-6d, 20°C, 30°C (2)
V. Successful dormancy-breaking treatments
A. densiflorus
Pre-soak (ISTA)
A. officinalis
Pre-chill: 5m (1); 10°-12°C, 30d, germinate at 30°C (3); 10°-12°C, 10-30d, then 15°C, 30d, germinate at 30°C (3); 0°-5°C, 30d, germinate at 30°C (3,4); 0°-5°C, 50-60d, germinate at 15°C, 20°C, 30°C (3,4); 0°-5°C, 10-40d, then 15°C, 30d, germinate at 30°C (3)
Scarification: concentrated sulphuric acid, 10 min, germinate at 15°C (4)
A. setaceus
Pre-soak (ISTA)
VI. Comment
It is important that the germination test substratum be prevented from drying out and that it be kept moist throughout the germination test (4, AOSA). Germination tests may have to be extended beyond the 21 to 35 days prescribed by ISTA/AOSA to as many as 71 days (1). Pre-soak treatments are not particularly beneficial (3), and although pre-chill treatments are effective in promoting the germination of dormant seeds, considerable treatment periods may be required (1,3,4).
It is suggested that the seeds be tested for germination at 20°/30°C (16h/8h) for up to 60 days following pre-chill treatments: either at 3°-5°C for 10 to 30 days; or at 10°C for 30 days. In addition check for hardseededness after 7 days or so in test (that is during the pre-chill treatment) and scarify (by hand) any seeds remaining hard at this time.
VII. References
1. Adams, J. (1927). The germination of the seeds of some plants with fleshy fruits. American Journal of Botany, 14, 415-428.
2. Borthwick, H.A. (1925). Factors influencing the rate of germination of the seed of Asparagus officinalis. University of California Agricultural Experiment Station, Technical Paper, 18, 1-17.
3. Komoti, S. (1956). [Studies on temperature treatments of seeds. I. Effects of temperature treatments on germination of garden asparagus seeds.] Hokkaido National Agricultural Experiment Station Research Bulletin, 70, 42-49.
4. Komoti, S. (1957). [Studies on temperature treatments of seeds. II. Dormancy and germinating temperature in garden asparagus seeds.] Hokkaido National Agricultural Experiment Station Research Bulletin, 73, 9-19.
5. Perry, L.P. and Boodley, J.W. (1980). Germination of foliage plant seeds in response to pre-sowing, ultrasonic exposures, water soaks and fungicides. HortScience, 15, 192-194.
6. Perry, L.P. and Boodley, J.W. (1980). Germination of foliage plant seeds in response to sowing media, depths of sowing, pH levels, and medium temperatures. HortScience, 15, 194-196.
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