The Oleaceae comprise over 500 species of trees and shrubs within about 20 genera which provide edible fruits (Olea europaea L., olive) and timber (Fraxinus spp., ash). The fruit may be a drupe (e.g. Olea spp.), a berry (e.g. Jasminum spp.), a capsule (e.g. Syringa spp.) or a samara (e.g. Fraxinus spp.). Seed storage behaviour is orthodox. For example, Jasminum beesianum Forrest & Diels. and Syringa spp. are maintained in the long-term seed store at the Wakehurst Place Gene Bank.
SEED DORMANCY AND GERMINATION
Seed covering structures are often hard, thereby delaying or preventing germination. Dormancy per se (that is innate seed dormancy, see Chapter 5, Volume I) may also prevent or delay germination. Treatments to the seed covering structures (see Chapter 7, Volume I), pre-chill treatments, and warm stratification/pre-chill treatments tend to promote germination. Detailed information on seed dormancy and germination is provided for the genus Olea in this chapter, and recommendations for suitable germination test procedures and dormancy-breaking treatments for other species are summarised in Table 51.1.
TABLE 51.1 Summary of germination test recommendations for species within the Oleaceae.
|
Species and Authority |
Substrate |
Temperature |
Duration |
Additional directions |
Source |
|
Fraxinus spp.
|
TP |
20°/30°C |
56d |
excise embryos, or pre-treat, 20°C, 2m, then pre-chill, 3°-5°C,
7m |
ISTA |
|
TP |
18°-22°C |
10-14d |
excise embryos, or pre-chill, 3°-5°C, 3m |
AOSA |
|
|
|
|
|
warm stratification, 20°-25°C, 0-12w, then pre-chill, 1°-5°C,
2-12w |
G&R |
|
|
Syringa reflexa Schneid. |
TP |
20°C |
21d |
two tests: with and without pre-chill, 3°-5°C, 27d |
ISTA |
|
Syringa villosa Vanl. |
TP |
20°/30°C |
21d |
|
ISTA |
|
Syringa vulgaris L. |
TP |
20°C |
21d |
|
ISTA/AOSA |
OLEA
|
O. cuspidata |
|
|
O. europaea L. |
olive |
|
O. welwitschii |
loliondo |
I. Evidence of dormancy
Olea spp. show orthodox seed storage behaviour (10,17,19), but freshly harvested intact seeds show poor germination (1,4,9,14,18-20). Although the seed covering structures (endocarp and testa) contribute to dormancy (1,4,9,11,12,16,18-20), the excised seeds also show dormancy (7,20). After-ripening for 22 months (8) or 3 years (17) is reported to result in loss of seed dormancy.
II. Germination regimes for non-dormant seeds
-
III. Unsuccessful dormancy-breaking treatments
O. cuspidata
Pre-soak: 100°C, allow to cool, 24h (9)
O. europaea
Constant temperatures: 15°C (11); 15°C, 25°C, dark or light/dark (12h/12h) (20); 25°C (2,11); 35°C (19)
Pre-chill: 13°C, 5-15d, germinate at 25°C (6)
Pre-soak: 2d, or more (19)
Light: light or dark (19); red, 3 W m-2, 2 min/h (20); far red, 5 W m-2, 2 min/h (20)
Scarification: sulphuric acid (16)
Removal of seed covering structures: excise embryos, germinate at 4°C, 25°C (7); excise embryos, germinate at 18°-20°C in dark (8); excise embryos, then GA3, co-applied, 100 ppm (18)
GA3: co-applied, 1.45x10-4 -5.8x10-4 M, at 15°C, 25°C, dark (20)
GA4/7: pre-applied, 36h, 10-1000 ppm, then 5°C, 10°C, 15°C, 20°C, 35°C, dark, 30d, then germinate at 25°C in light, 16h/d (18)
6-Benzylaminopurine: pre-applied, 36h, 10-1000 ppm, then 5°C, 10°C, 15°C, 20°C, 35°C, dark, 30d, then germinate at 25°C in light, 16h/d (18)
Abscisic acid: pre-applied, 36h, 10, 100 ppm, then 5°C, 10°C, 15°C, 20°C, 35°C, dark, 30d, then germinate at 25°C in light, 16h/d (18); co-applied, 2x10-5 -8x10-5 M, at 15°C, 25°C, dark (20)
Kinetin: pre-applied, 30s, 25-100 ppm (3); co-applied, 4.6x10-6 -9.2x10-6 M, at 15°C, 25°C, dark (20)
Zeatin: co-applied, 4.5x10-6 -9.1x10-6 M, at 15°C, 25°C, dark (20)
Ethrel: pre-applied, 30s, 50-200 ppm (3)
4-Chloro-5-2-3-pyridazinone: co-applied, 3.3x10-6 -66x10-6 M, at 15°C, dark (20)
IV. Partly-successful dormancy-breaking treatments
O. cuspidata
Scarification: concentrated sulphuric acid, 5 min (9)
Pre-soak: 7,15d (9)
O. europaea
Constant temperatures: 15°C (18)
Pre-chill: 13°C, 20-30d, germinate at 25°C (6); 15°C, dark, 30d, germinate at 25°C in light, 16h/d (18)
Pre-soak: 5-6d, then warm stratification, 1m (12)
Removal of seed covering structures: endocarp (15,16); excise embryo, germinate at 25°C (2); excise embryo, germinate at 10°C, 15°C, 18°C, in dark (7)
Potassium hydroxide: pre-applied, 6h, 0.5, 0.75% (15,16)
Sodium hydroxide: pre-applied, 6h, 0.5, 0.75% (15,16)
Sodium carbonate: pre-applied, 5h, 0.5, 0.75% (15,16); pre-wash, 5%, then warm stratification, 1m (12)
Scarification: sulphuric acid, 10%, 30s (3); sulphuric acid, 2% (15)
4-Chloro-5-2-3-pyridazinone: co-applied, 16.5x10-6 -33x10-6 M, at 25°C (20)
O. welwitschii
Pre-soak: then removal of seed covering structures (10)
V. Successful dormancy-breaking treatments
O. europaea
Constant temperatures: 13°C, 48d (6)
Pre-soak: 1d, germinate at 15°C, dark, 56d (12)
Removal of seed covering structures: endocarp and testa, germinate at 13°C, in light or in dark (5); excise embryo, germinate at 13°C in dark (5,7,8); excise embryo, germinate at 18°-20°C in light (8); excise embryo, germinate at 25°C (11,18,20); excise embryo, germinate at 15°C, 25°C, dark (19)
VI. Comment
The endocarp and testa of Olea spp. restrict imbibition (4,5). Consequently their removal promotes germination (5,10,11,19,20). Intact dormant seeds will not germinate at 25°C or higher (2,6,11,18-20), but embryos excised from slightly dormant seeds will germinate at 25°C (2,11,18-20). Germination of dormant and non-dormant intact seeds and excised embryos occurs at about 13°C in both light and dark (5-8,18,19), but at slightly supra-optimal temperatures, 15°-20°C, light can be promotory (8). Fluorescent, red, and far red light, however, have no effect on germination (19,20). Plant growth regulators have either no positive effect or may inhibit germination (3,18,20). It is suggested that gene banks test seeds of Olea spp. for germination at a constant temperature of 13°C in diffuse light after removing endocarps and pricking, or chipping away a part of the testa. Allow at least 7 weeks (6) for these tests.
VII. References
1. Basso, M. (1962). [Observations on the germinating capacity of olive seeds.] Agri. Ital., 7. (From Horticultural Abstracts, 1963, 33, 6063.)
2. Diamantoglou, S. and Mitrakos, K. (1979). Sur la culture in vitro de l'embryon d'olivier (Olea europaea L. var. oleaster). Comptes Rendus Hepdomadaires des Séances de l'Académie des Sciences (Paris), D, 288, 1537-1540.
3. Diana, G. and Gaetani, F.R. (1979/1980). [The germination of olive seeds in relation to pre-sowing treatments and to different harvesting dates.] Annali dell' Istituto Sperimentale per l'Olivicoltura, 6, 81-97.
4. Istanbouli, A. (1974). Etude de la "dormance" des semences d'olivier (Olea europaea L.). I. Rôle des enveloppes dans l'imbibition de la graine et de l'embryon. Revue Générale de Botanique, 81, 215-221.
5. Istanbouli, A. and Neville, P. (1974). Etude de la "dormance des semences d'olivier (Olea europaea L.). Mise en évidence d'une inhibition excerceé par l'albumen. Comptes Rendus Hepdomadaires des Séances de l'Academie des Sciences (Paris), D, 279, 1441-1442.
6. Istanbouli, A. and Neville, P. (1977). Distinction entre germination physiologique (ou activation) et germination morphologique chez l'olivier (Olea europaea L.). Comptes Rendus Hepdomadaires des Séances de l'Academie des Sciences (Paris), D, 284, 2235-2237.
7. Istanbouli, A. and Neville, P. (1977). Etude de la "dormance" des semences d'olivier (Olea europaea L.). Mise en évidence d'une dormance embryonnaire. Comptes Rendus Hepdomadaires des Séances de l'Academie des Sciences (Paris), D, 284, 2503-2506.
8. Istanbouli, A. and Neville, P. (1977). Etude de la "dormance" des semences d'olivier (Olea europaea L.). Influence favorable de la lumière en présence d'obstacles à la germination. Comptes Rendus Hepdomadaires des Séances de l'Académie des Sciences (Paris), D, 285, 41-44.
9. Khattak, G.M. (1962). Effect of locality of collection and seed pre-sowing treatments on the germination of Olea cuspidata. Pakistan Journal of Forestry, 12, 233-235.
10. Kimariyo, P.E. (1973). Handling hardwood seeds in Tanzania. In International Symposium on Seed Processing: Seed Problems, Bergen, Norway. IVFRO, Vol. II, Paper No. 16.
11. Lagarda, A., Martin, G.C. and Polito, V.S. (1983). Anatomical and morphological development of 'Manzanillo' olive seed in relation to germination. Journal of the American Society for Horticultural Science, 108, 741-743.
12. Lalatta, F. (1959). [Horticultural seeds: ripening of seeds of tree fruit species.] Sementi Elette, 5, 65-66. [From Horticultural Abstracts, 1959, 29, 2103.]
13. Macluskie, G. (1898). Effect of different temperatures of water on the germination of olive seeds. Bulletin of the Torrey Botanical Club, 25, 222-225.
14. Milella, A. (1960). [The germinative capacity of wild olive seeds in relation to the ripeness of the fruit.] Studi Sassar., Sez. 111, 8, 85-89. (From Horticultural Abstracts, 1962, 32, 3753.)
15. Rocha, G.G. de la (1957). [Trials with different treatments of olive seeds]. Inf. Mens. Estac. exp. Agric. La Molina, 31, 15-17. (From Horticultural Abstracts, 1958, 28, 1829.)
16. Rocha, G.G. de la (1960). [A trial of different treatments of olive seeds.] Inf. Estac. Mens. exp. Agric. La Molina, 34, 7-10. (From Horticultural Abstracts, 1961, 31, 5227.)
17. Scaramuzzi, F. (1957). [Studies on the germinating power of olive seeds of various ages.]. Agri. Ital., 56. (From Horticultural Abstracts, 1958, 28, 1828.]
18. Lagarda, A. and Martin, G.C. (1983). "Manzallino" olive seed dormancy as influenced by exogenous hormone application and endogenous abscisic acid concentration. HortScience, 18, 869-871.
19. Lagarda, A., Martin, G.C. and Kester, D.E. (1983). Influence of environment, seed tissue, and seed maturity on "Manzallino" olive seed germination. HortScience, 18, 868-869.
20. Mitrakos, K. and Diamantoglou, S. (1984). Endosperm dormancy breakage in olive seeds. Physiologia Plantarum, 62, 8-10.
