The Cucurbitaceae comprise more than 700 species of herbaceous plants within about 90 genera. They provide vegetables (e.g. Cucumis sativus L., cucumber), fruits (e.g. Cucumis melo L., melon), oils (e.g. Luffa cylindrica (L.) M.J. Roem., smooth loofah, and Telfairia pedata (Sims) Hook., oyster nut), and several other useful products. The fruits are usually pepos (fleshy berry-like structures with a rind and spongy seed interiors), but sometimes a papery bladdery pod. The seeds are usually flat and plate-like. Some care may be required when producing or collecting the seeds: seeds extracted from commercially ripe fruits may be immature. Consequently some storage in the fruit (very roughly until the fruit rinds go yellow) may be beneficial, although too long a period of storage in the fruit results in viviparous germination.
In general seed storage behaviour is orthodox. However, in two species we must correct our previous classification of seed storage behaviour. Telfairia occidentalis (Hook. f.) and Sechium edule Sw. must be classified as having uncertain seed storage behaviour at present. For the time being this will mean treating the seeds as if they are recalcitrant: certainly conventional drying treatments result in seed death. However, we suspect that the species are in fact orthodox and, whilst this has not yet been proved, investigations at Reading are continuing. Any progress in these investigations will be reported in Plant Genetic Resources Newsletter.
SEED DORMANCY AND GERMINATION
The seeds are non-endospermic and germination is epigeal. Dormancy can be a severe problem in some species: it is comparatively easy to induce dormancy by testing the seeds for germination in unfavourable environments. In particular the germination test substrate should not be too moist and only very low intensity light treatments should be applied; in most cases it is probably best to test the seeds for germination in darkness.
Detailed information is provided in this chapter for the genera Citrullus (including synonyms within Colocynthis), Cucumis, Cucurbita, Lagenaria (including synonyms within Cucurbita), Luffa and Momordica. Some advice is provided below for Benincasa and Trichosanthes spp., and for other species it may be possible to develop suitable germination test procedures using the algorithm provided below.
Benincasa hispida (Thunb.) Cogn. wax gourd, white gourd
Light inhibits seed germination (3). Cracking the seed coat (1) and testing at a constant temperature of 30°C in the dark (3) or at 30° to 35°C in moist sand (1) (i.e. a very low light intensity at the seed surface) have been suggested as suitable germination test regimes.
Trichosanthes spp. snake gourd, pointed gourd
Seed germination is promoted if the seeds have been extracted from ripe fruits with 3% hydrochloric acid added to aid extraction (2). Presumably the acid treatment affects the seed coats and in some way reduces their ability to act as a barrier to germination. Neither thiourea, pre-applied, 24h, 0.5% nor GA3, pre-applied, 24h, 50 ppm, promote the germination of seeds extracted in this way (2). It has been suggested that the seeds be tested for germination in moist sand at 30° to 35°C with removal of the seed coats if full germination does not occur (1). Alternatively try testing at 30°C in the dark.
References
1. Fursa, T.B. and Gvozdeva, Z.V. (1971). [Increasing of seed germination rate in some species of the family Cucurbitaceae Juss.] Trudy Po Prikladnoi Botanike Genetike I Selektsii, 44, 211-214.
2. Mukhopadhyay, G.K. and Chattopadhyay, T.K. (1976). Studies in propagation of pointed gourd (T. dioica, Rox.) - II. Progressive Horticulture, 7, 65-68.
3. 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.
RBG Kew Wakehurst Place algorithm
The first step of the algorithm is to test the seeds at a constant temperature of 31°C. If this does not result in full germination then test additional samples of seeds at constant temperatures of 26°C and 36°C.
If none of the above constant temperature regimes results in full germination then the second step of the algorithm is to test in an alternating temperature regime of 33°/19°C (12h/12h).
If this alternating temperature regime does not result in full germination then the third step of the algorithm is to co-apply 7 x 10-4 M GA3 to the germination test substrate and test at the most successful regime determined from the results in steps one and two.
No recommendation is made for the provision of light in the algorithm presented here in view of the problems mentioned already.
CITRULLUS
C. colocynthis (L.) Schrad.
C. lanatus (Thunb.) Mansfield [C. vulgaris Schrad.; Colocynthis citrullus (L.) Kuntze] water melon, citron
C. naudinianis
I. Evidence of dormancy
Although seeds of C. lanatus germinate readily when tested under favourable conditions (1,4,5,15), seed dormancy has been reported (12). Seeds of C. colocynthis may show strong dormancy (6,9).
II. Germination regimes for non-dormant seeds
C. lanatus
BP; S: 20°/30°C (16h/8h); 25°C: 14d (ISTA)
C. lanatus var caffer
BP; S: 20°/30°C (16h/8h); 25°C: 14d (AOSA)
AOSA rules emphasise that the germination test substrate should not be too moist. The following method is given by AOSA: the moistened substratum should be pressed against a dry absorbent surface such as a dry paper towel or blotter to remove excess moisture.
C. lanatus var citroides
BP: 20°/30°C (16h/8h): 14d (AOSA)
III. Unsuccessful dormancy-breaking treatments
C. colocynthis
Constant temperatures: 15°-40°C in light or dark (6); 20°C in light, 12h/d (9)
Alternating temperatures: 20°/30°C (16h/8h), continuous light or dark, or 2d dark, 15 min light, then dark (6)
Pre-chill: 5°C, 2d (6)
Light: white, 4-24h/d, at 25°C (6); far red (2)
Oxygen: 100%, at 26°C in dark (6); plus nitrogen, 1:4, 2:3, 3:2, 4:1, at 26°C in dark (6)
Nitrogen: 100%, at 26°C in dark (6)
Scarification: concentrated sulphuric acid, 4h (6); hydrochloric acid, 10%, 10 min (6); sodium hydroxide, 10%, 10 min (6)
Acetone: pre-applied, 30 min (6)
Pre-soak: 100°C, 10 min (6)
Pre-dry: 60°C, 2h (6); 90°C, 10 min (6)
Removal of seed covering structures: testa filed off (6); dehull, continuous white light, at 20°C (6); dehull, white light, 12h/d (9); dehull, continuous white light, 21-1400 lux, at 24°C (6); dehull, continuous green light, 670 nm (6); dehull, continuous blue light, 630 nm (6)
C. lanatus
Scarification: file (7); sulphuric acid, 50, 100%, 30,60 min (14); hydrochloric acid, 50, 100%, 30,60 min (14); nitric acid, 50, 100%, 30,60 min (14)
Acetone: pre-applied, 30,60 min (14)
Ethyl alcohol: pre-applied, 30,60 min (14)
GA3: pre-applied, 52h, 50, 100 ppm (7)
Pre-soak: 2h, then pre-dry, 25°C (11)
Light: continuous, white, 200-300 lux (10); continuous, far re 6.9x10-6 mol m-2 s-1 (8); continuous, far red, after 16h at 30°C in dark (8)
IV. Partly-successful dormancy-breaking treatments
C. colocynthis
Constant temperatures: 20°C, light, 8h/d (9)
Removal of seed covering structures: seed coat, germinate at 20°C in dark (6); seed coat, germinate at 25°-35°C in light (6); seed coat, germinate at 20°C, continuous red light, 530 nm (6); seed coat, germinate at 20°C, continuous yellow light, 450 nm (6); seed coat, germinate at 20°C, continuous violet light, 575 nm (6); seed coat, germinate at 20°C, continuous red blue light, 550 nm (6)
C. lanatus
Constant temperatures: 24°-35°C (3)
Scarification: mechanical at cotyledon end (8); mechanical, germinate at 30°C in dark for 20-32h, then continuous far red light, 6.9x10-6 mol m-2 s-1 (8); mechanical, continuous far red light, 3d, then 30°C in dark (8)
Ethephon: pre-applied, 16h, 3.5x10-3 M (11); 3.5x10-3 M, plus GA4/7' 10-3 M, pre-applied, 16h (11)
GA3: pre-applied, 24h, 25 ppm (13)
Indolebutyric acid: pre-applied, 24h, 25-100 ppm (13)
Boron: pre-applied, 24h, 25-100 ppm (13)
Napthaleneacetic acid: pre-applied, 24h, 25-100 ppm (13)
V. Successful dormancy-breaking treatments
C. colocynthis
Constant temperatures: 20°C in dark (9)
Removal of seed covering structures: seed coat, germinate at 25°C or 30°C in dark (6); seed coat, germinate at 35°C in light or dark (6); seed coat, germinate at 33°C, dark (2); seed coat, germinate at 22°C in red light, 5 min (2)
Scarification: crack seed coat, test in moist sand at 30°-35°C (16)
C. lanatus
Constant temperatures: 30°C, dark (10)
Scarification: mechanical, germinate at 30°C in dark (8); mechanical, germinate at 30°C in red light, 2.7x10-7 mol m-2 s-1 (8); crack seed coat, test in moist sand at 30°-35°C (16)
Pre-soak: 12,24h (14).
C. lanatus var caffer
Test at 30°C (AOSA)
C. lanatus var citroides
Pre-soak, test at 30°C (AOSA)
C. naudinianis
Scarification: crack seed coat, test in moist sand at 30°-35°C (16)
VI. Comment
Light is a strong inhibitor of seed germination in Citrullus spp. (2,6,8-10). Consequently it is recommended that the seeds be tested in the dark. Suitable temperatures are 20°/30°C (16h/8h) (1,4,5) or 30°C (8,10). Scarification or seed coat removal (the latter being preferable) may also be required (2,6,8,16).
VII. References
1. Andersen, A.M. and Justice, O.L. (1948). Germination of seeds of five kinds of Cucurbits at two temperatures. Proceedings of the Association of Official Seed Analysts, 38, 45-47.
2. Bhandari, M.C. and Sen, D.N. (1973). Phytochrome and seed germination in Citrullus colocynthis (Linn.) Schrad. Science and Culture, 39, 458-459.
3. Earhart, D.R., Fuqua, M.C., Tereskovich, G, and Downes, J. (1979). The effect of temperature and moisture levels on germination of the triploid watermelon, Citrullus vulgaris var caffer. HortScience, 14, 123.
4. Harrington, G.T. (1923). Use of alternating temperatures in the germination of seeds. Journal of Agricultural Research, 23, 295-332.
5. Harty, R.L. (1981). Report of the germination committee working group on Cucurbitaceae, 1977-1980. Seed Science and Technology, 9, 141-146.
6. Koller, D., Poljakoff-Mayber, A., Berg, A. and Diskin, T. (1963). Germination-regulating mechanisms in Citrullus colocynthis. American Journal of Botany, 50, 597-603.
7. Lopez, A.P. (1961). Effects of scarification and gibberellic acid on germination of Congo watermelon seed. Journal Agr. Univ. Puerto Rico, 45, 182-187.
8. Loy, J.B. and Evensen, K.B. (1979). Phytochrome regulation of seed germination in a dwarf strain of watermelon. Journal of the American Society of Horticultural Science, 104, 496-499.
9. Mayer, A.M. and Poljakoff-Mayber, A. (1963). The germination of seeds. Pergamon Press, Oxford.
10. Nakamura, S., Okasako, Y. and Yamada, Y. (1955). Effect of light on the germination of vegetable seeds. Journal of the Horticultural Association of Japan, 24, 17-28.
11. Nelson, J.M. and Sharples, G.C. (1980). Effect of growth regulators on germination of cucumber and other cucurbit seeds at suboptimal temperatures. HortScience, 15, 253-254.
12. Odland, M.J. (1937). Observations on dormancy in vegetable seed. Proceedings of the American Society for Horticultural Science, 35, 562-566.
13. Singh, B., Vashistha, R.N. and Singh, K. (1973). Note on the effect of certain chemicals on seed germination of bottle gourd, bitter gourd, watermelon and bhindi. Haryana Journal of Horticultural Sciences, 2, 70-71.
14. Singh, K. and Singh, A. (1969). Effect of various chemicals on the germination of some hard-coated vegetable seeds. Journal of Research, Ludhiana, 6, 801-807.
15. Smith, D.T. and Cooley, A.W. (1973). Wild watermelon emergence and control. Weed Science, 21, 570-573.
16. Fursa, T.B. and Gvozdeva, Z.V. (1971). [Increasing of seed germination rate in some species of the family Cucurbitaceae Juss.] Trudy Po Prikladnoi Botanike Genetike I Selektsii, 44, 211-214.
CUCUMIS
|
C. anguria L. [C. grossulariaeformis
Hort.] |
West Indian gherkin |
|
C. melo L. |
melon, muskmelon, cantaloupe |
|
C. myriocarpusNaud. |
|
|
C. sativus L. |
cucumber |
I. Evidence of dormancy
In a recent survey seeds of 12 Cucumis spp. - including the cultivated C. anguria, C. melo and C. sativus - were not dormant whereas seeds of four other Cucumis spp. which originated from Africa - C. africanus, C. ficifolius, C. leptodermis and C. myriocarpus - were strongly dormant - particularly C. myriocarpus (11). Despite the results of this survey, however, dormancy can be considerable in freshly harvested seeds of the cultivated species C. anguria (5,6,21), C. melo (10,22) and C. sativus (3,4,23,26). Reports from India indicate that dormancy is present in seeds of cultivated, wild and hybrid cucumbers (23).
Seeds of C. sativus have been reported to lose dormancy when after-ripened for 1 month (22), 1-2 months (26), 6 months (3) and 6-12 months (23), but seeds of C. myriocarpus retain strong dormancy after 1 year (11). It is particularly important to note that in C. sativus at least (and quite possibly other Cucumis spp.) unfavourable germination test conditions - continuous white, far red or blue light - result in the induction of secondary dormancy (15).
II. Germination regimes for non-dormant seeds
C. melo
BP; S: 20°/30°C (16h/8h); 25°C: 8d (ISTA)
BP; S: 20°/30°C (16h/8h): 10d (AOSA)
C. sativus
TP; BP; S: 20°/30°C (16h/8h); 25°C: 8d (ISTA)
BP; S: 20°/30°C (16h/8h): 7d (AOSA)
AOSA rules for the above two species emphasise that the germination test substrate should not be too moist. The following method is given by AOSA: the moistened substratum should be pressed against a dry absorbent surface such as a dry paper towel or blotter to remove excess moisture.
III. Unsuccessful dormancy-breaking treatments
C. anguria
Light: continuous, white, 1.2x10-6 W cm-2, germinate at 25°C (5,21); white, at 25°C, 1-3d, then 45°C, 45 min or 165 min, germinate at 25°C, continuous, white (5); 1d dark, 8d white, at 20°C (21); continuous, blue, 1.2x10-6 W cm-2, at 25°C (21); continuous, far red, 1.2x10-6 W cm-2 (5,21); far red/dark, at 25°/5°C (both 12h/12h) (5); far red/white, at 25°/5°C (both 12h/12h) (5)
6-Benzyladenine: co-applied, 10 ppm, at 25°C, continuous white light (6)
GA:3: co-applied, 100, 500, 1000 ppm, at 25°C, continuous far red light (6)
C. melo
Light: continuous (16); infra red (18); blue (18); white, continuous, 200-300 lux (18)
Removal of seed covering structures: plus white light, continuous, at 20°C (16)
C. myriocarpus
Constant temperatures: 15°C, light or dark (11); 20°C, light (11); 20°C, light, continuous (11)
Alternating temperatures: 20°/30°C, 15°/30°C (12h/12h) in light, 20°C, light, continuous (11)
Pre-chill: 3°-5°C, 150d, germinate at 15°C, light (11)
Removal of seed covering structures: (11); nick (11)
Scarification: concentrated sulphuric acid, 30 min (11)
Hydrogen peroxide: pre-applied, 8-24h, 5% (11)
Potassium nitrate: co-applied (11)
GA3: co-applied, 2-500 ppm (11)
C. sativus
Light: (17); red, at 30°C (23); far red, continuous, 7x10-4 W cm-2 (4,14,15,24,27); far red, continuous, at 30°C (23); far red, 30 min, 1h, 8x10-4 W cm-2 (25); incandescent filament lamp, continuous (15); white, 200-300 lux (18); 720, 730, 740 nm, continuous (4); 400-500 nm, 37x10-5 W cm-2, continuous (15)
GA3: (23)
Oxidising agents: (23)
Removal of seed covering structures: (23)
Chloroform: 4h fumigation (26)
Ether: 4h fumigation (26)
Mannitol: co-applied, 0.35, 0.45M (17)
Moisture: excess, in test substrate (10)
IV. Partly-successful dormancy-breaking treatments
C. anguria
Alternating temperatures: 0°/25°C, 15°/25°C, 20°/25°C, 20°/35°C, 25°/35°C (12h/12h), continuous white light (5); 5°/25°C, far red/dark (both 12h/12h) (5)
Light: continuous, white, at 25°C, 1-3d, then 0°C, 55 min or 3h, then 25°C (5); 1-7d white/2-8d dark, at 20°C (21); 3-7d dark/2-6d light, at 20°C (21); 6-18h dark/3d far red, at 25°C (21); 3d far red, then germinate at 25°C in dark (21)
6-Benzyladenine: co-applied, 25, 50, 75, 100 ppm, at 25°C, continuous light (6)
Ethrel: co-applied, 25, 50 ppm, at 25°C, continuous light (6); co-applied, 25, 50, 100 ppm, blue light (6); co-applied, 100 ppm, far red light (6)
GA3: co-applied, 50, 100, 250, 500, 2000 ppm, at 25°C, continuous light (6); co-applied, 100, 500, 1000 ppm, continuous blue light (6)
C. melo
Pre-soak: 24h, aerate (20)
Potassium nitrate: pre-applied, 24h, 3% (20)
Kinetin: pre-applied, 24h, 10-4 M (20)
Removal of seed covering structures: then germinate in light (18)
GA3: pre-applied, 24h, 10-4 M (20)
C. myriocarpus
Constant temperatures: 20°C, 25°C, dark (11)
Alternating temperatures: 10°/30°C, 15°/30°C (12h/12h), light (11); 20°/30°C (12h/12h) (11)
Pre-chill: 3°-5°C, 45d, germinate at 20°C, dark (11); 3°-5°C, 150d, germinate at 15°C, 20°C, 10°/30°C, 20°/30°C (12h/12h), light (11)
C. sativus
Constant temperatures: 30°C (26)
Removal of seed covering structures: (26); then germinate in light (18)
V. Successful dormancy-breaking treatments
C. anguria
Constant temperatures: 25°C, dark (5,21,23)
Alternating temperatures: 5°/25°C, 10°/25°C, 15°/35°C, (12h/12h), light or dark (5)
Light: red, at 25°C (21)
Ethrel: co-applied, 100, 250 ppm (6)
GA3: co-applied, 1000 ppm (6)
C. melo
Constant temperatures: 25°C (9,20); 30°C (1); 32°C (9)
Alternating temperatures: 20°/33°C (9h/15h) (7); 20°/30°C (16h/8h) (1,9,10)
Removal of seed covering structures: then germinate at 17.5°-20°C in dark (16)
Light: dark (18); dark, at 17.5°-20°C (16); dark, at 25°C (20)
C. myriocarpus
Alternating temperatures: 10°/30°C (12h/12h) (11)
Pre-chill: 3°-5°C, 20,30,45d, germinate at 25°C, dark, or 10°/30°C, 20°/30°C (12h/12h) (11); 15°C, 28d, germinate at 25°C in dark (11)
C. sativus
Constant temperatures: 18°C, dark (15); 20°C, 25°C, dark (4,14,24,25,27); 27°C (13); 30°C (1)
Alternating temperatures: 20°/30°C (16h/8h) (1,2,12); 20°/33°C (9h/15h) (7)
Light: dark (4,14,15,18,24,25,27); red, continuous or 1 min, 6.35x10-4 W cm-2 (4,15); red, 30 min, 8x10-4 W cm-2 (25)
Removal of seed covering structures: inner seed coat (3); cut end of cotyledon (26)
Pre-dry: 50°C, 6d (23)
GA4/7: pre-applied, 16h, 10-3 M, in acetone (19); pre-applied, 16h, 10-3 M combined with kinetin, 0.5x10-3 M (19); pre-applied, 16h, 10-3 M combined with ethephon, 3.5x10-3 M (19); pre-applied, 16h, 10-3 M combined with kinetin, 0.5x10-3 M, and ethephon, 3.5x10-3 M (19)
Fusicoccin: pre-applied, 16h, 0.5x10-3 M, in acetone (19)
Cucumis spp.
Removal of seed covering structures: then test at 20°C in dark (11)
VI. Comment
Light strongly inhibits the germination of seeds of all Cucumis spp. (4,5,11,14-16,18,21,23-25,27) - even at optimum temperatures for germination (5,21). In C. sativus continuous light at 20°C induces secondary dormancy: if subsequently tested in darkness no germination occurs unless the seeds are exposed to red light for a short period or the germination test temperature is increased (15). Thus, in contrast to previous ISTA recommendations, darkness is essential for testing the germination of seeds of Cucumis spp. Germination, particularly of dormant seeds, is reduced if the germination test substratum is excessively moist (10). Gene bank staff should take care to avoid this problem: see the AOSA advice in the section on germination regimes for non-dormant seeds.
Suggested germination test conditions for seeds of C. melo and C. sativus are 25°C, 30°C or 20°/30°C (16h/8h or possibly 8h/16h) in the dark with a relatively dry germination test substratum. However, this procedure may be inadequate for the most dormant accessions (11,23). It is suggested that brief light treatments (20 minutes irradiance of white light, 0.16 W m-2 per day or 30 minutes irradiance of red light, 8x10-4 W cm-2) may be a suitable further stimulus to promote the germination of the more dormant seeds (e.g. 25), and it is further suggested that the seed coats be removed from the ungerminated seeds after 10 to 14 days in test and that these seeds be tested for at least one further week. For the more dormant Cucumis spp. pre-chilling treatments at 3° to 5°C for between 20 and 45 days are suggested. Subsequent alternating temperature regimes of 25°/5°C, 25°/10°C, or 15°/35°C (12h/12h) for seeds of C. anguria, and 10°/30°C (12h/12h) for seeds of C. myriocarpus can be particularly effective in promoting germination (5, 12).
VII. References
1. Andersen, A.M. and Justice, O.L. (1948). Germination of seeds of five kinds of cucurbits at two temperatures. Proceedings of the Association of Official Seed Analysts, 38, 45-47.
2. Davis, G.N. (1938). Germination of cucurbit seed in sand. Proceedings of the Association of Official Seed Analysts, 30, 133-135.
3. Dzhein, B.P. and Kaloshina, Z.M. (1971). [On seed dormancy in Indian varieties of Cucumber.] Izvestiya Timiryazevskoi sel'skokhozyaistvennoi akademii, 3, 15-19. (From Horticultural Abstracts, 1972, 42, 1130.)
4. Eisenstadt, F.A. and Mancinelli, A.L. (1974). Phytochrome and seed germination. VI. Phytochrome and temperature interaction in the control of cucumber seed germination. Plant Physiology, 53, 114-117.
5. Felippe, G.M. (1980). Germination of the light-sensitive seeds of Cucumis anguria and Rumex obtusifolius: effects of temperature. New Phytologist, 84, 439-448.
6. Felippe, G.M. and Litjens, M.H.M. (1979). Effect of growth regulators on overcoming the light inhibition on germination of Cucumis anguria L. Biologia Plantarum, 21, 407-411.
7. Harrington, G.R. (1923). Use of alternating temperatures in the germination of seeds. Journal of Agricultural Research, 23, 295-332.
8. Harty, R.L. (1978). Report of the germination committee working group on Cucurbitaceae, 1974-1977. Seed Science and Technology, 6 187-192.
9. Harty, R.L. (1981). Report of the germination committee working group on Cucurbitaceae, 1977-1980. Seed Science and Technology, 9, 141-146.
10. Heit, C.E. (1948). Report of subcommittee on dormancy in seeds. Proceedings of the Association of Official Seed Analysts, 38, 25-26.
11. Heit, C., Robinson, R.W. and Mishanec, W. (1978). Dormancy of Cucumis species. Cucurbit Genetics Co-operative, 1, 36-37.
12. Kamra, S.K. (1964). Determination of germinability of cucumber seed with X-ray contrast method. Proceedings of the International Seed Testing Association, 29, 519-534.
13. MacNeil, M.M. and Hall, B. (1982). Factors affecting the germination of cucumber seed (Cucumis sativus L.). The Plantsman, 3, 251-253.
14. Mancinelli, A.L. and Tolkowsky, A. (1968). Phytochrome and seed germination. V. Changes in phytochrome content during the germination of cucumber seeds. Plant Physiology, 43, 489-494.
15. Mancinelli, A.L., Lindquist, P., Anderson, O.R. and Eisenstadt, F.A. (1975). Photocontrol of seed germination. VII. Preliminary observation on the development of the photosynthetic apparatus in light-inhibited seeds of Cucumber (Cucumis sativus). Bulletin of the Torrey Botanical Club, 102, 93-99.
16. Mayer, A.M. and Poljakoff-Mayber, A. (1963). The germination of seeds. Pergamon, Oxford.
17. McDonough, W.T. (1967). Dormant and non-dormant seeds: similar germination reponses when osmotically inhibited. Nature, 214, 1147-1148.
18. Nakamura, S., Okasado, Y. and Yamada, Y. (1955). Effect of light on the germination of vegetable seeds. Journal of the Horticultural Association of Japan, 24, 17-28.
19. Nelson, J.M. and Sharples, G.C. (1980). Effect of growth regulators on germination of cucumber and other cucurbit seeds at sub-optimal temperatures. HortScience, 15, 253-254.
20. Nerson, H., Cantliffe, D.L., Paris, H.S. and Karchi, Z. (1982). Low-temperature germination of birdsnest-type muskmelon. HortScience, 17, 639-640.
21. Noronha, A., Vicente, M. and Felippe, G.M. (1978). Photocontrol of germination of Cucumis anguria. Biologia Plantarum, 20, 281-286.
22. Odland, M.J. (1937). Observations on dormancy in vegetable seed. Proceedings of the American Society for Horticultural Science, 35, 562-566.
23. Shifriss, O. and George, W.L. (1965). Delayed germination and flowering in cucumber. Nature, 206, 424-425.
24. Spruit, C.J.P. and Mancinelli, A.L. (1969). Phytochrome in cucumber seed. Planta, 88, 303-310.
25. Suzuki, Y. and Takahashi, N. (1969). Red and far red reversible photoreactions on seed germination of Cucumis sativa. Plant and Cell Physiology, 10, 475-479.
26. Watts, V.M. (1938). Rest period in cucumber seeds. Proceedings of the American Society for Horticultural Science, 36, 652-654.
27. Yaniv, Z., Mancinelli, A.L. and Smith, P. (1967). Phytochrome and seed germination. III. Action of prolonged far red irradiation on the germination of tomato and cucumber seeds. Plant Physiology, 42, 1479-1482.
CUCURBITA
|
C. foetidissima HBK |
buffalo gourd |
|
C. maxima Duchesne squashes |
pumpkin, autumn and winter |
|
C. moschata Duchesne ex Poir. squashes |
pumpkin, cushaw, winter crookneck |
|
C. pepo L. [C. verrucosa L.; C.
polymorpha Duchesne] squash |
field pumpkin, marrow, butternut |
|
C. Texana Gray |
Texas gourd |
I. Evidence of dormancy
Seeds extracted from mature fruits of Cucurbita spp. can show dormancy (6,10,13-16). After-ripening periods of 1 to 2 months (6) and 5 months (10) are reported to be required to remove dormancy from seeds of C. pepo and C. maxima respectively. The storage of ripe fruits of C. foetidissima, C. pepo and C. Texana for 3 weeks or so at room temperature prior to seed extraction can also result in loss in dormancy (10,14-16), but immature fruits may require 2 to 3 months storage before dormancy is lost (13).
II. Germination regimes for non-dormant seeds
C. foetidissima
Constant temperatures: 30°C, dark (14-16)
C. maxima
BP; S: 20°/30°C (16h/8h); 25°C: 8d (ISTA)
BP; S: 20°/30°C (16h/8h); 7d (AOSA)
Alternating temperatures: 20°/30°C (16h/8h) (5)
C. moschata
BP; S: 20°/30°C (16h/8h); 25°C: 8d (ISTA)
BP; S: 20°/30°C (16h/8h); 7d (AOSA)
Alternating temperatures: 20°/30°C (16h/8h) (5)
C. pepo
BP; S: 20°/30°C (16h/8h); 25°C: 8d (ISTA)
BP; S: 20°/30°C (16h/8h): 7d (AOSA)
Constant temperatures: 30°C (12)
Alternating temperatures: 20°/30°C (16h/8h) (5)
C. Texana
Constant temperatures: 30°C, dark (14-16)
Cucurbita spp.
TP;BP: 20°/30°C (16h/8h): 7-10d (AOSA)
AOSA rules for Cucurbita spp. emphasise that the germination test substrate should not be too moist. The following method is given by AOSA: the moistened substratum should be pressed against a dry absorbent surface such as a dry paper towel of blotter to remove excess moisture.
III. Unsuccessful dormancy-breaking treatments
C. maxima
Light: (11)
C. moschata
Constant temperatures: 20°C, 24°C, light (7)
Light: (8)
C. pepo
Constant temperatures: 18°C (2); 20°C (6)
Oxygen: low partial pressure (6)
Light: (2,8); infra red, blue, green (8); far red, 4.2x10-4 W cm-2, 15 min, 1,2d, at 20°C, 25°C (2)
Removal of seed covering structures: puncture (6)
C. Texana
Constant temperatures: 10°C, 40°C (16)
Light: 8,16,24h/d (16)
IV. Partly-successful dormancy-breaking treatments
C. foetidissima
Constant temperatures: 30°C (14); 29°C (15)
C. moschata
Sodium thiosulphate: pre-applied, 2-6h, 10-3 M (9)
C. pepo
Constant temperatures: 30°C (6); 25°C in light (2)
Alternating temperatures: 12°/30°C (15h/9h) (6)
Oxygen: high partial pressure (6)
Pre-dry: 37°C, 7d (6)
C. Texana
Constant temperatures: 30°C in light, 16h/d (16)
V. Successful dormancy-breaking treatments
C. moschata
Constant temperatures: 20°C, 24°C, dark (7); 30°C, dark (8)
Alternating temperatures: 20°/33°C (9h/15h) (4)
C. pepo
Constant temperatures: 25°C in dark (2); 30°C, 100d (6)
Removal of seed covering structures: naked caryopses, germinate at 30°C in dark (6)
Pre-dry: 37°C, 14-30d (6)
Hydrogen peroxide: pre-applied, 16h, 5%, germinate at 30°C in dark, 30d (6)
Cucurbita spp.
Clip radicle end of seeds (AOSA)
VI. Comment
The storage of fruits at room temperature for several weeks prior to seed extraction is not recommended as a dormancy-breaking treatment. However, where immature fruits have been collected, a short period of fruit storage can enable seed development to continue in the fruit (13-16) and may, therefore, be worthwhile in such circumstances, but prolonged fruit storage, e.g. 6 months (3), results in viviparous germination.
Light can inhibit the germination of seeds of all Cucurbita spp. (2,7,8,11,16). Moreover, not only can light severely reduce the percentage of seeds germinating, but it can also result in a high proportion of abnormal seedlings (7). It is suggested that germination in the dark at an alternating temperature of 20°/30°C (16h/8h) (1,4,5) or (if this alternating temperature regime cannot be provided) at a constant temperature of 30°C (1,6,12) will be satisfactory for seeds of C. maxima and C. moschata. For very dormant seeds of C. pepo - and possibly C. foetidissima and C. Texana - however, the removal of the seed covering structures may also be necessary (6).
VII. References
1. Andersen, A.M. and Justice, O.L. (1948). Germination of seeds of five kinds of Cucurbits at two temperatures. Proceedings of the Association of Official Seed Analysts, 38, 45-47.
2. Boisard, J. and Malcoste, R. (1970). Le photocontrôle de la germination des graines de Cucurbita pepo L. (Courge) et le site de photosensibilité. Comptes Rendus de l'Académie de Science, Paris, 271, 304-307.
3. De, R.N. (1955). Peculiar germination of Cucurbita pepo DC. Science and Culture (Calcutta), 20, 342.
4. Harrington, G.T. (1923). Use of alternating temperatures in the germination of seeds. Journal of Agricultural Research, 23, 295-332.
5. Harty, R.L. (1981). Report of the germination committee working group on Cucurbitaceae, 1977-1980. Seed Science and Technology, 9, 141-146.
6. Ingold, M. (1960). Contribution à l'étude de la germination des semences d'Allium cepa L. et Cucurbita pepo L. Proceedings of the International Seed Testing Association, 25, 787-799.
7. Kasahara, Y. and Akita, S. (1951). The abnormality in the germination of squash, Cucurbita moschata Duch., caused by light. Ohara Inst. Landwirtsch. Forsch. Ber., 9, 451-453.
8. Nakamura, S., Okasako, Y. and Yamada, Y. (1955). [Effect of light on the germination of vegetable seeds.] Journal of the Horticultural Association of Japan, 24, 17-28.
9. Nandi, A. and Mallik, S.C. (1982). Effect of pre-soaking seeds of pumpkin (Cucurbita moschata Poir) in different chemicals on seedling emergence and growth. Indian Agriculturist, 26, 65-68.
10. Odland, M.J. (1937). Observations on dormancy in vegetable seed. Proceedings of the American Society for Horticultural Science, 35, 562-566.
11. Ogawara, K. and Watanabe, I. (1953). [Studies on the germination of squash seeds. 1. On the relation of light to the germination of Cucurbita maxima Duch. seeds.] Bull. Hort. Jap. Soc., 22, 45-49. (From Horticultural Abstracts, 1954, 24, 444.)
12. Solanki, S.S., Singh, R.D. and Yadav, J.P. (1980). Studies on the temperature and media relations and coefficient velocity of germination of vegetable seeds. II. Summer squash (Cucurbita pepo L.) and okra (Abelmoschus esculentus (L.) Moench.). Progressive Horticulture, 12, 59-65.
13. Young, R.E. (1949). The effect of maturity and storage on germination of butternut squash seed. Proceedings of the American Society for Horticultural Science, 53, 345-346.
14. Ba-Amer, M.A. and Bemis, W.P. (1968). Fruit and seed development in Cucurbita foetidissima. Economic Botany, 22, 297-299.
15. Costa, J.T.A. and Bemis, W.P. (1972). After-ripening effect on seed germination and viability of Cucurbita foetidissima seed. Turrialba, 22, 207-209.
16. Oliver, L.R., Harrison, S.A. and McClelland, M. (1983). Germination of Texas gourd (Cucurbita Texana) and its control in soybeans (Glycine max). Weed Science, 31, 700-706.
LAGENARIA
L. siceraria (Molina) Standl. [L. vulgaris Ser.; L. leucantha (Duchesne) Rusby; bottle gourd Cucurbita siceraria Molina; Cucurbita leucantha Duchesne]
I. Evidence of dormancy
Seeds of L. siceraria can show dormancy and require 2.5 months after-ripening for dormancy to be lost (2).
II. Germination regimes for non-dormant seeds
L. siceraria
BP; S: 20°/30°C (16h/8h): 14d (ISTA)
Constant temperatures: 20°C (5); 25°C (2); 30°C, moist sand (5,7)
Alternating temperatures: 20°/30°C (16h/8h) (5)
Lagenaria spp.
TP; BP: 20°/30°C (16h/8h): 7-10d (AOSA)
III. Unsuccessful dormancy-breaking treatments
L. siceraria
Scarification: sulphuric acid, 50, 100%, 30,60 min (4); concentrated nitric acid, 30,60 min (4); hydrochloric acid, 50%, 30,60 min (4)
Alcohol: pre-applied, 30,60 min (4)
Urea: pre-applied, 6-24h, 150-250 ppm (3)
IV. Partly-successful dormancy-breaking treatments
L. siceraria
Pre-soak: 6-24h (3)
Acetone: pre-applied, 30,60 min (4)
Succinic acid: pre-applied, 12h, 600 ppm (3)
GA3: pre-applied, 24h, 25-100 ppm (6)
Indolebutyric acid: pre-applied, 24h, 25-100ppm (6)
Boron: pre-applied, 24h, 25-100 ppm (6)
Napthaleneacetic acid: pre-applied, 24h, 25-100 ppm (6)
V. Successful dormancy-breaking treatments
L. siceraria
Constant temperatures: 30°-35°C, scarified seeds in moist sand (1)
Pre-dry: 40°C, 75°C, 3-9d (2)
Lagenaria spp.
Clip radicle end of seeds (AOSA)
VI. Comment
On the basis of the evidence available at present it is suggested that the seeds be tested at a constant temperature of 30°C or an alternating temperature of 20°/30°C (16h/8h or possibly 8h/16h) in the dark. In addition it may be necessary for the seed covering structures to be removed or clipped.
VII. References
1. Fursa, T.B. and Gvozdeva, Z.V. (1971). [Increasing of seed germination rate in some species of the family Cucurbitaceae Juss.] Trudy Po Prikladnoi Botanike, Genetike i selektsii, 44, 211-214.
2. Nakamura, H., Yamada, H. and Shimizu, T. (1978). Several factors affecting the heat resistance of the seeds of bottle gourd, Lagenaria siceraria. Bulletin of the Vegetable and Ornamental Crops Research Station, Japan, Series A, 4, 119-147.
3. Singh, A. and Singh, H.N. (1976). A note on effect of pre-soaking of seeds in nitrogen and succinic acid solution on germination and seedling growth in bottle gourd. Progressive Horticulture, 7, 35-38.
4. Singh, K. and Singh, A. (1969). Effect of various chemicals on the germination of some hard-coated vegetable seed. Journal of Research, Ludhiana, 6, 801-807.
5. Singh, P.V., Singh, M.B. and Khanna, A.N. (1973). Germination studies on bottle gourd (Lagenaria siceraria). Seed Research, 1, 63-66.
6. Singh, B., Vashistha, R.N. and Singh, K. (1973). Note on the effect of certain chemicals on seed germination of bottle gourd, bitter gourd, watermelon and bhindi. Haryana Journal of Horticultural Sciences, 2, 70-71.
7. Solanki, S.S. and Seth, J.N. (1981). A note on the physical factors affecting coefficient of germination of bottle gourd (Lagenaria siceraria (Mol.) Standl.) and methi (Trigonella foenum-graecum) seeds. Progressive Horticulture, 13, 57-60.
LUFFA
|
L. acutangula (L.) Roxb. |
angled loofah |
|
L. cylindrica (L.) Roem. [L. aegyptiaca Mill.;
L. aegyptica (L.) Roem.] |
smooth loofah, rag gourd |
I. Evidence of dormancy
Alternating temperatures and light can promote seed germination in L. cylindrica (2). Consequently it is assumed that seed dormancy can prevent germination.
II. Germination regimes for non-dormant seeds
L. acutangula
BP; S: 30°C: 14d (ISTA)
L. cylindrica
BP; S: 20°/30°C (16h/8h); 30°C: 14d (ISTA)
Constant temperatures: 21°C, 31°C (2)
III. Unsuccessful dormancy-breaking treatments
L. acutangula
Acetone: pre-applied, 30,60 min (3)
Ethyl alcohol: pre-applied, 30,60 min (3)
Scarification: sulphuric acid, 50, 100%, 30,60 min (3);
hydrochloric acid, 50, 100%, 30,60 min (3); nitric acid, 50, 100%, 30,60 min (3)
L. cylindrica
Constant temperatures: 15°C, 31°C, 41°C (2)
Alternating temperatures: 21°/41°C, 31°/41°C (12h/12h) (2)
IV. Partly-successful dormancy-breaking treatments
L. cylindrica
Alternating temperatures: 21°/31°C (12h/12h) (2)
Light: white, 12h, 2500-5000 lux (2)
V. Successful dormancy-breaking treatments
L. acutangula
Constant temperatures: 30°-35°C, scarified seeds, crack seed coat, moist sand (1)
Pre-soak: 12,24h (3)
L. cylindrica
Constant temperatures: 30°-35°C, scarified seeds, crack seed coat, moist sand (1)
VI. Comment
In contrast to other members of the Cucurbitaceae the germination of seeds of L. cylindrica is reported to be promoted by light (2). On the basis of the limited evidence available it is suggested that the seeds be tested in an alternating temperature environment of 20°/30°C (12h/12h) with light for 12 hours per day (2). Nevertheless, the apparent requirement for light is not proven: the germination of seeds when tested buried in sand is promoted (1); and seeds buried in soil germinate equally as well as those in a laboratory test in the presence of light (2). Finally, the response of germination to constant temperatures appears to differ between seed lots (1,2); hence the suggestion to test the seeds in an alternating temperature regime.
VII. References
1. Fursa, T.B. and Gvozdeva, Z.V. (1971). [Increasing of seed germination rate in some species of the family Cucurbitaceae Juss.] Trudy Po Prikladnoi Botanike, Genetike i selektsii, 44, 211-214.
2. Okusanya, O.T. (1978). The effects of light and temperature on germination and growth of Luffa aegyptica. Physiologia Plantarum, 44, 429-433.
3. Singh, K. and Singh, A. (1969). Effect of various chemicals on the germination of some hard-coated vegetable seeds. Journal of Research, Ludhiana, 6, 801-807.
MOMORDICA
|
M. balsamina L. |
balsam-apple |
|
M. charantia L. |
balsam-pear, bitter gourd |
I. Evidence of dormancy
Considerable dormancy is shown by the seeds of M. charantia (A). Light inhibits germination (1) and the problem of seed dormancy appears to be similar to most other members of the Cucurbitaceae.
II. Germination regimes for non-dormant seeds
M. balsamina
Constant temperatures: 30°C, dark (1)
M. charantia
BP; S: 20°/30°C (16h/8h); 30°C: 14d (ISTA)
III. Unsuccessful dormancy-breaking treatments
M. balsamina
Light: (1)
M. charantia
Scarification: concentrated sulphuric acid, 30,60 min (3); concentrated nitric acid, 30,60 min (3); concentrated hydrochloric acid, 30,60 min (3)
Alcohol: pre-applied, 30,60 min (3)
Acetone: pre-applied, 30,60 min (3)
IV. Partly-successful dormancy-breaking treatments
M. charantia
Pre-wash: 12,24h (3)
GA3: pre-applied, 24h, 75, 100 ppm (2)
Indolebutyric acid: pre-applied, 24h, 25-100 ppm (2)
Napthaleneacetic acid: pre-applied, 24h, 25-100 ppm (2)
Boron: pre-applied, 24h, 25-100 ppm (2) 2,4-Dichlorophenoxyacetic acid: pre-applied, 24h, 25-100 ppm (2)
V. Successful dormancy-breaking treatments
M. balsamina
Constant temperatures: 30°C, dark (1)
M. charantia
GA3: pre-applied, 24h, 25, 50 ppm (2)
VI. Comment
It is suggested that the seeds be tested in the dark at either 30°C or, preferably, 20°/30°C (16h/8h). In addition we have found it necessary to remove the seed covering structures (endocarp and testa) and to test for more than 56 days (A). Pre-treatment with gibberellins may also be promotory (2).
VII. References
1. Nakamura, S., Okasako, Y. and Yamada, Y. (1955). [Effect of light on the germination of vegetable seeds.] Journal of the Horticultural Association of Japan, 24, 17-28.
2. Singh, B., Vashistha, R.N. and Singh, K. (1973). Note on the effect of certain chemicals on seed germination of bottle gourd, bitter gourd, watermelon and bhindi. Haryana Journal of Horticultural Sciences, 2, 70-71.
3. Singh, K. and Singh, A. (1969). Effect of various chemicals on the germination of some hard-coated vegetable seeds. Journal of Research, Ludhiana, 6, 801-807.
