The Chenopodiaceae comprise about 1400 species of herbaceous plants in more than 100 genera which provide edible roots (e.g. Beta vulgaris L., beetroot), leaf vegetables (e.g. Spinacia oleracea L., spinach), oils (e.g. Chenopodium ambrosioides L., wormseed) and grain (e.g. Chenopodium quinoa Willd., quinoa). The fruits are utricles (see Chapter 3, Volume I) and the seeds show orthodox storage behaviour.
SEED DORMANCY AND GERMINATION
The seeds can show considerable dormancy and, in addition, the presence of the fruit structures may also hinder seed germination. B.R. Atwater classifies seed morphology as endospermic seeds with peripheral linear embryos (see Table 17.1, Chapter 17). Light can be particularly promotory. Detailed information on seed germination is provided in this chapter for the genera Beta, Chenopodium and Spinacia. Additional information on germination test regimes for the Chenopodiaceae is summarised in Table 29.1, and the algorithm below may be helpful in developing germination test procedures for difficult accessions.
RBG Kew Wakehurst Place algorithm
The first step in the algorithm is to test four samples of seeds at constant temperatures of 6°C, 16°C, 21°C and 31°C; in each environment light is applied for 12h/d. If the results of these germination tests appear to show a trend in response to constant temperatures then test at either more extreme temperatures (e.g. if germination is greatest at 31°C then test a further group of seeds at 36°C) or at intermediate constant temperatures (e.g. if germination is greatest at 6°C and 16°C then test a further sample of seeds at 11°C). In all cases apply light for 12h/d.
If none of the above constant-temperature regimes is successful in promoting full germination then the second step of this algorithm is to test in an alternating-temperature regime. The alternating-temperature regime used depends upon the comparative results obtained in the first step: if the greatest proportion of seeds germinated in the test at constant temperatures of 16°C or below, the alternating temperature regime 23°/9°C (12h/12h) is used for the second step; if the greatest proportion of seeds germinated in tests at 31°C or above, the alternating temperature regime 33°/19°C (12h/12h) is used for the second step; if the greatest proportion of seeds germinated in tests at constant temperatures between 17° and 30°C, or if there was little difference between the results at different constant temperatures, then two samples of seeds are drawn and tested at 23°/9°C (12h/12h) and 33°/19°C (12h/12h) for the second step of the algorithm. Whether one or both alternating temperature regimes is used, light is applied for 12h/d during the period spent at the upper temperature.
If an alternating temperature regime is not successful in promoting full germination then the third step of the algorithm is to pre-chill a fresh sample of seeds at 2° to 6°C for 8w and then test for germination in the most successful regime determined from a comparison of the results of steps one and two.
If this is not successful in promoting full germination then the fourth step of the algorithm is to co-apply 10-3 M potassium nitrate to the germination test substrate and test a fresh sample of seeds in the most successful regime determined from the tests carried out in steps one to three. If this includes a requirement for pre-chilling then the potassium nitrate is co-applied to the pre-chill as well as the germination test substrate.
If full germination has not been promoted, the fifth step of the algorithm is to estimate viability using a tetrazolium test (see Chapter 11, Volume I).
TABLE 29.1 Summary of germination test recommendations for species within the Chenopodiaceae
|
Species and Authority |
Substrate |
Temperature |
Duration |
Additional directions |
Source |
|
Atriplex hortensis L. |
TP; BP |
20°/30°C |
28d |
|
ISTA |
|
Atriplex semi-baccata R. Br. |
|
20°C |
14d |
pre-soak and remove calyx |
Atwater |
|
Atriplex polycarpa (Torr.) Wats. |
|
20°C |
5d |
pre-wash, test in light |
Atwater |
|
Corispermum hyssopifolium |
TP |
20°/30°C |
|
pre-chill, 2-3w |
M&O |
|
Kochia scoparia (L.) Schrad. |
TP; BP |
20°/30°C; 20°C |
14d |
pre-chill, GA |
ISTA |
|
TP |
20°/30°C |
6d |
light |
AOSA |
|
|
|
20°/30°C |
7d |
light |
Atwater |
|
|
TP |
20°/30°C |
|
light |
M&O |
|
|
TP; S |
15°/30°C |
5d |
light |
Everson |
BETA
B. vulgaris L.
beet, beetroot, sugar-beet, mangel, swiss chard
I. Evidence of dormancy
Seed germination can be erratic (6, 13, 16, 32) and dormancy can create severe problems for seed testing (4-6, 13, 15,36). The seed is contained within a fruit structure and this is the cause of most problems: germination inhibitors are present within this structure (4-6, 13, 17), and the tight ovary cap can act as a physical barrier to germination (17,24,29). In seed testing stations fungal infections can affect the reliability of germination tests and consequently fungicides may be applied: see Chapter 9 for details.
II. Germination regimes for non-dormant seeds
BP; TP; S: 20°C: 14d (ISTA)
BP; S: 20°/30°C (16h/8h); 20°C: 10d (AOSA)
BP; S: 20°/30°C (16h/8h): 14d (AOSA)
III. Unsuccessful dormancy-breaking treatments
Pre-chill: 4°C, 1-3w (15); 12°C, 3d (22)
Pre-dry: 16h, after 8h imbibition (15)
Pre-soak: 24h (37)
GA3: pre-applied, 1.5,3h, 250 ppm (31); pre-applied, 4h, 100, 1000 ppm (12); pre-applied, 4h, 100-10000 ppm (31); pre-applied, 18h, 125, 250 ppm (31)
Hydrochloric acid: pre-applied, 8h, 1 N (2); pre-applied, 3-8h, 2 N (2)
Scarification: rub (9, 17); shake, 45 min (9)
IV. Partly-successful dormancy-breaking treatments
Alternating temperatures: 8°/25°C, 11°/25°C, 25°/4°C, 25°/8°C (16h/8h) (23)
Pre-soak: 2h (29); 2-15h, 25°C (25); 4-24h (13); 12h (34); 24h (30, 35); 8h, then pre-dry, 16h, 1-10 cycles (15); 1h, then pre-dry, 1h, 3,4 cycles (29)
Pre-wash: 2h, 20°C (4); 2h, 25°C, with or without pre-dry (28); 2h, then pre-dry (19); 3.5h, 25°C, germinate at 10°C (27); 6-7h (25); 8h, 20°C (36); 20h (15); 1.5-24h, 25°C, germinate at 15°C (26); 4-24h (13); 1-24h, 15°C, germinate at 20°C (37)
Scarification: rub (4,11,28,36); chip (29); notch (32); concentrated sulphuric acid, 20 min, then pre-wash, 20 min (15); concentrated sulphuric acid, 20 min, then pre-wash, 30 min, then pre-chill, 4°C, 1-3w (15); sulphuric acid, 3%, 2h, then pre-wash, 2h (24); hydrochloric acid, 3%, 2h, then pre-wash, 2h (24,29); phosphoric acid, 2h (29)
Hemicellulase: pre-applied, 2h, 0.01-1% (29)
Pectinase: pre-applied, 2h, 0.01-1% (29)
GA3: co-applied, 10-1000 ppm (30); pre-applied, 24h, 100, 500 ppm (30,35)
Kinetin: co-applied, 10-100 ppm (30); pre-applied, 24h, 40, 80 ppm (30,35)
6-Benzylaminopurine: co-applied, 10 ppm (30); pre-applied, 24h, 10, 40 ppm (30,35)
Magnesium sulphate: pre-applied, 2h, 0.5% (11)
Removal of seed covering structures: (32)
V. Successful dormancy-breaking treatments
Pre-wash (AOSA, ISTA)
Pre-chill: 5°C, 5°/7°C (20h/4h), 3m, germinate at 20°C (7)
Pre-wash: 2h, germinate at 20°/30°C (16h/8h) (3); 2h, then pre-dry (9); 2h, 25°C, then pre-dry, 30°C, 16h, germinate at 20°/30°C (16h/8h) (28); 3.5h, 25°C (26); 4h, germinate at 20°C or 20°/30°C (16h/8h) (11); 1-8h, germinate at 20°/30°C, 15°/25°C (16h/8h) (22); 20h (16, 17)
Pre-soak: then pre-dry (18); then germinate at 20°/30°C (18h/8h) (14)
Removal of seed covering structures: pericarp (2); ovary cap (17); excise seed (17,37)
GA3: pre-applied, 4 ppm (9)
Cytokinin: pre-applied, 12h, 1%, germinate at 15°C (34)
Oxygen: (17)
Hydrochloric acid: pre-applied, 0.5-8h, 0.5 N (2); pre-applied, 0.5-6h, 1 N (2); pre-applied, 0.5-2h, 2 N (2); pre-applied, 2,3h, 26%, then pre-wash, then pre-dry, 2-3h (29); pre-applied, 2h, 1 N, then pre-wash, 5 min, then hydrochloric acid, pre-applied, 2h, 1 N plus either GA3, 10, 100 ppm, or kinetin, 10, 100 ppm, germinate at 20°/30°C (8h/16h), 9°C, -10, -15 bar (1)
Hydrogen peroxide: co-applied, 2% (9, 10); co-applied, 1-3% (17); co-applied, 1% (18); pre-applied (21)
VI. Comment
Pre-wash or pre-soak treatments are the most effective method of removing germination inhibitors from the fruit. Percentage germination in subsequent tests increases with increase in the duration of either treatment (13,22,25,26), until maximum promotion is reached after 8 to 16 hours for pre-wash or 16 to 20 hours for pre-soak treatments (13). Drying, subsequent to either pre-wash or pre-soak treatments, may also further improve germination (22,28).
The ISTA recommend 2 or 4 hour pre-wash treatments at 25°C for multigerm and genetically monogerm fruits respectively, with subsequent pre-drying at 25°C. The AOSA recommendations vary between the various crops: 2 hours' pre-soaking at 20°C (250 ml of water per 100 fruits) or 3 hours' pre-washing at 20°C is recommended for beet, mangel and swiss chard; but for sugar beet 16 hours' pre-soaking at 25°C may be necessary, followed by rinsing and 2 hours' drying at room temperature.
Despite the removal of germination inhibitors by pre-washing or pre-soaking, successive germination tests may produce erratic results. The major difficulty remaining is the moisture of the germination test substrate (14): dry seeds require a moist substratum, whilst pre-soaked or pre-washed seeds require a relatively dry substratum (9,16-19,22,33). For the more dormant seeds hydrogen peroxide, co-applied at 1%, can be beneficial (9,10,17,18,21).
Optimum constant temperatures for germination of 11°-25°C (23), 15°-25°C (8), 15°C (20,34), 20°C (7,11,20), and 25°C (15,25) have been reported, as have optimum alternating temperatures of 20°/30°C (16h/8h) (1,3,11,14,19,20,22,28), 15°/25°C (16h/8h) (22), 5°/30°C, 5°/25°C (16h/8h) (15), 25°/11°C and 4°/25°C (16h/8h) (23). It is unlikely that there is any advantage to testing in alternating temperature rather than constant temperature regimes (11,15,20,22,23).
It is suggested that the AOSA prescriptions and recommendations be followed, but with an additional hydrogen peroxide treatment (see above) for the most dormant seeds. However, one of the problems with pre-soak treatments of 16 hours for seeds of sugar beet is that treatments of such length may be damaging to some accessions. One way for gene banks to avoid this is to extract the seed from the fruits by hand and thus avoid the requirement for a pre-soaking treatment. (The ovary caps can be lifted with a scalpel and the seed dropped out.) This has further advantages in easing the scoring of seedlings during subsequent seedling evaluation (which can be difficult with multigerm fruits) and avoiding ovary caps hindering seedling emergence.
VII. References
1. Akeson, W.R., Freytag, A.H. and Henson, M.A. (1981). Improvement of sugar beet seed emergence with dilute acid and growth regulator treatments. Crop Science, 21, 307-312.
2. Akeson, W.R., Henson, M.A., Freytag, A.H. and Westfall, D.G. (1980). Sugar beet fruit germination and emergence under moisture and temperature stress. Crop Science, 20, 735-739.
3. Andersen, A.M. (1948). The effect of pretreatment and substrata on the germination of sugar beet (Beta vulgaris L.) seedballs. Proceedings of the American Society of Sugar Beet Technologists, 5, 95-99.
4. Barthodeiszky, A. and Gáspár, S. (1965). Studies on the possibility to terminate the lability of germination in the seeds of beet (Beta vulgaris L.). Proceedings of the International Seed Testing Association, 30, 677-688.
5. Battle, J.P. and Whittington, W.J. (1968). Genetic and environmental control of germination in sugar beet. University of Nottingham School of Agriculture, Report of the School of Agriculture 1967-1968, 111-114.
6. Battle, J.P. and Whittington, W.J. (1971). Genetic variability in time to germination of sugar-beet clusters. Journal of Agricultural Science, Cambridge, 76, 27-32.
7. Brown, S.J. (1980). Variation in germination and seedling emergence of sugar beet at sub-optimal temperatures. Annals of Applied Biology, 95, 143-150.
8. Chamberland, E. (1974). [Germination tests of sweet sorghum and sugar beet cultivars.] Canadian Journal of Plant Science, 54, 855-857.
9. Chetram, R.S. and Heydecker, W. (1967). Moisture sensitivity, mechanical injury and gibberellin treatment of Beta vulgaris seeds. Nature, 215, 210-211.
10. Coumans, M. (1974). [Action of perhydrol on the germination of sugarbeet.] Bulletin de la Societé Royale de Botanique de Belgique, 107, 27-31.
11. Cuddy, T.F. (1960). Studies on the germination of sugarbeet seed. Proceedings of the Association of Official Seed Analysts, 49, 98-102.
12. Doxtator, C.W. (1958). Gibberellic acid effects on seed and seedlings of sugarbeet. Journal of the American Society of Sugar Beet Technologists, 10, 117-123.
13. El-Gharbawy, A.-H.A. and Moustafa, S.M.A. (1975). Some physiological studies on germination of sugarbeet seeds. Agricultural Research Review, 53, 87-97.
14. 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.
15. Heide, O.M., Juntilla, O. and Samuelsen, R.T. (1976). Seed germination and bolting in red beet as affected by parent plant environment. Physiologia Plantarum, 36, 343-349.
16. Heydecker, W. and Chetram, R.S. (1971). Water relations of beetroot seed germination. I. Microbial factors, with special reference to laboratory germination. Annals of Botany, 35, 17-29.
17. Heydecker, W., Chetram, R.S. and Heydecker, J.C. (1971). Water relations of beetroot seed germination. II. Effects of the ovary cap and of the endogenous imhibitors. Annals of Botany, 35, 31-42.
18. Heydecker, W., Orphanos, P.I. and Chetram, R.S. (1969). The importance of air supply during seed germination. Proceedings of the International Seed Testing Association, 34, 297-304.
19. Hibbert, D. and Woodwark, W. (1965). The effect of various analytical factors on the germination test results obtained on some British sugar-beet seeds. Proceedings of the International Seed Testing Association, 30, 689-704.
20. Hibbert, D. and Woodwark, W. (1970). Germination testing of sugar beet seed on different types of paper substrate. Journal of the International Institute of Sugar Beet Research, 4, 169-174.
21. Jensen (1962). [Contribution to discussion.] Proceedings of the International Seed Testing Association, 27, 756.
22. Klitgard, K. (1978). Report of the germination committee working group on germination methods of Beta vulgaris. Seed Science and Technology, 6, 215-224.
23. Kotowski, F. (1927). Temperature alternation and germination of vegetable seed. Acta Societatis Botanicorum Poloniae, 5, 71-78.
24. Lackey, C.F. (1948). Chemical loosening of seed caps in relation to germination of sugar-beet seed. Proceedings of the American Society of Sugar Beet Technologists, 5, 66-69.
25. Lexander, K. (1980). Seed composition in connection with germination and bolting of Beta vulgaris L. (sugar beet). In Seed Production (ed. P.D. Hebblethwaite), pp. 271-291, Butterworths, London.
26. Longden, P.C. (1974). Washing sugar-beet seed. Journal of the International Institute of Sugar Beet Research, 6, 154-162.
27. Longden, P.C. (1976). Seed treatments to lengthen the sugar-beet growing period. Annals of Applied Biology, 83, 87-92.
28. MacKay, D.B. (1961). The effect of pre-washing on the germination of sugar beet. Journal of the National Institute of Agricultural Botany, 9, 99-103.
29. Peto, F.H. (1964). Methods of loosening tight seed caps in monogerm seed to improve germination. Journal of the American Society of Sugar Beet Technologists, 13, 281-286.
30. Scott, R.K., Wood, D.W. and Harper, F. (1972). Plant growth regulators as a pretreatment for sugar beet seeds. Proceedings of the 11th British Weed Control Conference, 2, 752-759.
31. Snyder, F.W. (1959). Effect of gibberellin on germination and early growth of sugar beet. Journal of the American Society of Sugar Beet Technologists, 10, 394-396.
32. Snyder, F.W. (1959). Influence of the seedball on speed of germination of sugar beet seeds. Journal of the American Society of Sugar Beet Technologists, 10, 513-520.
33. Snyder, F.W. and Zielke, R.C. (1973). Water requirement for maximum germination and emergence of sugar beet seeds. Journal of the American Society of Sugar Beet Technologist, 17, 323-331.
34. Wilczek, C.A. and Ng, T.J. (1982). Promotion of seed germination in table beet by an aqueous seaweed extract. HortScience, 17, 62 9-630.
35. Wood, D.W. (1973). Agronomic effects of fruit size and fruit treatment of sugar beet. In Seed Ecology (ed. W. Heydecker), p. 546, Butterworths, London.
36. Wood, D.W., Scott, R.K. and Longden, P.C. (1980). The effect of mother-plant temperature on seed quality in Beta vulgaris L. (sugar beet). In Seed Production (ed. P.D. Hebblethwaite), pp. 257-270, Butterworths, London.
37. Morris, P.C., Grierson, O. and Whittington, W.J. (1984). Endogenous inhibitors and germination of Beta vulgaris. Journal of Experimental Botany, 35, 994-1002.
CHENOPODIUM
|
C. album L. |
lambsquarters, common pigweed, fat hen |
|
C. ambrosioides L. |
American wormseed, Mexican tea |
|
C. berlandieri Moq. |
|
|
C. bonus-henricus L. |
good King Henry, mercury |
|
C. botrys L. |
feather geranium, Jerusalem-oak |
|
C. capitatum Aschers. |
|
|
C. glaucum L. |
oakleaf goosefoot |
|
C. humile L. |
|
|
C. hybridum L. |
|
|
C. murale L. |
|
|
C. paganum Reichb. |
|
|
C. polyspermum L. |
|
|
C. quinoa Willd. |
quinoa |
|
C. rubrum L. |
red goosefoot |
|
C. strictum Roth. |
|
|
C. urbicum L. |
|
I. Evidence of dormancy
Seeds of C. quinoa (A) and C. glaucum (5) generally exhibit little or no dormancy and germinate satisfactorily over a wide range of conditions. However, seeds of C. humile (8) and the remaining species listed above can show considerable dormancy (5) and may require, for example, up to 2 years after-ripening at room temperature before dormancy is removed from all seeds (5). Secondary dormancy may be induced if the seeds are prevented from germinating, for example if tested in darkness with insufficient moisture, and this dormancy may be more difficult to remove than primary (innate) dormancy (14).
C. album is rarely cultivated and all citations here to seed dormancy in this and the other Chenopodium spp. concern investigations with seeds collected from plants growing wild or as weeds. Since the literature on the weed seed dormancy of Chenopodium spp. is large only the more important information has been summarised here.
II. Germination regimes for non-dormant seeds
C. album
Constant temperatures: 25°C (15)
Alternating temperatures: 20°/30°C (16h/8h), light, 14d (3)
III. Unsuccessful dormancy-breaking treatments
C. album
Alternating temperatures: 25°/15°C, 15°/25°C, 25°/1°C, 1°/25°C, 15°/1°C, 1°/15°C (8h/16h) in dark (19)
Pre-chill: 6m, germinate in light (6)
C. botrys
Light: dark, at 10°-35°C, 10°/20°C, 10°/30°C, 15°/25°C, 15°/35°C, 20°/30°C, 25°/35°C (16h/8h) (2)
C. polyspermum
Constant temperatures: 1°C, 15°C, 25°C, with or without potassium nitrate, co-applied, 10-2 M, in light or dark (20)
Alternating temperatures: 25°/15°C, 15°/25°C, 25°/1°C, 1°/25°C, 15°/1°C, 1°/15°C (8h/16h) in dark (19)
IV. Partly-successful dormancy-breaking treatments
C. album
Alternating temperatures: 30°/10°C, 25°/3°C (16h/8h) in light, diffuse, with potassium nitrate, co-applied, 10-2 M, 6w (17)
Pre-chill: 3°C, 3-5m (5); 4°C, 4,7d, in dark, germinate at 25°C in light, brief exposure, diffuse, with potassium nitrate, co-applied, 10-3 M, 28d (18)
Light: fluorescent, continuous, 5.25x10-4 W cm-2, at 23°C (10); red, 200s, 5x10-2, J cm-2, after 24h at 23°C in dark, germinate at 23°C in dark (9); dark, 24-40h, at 23°C, then red light, 15 min, 0.18 J cm-2, germinate at 23°C in dark (11)
Removal of seed covering structures: perianth (1)
Pre-wash: 8,24,70h, 20°C (1)
Thiourea: co-applied, 0.2%, at 27°C in light (16)
GA3: co-applied, 10-3 M, at 23°C in dark (7)
2-Chloroethylphosphonic acid: co-applied, 500 ppm, at 23°C in dark (7)
C. ambrosioides, C. berlandieri, C. bonus-henricus,
C. botrys, C. capitatum
Pre-chill: 3°C, 3-5m (5)
C. humile
Pre-wash: 24h (8)
Pre-soak: 30 min (8)
Ethanol: pre-applied, 3h, 2%, shaken (8)
Scarification: sulphuric acid, 20%, 30 min (8)
C. hybridum, C. murale, C. paganum, C. polyspermum, C. rubrum, C. strictum, C. urbicum
Pre-chill: 3°C, 3-5m (5)
V. Successful dormancy-breaking treatments
C. album
Alternating temperatures: 1°/25°C, 15°/25°C (8h/16h) in light, brief exposure, diffuse, with potassium nitrate, co-applied, 10-2 M (19); 15°/25°C in light, 14h/d, 17120 lux, with potassium nitrate, co-applied, 10-1 M (4)
Pre-chill: 6m, germinate in dark (6)
Light: fluorescent, 120 fc, 0.5,0.75,8,16,24h/d at 30°C, 7d (2) Removal of seed covering structures: then germinate at 20°-35°C (15); seed coat and endosperm (12)
GA4/7: co-applied, 3x10-4 M, with red light, 32 min, 1.9x10-4 W cm-2, after 24h dark imbibition (13)
Thiourea: co-applied, 10-2 M, at 23°C in dark (7)
Potassium nitrate: co-applied, 10-2 M, at 20°C, with or without pre-chill, 5°C, 4w (22)
C. bonus-henricus
Alternating temperatures: 22°/12°C (12h/12h), light, 12h/d (14)
Pre-chill: 4°C, 28d (14)
C. botrys
Light: fluorescent, 8h/d, 300 fc, at 30°C, 35°C, 10°/30°C, 15°/35°C, 20°/30°C, 25°/35°C (16h/8h) (2); fluorescent, continuous, 300 fc, at 25°C, 30°C, 35°C, 15°/35°C, 20°/30°C, 25°/35°C (16h/8h) (2); dark, 20d, then fluorescent light, 1 min, 300 fc, then dark, at 10°/30°C (16h/8h) throughout (2); fluorescent, 300 fc, 16h/d, at 25°-35°C (2)
C. humile
Removal of seed covering structures: pericarp, germinate at 30°/13°C, light/dark (16h/8h) (8)
Scarification: sandpaper (8)
GA3: pre-applied, 24h, 1000 ppm, germinate at 30°C, dark (8)
Thiourea: pre-applied, 24h, 1000 ppm, germinate at 30°C, dark (8)
Ethanol: co-applied, 50%, at 30°C, dark (8); co-applied, 50%, at 30°/13°C, light/dark (16h/8h or 8h/16h) (8)
C. polyspermum
Pre-chill: 1°C, 4w, in light, germinate at 25°C in light, with potassium nitrate, co-applied, 10-2 M (20); 1°C, 4w, germinate at 25°/1°C (8h/16h) in light, brief exposure, diffuse, with potassium nitrate, co-applied, 10-2 M (19)
VI. Comment
The four most important factors in the promotion of germination of dormant seeds of Chenopodium spp. are light, (potassium) nitrate, alternating temperatures, and pre-chill. In the absence of the other three, pre-chill treatments generally appear promotory (17,21,22), though not in all cases (18, 19). However, in the presence of some, or all, of the other stimulatory agents the benefit from pre-chill is only marginal (17,22). The principal stimulatory agents are light, potassium nitrate, alternating temperatures, and particularly interactions between the latter two (17). Very short duration light treatments are sufficient (2). Diffuse laboratory light reaching the seeds from irregular opening of germination cabinet doors is sufficient (17), although a regular intermittent, treatment with red light as described in Chapter 6 can be provided if this is possible. Potassium nitrate treatments should be co-applied at 10-2 M (17,19,20,22) or possibly 10-1 M (4). Stimulatory alternating temperature regimes are 10°/30°C, 15°/35°C, 20°/30°C, 25°/35°C (16h/8h) (2), 20°-30°/5°C (day/night) (21), 25°/3°C and 30°/10°C (16h/8h) (17). The alternating temperature regime 25°/3°C (16h/8h) is recommended for germination tests with seeds of Chenopodium spp.
VII. References
1. Chu, C.C., Sweet, R.D. and Ozbun, J.L. (1978). Some germination characteristics in common lambsquarters (Chenopodium album). Weed Science, 26, 255-258.
2. Cumming, B.G. (1963). The dependence of germination of photoperiod, light quality, and temperature in Chenopodium spp. Canadian Journal of Botany, 41, 1211-1233.
3. Everson, L. (1949). Preliminary studies to establish laboratory methods for the germination of weed seed. Proceedings of the International Seed Testing Association, 39, 84-89.
4. Henson, I.E. (1970). The effect of light, potassium nitrate and temperature on the germination of Chenopodium album L. Weed Research, 10, 27-39.
5. Herron, J.W. (1953). Study of seed production, seed identification, and seed germination of Chenopodium spp. Memoirs of Cornell University Agricultural Experiment Station, 320, 1-24.
6. Hoffman, G.R., Hogan, M.B. and Stanley, L.D. (1980). Germination of plant species common to reservoir shores in the northern Great Plains.
Bulletin of the Torrey Botanical Club, 107, 506-513.
7. Holm, R.E. and Miller, M.R. (1972). Weed seed germination responses to chemical and physical treatments. Weed Science, 20, 150-153.
8. Jordan, L.S. and Jolliffe, V.A. (1970). Germination and maturation of Chenopodium humile L. Weed Science, 18, 382-385.
9. Karssen, C.M. (1967). The light promoted germination of the seeds of Chenopodium album L. 1. The influence of the incubation time on quantity and rate of the response to red light. Acta Botanica Neerlandica, 16, 156-160.
10. Karssen, C.M. (1970). The light promoted germination of the seeds of Chenopodium album L. III. Effect of the photoperiod during growth and development of the plants on the dormancy of the produced seeds. Acta Botanica Neerlandica, 19, 81-84.
11. Karssen, C.M. (1970). The light promoted germination of the seeds of Chenopodium album L. V. Dark reactions regulating quantity and rate of the response to red light. Acta Botanica Neerlandica, 19, 187-196.
12. Karssen, C.M. (1970). The light promoted germination of the seeds of Chenopodium album L. VI. Pfr requirement during different stages of the germination process. Acta Botanica Neerlandica, 19, 297-312.
13. Karssen, C.M. (1976). Two sites of hormonal action during germination of Chenopodium album seeds. Physiologia Plantarum, 36, 264-270.
14. Khan, A.A. and Karssen, C.M. (1980). Induction of secondary dormancy in Chenopodium bonus-henricus L. seeds by osmotic and high temperature treatments and its prevention by light and growth regulators. Plant Physiology, 66, 175-181.
15. Martin, J.N. (1943). Germination studies of the seeds of some common weeds. Proceedings of the Iowa Academy of Sciences, 50, 221-228.
16. Moursi, M.A., Rizk, T.Y. and El-Deepah, H.R. (1977). Weed seed germination responses to some chemical treatments. Egyptian Journal of Agronomy, 2, 197-209.
17. Murdoch, A.J. (1982). Factors influencing the depletion of annual weed seeds in the soil. Ph.D. Thesis, University of Reading.
18. Roberts, E.H. and Benjamin, S.K. (1979). The interaction of light, nitrate and alternating temperature on the germination of Chenopodium album, Capsella bursa-pastoris and Poa annua before and after chilling. Seed Science and Technology, 7, 379-392.
19. Vincent, E.M. and Roberts, E.H. (1977). The interaction of light, nitrate and alternating temperature in promoting the germination of dormant seeds of common weed species. Seed Science and Technology, 5, 659-670.
20. Vincent, E.M. and Roberts, E.H. (1979). The influence of chilling, light and nitrate on the germination of dormant seeds of common weed species. Seed Science and Technology, 7, 3-14.
21. Watanabe, Y. (1978). [Physiological and ecological studies on upland weeds in Hokkaido.] Research Bulletin of the Hokkaido National Agricultural Experiment Station, 123, 17-77.
22. Williams, J.T. and Harper, J.L. (1965). Seed polymorphism and germination. I. The influence of nitrates and low temperatures on the germination of Chenopodium album. Weed Research, 5, 141-150.
SPINACIA
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S. glabra |
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S. oleracea L. |
spinach, spinage |
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S. turkestanica |
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I. Evidence of dormancy
Seeds of S. oleracea tested for germination at about 20°C or above may exhibit dormancy (1, 12, 18, 20). After-ripening of such seeds at room temperature for 2 months is reported to increase germination from 3% to 29% (20). Seeds of S. turkestanica may show deeper dormancy, requiring 21 months after-ripening to remove dormancy (16).
II. Germination regimes for non-dormant seeds
S. oleracea
TP; BP: 15°C; 10°C: 21d (ISTA)
TP: 15°C; 10°C: 21d (AOSA)
AOSA rules state that the germination test substratum should be relatively dry.
Constant temperatures: 25°C, 10d (7, 19)
S. turkestanica
Constant temperatures: 20°C (16)
III. Unsuccessful dormancy-breaking treatments
S. glabra
Pre-dry: 35°C, 5-7d (5)
S. oleracea
Constant temperatures: 36°C (8); above 35°C (11); 20°C, plus excess moisture (12, 13)
Potassium nitrate: co-applied, 0.6% (12)
Potassium ferricyanide: pre-applied, 2-5h, 0.75-6% (12)
Calcium chloride: pre-applied, 3-6h, 1-10% (12)
Mercuric chloride: pre-applied, 1h, 0.06%, then pre-wash (12)
GA1-3: co-applied, 50 ppm (12)
Hydrogen peroxide: (15)
Polyethylene glycol: pre-applied, 7, 14d, -10 bars, 15°C, germinate at 30°C (17)
Pre-wash: 20°C, 48h, germinate at 30°C (1); 30°C, 24,48h, germinate at 30°C (1)
Pre-soak: plus oxygen, 1, 6 bar (12)
IV. Partly-successful dormancy-breaking treatments
S. oleracea
Constant temperatures: 25°C, 30°C (1); 4°C, 29°C (9); 15°-30°C (11); 10°-20°C, plus excess moisture (12); 18°-20°C (18)
Pre-chill: 0°-2°C, 3-5d (20)
Pre-dry: 30°C, 40°C, 1-60d (20); 50°-60°C, 7d (21); 70°-75°C, 1h (21)
Pre-wash: 5°C, 10°C, 1-48h, germinate at 30°C (1); 20°C, 1-24h, germinate at 30°C (1); 30°C, 1-12h, germinate at 30°C (1)
Pre-soak: plus oxygen, 1.5, 4, 5 bar (12)
Removal of seed covering structures: pericarp, germinate at 30°C (1); cut (10)
Scarification: concentrated sulphuric acid, 20 min (15); sulphuric acid, 50%, 60°C, 5 min (12)
Hydrogen peroxide: pre-applied, 2-6% (12)
Sodium carbonate: pre-applied, 24h, 10% (12)
Calcium hypochlorite: pre-applied, 2h, 0.6% (12)
Polyethylene glycol: pre-applied, 7d, -12.5 bar, 10°C, germinate at 30°C (2); pre-applied, 14d, -12.5 bar, 5°-30°C, germinate at 30°C (2); pre-applied, 14d, -15 to -20 bar, 10°C, germinate at 30°C (2); co-applied, -5.5 bar, at 20°C (12)
V. Successful dormancy-breaking treatments
S. glabra
Constant temperatures: 10°C (5)
S. oleracea
Pre-chill (ISTA)
Constant temperatures: 0°-5°C, plus excess moisture (12); 0°-10°C (11); 0°-25°C (12); 1°-4°C (18); 3°-17°C (3); 5°-20°C (1); 8°-22°C (8,9); 10°C (4,6)
Pre-chill: 5°C, 5d, germinate at 10°C (4)
Pre-soak: plus oxygen, 2-3 bar (12)
Removal of seed covering structures: fruit coat (12, 13); pericarp (18); pericarp, then pre-wash, 24h, 10°C, germinate at 30°C (1); perforate husk in region of root (10)
Oxygen: 100% (18)
Hydrogen peroxide: (14); pre-applied, 3h, 6% (13); pre-applied, 8% (12)
Polyethylene glycol: pre-applied, 14,21d, -12.5 bar, 10°C, germinate at 30°C (2); pre-applied, 7,14d, -10 bar, 20°C, 25°C, germinate at 30°C (17)
S. turkestanica
Constant temperatures: 5°-27°C (16)
VI. Comment
Provided that low temperatures and long enough test periods are provided, problems from seed dormancy in germination tests of accessions of Spinacia spp. will be minimised. Although the rate of germination is highest at 20° or 25°C, the optimum temperature range for total germination is 5°-10°C (11). Consequently it is suggested that the lower of the two constant temperature regimes prescribed by ISTA/AOSA (10°C) be used in gene banks for testing seeds of Spinacia spp.
One possible source of difficulty may be the moisture of the filter papers used in germination tests; if the substratum is too wet percentage germination will be reduced (12,13). Testing for germination at a low temperature should minimise the likelihood of such problems arising (12,13), but nevertheless attempts should be made to maintain a relatively dry germination test substrate.
VII. References
1. Atherton, J.G. and Farooque, A.M. (1983). High temperature and germination in spinach. I. The role of the pericarp. Scientia Horticulturae, 19, 25-32.
2. Atherton, J.G. and Farooque, A.M. (1983). High temperature and germination in spinach. II. Effects of osmotic priming. Scientia Horticulturae, 19, 221-227.
3. Bierhuizen, J.F. and Wagenvoort, W.A. (1974). Some aspects of seed germination in vegetables. I. The determination and application of heat sums and minimum temperature for germination. Scientia Horticulturae, 2, 213-219.
4. Fornerod, C. (1975). Remarques sur la germination des semences potagères en laboratoire. Revue Horticole Suisse, 48, 6-9.
5. Frank, W.J. and Wieringa, G. (1928). Artificial drying and low temperature as means employed in obtaining an increase in germination of some vegetable seeds. Proceedings of the Association of Official Seed Analysts, 19, 24-27.
6. 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.
7. Goyal, R.D., Singh, M.B. and Singh, P.V. (1978). Enhancement of germination of the seeds of spinach (Spinacia oleracea). Seed Research, 6, 145-150.
8. 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.
9. Guy, R. (1981). Influence de la temperature sur la duree de germination des semences de dix espèces potagères. Revue Suisse de Viticulture, d'Arboriculture et d'Horticulture, 13, 219-225.
10. Hagiya, K. (1949). [Studies on the delayed germination in spinach seed.] Journal of the Horticultural Association of Japan, 18, 198-201.
11. Harrington, J.F. (1963). The effect of temperature on the germination of several kinds of vegetable. Proceedings of the 16th International Horticulture Congress, 2, 435-441.
12. Heydecker, W. and Orphanos, P.I. (1968). The effect of excess moisture on the germination of Spinacia oleracea L. Planta, 83, 237-247.
13. Heydecker, W., Orphanos, P.I. and Chetram, R.S. (1969). The importance of air supply during seed germination. Proceedings of the International Seed Testing Association, 34, 297-304.
14. Jensen (1962). [Contribution to discussion.] Proceedings of the International Seed Testing Association, 27, 756.
15. Kerin, V. (1975). [The effect of the chemical treatment of spinach seed on germination.] Gradinarska i Lozarska Nauka, 12, 61-66. (From Horticultural Abstracts, 1975, 45, 8338.)
16. Khalilov, M. Kh. (1977). [Biology of germination of Spinacia turkestanica seeds.] Rastitel'nye Resursy, 13, 518-520. (From Horticultural Abstracts, 1978, 48, 1352.)
17. Nakamura, S., Teranishi, T. and Aoki, M. (1982). [Beneficial effect of polyethylene glycol on the germination of celery and spinach seeds.] Journal of the Japanese Society for Horticultural Science, 50, 461-467.
18. Sifton, H.B. (1927). On the germination of the seed of Spinacia oleracea L. at low temperatures. Annals of Botany, 41, 557 -569.
19. Singh, H. and Kumar, A. (1979). Germination studies on vegetable crops onion, pea and spinach. Journal of Research, India, 16, 164-168.
20. Tamura, T., Ito, K. and Takano, S. (1957). [Breaking of the dormancy of spinach seeds.] Kyushu Agricultural Research, 19, 54-56.
21. Watanabe, S. and Aki, S. (1959). [Effect of heat treatment on germination of spinach, Spinacia oleracea L.J Technical Bulletin of the Faculty of Agriculture, Kagawa University, 10, 20-26.
