The Zingiberaceae comprise about 1400 species of herbaceous plants within about 47 genera which provide spices (e.g. Curcuma domestica Val., turmeric) and medicines (e.g. Languas galanga (L.) Stuntz, greater galangal). The fruits are generally dehiscent capsules or fleshy barries. Seed storage behaviour, where known, is orthodox, but in many genera seed production is irregular and there is little experience of seed storage.
SEED DORMANCY AND GERMINATION
The seeds are generally surrounded by an aril, and possess a linear embryo and both perisperm and endosperm. Dormancy can be considerable. Much of the problem is associated with the seed covering structures and can be reduced by appropriate treatments (see Chapter 7, Volume I). Comparatively high germination test temperatures (e.g. 25°C) may be necessary. Because of the irregularity of fruiting and seed production comparatively few investigations have been undertaken on seed dormancy and germination in the Zingiberaceae. Consequently the information on seed dormancy and germination provided in this chapter is limited to the genera Amomum and Elettaria.
AMOMUM
|
A. subulatum Roxb. |
larger cardamom |
I. Evidence of dormancy
A. subulatum shows orthodox seed storage behaviour and seed dormancy can be considerable with the seeds remaining dormant for 7 to 8 months in nursery sowings (1). Consequently germination is low and the pattern of germination very irregular (1).
II. Germination regimes for non-dormant seeds
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III. Unsuccessful dormancy-breaking treatments
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IV. Partly-successful dormancy-breaking treatments
Alternating temperatures: 30°/17°C (day/night) (1)
V. Successful dormancy-breaking treatments
-
VI. Comment
It is suggested that seeds of Amomum spp. be tested for germination on top of filter papers at 25°C or (preferably) 20°/30°C (16h/8h) in light for at least 3 months. Chipping the imbibed seeds in the germination test may reduce the time taken to germinate.
VII. References
1. Bhowmick, T.P. and Chattopadhyay, S.B. (1960). Germination of seeds of larger cardamom. Science and Culture, 26, 185-186.
ELETTARIA
|
E. cardamomum Maton |
cardamom |
I. Evidence of dormancy
E. cardamomum shows orthodox seed storage behaviour (7), although, of course, longevity is short when air-dry seeds are stored in ambient conditions in the tropics (1,6). Germination is often poor and very irregular (4), with some seeds taking over a year to germinate (4): that is under natural conditions the seeds can remain dormant for considerable periods (1,4). The hard, stony, seed coat is reported to be responsible for the delay to germination in seeds of Elettaria spp. (1).
II. Germination regimes for non-dormant seeds
-
III. Unsuccessful dormancy-breaking treatments
Pre-soak: 12h (1)
IV. Partly-successful dormancy-breaking treatments
Scarification: mechanical, shake with coarse sand (1); concentrated nitric acid, 5 min (3); nitric acid, 25%, 10 min (7,8); acid (2); acid plus 2,4-dichlorophenoxyacetic acid (2); acid, then pre-soak (2); acid, then ethrel, pre-applied (2); concentrated nitric acid, 3,5,10 min (5); nitric acid, 25, 50%, 3 min (5); concentrated acetic acid, 3,5,10 min (5); acetic acid, 50%, 3,5,10 min (5); concentrated hydrochloric acid, 3,5,10 min (5); hydrochloric acid, 50%, 3 min (5); hydrochloric acid, 25%, 3,5,10 min (5)
V. Successful dormancy-breaking treatments
Scarification: acetic acid, 25%, 3,5,10 min (5); nitric acid, 25, 50%, 5,10 min (5); hydrochloric acid, 50%, 5,10 min (5)
VI. Comment
It is evident that the dormancy reported in seeds of Elettaria spp. results from the impermeable seed coat: any procedure which enables the seeds to imbibe moisture promotes germination (1-3,5,7,8). The information summarised above concerns nursery sowings, and information of the precise conditions for germinating seeds of Elettaria spp. is lacking. It is known, however, that relatively high temperatures are required for seed germination, around 25°C or higher (1,3,7). Light and alternating temperatures are probably also beneficial judging from the response of the seeds in the wild (1,4).
It is therefore suggested that seeds of Elettaria spp. be tested for germination on top of filter papers at 25°C or 20°/30°C (16h/8h) in light after chipping the seeds. If acid scarification is preferred then, for one seed lot at least, a 10 minute treatment in either 25% acetic acid or 25% nitric acid was very effective in promoting germination (5). The germination test period should be at least 3 months (1,7,8).
VII. References
1. Abraham, P. (1958). New knowledge for cardamom growers. Indian Farming, 8, 34-38.
2. Anonymous (1978). Cardamom. University of Agricultural Sciences, 14th Annual Report, 1977/1978, Bangalore, India, pp. 147-148.
3. Kololgi, S.D., Pattanshetti, H.V. and Prasad, A.B.N. (1973). Germination of cardamom seeds can be improved by treatment with nitric acid and sowing in plastic house. Current Research, 2, 3.
4. Purseglove, J.W. (1972). Elettaria. In Tropical Crops. Monocotyledons, pp. 528-533. Longmans, London.
5. Reddy, B.G.S., Siddaramaiah, A.L. and Parameswar, N.S. (1973). Ten minutes presowing treatment of cardamom with 50 per cent hydrochloric acid ensures good germination. Current Research, 2, 22.
6. Singh, H.B. (1974). Cardamom (Eletaria cardamomum). In Handbook of plant Introduction in Tropical crops, pp. 130-132, Plant Production and Protection Division, FAO, Rome.
7. Sulikeri, G.S. and Kololgi, S.D. (1977). Seed viability in Cardamom (Elettaria cardamomum Maton). Current Research, 6, 163-164.
8. Sulikeri, G.S. and Kololgi, S.D. (1978). Phyllanthus leaves - a suitable much for cardamom nursery beds. Current Research, 7, 3-4.
