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Watermelon seed germination. 1. Effects of light, temperature and osmotica

Published online by Cambridge University Press:  19 September 2008

C. A. Thanos  and
K. Mitrakos
C. A. Thanos*
Affiliation:
Institute of General Botany, University of Athens, 15784 Athens, Greece
K. Mitrakos
Affiliation:
Institute of General Botany, University of Athens, 15784 Athens, Greece
*
* Correspondence
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Abstract

Seeds of watermelon (Citrullus lanatus cv. Sugar Baby) germinated optimally in the dark, throughout the range 20–40°C. Germination was inhibited by continuous (c) irradiation with farred (FR), blue or white incandescent light; short pulses were ineffective. Intermittent FR could fully substitute for cFR; the effect of alternating red and FR pulses during 30-min dark cycles depended upon the timing of the illuminations within each cycle. It is concluded that germination in watermelon is controlled by the low-energy reaction of phytochrome. However, continuous and intermittent red light resulted in partial reductions in germinability. Opening the seed coat at the radicle end enhanced germination in the dark and reduced photosensitivity towards FR. The outer, lignified part of the testa exerted a mechanically restrictive force upon the expanding radicle; this force was estimated to be equivalent to 0.3 MPa. The kinetics, at 25°C in the dark, of the time course of germination and the escape from the inhibitory actions of cFR and osmoticum (0.5m mannitol) were all sigmoid curves, which, upon transformation to normal distributions, had different means, but statistically similar variances. The cFR-irreversible activation of germination by phytochrome and the mannitol-irreversible onset of radicle elongation preceded radicle protrusion (mean at 32 h, 25°C) by 8 and 6 h, respectively. From the results and data on imbition, it is concluded that activation of germination in watermelon takes place during the second, stationary phase of imbibition (20–30 h after sowing at 25°C).

Keywords

Citrullus lanatusosmotic inhibitionphotoinhibitionphytochromeseed coatgerminationwatermelon
Type
Research Papers
Information
Seed Science Research , Volume 2 , Issue 3 , September 1992 , pp. 155 - 162
Copyright
Copyright © Cambridge University Press 1992

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References

Bartley, M.R. and Frankland, B. (1982) Analysis of the dual role of phytochrome in the photoinhibition of seed germination. Nature 300, 750–752.CrossRefGoogle Scholar
Bewley, J.D. and Black, M. (1982) Physiology and biochemistry of seeds in relation to germination. Vol. 2, Viability, dormancy and environmental control. Berlin, Springer-Verlag.Google Scholar
Bhatnagar, S.P. and Johri, B.M. (1972) Development of angiosperm seeds. pp. 77–149 in Kozlowski, T.T. (Ed.) Seed biology. Vol. I. Importance, development and germination. New York, Academic Press.Google Scholar
Botha, F.C. and Small, J.G.C. (1988) The germination response of the negatively photoblastic seeds of Citrullus lanatus to light of different spectral compositions. Journal of Plant Physiology 132, 750–753.CrossRefGoogle Scholar
Botha, F.C., Grobbelaar, N. and Small, J.G.C. (1982a) Seed germination of Citrullus lanatus. Part 1. Effect of white light and growth substances on germination. South African Journal of Botany 1, 10–13.Google Scholar
Botha, F.C., Small, J.G.C. and Grobbelaar, N. (1982b) Seed germination of Citrullus lanatus. Part 2. The involvement of phytochrome and ethylene in controlling light sensitivity. South African Journal of Botany 1, 131–133.CrossRefGoogle Scholar
Botha, F.C., Grobbelaar, N. and Small, J.G.C. (1984) The effect of water stress on the germination of Citrullus lanatus seeds. South African Journal of Botany 3, 111–114.Google Scholar
Koller, D., Poljakoff-Mayber, A., Berg, A. and Diskin, T. (1963) Germination-regulating mechanisms in Citrullus colocynthis. American Journal of Botany 50, 597–603.Google Scholar
Lorenz, O.A. and Maynard, D.N. (1980) Knott's handbook for vegetable growers, 2nd edn. New York Wiley.Google Scholar
Loy, J.B. and Evensen, K.B. (1979) Phytochrome regulation of seed germination in a dwarf strain of watermelon. Journal of the American Society for Horticultural Science 104, 496–499.Google Scholar
McDonough, W.T. (1967) Dormant and non-dormant seeds: similar germination responses when osmotically inhibited. Nature 214, 1147–1148.CrossRefGoogle Scholar
Nakamura, S., Okasako, Y. and Yamada, E. (1955) Effect of light on the germination of vegetable seeds. Engei Gakkai Zasshi 24, 17–28 [in Japanese].Google Scholar
Noronha, A., Vicente, M. and Felippe, G.M. (1978) Photocontrol of germination of Cucumis anguria L. Biologia Plantarum 20, 281–286.CrossRefGoogle Scholar
Sachs, M. (1977) Priming of watermelon seeds for low-temperature germination. Journal of the American Society for Horticultural Science 102, 175–178.CrossRefGoogle Scholar
Taylorson, R.B. (1991) Inhibition of germination in Amaranthus albus seeds by prolonged irradiation: a physiological basis. Seed Science Research 1, 51–56.Google Scholar
Thanos, C.A. (1984) Phytochrome-mediated accumulation of free amino acids in radicles of germinating watermelon seeds. Physiologia Plantarum 60, 422–426.CrossRefGoogle Scholar
Thanos, C.A., Georghiou, K., Douma, D.J. and Marangaki, C.J. (1991) Photoinhibition of seed germination in Mediterranean maritime plants. Annals of Botany 68, 469–475.Google Scholar
van der Pijl, L. (1972) Principles of dispersal in higher plants, 2nd edn. Berlin, Springer-Verlag.CrossRefGoogle Scholar
Welbaum, G.E. and Bradford, K.J. (1990) Water relations of seed development and germination in muskmelon (Cucumis melo L.). IV. Characteristics of the perisperm during seed development. Plant Physiology 92, 1038–1045.CrossRefGoogle ScholarPubMed
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.Google Scholar