| Budget Amount *help |
¥3,800,000 (Direct Cost: ¥3,800,000)
Fiscal Year 1987: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 1986: ¥2,500,000 (Direct Cost: ¥2,500,000)
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| Research Abstract |
In order to understand the self-defense mechanism of plants against biotic and abiotic environmental stresses, we studied 1) physiological genetics of internodal elongation under submergence in floating rice, 2) formation of healing callus and susceptibility to fungal disease infection in bean plants as affected by mechanical stimulus, 3) gravity-regulated peg development in cucumber seedlings, and 4) gravitropism and plumular hook formation in an agravitropic mutant pea, ageotropum.
The inheritance of elongating ability under submergence in floating rice was studied using a cross Tan-ginbozu x Aswina. Internodal elongation of F1 plants under submergence showed incomplete dominance. Ability of internodal elongation can be explained in terms of complementary genes, one controls gibberellin production and the other controls responsiveness to ethylene. Mechanical stimulus was found to enhance disease resistance against Phytophthora capsici in bean stem tissues. The mechanical stimulus also
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promoted the formation of healing callus caused by a wounding in bean stem tissues. Endogenous level of cytokinin as affected by mechanical stimulus was suggested to be responsible for the promotive effect on the formation of healing callus. Auxin redistribution induced by gravitational stimulus around the transition zone between the hypocotyl and the roots may be essential for the development of peg in Cucurbitaseae seedlings. A high ethylene level (possibly auxin induced ethylene)in the hook region is, however, required for the peg development. In etiolated seedlings, a mutant pea, ageotropum exhibited agravitropic growth and less ability in forming a plumular hook. This agravitropic growth of the mutant shoots in the dark was suggested to be caused by the lack of the gravity-induced auxin redistribution. The less ability of the mutant shoots in hook formation may be attributed, at least in part, to both the less lateral movement of auxin and the less ethylene production. The results also support the ideas that an increase in ethylene production due to the lateral auxin redistribution plays some role in shoot gravitropism and that gravity may play an important role in the hook formation by means of the modulation of auxin transport and ethylene production. Less
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