| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1989: ¥200,000 (Direct Cost: ¥200,000)
Fiscal Year 1988: ¥200,000 (Direct Cost: ¥200,000)
Fiscal Year 1987: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Research Abstract |
To look into the adaptive strategies of plant populations to high density stress, two cultivars in Brassica juncea C_<ZERN>.et Coss were grown for several generations at high density about 10,000 seeds sown per square meter ( H form ) and at low density, 1 plant / m^2 ( C form, as control).
The H and C forms were initially very similar to characteristics each other, but after a few generations, they began to diverge in several characteristics. The H form had larger seeds, fewer seeds and earlier flowering time than the C form. Also, under high density conditions, the H form had stronger competitive ability than the C form.
To clarify the adaptive strategies to high density stress, variations in seed size and its role in competitive ability were investigated.
The selection for seed size was effective, suggesting that both the H and C forms contained the genetic variations of seed size.
In dense sowing experiments, plants from larger seeds always had an advantage over those from smaller seed
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s. However, in mixed-stand of the H and C forms from the same size seeds, the H form had higher competitive ability than the C form.
Therefore, it appeared that the competitive success of the H form could be affected not only by the seed size, but also by other unknown factors, contributing to the competitive ability.
Although larger seeds germinated more slowly than smaller seeds, the C form was more strongly influenced by seed size at the time of germination than the H form. Also, seed size positively correlated to plant size during the juvenile phase. The attribution of seed size to plant size in the H form was maintained for longer growth periods than in the C form. It was found that the H form had a combination of adaptive characteristics to high density stress.
These results showed that the plant was ensured survival by a high competitive ability under high density stress. The competitive ability could be achieved by a combination of several characteristics including seed size. Seed size characteristics had high heritability and then the remarkable increase of seed size seemed to be attained in the H form. Less
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