Trade-offs among traits related with stress tolerance and the morphological and physiological basis for optimum regulation of them for improved crop yield

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In rice study group, eco-physiological basis for the possible abiotic stresses was studied and the followings were the major outputs : (1) seedling emergence in low and submerged condition was closely associated with the expression of beta-amylase in aleuron layr, which is regulated in the transcription process of m-RNA (Akita) ; (2) remarkable increase of growth of Cyperus was observed when it was grown in the lake water in which nutrient content is low in comparison with the limited increase of growth in rice (Kubota) ; (3) physiological background for the tolerance to low temperature was elucidated (Terashima) ; (4) tolerance mechanism of upland rice to drought was clarified (Kobata) ; (5) mechanism of tolerance to salt stress was clarified (Tsuchiya and Hirai) ; and sldo (6) mechanism of tolerance to acid soil was elucidated (Yamagishi).In upland crops group, the mechanism of the drought stress tolerance was studied and the following results were obtained : (1) the differential dry matter partitioning to underground and aerial parts affects the tolerance to drought and the regulation of this partitioning ratio resulted in the increased growth under water stress condition (Iwama) ; (2) the relationship between root growth pattern and the tolerance were clarified (Yamauchi) ; (3) the physiological mechanism of differential growth of soybean to stress condition in late growth stage was clarified (Ishihara). Through these experiments, the trade-offs between stress tolerance and crop yield were also elucidated as well as the eco-physiological basis for stress tolerance.