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

在水稻研究组，研究了可能的非生物胁迫的生态生理基础，主要成果如下：(1)低淹条件下出苗与糊粉层中受m-RNA转录过程调控的β-淀粉酶的表达密切相关，(2)香附在营养含量较低的湖水中生长显著高于水稻(Kubota)的生长，(3)阐明了香附耐低温的生理背景(Terashima)；(4)阐明了旱稻的耐旱机制(Kobata)；(5)阐明了旱稻的耐盐机制(土屋和平井)；(6)阐明了旱稻对酸性土壤的耐性机制(Yamagishi)。在旱作群体中，研究了旱作作物的耐旱机制，得出以下结论：(1)干物质向地下和地上部分分配的不同影响了旱稻的耐旱性，这种分配比例的调节导致了水分胁迫条件下生长的增加(岩间)；(2)阐明了根系生长模式与耐性的关系(Yamuchi)；(3)阐明了大豆生长后期对逆境的差异生长的生理机制(Ishihara)。通过这些试验，阐明了作物耐逆性与产量之间的权衡关系以及耐逆性的生态生理基础。

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.