A contrasting modulation of biomass partitioning toward seed filing as strategy in response to water limitation.
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A strong dynamic variation in number of complete seeds occurs independently of susceptibility and the tolerance genotype.
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The soluble sugars and starch accumulation in source tissues is modified in seed filling.
Abstract
Common bean (Phaseolus vulgaris L.) is one of the major sources of dietary protein for humans in Africa and Latin America. Efficient remobilization of storage materials accumulated in different tissues to seeds is one of the few alternatives that plants have to produce viable seeds under stress conditions. The aim of this study was to evaluate the biomass remobilization in two common bean (Phaseolus vulgaris L.) cultivars under water restriction. We hypothesize that under water restriction both cultivars exhibit a different pattern of remobilization of assimilates toward the seed. Plants of cv. V8025 and Canario-60 were irrigated to field capacity until starting seed filling stage under greenhouse conditions. At 63 days after sowing, one group of plants was continued watering and another group was suspended watering. Five plants of each treatment were harvested starting watering halted (0 days) and after 5, 10 and 20 days. Dry mass of stem, branch, leaves, pod wall, seeds and yield components were evaluated; glucose, fructose, sucrose and starch in leaves and pods wall were calculated. In Canario-60 number of seeds and harvest index were not affected by water restriction; in contrast, in V8025 were strongly reduced. Both cultivars modified pattern of soluble sugars and starch accumulation in leaves in response to water restriction. Pods of both cultivars showed efficient degradation of starch. Canario-60 was also efficient for soluble sugars remobilization and contrasted with V8025. Results suggest that the capacity to translocate soluble sugars from pod wall or leaves to seeds filling could be an important adaptive response of common bean cultivars when stress for water restriction affects plants during grain filling periods.
