Desiccation-Tolerant and Desiccation-Intolerant Stages during the Development and Germination ofPhaseolus vulgarisSeeds

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Abstract
Embryonic axes of Phaseolus vulgaris undergo a transition from desiccation-intolerance to desiccation-tolerance in the course of their development. Biochemical and ultrastructural observations indicate that desiccation and rehydration during the early intolerant developmental stages drastically reduces the metabolic and cellular integrity of the axis. During the desiccation-tolerant stage such perturbations do not occur. Coincident with the acquisition of desiccation-tolerance during development the seeds gain the capacity to germinate upon subsequent rehydration. Drying presumably acts to terminate developmental processes and to initiate the metabolic processes essential for the completion of germination. During germination of the mature axis, desiccation and rehydration, up to 12 h from the start of imbibition, does not affect subsequent seedling growth and development. But gradually desiccation-tolerance decreases and metabolism is severely and irreversibly reduced by drying.