The Role of Maturation Drying in the Transition from Seed Development to Germination

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Abstract
Kermode, A. R. and Bewley, J. D. 1985. The role of maturation drying in the transition from seed development to germination. 1. Acquisition of desiccation–tolerance and germinability during development of Ricinus communis L. seeds.—J. exp. Bot. 36: 1906–1915. Seeds of Ricinus communis L. cv. Hale (castor bean) undergo a transition from desiccation–intolerance to desiccation–tolerance approximately midway through their development. Tolerance of slow desiccation is gained over only a few days of development (between 20 and 25 d) and is achieved well before the completion of major developmental events, such as reserve deposition and the onset of normal maturation drying. A tolerance of very rapid water loss brought about by drying over silica gel is not acquired by this seed until near maturity. Coincident with the acquisition of tolerance to slow desiccation the seeds gain the capacity to germinate upon subsequent rehydration. Germinability and capacity for normal post–germinative growth during the tolerant phase are not fully expressed unless the seed is dried at an optimal rate, which is dependent upon the developmental stage of the seed. Drying presumably acts to terminate developmental processes and to initiate those metabolic processes necessary to prepare the seed for germination and growth.