A memória hídrica envolve mudanças na mobilização de reservas durante a germinação de sementes na espécie nativa da Caatinga Cenostigma pyramidale

Abstract

Given that water availability plays a central role in seed germination and is a limiting resource in arid and semi-arid environments, a series of experiments were performed to characterize hydration kinetics, reserve mobilization, and water memory in seeds of Cenostigma pyramidale, a tree legume native to the Caatinga. Germination tests were carried out using the paper roll technique, and the contents of water, reserves, and metabolites were assessed during seed hydration until radicle protrusion. Hydration kinetics during germination fitted into the triphasic pattern, although imbibition began slowly and became fast during phase I. Since water uptake by the testa was slower than that by the embryo during phase I, the testa was clearly involved in the regulation of seed imbibition. In seeds germinated under continuous hydration, oils were mobilized in the cotyledons during phases I and III, and non-reducing sugars in the embryonic axis supported phase II. Seeds exposed to a hydration-dehydration cycle revealed changes in the germination process when they were rehydrated. Water uptake became faster by the intact seed and its different parts (testa, embryonic axis, and cotyledons). Also, seeds germinated under discontinuous hydration retained oils but mobilized carbohydrates in the cotyledons. These findings can contribute to understanding the mechanisms used by C. pyramidale seeds to respond to discontinuous hydration and can be applied to protocols for seedling production.