Discontinuous hydration changes reserve mobilization during seed germination in the Caatinga native species Cenostigma pyramidale

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 and reserve mobilization under continuous and discontinuous hydration in the seeds of Cenostigma pyramidale, a tree legume native to the Brazilian dry forest known as 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 revealed a biphasic pattern, although imbibition began slowly and became fast during phase I. Since water uptake by the testa and cotyledons was slower than that by the embryonic axis during phase I, both testa and cotyledons seem to be involved in the regulation of seed imbibition. In seeds germinated under continuous hydration, oils were mobilized in the cotyledons during phase I and radicle protrusion, and non-reducing sugars in the embryonic axis supported phase II. Seeds exposed to a hydration-dehydration cycle took up water faster than seeds that had not previously been exposed to water. 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.