Alterações na tolerância à dessecação e nas taxas respiratórias de sementes imaturas de Caesalpinia echinata Lam

Abstract

Seed storage is an important tool for ex situ conservation. Orthodox seeds can be stored for long periods, but recalcitrant seeds generally only for short periods. There is wide variation in the degree of desiccation tolerance between orthodox and recalcitrant seeds, leading authors to suggest levels of recalcitrance and, more recently, that there are variations in the stage of maturity at seed dispersal. Thus, recalcitrant behavior would be a result of premature dispersal from the mother plant. In this study, we sought to establish physiological relationships between different stages of development of immature orthodox Caesalpinia echinata seeds and the stages described for recalcitrant seeds to verify similarity of behavior. Therefore, we analyzed the desiccation tolerance of seeds collected at different ages, with and without PEG treatment, at different levels of drying (40%, 30%, 20% and 10% water content, wet basis). Changes in water potential, germination, vigor, and respiratory rates of the seeds were analyzed, and the results showed that: 1) desiccation tolerance increased as maturation proceeded; 2) PEG treatment did not induce desiccation tolerance; and 3) PEG treatment decreased the seed oxidation rate, which is the main factor in rapid seed deterioration of C. echinata in storage.