Aspectos fisiológicos, celulares e moleculares da tolerância à dessecação em sementes de Anadenanthera colubrina durante a germinação

Abstract

During germination, orthodox seeds gradually become tolerant to desiccation, and start behaving as recalcitrant seeds. In this work, Anadenanthera colubrina seeds in germination process were used for the better understanding of the sensitivity to desiccation during germination. Initially, the seeds were soaked for 0 (control), 2, 8, 12 and approximately 16 hours (germinated seeds with 1 mm of radicle). Subsequently, we performed drying for 72 hours and up to 70, 50 and 30% of registered humidity in each soaking period of time. The seeds were rehydrated and the survival was evaluated. During the soaking we performed cytometric and ultra-structural, enzyme peroxidase analyses and extraction of proteins resistant to heat. After the soaking and drying we evaluated the DNA integrity and ultra-structural damages. The tolerance to desiccation was completely lots after radicular protrusion. There was no integrity loss and increase of 4C DNA content after the tolerance to desiccation was lost. Ultra-structural characteristics of 1 mm radicular cells were similar to those found in recalcitrant seeds in the hydrated state as well as in the dehydrated state. The loss of tolerance to desiccation was concluded with the reduction of the content of proteins resistant to heat and of the peroxidase enzyme