Abscisic acid and the antioxidant system are involved in germination of Butia capitata seeds

Abstract

Seed germination is an important step for plants without vegetative propagation and is a physiological process that begins with specific environmental cues resulting in biochemical responses. Breaking-dormancy is necessary to study germination in dormant seeds with asynchronous germination. We investigated the processes of breaking dormancy and germination of Butia capitata (Arecaceae) seeds, in which germination is slow and asynchronous, by operculum removal. This treatment increased germination of B. capitata to 90 %. Embryos of dry, imbibed, 24-hours post-operculum removal and early-germinated seeds were collected for biochemical analysis of the following: quantification of abscisic acid (ABA) and hydrogen peroxide (H2O2), activities of antioxidant enzymes (catalase - CAT, superoxide dismutase - SOD, glutathione reductase - GR) and histolocalization of superoxide anion (O2 -). Decreases in H2O2 and ABA were recorded 24 hours post-operculum removal. Increased GR and SOD activities during imbibition, and CAT upon germination, indicate a role in controlling reactive oxygen species. Interestingly, the accumulation of O2 - on the haustorium upon imbibition seems to be involved in germination, instead of H2O2. For B. capitata seeds, signaling from the removal of the operculum probably resulted in ABA catabolism mediated by O2 -, which thus promoted seed germination.