Germination associated ROS production and glutathione redox capacity in two recalcitrant-seeded species differing in seed longevity

Abstract

This study investigated the relationship between germination rate and storage lifespan in two recalcitrant-seeded species, Avicennia marina (Forssk.) Vierh. and Trichilia dregeana Sond., in relation to water uptake and oxidative metabolism. Seeds of A. marina had a higher germination rate and shorter hydrated storage lifespan than T. dregeana. Rapid germination of A. marina seeds was associated with high water uptake rates and an early increase in reactive oxygen species (ROS) production and decline in GSH:GSSG ratio. Slower germination in T. dregeana seeds was associated with lower water uptake rates, delayed onset of the ROS-based trigger for germination, and high GSH:GSSG ratio. Positive correlations (p < 0.05) between ROS production and percent water uptake, and inhibition of germination by ROS scavenging agents confirmed the requirement for heightened ROS levels for germination in both species. Germination rate in recalcitrant seeds appears to be governed by the rate of water uptake and ROS production; the latter being dependent on antioxidant activity. We propose that poor longevity in recalcitrant seeds, such as those of A. marina, is based on high rates of water uptake and low levels of ROS scavenging activity that promote the ROS-based trigger for germination during hydrated storage.