Sunflower seed development as related to antioxidant enzyme activities.

Abstract

AbstractTo determine the effect of changes in detoxifying enzyme activities on seed vigour during seed development and the effects of artificial drying on free-radical scavenging and lipid peroxidation, sunflower (cv. Fructidor) plants were grown in 1999 in France. Flower-heads harvested at 29-55 days after anthesis (DAA) were air-dried at room temperature for at least 7 days until seed moisture content (SMC) reached ∼4.5% FW. Vigour was estimated by the mean time to germination (MTG) of seeds placed at 15 or 20°C in darkness on water- or polyethylene glycol-soaked filter paper. SMC decreased during seed development and was ∼15% FW at full maturity (58 DAA). At the end of seed filling (∼42 DAA), the mean SMC was 38% FW, while the mean seed dry weight was 53 mg. As the medium water potential decreased, the germination rate decreased; but the sensitivity of seeds to water potential progressively decreased during their development. A linear positive relationship existed between seed resistance to controlled deterioration and SMC at harvest. Superoxide dismutase activity was slightly higher in dried seeds than fresh seeds, regardless of the developmental stage. Catalase activity increased during reserve accumulation and seed desiccation in plant until SMC dropped to ∼30% FW (47 DAA) and then remained constant. Fresh seed artificial desiccation resulted in catalase activity increase, at least when initial SMC was >30% FW. Glutathione reductase [glutathione reductase (NADPH)] (GR) activity decreased during seed filling then remained almost constant during further dehydration. Artificial drying decreased GR activity at all developmental stages.