Sunflower seed development as related to antioxidant enzyme activities.

Abstract

To 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.

The Role - Activity and/or Processing - Of (Re) Active Oxygen Species in Desiccation Sensitivity and/or Tolerance, Development, Dormancy and/or Germination in Seeds

“…Interestingly, it has also been demonstrated that desiccation of developing sunflower seeds is associated with an increase in CAT activity thus leading to decreased H 2 O 2 content and lipid peroxidation damage [94,95]. This study has made it possible to identify the catalase gene as being finely regulated at the transcriptional level by the loss of water which is in accordance with the data obtained with cotton [96] and maize [64] seeds.…”

“…For example, GR activity increases at the onset of dehydration tolerance in French bean seeds [92] whereas it does not change significantly during desiccation of sunflower seeds [94] and decreases in the case of wheat seeds [83].…”

Oxidative events during in vitro regeneration of sunflower

“…Response of antioxidant system to water loss depends on dehydration severity and plant species. For example in leaves of grasses the decline of CAT activity in response to drought was observed, but in sunflower and bean embryos the activity of CAT increased during successive dehydration (Bailly et al 2001(Bailly et al , 2003Fu and Huang 2001). Previously, Siminis et al (1994) and de Marco and Roubelakis- Angelakis (1996) reported in tobacco protoplasts that expression of CAT isoenzyme exhibiting relatively low catalytic activity could be related to the induction of totipotency.…”

Physiological changes and sHSPs genes relative transcription in relation to the acquisition of seed germination during maturation of hybrid rice seed

“…Reactive oxygen species (ROS) are known to occur during seed development, where they have a dual function being either cytotoxic or playing a role in development, dormancy breakage, and defence against biotic and abiotic stresses . The activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) significantly changed during seed development . The small heat shock proteins (sHSPs) are usually undetectable in vegetative tissues under normal growth conditions, but can be induced by environmental stresses and developmental stimuli.…”