Effects Of PEG Pretreatment On Antioxidant System And ROS Of Rice Under Water Stress

Drought stress is one of the most important abiotic of plant, and it often hinders the growth and development. Rice (Oryza sativa L.) is an important cereal crop and the model species of monocots. It has mechanism response on environmental stress, which is formed in long-term evolution. The response to all biotic or abiotic stress showed an advance indication. Namely pretreatment enhanced the resistance of rice to the following stress.In this paper, used rice seedlings, antioxidant enzymes (superoxide dismutase SOD, peroxidase POD, catalase CAT, ascorbate peroxidase APX, glutathione reductase GR), antioxidant substances (ascorbic acid AsA and glutathione GsH), and active oxygen (hydrogen peroxide H2O2, superoxide radical O2-) were determined when rice were pretreated 10% PEG before 15% PEG stress. We analysized the effect of PEG pretreatment on enhancing the resistance of rice to the future stress from the antioxidant system.The results were as follows:The defense mechanisms of antioxidant were activated under 15% PEG stress. There was different change tendency of antioxidant enzymes/substances and ROS. SOD, CAT and POD activity were enhanced. However APX and GR activity were enhanced first and then depressed. AsA and GsH content were decreased. H2O2 and O2- content were increased.Effects of PEG pretreatment on antioxidant system and active oxygen (ROS) of rice under water stress indicated that 10% PEG pretreatment enhanced oxidative stress resistance of rice seedlings and then increased its resistance. After 10% PEG pretreatment, the activity of antioxidant enzymes/substances was promoted in comparison with the non-treatment. The content of ROS (H2O2, O2-) was promoted compared with the non-pretreatment. ROS was not scavenged. Under 15% PEG stress again, the activity of antioxidant enzymes and the content of antioxidant substances decreased. The content of ROS increased.Effects of rewatering or non-rewatering treatment on antioxidant system and active oxygen (ROS) of rice under water stress showed that the activity of antioxidant enzyme/substances of rice under rewatering treatment was lower than non-treatment. When seedlings were rewatered, ROS was partly scavenged. The ROS content of rice rewatered was lower than that of non-rewatering. The activity of antioxidant enzymes had different performance under 15% PEG stress again. Except for SOD, the activity of antioxidant enzymes (POD, CAT, APX, GR) of rice rewatered was higher than that of non-rewatering. The rice rewatered of AsA content decreased slower than non-rewatering. The AsA content of rice non-rewaterd was increased and then decreased. The ROS content of rice non-rewatered was increased.