Studies on the Effects of Exogenous Nitric Oxide on Rice under Cadmium Stress
|School||Nanjing Agricultural College|
|Keywords||rice (Oryza sativa L.) Cd stress nitric oxide reactive oxygen species (ROS) antioxidant enzymes|
Cadmium (Cd) was a highly toxic and persistent environmental poison, its increasing level in soil environment exerted a wild range of adverse effects on plants and even the healthy of human beings by food chains. Nitric Oxide (NO) was a ubiquitous messenger and effective molecule in biology, and it participated in a series of key physiological processes such as seed germination, plant growth and development, leaf and fruit senescence, programmed cell death, responses to biotic and abiotic stresses such as pest and disease challenge, drought, salinity, low temperature and heavy metal. However, no more information is available regarding the role of NO, a signaling and messenger molecule, in regulation the growth, oxidation and anti-oxidant system of rice seedling under Cd stress. Further, information is lacking whether exogenous NO can alleviate the Cd-induced oxidative stress by quenching ROS and thus prevent cellular membrane lipid peroxidation damage. With this background in mind, a study was conducted to elucidate the role of NO in regulating Cd-induced oxidative stress and physiological changes in rice seedling under hydroponics conditions, and this must will be a great significance to enhance the tolerance to disadvantage environment condition and improve rice yield and quality.In this paper, the rice variety R109 (Oryza sativa L. ssp. Japonica, R109) was selected for the trial to study the effect of exogenous NO donor nitroprusside (solidium nitroprusside, SNP) on growth and membrance lipid peroxidation in rice seedling root and leaf under Cd stress, the main results were presented as follows:1.When the rice seedlings were stressed by 30 mg/L CdCl2 for ten days, the fresh and dry weight of the leaves and roots were all decreased, and the increment of seedling height and root length were also restrained. However, the above inhibited effects of Cd2+ stress could be significant alleviated by certain concentration SNP treatment. The results indicated that exogenous NO can alleviate the inhibited effect of Cd stress on growth of rice seedlings.2. When the rice seedlings were stressed by 30 mg/L CdCl2 for ten days, the content of chlorophyll was significantly inhibited. Pretreatment with lower concentration of exogenous SNP (0 mmol/L～0.1 mmol/L) significantly alleviated the reduced of chlorophyll content in rice seedlings leaves under Cd stress, but exogenous higher concentration of 0.5 mmol/L SNP treatment can exacerbated the reduced of chlorophyll content in rice seedling under Cd stress. These results indicated that exogenous lower concentration NO treatment can alleviate the reduced of chlorophyll content in rice seedling under Cd stress, but higher concentration SNP treatment can exacerbated the damage of photosynthesis of rice seedling leaf under exposure to Cd.3. Compared to control treatment, Cd2+ stressed for ten days caused the raise of MDA content and H2O2 level, and exacerbated the damage of membrance lipid peroxidation in rice seedling leaf and root, it means that oxidant damage was induced in the plant cell under Cd stress. Cd stress also caused the raise of SOD, CAT, GPX and APX activities in leaf and root of rice seedling, so enhanced the ability of scavenging reactive oxygen species (ROS) in plant cell. Exogenous lower concentrations SNP treatment cause a decrease of H2O2 level and MDA contents in leaf and root of rice seedling under Cd stress, and alleviated the membrance lipid peroxidation damage caused by Cd stress. However, there is no significant changes respect to the controls were observed when plants were treated with more higher concentration of SNP in rice seedling leaf and root under Cd stress. Exogenous SNP treatment also can caused an inhibition in the activities of SOD et al antioxidant enzymes in rice seedling exposed to Cd, indicating that exogenous NO treatment alleviated the damage of membrance lipid peroxidation and inhibited the activities of antioxidant enzymes was a results of NO quenching the accumulation of ROS in plant cell.