Studies On Anti-oxidative Stress Mechanisms Of Selenium Alleviates Salt Toxicity In Processing Tomato

In this paper, two processing tomato varieties with different salt tolerance were used asexperimental materials and grown hydroponically to study the effects of exogenous selenium（0.05mmol/L Na₂SeO₃） on the photosynthetic characteristics and antioxidant capacity inleaves and the reactive oxygen species （ROS） metabolism and antioxidative system inchloroplast, mitochondria and peroxisomes of processing tomato under NaCl （100mmol/L）stress. The objective was to clarify the possible anti-oxidative stress mechanism of Se onalleviating salt toxicity in processing tomato.The main results are summarized as follows:1. Under salt stress, exogenous selenium can decrease the contents of H₂O₂and MDA,increase SOD, POD and GR activities and the GSH and AsA contents, slow the decline rateof E, Pn and Gs in leaves of processing tomato seedling. So the exogenous Se can improvethe adaptability of processing tomato to salt stress and maintain higher photosynthetic rate bydecreasing the accumulation of reactive oxygen species H₂O₂and alleviating the degree ofmembrane lipid peroxidation.2. Under salt stress, application of exogenous selenium remarkly improved the ratio ofGSH/GSSH, AsA/DHA and NADPH/NADP⁺and the activities of GR, GPX, TrxR andother antioxidant enzyme involved in AsA-GSH cycle and Grx and Trx system and reducedthe H₂O₂and membrane lipid peroxidation level in chloroplasts and mitochondria ofprocessing tomato. So, selenium increased the ability of scavenging ROS in chloroplast andmitochondria, resulting in lower H₂O₂content and lipid peroxidation, and higher membranestability under salt stress, which eventually led to the remarkable increase of respiration andphotosynthesis. Therefore exogenous Se can improve the salt tolerance and anti-oxidativestress ability of processing tomato by enhancing the ROS scavenging capacity and maintainhigher levels of redox ratio in chloroplasts of leaves and mitochondrials of leaves and rootsunder salt stress.3. Additional Se for salt-stressed processing tomato significantly decreased H₂O₂andMDA contents, but increased CAT, APX and MDHAR activity and AsA content, ASA/DHAratio in peroxisomes of processing tomato leaf, thus easing the salt poisoning. Se also canalleviate the damage caused by the salt poisoning by increasing the scavenging capacity ofH₂O₂in peroxisomes of leaves under salt stess.From above results, it could be concluded thatselenium nutrition alleviated the salt damage by improving antioxididant responses andphysiological activity in leaves and the sub-cellular fractions of processing tomato, andimproving its adaptability to salt stress.4. Salt tolerance of processing tomato related to antioxidant enzyme activity andreduction capability. Under salt stress, the processing tomato varieties with stronger salttolerance had higher antioxidant enzyme activity and reduce capability, and stronger ROS scavenging ability and lower degree of membrane lipid peroxidation in leaf tissue,chloroplasts, mitochondria and peroxisomes of processing tomato, which can reduce the saltstress injury.