Effects Of Isoproturon On The Tolerance To Low-Temperature Stress And The Remission Of Exogenous Sunstance To Freezing Stress In Wheat Seedlings

Low-temperature stress is one of the major abiotic stress which affect wheat growth. And herbicides low-temperature stress after herbicide treatment may lead to growth inhibition and wheat death. Therefore, exploring the effects and physiological mechanisms of isoproturon onthe tolerance to low-temperature stress in wheat seedlings and the remission mechanisms of the cold injury is very important. In this research, three experiments were included:(1) after one day of isoproturon treatment, wheat seedlings were subjected to -2℃ for two days, and then research the effects and physiological mechanisms of isoproturon on the tolerance to low-temperature stress. (2) wheat seedlings were sprayed ABA, AsA and JA, the objective was to research the remission mechanisms of the cold injury. (3) Before sowing, the wheat seeds were subjected to 4℃ and 25℃ for germination. And the objective was to research the physiological mechanisms of cold hardening in germination periodincreased the tolerance to low-temperature stress in wheat seedlings. The main research results are as follows:1. Isoproturon treatment reduced the tolerance to low-temperature stress in wheat seedlingsCompared with the control, isoproturon treatment decreased net photosynthetic rate, maximal photochemical efficiency (Fv/Fm) and actual photochemical efficiency of photosystem Ⅱ (φPSⅡ), and increased the content of MDA, relative conductivity, the superoxide radical production rate (O2.-), the content of (H2O2), the activities of superoxide dismutase (SOD) and peroxidase(POD), and the contents of soluble protein, soluble sugar and free amino acid. In conclusion, isoproturon decreased the tolerance to low-temperature stress in wheat seedlings.2. Exogenous substance enhanced the tolerance to low-temperature stress in wheat seedlingsCompared with the control, exogenousABA, AsA and JA increased maximal photochemical efficiency (Fv/Fm) and actual photochemical efficiency of photosystem Ⅱ (OPSII), and decreased the content of MDA, the superoxide radical production rate (O2.-) and the content of (H2O2), and increased the activities of superoxide dismutase (SOD) and peroxidase(POD) and the contents of osmotic substance. In conclusion, the treatments of exogenous ABA, AsA and JA increased the tolerance to low-temperature stress in wheat seedlings.3. Cold hardening in germination period enhanced the tolerance to low-temperature stress in wheat seedlingsCompared with the control, the treatment of cold hardening in germination periodincreased net photosynthetic rate, maximal photochemical efficiency (Fv/Fm) and actual photochemical efficiency of photosystem II (OPSII), and decreased MDA content and relative conductivity values, and increased the activities of superoxide dismutase (SOD), peroxidase(POD), ascorbate peroxidase (APX), glutathione reductase (GR) and the contents of osmotic substance. In conclusion, the treatments of cold hardening in germination period increased the tolerance to low-temperature stress in wheat seedlings.In conclusion, isoproturon treatment significantly reduced the photosynthetic capacity, increased the production of ROS, decreased osmotic substance contents, enhanced the damage of peroxidation, and eventually decreased the tolerance to low-temperature stress in wheat seedlings. The treatments of exogenous substance and cold hardeningin germination period enhanced the photosynthetic capacity, decreased the production of ROS, increased osmotic substance contents, increased the activities of antioxidant enzyme, decreased the damage of peroxidation, and eventually increased the tolerance to low-temperature stress in wheat seedlings.