Effects Of Low Temperature And Strong Light Stress On Physiological And Photosynthetic Characteristics Of Red Kidney Bean Seedlings

In order to clarify the changes in the photosynthetic fluorescence and antioxidant system parameters of red kidney bean seedlings under low temperature and strong light,the effects of low temperature and strong light on red kidney bean were analyzed.The experiments were conducted under conditions of low temperature and strong light（light intensity of 30000Lx,photoperiod of 8h/16h,and day/night temperature of 15°C/8°C）.Red kidney beans and kidney beans of Shanxi were used as materials to determine the relevant indexes of photosynthetic and physiological characteristics.,The results show:1.With the prolongation of stress time,the oxygen free radicals(O^2-content,H₂O₂content)and MDA content in the leaves of two species of cowpea bean increased continuously,and the contents of antioxidative substance AsA,antioxidant enzyme SOD activity,CAT activity and APX activity were both increased.The activity of POD increased continuously;after returning to normal conditions,the content of O^2-and H₂O₂ gradually returned to the control level,while the content of MDA was still significantly higher than that of the control,and the activity of enzyme POD was still rising,starting at the second day of recovery.After the decrease,the APX and CAT activities basically recovered to the control level,while the POD and SOD changed significantly,but did not return to the control level.These results indicate that the balance of production and clearance of active oxygen in red kidney bean leaves under low temperature and high light stress is destroyed,and the degree of membrane peroxidation continues to deepen,but active oxygen can be eliminated after recovering to normal light and temperature conditions.All of them have undergone significant changes,indicating that the damages caused by the established treatments can be gradually restored under normal conditions,and the response mechanisms between varieties to low temperature,strong light stress and recovery are significantly different.2.The prolongation of time under low temperature and strong light stress,and the intercellular CO₂ concentration gradually increased.After normal conditions were restored,they were compared with the control.The differences were all decreasing;the total chlorophyll content and chlorophyll a content both showed a downward trend under low temperature and high light stress,and Chla/b increased significantly.Chlorophyll a decreased significantly at the 5th day and the chlorophyll b changed little.After a downward trend and return to normal conditions,the chlorophyll content keeps rising and changes obviously,but it is still lower than the control on the 3rd day of recovery.The stomatal density of two red kidney beans increased at low temperature and strong light,while the stomatal opening and stomatal opening ratios both showed a decreasing trend,and all had significant changes in the recovery phase.The results showed that the photosynthetic pigment degradation and the stomatal conductance and opening degree of the red kidney bean were degraded by low temperature and strong light,which led to the decrease of photosynthetic rate.The number of stomata increased and Ci increased significantly.The non-stomatal factor decreased the net photosynthetic rate of red kidney bean.The main reason.3.The results showed that the decrease of D₁ protein content resulted in the destruction of the reaction center of PSII;the decrease in antenna light trapping efficiency Fv’/Fm’,the opening degree of the PSII reaction center qp,and the heat dissipation capacity of the antenna pigment（NPQ）rose.High the reduction in quantum yieldφPSII for photosynthetic electron transport indicates that the photosynthesis intensity is directly related to the absorption and utilization of light energy in the PSII reaction center and the protection capability of the photosynthetic apparatus（NPQ）;the photochemical quenching coefficient is decreased,not The photochemical quenching coefficient is increased,and the light energy captured by the antenna pigment is used to reduce the photochemical reaction.Through the antenna heat dissipation and other heat dissipation energy increases,the excess light energy causes greater damage to the red kidney bean.