Effect Of Low Temperature And Weak Light Stress On Physiological Characteristics And Leaf Microstructure In Red Kidney Bean Seedlings

In this study,two different varieties of kidney bean seedlings(Phaseolus vulgaris L.)’red kidney bean’and’Xiaohong kidney bean’were used as experimental materials to study the growth,antioxidant system,photosynthetic parameters,chlorophyll fluorescence parameters and leaf microstructure of red kidney bean seedlings under low temperature and weak light[12℃/8℃,and 60μmol/(m~2.s).Foremore,the stree indurance capabilities of the two varieties were compared.The main results are as follows:1.Compared with the control,the plant height,stem diameter,and leaf area of the two varieties of red kidney bean seedlings under low temperature and weak light stress were significantly inhibited,indicating that low temperature and low light reduced the biological yield.The plant height,stem diameter,and leaf area of S.vulgare seedlings were reduced by19%,18%,and 15%,respectively,compared with the control after 7 days of stress treatment.British red kidney beans were reduced by 13.2%,16%,and 13%,respectively,compared to the control.2.Under low temperature and weak light stress,the accumulation rate of oxygen free radicals in red kidney bean leaves increased with the prolong of stress duration,and the MDA content also increased,indicating that membrane lipid peroxidation increased.The activities of antioxidant enzymes SOD,POD and CAT all showed a trend of increasing first and then decreasing.SOD and POD began to decrease after 5 days treatment,and will reach a minimum at 7 days.However,the activity of APX and GSH content showed a downward trend under stress,and all of them were close to normal during the recovery process,indicating that red kidney bean seedlings were synergistically antioxidant by antioxidative substances and antioxidant enzymes.Compared with the British red kidney beans,the S.vulgare beans had a higher rate of oxygen radical accumulation,lower antioxidant enzyme activity and lower GSH content,indicating that the S.vulgare beans were less resistant.3.As low temperature and weak light stress incresed,the content of Chla,Chlb,Chla/b and total chlorophyll content decreased.The Net photosynthetic rate(Pn),Stomatal conductance(Gs)and transpiration rate(Tr)decreased,while intercellular carbon dioxide concentration(Ci)increased.The Maximal efficiency PS II(Fv/Fm),the antenna pigment light harvesting efficiency(Fv’/Fm’),the openness of the PSII reaction center(qP)and the quantum yield of PSII(ФPSⅡ)decreased but antenna heat dissipation(NPQ)increased.Compared to the British red kidney beans,the low temperature and poor light caused more damage to the PSII reaction center of the S.vulgare seedlings.4.Under low temperature and weak light stress,the stomatal density,stomatal opening degree and stomatal opening ratio of leaves all decreased,which may be due to low temperature and weak light inhibiting the carbon assimilation ability of red kidney beans.The partial closure of stomata in leaves maybe a self-regulating effect.Under the stress,the leaf thickness,palisade tissue spongy tissue thickness,and tissue ratio were all decreased,indicating that the arrangement between the cells is loose,which helps to prevent intracellular ice formation,and the leaf area has an increasing trend,which facilitates the plants to capture more light energy.Compared with the British red kidney beans,the low temperature and weak light inhibited the S.vulgare more significantly.In summary,the resistance capability of British red kidney beans to low-temperature and weak light stress is stronger than that of S.vulgare kidney beans,and the damage treatmented with 7d is more significant.Therefore,light should be supplemented in time to relieve the damage caused by the stress.