The Protection Of Calcium To Peanut Seedlings Under High Temperature And High Light

Peanut is an important oil crop in China and its cultivation area is very large. Peanutplays an important role in the national economy. In the field, it must face to all kinds ofenvironment stresses. In the northern of China, peanuts usually suffer severe environmentstress induced by high light and high temperature in summer. Studies have reported thatcalcium can reduce environmental damage to cell membranes when plants subjected to heatand high light stress. However, most of which focused on the phenotype with lacking ofspecific physiological indicators. In our study, the role of calcium to peanuts photosystemswas studied under heat and high light by using0mM Ca²⁺（CK）,6mM Ca²⁺,12mM Ca²⁺（experiment group）Hoagland nutrient solution to culture peanut variety HuaYu22,respectively. After20-25days, seedlings were used to be as materials for determination. Themain results are as follows:（1） Under normal growth conditions, plant height, fresh weight, root to shoot ratio, dryweight of the experimental groups are significantly higher than that of the control groups,especially those of the plants cultured with12mM Ca²⁺. The height of plants cultured in6mM Ca²⁺and12mM Ca²⁺Hoagland nutrient solution was1.12and1.19-fold of that of thecontrol group, respectively; fresh weight was1.33and1.29-fold, respectively; and dryweight was1.32and1.47fold, respectively. The roots of the experimental group weresignificantly longer than those of the control group, and the number of lateral roots was alsomore than that of the control group.（2） The experimental group’s chlorophyll content, root activity and soluble proteincontent are obvious higher than that of the control group under both normal growth conditionsand high temperature high light stress. The maximum photochemical efficiency of PSII（Fv/Fm） and fluorescence quenching （qp） of the experimental group were higher comparedwith those of the control group under both normal growth conditions and stress.（3） The contents of some protective substances, e.g. soluble sugar, proline and ascorbicacid in experimental group, were significantly higher than those of the control. The SOD,CAT and APX activity were significantly inhibited by calcium ion depressor, and thedifference among effects of different calcium antagonists was little on peanut plants. Thecontents of reactive oxygen species in experimental plant leaves were lower than those in thecontrol group. DAB and NBT staining showed that the color of staining was deeper in the control group, while the experimental group showed no obvious change. MDA as a plantmembrane lipid oxidation of the main indicators, its content of the experimental group undernormal growth conditions was significantly lower than that in the control group, andsignificantly higher when treatment with calcium antagonist.（4） Calcium could protect peanut thylakoid membrane. After5h heat and light stress,peanut thylakoid membrane complex are damaged by the stress in different degrees. Whilephotosystem II monomer in the control group has been a serious injury compared with theexperimental group. In order to further validate our experimental results, western blot analysiswas used to analyze peanut thylakoid membrane protein LHCII, D1and D2protein. Theresults showed that calcium ions in different levels can protect peanut membrane proteincomponents under both normal conditions and heat and high light stress.In short, calcium ions can protect the photosystems of peanut under high temperature andirradiation by improving the enzyme activities to alleviate the accumulation of ROS.