Regulation Effect Of Calcium Chloride On The Growth Of Summer Maize Under Flooding Stress

Corn is an important food crop in China,which has an important influence on the development of agricultural production in China.Flooding is one of the common natural disasters in the growth of maize.In order to reduce the loss of maize yield under flooding stress,this experiment took summer maize Denghai 662 as the experimental material,and carried out the flooding experiment at the seedling stage and tasseling stage respectively by means of indoor pot experiment and field experiment.The effects of CaCl2 on physiology,morphology and yield of summer maize under waterlogging stress were studied with no flooding as control（CK）,so as to provide a theoretical basis for alleviating summer maize under waterlogging stress.The main research results are as follows:1.After indoor pot waterlogging of maize seedlings,the activities of peroxidase（POD）and catalase（CAT）decreased,the contents of soluble protein and chlorophyll decreased,the content of malondialdehyde（MDA）and the production rate of superoxide anion(O₂^.-)increased,and increased with the extension of waterlogging time.Under the same flooding stress,the antioxidant enzyme POD activity was increased,soluble protein and chlorophyll contents were increased,MDA content and O₂^.-production rate were decreased in the leaves of maize seedlings treated with CaCl2 pretreatment.In seedling stage,MDA content,soluble protein content and chlorophyll content reached significant level after 3 days of flooding stress,and POD activity and O₂^.-production rate all reached significant level after 5 days of flooding stress.These results indicated that leaf spraying CaCl2 could alleviate the damage caused by flooding stress on the growth of maize seedlings and improve the ability of maize seedlings to resist flooding.In addition,under the condition of no flooding,the pretreatment of maize seedlings with CaCl2 pretreatment could increase the dry weight and soluble protein content of shoot to a certain extent,and reduce MDA content and O₂^.-production rate,but the effect was not significant.2.Compared with CK,the root growth of maize seedlings under water was restricted,root activity decreased significantly,root dry weight,total root length,total root surface area,average diameter,number of root tips and number of root tips all showed a downward trend.After pretreatment with leaf spraying CaCl2,the contents of total root length and root dry weight of maize seedlings increased significantly,indicating that CaCl2 could alleviate the damage caused by flooding stress to summer maize roots to a certain extent,and then alleviate the inhibition effect of flooding stress on maize root growth.Under the condition of no flooding,pretreatment with CaCl2 could increase the total root length,total root surface area,root volume and root tip number of maize seedlings to a certain extent,but did not reach a significant level.3.Under field conditions,summer maize was flooded during tasseling stage.The results showed that the activities of antioxidant enzymes POD and CAT decreased significantly,while the content of malondialdehyde and the production rate of superoxide anion(O₂^.-)increased significantly in the leaves of summer maize under 5and 7d flooding stress.Under the same flooding stress,the contents of POD and CAT in leaves of summer corn plants pretreated by foliar spraying of CaCl2 were significantly increased,while the content of MDA and the production rate of O₂^.-were significantly decreased,indicating that foliar spraying of CaCl2 could alleviate the damage caused by flooding stress on summer corn plants.Under the condition of no flooding,the activities of POD and CAT,the content of MDA and the production rate of O₂^.-in the leaves of summer maize sprayed with CaCl2 had no significant changes.Under waterlogging stress,the content of soluble protein in summer maize leaves decreased significantly,while the content of soluble protein in leaves after pretreatment with CaCl2 was increased significantly.These results indicated that foliar spraying CaCl2 was beneficial to osmotic regulation of summer maize under flooding conditions.In the process of flooding stress of summer maize,the relative content of chlorophyll was measured by SPAD using SPAD analyzer,and the SPAD value of summer maize was significantly lower than that of CK when the flooding time was 7days,but the SPAD value of summer maize pre-sprayed with CaCl2 on leaf surface was higher than that of the pure flooded plants,reaching a significant level.These results indicated that leaf spraying CaCl2 could inhibit the decomposition of chlorophyll and reduce the damage caused by flooding stress on summer maize plants.However,under normal growth conditions,leaf spraying CaCl2 had no significant effect on SPAD value in summer maize leaves.4.During tasseling stage,summer maize could significantly reduce the production of wound discharge after being subjected to flooding stress.After 7 days of flooding stress,the damage discharge of summer maize decreased significantly,and the damage discharge of summer maize treated with foliar spraying CaCl2 was higher than that of pure flooding treatment,which reached a significant level.Compared with CK,injury flow was significantly reduced.These results indicated that leaf spraying CaCl2 could alleviate the effect of root growth of summer maize under the condition of flooding.Under normal conditions,spraying CaCl2 had no significant change in the rate of maize damage.Under the treatment of flooding,the total dry matter of summer maize decreased with the extension of flooding time,and the total dry matter of summer maize decreased by 32.8% and 37.7%,respectively,at 5d and 7d of flooding.All reached the level of significance.In terms of the quality of dry matter distribution,quality of dry matter from big to small in turn as follows: grain stem leaf cob bracts sheath.The effect on grain dry matter was the greatest.During the grain filling stage,the grain filling rate and grain weight of summer maize decreased continuously under the influence of flooding stress.At 24 days after flowering,the filling rate of summer maize treated with 7 days of flooding decreased the most,which reached 55.9%.After spraying CaCl2 on the leaves,the dry matter weight of summer maize plants increased,and the dry matter weight of tissues and organs increased.Grain filling rate and grain weight increased.The grain-filling rate increased by 36.7% after 5 days of flooding.After 7 days of flooding,it increased by 3.4%.In terms of yield and its components,compared with CK,panicle length,panicle diameter,number of rows per panicle,number of grains per row,100-grain weight and yield were decreased in different degrees under pure waterlogging treatment.The maximum decrease rate was 21.2%,16.%,15%,24.7%,20.5%,49.3% after 7 days of flooding,respectively.All of them reached significant difference.Under flooding stress,the yield and component factors of summer maize pre-sprayed CaCl2 on leaf surface were increased compared with those of the pure flooding treatment,and the spike length,row number of grains,100-grain weight and yield reached significant water after 5 days of flooding,which were increased by 9.7%,7%,9% and 19.8%,respectively.After 7 days of flooding,panicle diameter,grain number in row and yield reached significant level,which increased by 6%,8.5% and 15.8%,respectively.The results indicated that CaCl2 treatment was helpful to reduce the yield of summer maize under flooding stress.In conclusion,under waterlogging stress,summer maize will cause continuous accumulation of reactive oxygen species,membrane peroxidation,and decreased activity of antioxidant enzymes,which will lead to physiological metabolism abnormalities and affect plant growth and development.To a certain extent,spraying CaCl2 could effectively alleviate the effects of flooding stress on maize physiology and yield.