Physiological Effects Of ALA On Chilling Tolerance Of Maize Seedlings

Maize(Zea mays L.)is the largest grain crops in Heilongjiang Province.The area of maize production in Heilongjiang Province was about 5.82×106 hm2 and produced about35.44 million tones of maize.Therefore,it's important to guarantee higher yield.As a C4 plant,maize may suffer from several abiotic stress continuously in every phases from germination to maturity.Chilling is one of the commonest meteorological disasters in Heilongjiang Province,it's also one of the major factors which produces adverse effects on maize growth and development.5-aminolevulinic acid(ALA)can improve the low temperature resistance of crops.The objective of this study was to investigate the physiological mechanism of ALA-enhanced low-temperature resistance in maize seedlings as well as the optimal foliar spraying concentration of ALA.The objective of this study was to investigate the seedling growth of exogenous ALAenhanced low-temperature resistance in maize seedlings.This experiment was conducted with maize cultivar ‘Zhengdan958'.According to the result of the preliminary screening test,we decided to use 20mg·L-1 ALA as the treatment concentration at seedling stages at low temperature of 14?/5?(day/night)for 48 h.Plant morphological growth,osmotic adjustment,antioxidant system,photosynthetic system and endogenous hormones were measured.The results showed:Under low temperature stress,different concentrations ALA could promote the growth of maize seedlings,increase antioxid antenzyme activity,reduce the damage to the cell membrance.Put all of these together,20mg·L-1 ALA has the best effect.Compared with low temperature stress treatment,the treatment of 20mg·L-1 ALA,seedling height,leaf area and fresh(dry)weight increased by 30.08% ? 17.66% ? 38.76% and 37.5%,SOD activity and POD activity increased by 27.78% and 36.01%,malondialdehyde(MDA)content and relative electrical conductivity decreased by 25.27% and 38.37%.Under low temperature stress,applying exogenous ALA could increase plant height,leaf area,fresh weight and dry weight,increase contents of proline,soluble sugar and soluble protein.ALA is beneficial to the morphogenesis and material accumulation,enhance the osmotic adjustment ability of seedlings,increased cell concentration to improve the waterholding capacity of cells or tissues and prevent and control the dehydration of cells,so as to stabilize the membrane integrity.(3)Applying exogenous ALA could reduce the contents of MDA,control membrane lipid peroxidation,let down the relative conductivity,and prevent a large number of electrolyte leakage.By increasing the antioxidant enzymes such as SOD,POD,CAT,APX and GR,the contents of antioxidant such as As A and GSH are also increased by accelerating the reduction of O2?-and H2O2,so as to maintain the balance of active oxygen metabolism,enhance the cold resistance of plants.(4)Applying exogenous ALA significantly increased the contents of chlorophyll,chlorophyll a,chlorophyll b and carotenoid,Pn,Gs,Tr and Ci increased significantly,which could increase the net photosynthetic rate and promote stomatal opening and alleviate stomatal limitation.The activity of Ru BP Case and PEP Case increased,ALA alleviate the inhibition of photosynthetic enzyme,so that photosynthetic carbon assimilation could be normal.(5)Under the low temperature stress,exogenous ALA increased the contents of GA and ZR,decreased the content of ABA,and improved the ratio of GA / ABA and ZR / ABA.ALA regulated the endogenous hormone content and balance to alleviate the low temperature stress,thereby improving the cold resistance of maize.