Effects Of Acid And Alkali Stress On The Growth And Physiological Characteristics Of Winter Wheat Seedlings

Soil acidity-alkalinity is an important environmental factor affecting crop growth.The optimum soil p H for wheat growth is 6.5-7.0,and both acidic or alkaline soil are not conducive to the growth of wheat.Human activities and changes of natural environment accelerate the process of soil degradation,but soil improvement has problems such as long cost cycle and high cost.It is important to study the changes of physiological characteristics of wheat under acid and alkali stress for wheat stress resistance cultivation.This study was conducted in the Wheat Center of Henan Institute of Science and Technology from 2019 to 2020.Aikang 58（AK58）and Bainong 4199（BN4199）were selected as experimental materials,and the nutrient solution hydroponic method was used to set p H 4.0（acid treatment）and p H 6.5（Control）and p H 9.0（alkali treatment）three p H gradient to study the effect of acid-alkali stress on the growth and physiological characteristics of winter wheat at seedling stage.The main research results were as follows:1 Effects of acid-alkali stress on the growth of wheat seedlingsAcid and alkali treatments inhibited the accumulation of root and shoot biomass of the two cultivars, and acid stress inhibited the accumulation of plant biomass more than alkali stress.Compared with the control,the root/shoot ratio of the two varieties decreased under acid stress but increased under alkaline stress.The plant biomass accumulation and root/shoot ratio of BN4199 were higher than those of AK58 under acid-alkali stress.2 Effects of acid-alkali stress on antioxidant enzyme activities and root structure of wheat seedlingsThe activities of SOD,POD and CAT in root of the two cultivars under acid and alkali treatment decreased compared with the control.Compared with the control,the shoot of SOD activity increased under alkali stress,but the CAT activity decreased,while the shoot of SOD and CAT activity decreased under acid stress.The MDA content in root and shoot of both cultivars were increased compared with the control.The activities of antioxidant enzymes in roots and shoots of both cultivars under alkali stress were higher than those under acid stress,and the degree of membrane lipid peroxidation was lower than that under acid stress.Under acid-alkali stress,the antioxidant enzymes activities of BN4199 were higher than those of AK58,and MDA content is lower than that of AK58.3 Effects of acid-alkali stress on the root structure of wheat seedlingsThe root length,root surface area,root volume and root tip number of the two varieties were showed p H 6.5>p H 9.0>p H 4.0 under acid and alkali treatments,and the root diameter decreased with the increase of p H.The root anatomical structure of the two varieties was less damaged under alkali treatment than that of control,and acid treatment was more damaged than that of control,and the root anatomical structure under alkali treatment was better than that under acid treatment.The root structure of BN4199 was better than that of AK58 under acid-alkali stress.4 Effects of acid-alkali stress on physiological characteristics of wheat seedling rootsCompared with the control,the root H⁺net flux of the two varieties was reduced under acid treatment,but it increased under alkali treatment.The root vigor and root p H of both varieties increased with the increase of p H,and the root p H was close to neutral regardless of whether the rhizosphere was acidic or alkaline.Under acid-alkali stress,the root H⁺net efflux rate and root vigor of BN4199 were higher than those of AK58,and changes of root p H was smaller than that of AK58.5 Effect of acid-alkali stress on nitrogen metabolism of wheat seedlingsUnder acid treatment,the root NO₃^-net flux of the two varieties showed a decreasing-increasing-decreasing trend,but the NO₃^-net flux was significantly lower than that of the control.Under alkali treatment,the root NO₃^-net flux increased significantly compared with the control and then began to decrease.There was no significant difference in root NO₃^-net flux between the two varieties at p H 6.5 and p H 9.0,but the root NO₃^-net flux of BN4199 was significantly higher than that of AK58 at p H 4.0.The NR activity in the root of AK58 was showed p H 6.5>p H 9.0>p H 4.0,and the NR activity in the shoot increased with the increase of p H.The NR activity in root and shoot of BN4199 under different p H conditions showed p H 9.0>p H 6.5>p H 4.0,and the difference between treatments was significant.The GS activity in the roots of the two varieties showed p H 6.5>p H 9.0>p H 4.0.The GS activity in root and shoot of BN4199 was significantly higher than that of AK58 under different p H conditions.The N content in roots of the two cultivars was significantly higher at p H 9.0 than that of other p H treatments,and there was no significant difference of N content in roots of the two cultivars at p H 6.5 and p H 4.0.The N content in root of BN4199was significantly higher than that of AK58 at p H 9.0.The N content in shoot of BN4199 showed no significant difference between p H values,which was showed p H 9.0>p H 6.5>p H 4.0,the N content in shoots of AK58 was showed p H 6.5>p H 9.0>p H 4.0,and N content in shoot of BN4199 was significantly higher than that of AK58 under acid-alkali stress.6 Effects of acid-alkali stress on endogenous hormone content in wheat seedlings.Compared with the control,the contents of ZT and IAA decreased and ABA increased under acid stress,while the content of IAA decreased and the contents of ZT and ABA increased under alkali stress,and the ratios of ZT/ABA and IAA/ABA of the two cultivars under acid stress were lower than those of the control,while the ratio of ZT/ABA under alkali stress was higher than that of the control,and the ratio of IAA/ABA was lower than that of the control,and the ratios of ZT/ABA and IAA/ABA decreased more under acidic condition than alkaline condition.The contents of ZT and IAA in the shoot of BN4199 were significantly higher than that of AK58 under acid-alkali stress,but there was no significant difference in the content of ABA between them.