Effects of foliar spraying plant growth regulator on growth and physiological indexes of wheat seedlings under saline-alkali stress
In order to investigate the effect of foliar spraying of plant growth regulators on seedling growth of wheat under saline-alkali stress,a two-factor completely randomised trial was used in this study.Four treatment groups with different saline-alkali(NaCl∶NaHCO3=1∶1)concentrations(0,50,100 mmol·L-1 and 150 mmol·L-1)and four foliar spraying groups[water,0.1 mmol·L-1 salicylic acid,0.1 mmol·L-1 suberic acid,100 mmol·L-1 5-aminolevulinic acid(5-ALA)]were used to analyse the changes in antioxidant enzyme activities,osmoregulatory substances,and endogenous hormone contents in wheat during the seedling stage.Compared with no growth regulator spraying,spraying growth regulator under 150 mmol·L-1 saline-alkali stress increased the height of wheat seedlings by 7.69%-13.15%,12.66%-15.50%and 1.01%-12.68%,respectively;root length by 7.44%-25.28%,2.21%-19.62%and 30.38%-60.52%;stem fresh mass increased by 3.58%-16.59%,12.50%-47.61%and 20.00%-96.19%,respectively.Spraying growth regulators improved antioxidant enzyme activities of wheat seedlings compared with clear water treatment,among which spraying salicylic acid had the best effect in enhancing antioxidant enzyme activities of wheat seedlings.Under all saline-alkali stress,spraying salicylic acid and spermidine significantly increased the soluble sugar and soluble protein contents of wheat leaves by 13.19%-23.11%,8.99%-27.65%and 3.18%-28.76%and 7.50%-29.31%,respectively,compared with that of clear water treatment.The growth hormone content of wheat leaves sprayed with salicylic acid was significantly higher than those of other treatments under 0,100,and 150 mmol·L-1 saline-alkali stress;the gibberellin content was significantly increased by spraying salicylic acid under 50,100 mmol·L-1 saline-alkali stress;the cytokinin content of the sprayed salicylic acid and spermidine treatments was significantly higher than that of 5-ALA under 50 and 150 mmol·L-1 saline-alkali stress;the cytokinin content of the sprayed salicylic acid and spermidine treatments was significantly higher than that of 5-ALA under 0 and 100 mmol·L-1 saline-alkali stress,spraying 5-ALA significantly decreased the abscisic acid content and increased the cytokinin content of leaves.Salicylic acid and spermidine sprayed under saline-alkali stress promoted the seedling growth of wheat better than 5-ALA,which helped to alleviate the inhibitory effect of saline-alkali stress on its growth and improve the salinity tolerance of wheat.
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