Effects Of Salicylic Acid On The Growth And Physiological Characteristics Of Hosta Ensata Under NaCl Stress

Hosta ensata is an excellent landscaping material in Northeast China because of its ornamental value.The wide distribution of salinized alkali land in China limits the planting range of H.ensata,and affects its growth and landscape construction.Previous studies have found that salicylic acid(SA)can improve the salt tolerance of plants.In this experiment,H.ensata was used as the experimental material and the pot experiment method was adopted.After spraying 0 mmol·L-1(SA0),0.25 mmol·L-1(SA0.25),0.5 mmol·L-1(SA0.5),1.0 mmol·L-1(SA1.0)SA on leaves,the plants were treated with 0 mmol·L-1(T0,100 mmol·L-1(T1),200 mmol·L-1(T2)NaCl,to explore the effects of exogenous SA on the growth status,photosynthetic characteristics and physiological characteristics of H.ensata under NaCl stress.The main findings are as follows:1.SA0.25,SA0.5,and SA1.0 treatments all increased plant height,leaf length,leaf width,and biomass of H.ensata under NaCl stress,reduced salt damage index,improved salt tolerance and salt sensitivity index,and the effect of SA0.5 treatment was the most significant.The height of H.ensata under SA0.5 treatment was 0.37%-5.76%higher than that of the control under T2 condition.The dry matter of H.ensata under SA0.5 treatment increased by 56.99%and 54.67%compared with the control under T1 and T2 conditions,respectively.SA0.5 treatment reduced the salt injry index of H.ensata by 33.34%-80.59%and 25.97%-66.09%under T1 and T2 conditions,respectively,compared with the control,while the salt tolerance index and salt sensitivity index increased 1.72-2.5-fold and 1.45-1.71-fold,respectively,under SA0.5 treatment compared with the control.2.SA0.25,SA0.5,and SA1.0 treatments all increased the net photosynthetic rate(Pn)and total chlorophyll content of H.ensata under NaCl stress,and the effect of SA0.5 treatment was the most significant.SA0.5 significantly increased the Pn of H.ensata by 29.58%-207.26%and 39.74%-139.13%compared with control under T1 and T2 conditions,respectively.And SA0.5 treatment significantly increased the total chlorophyll content of H.ensata at the 20th day under T2 condition,which was 107.94%higher than that of the control.3.SA0.25,SA0.5 and SA1.0 treatments could promoted the accumulation of osmoregulatory substances,increased SOD,POD,CAT activities,total phenol and flavonoid contents,and decreased MDA content of H.ensata under NaCl stress,with the most significant effect of SA0.5 treatment.SA0.5 treatment increased the soluble sugar content of H.ensata by 5.21%-56.86%and 7.05%-37.61%,the proline content by 11.04%-74.83%,13.00%-136.51%,and soluble protein content by 25.83%-192.08%,21.76%-123.05%,respectively,compared with the control under Tland T2 conditions.SOD,POD and CAT activities of H.ensata treated with SA0.5 were maximally increased by 27.15%,10.18%and 59.04%on days 3,15 and 10,respectively,compared with the control under T1 condition.SOD,POD and CAT activities of H.ensata treated with SA0.5 were maximally increased by 27.45%,19.61%and 44.16%compared with the control under T2 condition on days 3,7 and 10,respectively.Compared with the control under T1 and T2 condtions,the content of total phenols in H.ensata was increased by 8.16%-51.66%and 10.9%-30.22%by SA0.5 treatment,and the flavonoids were increased by 24.96%and 18.99%by SA0.5 treatment on the 20th day,respectively.4.Pearson correlation coefficient analysis showed that NaCl injury index of H.ensata was highly positively correlated with MDA content,meanwhile,the antioxidant enzyme activities and osmoregulatory substances of H.ensata were significantly or highly negatively correlated with MDA content.The value of D reflects the comprehensive salt tolerance capacity of H.ensata under different SA treatments,and the larger the value,the stronger the salinity tolerance.According to the membership function analysis,the D value of each group under the treatment of SA0.5 reached the maximum value,which indicated that the salt tolerance of H.ensata was stronger under 0.5 mmol-L-1 SA treatment,and the salt tolerance of H.ensata induced by SA under NaCl stress was in the order of SA0.5>SA1.0>SA0.25.