The Impacts Of Trichoderma Inoculation On The Physiological Traits Of Populus Davidiana ×P.alba Var.Pyramidali Saplings In Response To Heat And Drought Stresses

In order to reveal the effect of Trichoderma's resistance to high temperature and drought stress of Populus davidiana × P.alba var.pyramidalis(Shanxin poplar),in this study,Shanxin poplar grown in the soil for 30 days after transplanting was used as the material.Untreated seedlings were used as the control group(CK),and those with different concentrations of Trichoderma conidium solution were used as the experimental group(T),after culture for 30 d and 60 d,they were treated with single/double combined stress of high temperature and drought.The effects of abiotic stress on plant growth and physiology were studied from three aspects:growth character,physiological index and hormone level.The main research results are as follows:1.Eleven Trichoderma species were screened for their high temperature and osmotic pressure resistance.The dominant strain was T.asperellum Ta536.The strain was still isolated from the T group rhizosphere soil after 96 hours of combined stress.2.After Trichoderma treatment,the growth of plant height and ground diameter were increased compared with CK group.The content of some hormones and defense enzymes increased,and the content of chlorophyll also increased.It indicated that the application of Trichoderma was beneficial to the growth of poplar.Moreover,the application of different concentrations of Trichoderma conidium can promote the growth of poplar in different degrees3.During the 72 hours of combined stress,the SA,IAA and GA3 contents in CK group and T group increased first and then decreased,JA content first decreased and then increased,while ABA content increased.Moreover,the change of SA,IAA and GA3 contents in CK group was greater than that in T group.This indicated that Trichoderma had a stabilizing effect on the change of hormone content in shanxin poplar leaf tablets during the period of stress.Moreover,during this period,SA and ABA indexes were more sensitive to high temperature factors,JA and GA3 indexes were more sensitive to drought factors.Secondly,during the stress period,SOD activity of Shanxin poplar increased,POD and MDA activity decreased first and then increased,CAT,APX and PPO decreased,but the activity of APX in group T increased after the second high temperature,and MDA activity decreased all the time,and the total change was lower than that of CK group.This indicated that Trichoderma under the combined stress of high temperature and drought had a certain influence on the enzyme activity of poplar.4.During the 96 hours of combined stress,compared with the CK group during the stress period,it was found that the content of SA in the bud tip tissues of group T peaked at 30 hours of stress,the content of JA and IAA increased significantly after high temperature stress,and the content of ABA decreased slowly after 48 hours of stress.The content of SA in the leaf tissue peaked at 30 hours of stress and then decreased,JA content decreased instead of increasing,ABA content increased at a higher rate,and the content of SA,JA and ABA in the root tissue decreased instead of increasing.The results showed that different tissue parts under stress were affected by the positive effect of Trichoderma,which could improve the resistance of Shanxin poplar by adjusting the hormone content.In addition,compared with the previous results,the application dose and interaction time of Trichoderma had different effects on JA content in the tissues of poplar leaves under stress.Secondly,the activity changes of some defense enzymes in leaves during stress were also different from those in the CK group.POD activity of group T showed a trend of continuous increase,CAT activity increased significantly after 6 hours of high temperature stress,and APX activity was relatively stable after long-term drought stress without a significant decline.The results indicated that Trichoderma had positive effects on POD,CAT and APX activity of poplar under stress.It was further proved that the changes of hormone level and enzyme activity of Shanxin poplar under the combined stress of high temperature and drought were greatly affected by Trichoderma.In addition,the influence of high temperature factors was greater during the total stress,and the influence of compound stress was greater than that of single stress.