| Biosolid is rich in inorganic elements and organic nutrients,can be used as plant fertilizers,and biosolid in the presence of heavy metal ions and other substances make the sludge land use risk.In order to figure out the perennial ryegrass(Lolium perenne L.)available nitrogen content in biosolid,a complete randomized regional group test was designed.And then the test was designed with a crack zone experiment.There were well-watered and drought stress in split-plot.Subplots treatments were all received 75 mg·kg-1 soil nitrogen of three treatment:1)biosolid at 1×rate(by the biosolid to provide plant growth of 75 mg·kg-1 soil nitrogen;2)biosolid at 0.5×rate(plant growth needs of 75 mg·kg-1 soil nitrogen half from the biosolid and half from NH4NO3 solution;3)control(by NH4NO3 solution to provide plant growth of 75 mg·kg-1 soil nitrogen.Drought stress took 30%deficient irrigation methods,and samples were taken at 0,14,27,39 and 50 d after the drought stress began.The research results showed that:1)Under two kinds of water conditions,biosolid at 1×rate and 0.5×rate improved the turf quality,leaf chlorophyll content,leaf relative water content,leaf net photosynthetic rate and stomatal conductance.They also retard the wilting of perennial ryegrass leaves in drought stress.Biosolid at 1×rate and 0.5xrate decreased leaf wilting by 28.9%and 24.7%compered with control and maintain cell stability in drought stress.At the end of drought stress,biosolid at 1×rate and 0.5×rate decreased leaf electrical conductivity by 7.7%and 19.2%.Biosolid at 1×rate and 0.5xrate increased root biomass by 241%and 161%at the end of drought stress,indicating that the application amount of biosolid in this experiment could make the roots of perennial ryegrass maintain better growth under drought stress,which may be one of the reasons for the perennial ryegrass drought resistance of using biosolid.2)Biosolid at 1×rate and 0.5xrate improved the activity of SOD,CAT and APX in perennial ryegrass in well-watered condition.Under drought stress,four kinds of antioxidant enzymes showed different trends,which indicated that the antioxidant enzymes in perennial ryegrass had a different stress mechanism in response to stress.At the end of drought stress,when compared with control,the relative expression of Cu/Zn SOD in biosolid at 1 xrate and 0.5×rate increased 10.9%and 123%,pAPX was increased 10.9%and 123%,respectively.The relative expression of Mn SOD in biosolid at 1 xrate and 0.5xrate was 4.5 and 11.3 times higher than control,which indicated that the application of biosolid could increase the antioxidant enzyme activity of perennial ryegrass in drought stress and increase the relative expression of the related genes.3)Under two kinds of water conditions,there were no difference in perennial ryegrass leaves Trp and soil IAA content between biosolid treatments and control.And there was no difference in leaves IAA content between three treatments in well-watered condition.Biosolid at 1×rate and 0.5 xrate increased the content of root Trp,IAA and t-ZR under well-watered condition by 102.4%,2.1%and 85.4%when compared with control,which indicated that the promoting effect of the biosolid on perennial ryegrass growth was related to the increase of the root hormone content.Biosolid treatments increased leaf and root IAA and t-ZR level of perennial ryegrass at the later of stress,which may be one of the reasons that biosolid can improve drought resistance of perennial ryegrassIn summary,the application of biosolid could maintain a better growth state of perennial ryegrass in both well-watered condition and drought stress condition,especially in drought stress.Biosolid could improved perennial ryegrass antioxidant enzyme system activity and regulate plant hormone levels,which could be one of the reasons that biosolid enhance the ability of perennial ryegrass to cope with drought stress. |
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