| China's acid rain area accounts for 7.2% of the land area,and the proportion of acid rain cities is 19.8%.Indocalamus decorus is native to southern China,an excellent ornamental bamboo,and has very high application value in landscape greening.Indocalamus decorus inevitably encounters in the promotion of planting on acid rain.In order to reveal the impact of acid rain on photosynthetic capacity and soil properties of Indocalamus decorus,and to explore ways to improve the resistance to acid,this experiment simulated acid rain and set p H3.5,5.0 and 6.8(CK),with which to spray Indocalamus decorus potted seedlings in short-term.The relative chlorophyll content,gas exchange parameters,chlorophyll fluorescence parameters,root activity,soil p H,alumina content and available nutrient content were mensurated and analysed.The main results are as follows.(1)Relative chlorophyll content(SPADR),net photosynthetic rate(A),intercellular CO2 concentration(Ci),stomatal conductance(GH2O)and transpiration rate(E)showed an downward trend under acid rain.There were significant differences in SPADR,A,GH2 O and E between acid rain treatments and CK in the last stage of treatments.Acid rain also reduced the initial conversion efficiency(Fv/Fm),the opening ratio of PSII reaction center and the photochemical reaction efficiency and increased the excess light energy and light inhibition.However,in the early and middle stages of treatments,the actual photochemical efficiency of PSII(Yield)of p H5.0 treatment was obviously promoted,and its photoinhibition coefficient(Ki)was also obviously lower.(2)After the end of treatments,the highest root activity of Indocalamus decorus was p H3.5 treatment,the lowest was CK,and their difference was significant.The p H values of surface soil and bottom soil treated by acid rain was lower than that in CK,but they had no significant difference from CK.However,the contents of alumina in surface soil treated by acid rain were lower than that in CK,and the difference was extremely significant.The contents of available nutrients in surface soil decreased obviously under acid rain treatments,and the contents of available nitrogen and available phosphorus of p H5.0 treatment were extremely different from those in CK.The contents of available nutrients in the bottom soil were higher than those in the surface soil for the influence of nutrient downward migration.But the available potassium content in the bottom soil of p H3.5 treatment was significantly lower than that in the other two treatments..(3)Correlation analysis showed that GH2 O was the main limiting factor for A and E under acid rain treatments.The negative correlation between Yield and Ki was due to the injury of PSII reaction center,whose activity decreased.The p H value of surface soil had a significant effect on alumina content of surface soil.The contents of available nitrogen and available phosphorus in surface soil had similar change rule under acid rain treatments.This paper concluded that mild acid rain had a certain positive effect on the photochemical efficiency of Indocalamus decorus.With the increase of acidity and treatment time,photosynthetic capacity of Indocalamus decorus declined on the whole.Acid rain also acidified the potted soil,dissolved the alumina and promoted the downward leaching of available nutrient,which made the soil conditions of Indocalamus decorus growing worse.Enhancing the soil's ability to buffer the acid rain and improving the soil conditions might be one of the effective ways to improve the acid resistance of Indocalamus decorus. |
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