Studies On Growth And Chlorophyll Fluorescence Parameters Of3Types Of Simulated Acid Rain Stress On Camellia Sinensis And Quercus Glauca

The impact of acid rain on terrestrial ecosystems has become a global environmental problem，theharm of acid rain to the trees, and the trees’ adaptive mechanism are the hotpots of forestry study. Bytaking Camellia sinensis and Quercus glauca seedlings of subtropical evergreen broadleaved forestspecies as the research object,setting severe acid rain（pH2.5）, moderate acid rain（pH4.0）and weakacidic acid rain（pH5.6）,we design4different treatment methods:（1）the seedlings and soil are bothexposed to acid rain（2）only the aboveground of seedlings are exposed to acid rain（3）only the soil thatseedlings lived is exposed to acid rain（4）the blank control group.We measured growth increment（height and ground diameter）,relative chlorophyll content and chlorophyll fluorescence parametersof the two plant,and then we carried systematical analysis and statistical test, so as to reveal the directeffect,indirect effect,comprehensive effect of acid rain to seedlings and their difference, so we canelucidate the seedlings’ response mechanism to acid rain on morphology,physiology and nutrition,whichwill provide some referential theoretical basis for selecting anti-acid rain tree species,forestrestoration,evaluating and preventing the damage of acid rain to forest.The results show that:（1）From3types of simulated acid rain stress aspect,compared with the control group,acid rainhad significantly inhibited the height of Camellia sinensis,while it had remarkably promoted thechlorophyll content and chlorophyll fluorescence parameters（F_v/F_m, F_v/F_o, Yield）,and the order of thepromoting effect is direct effect＞comprehensive effect＞indirect effect.When Quercus glaucaseedlings were treated by severe acid rain,their height,chlorophyll content and chlorophyll fluorescenceparameters（F_v/F_m, F_v/F_o, Yield）were inhibited, direct effect and comprehensive effect of acid rain issignificantly higher than the indirect effect of acid rain,that was because the soil that the plant livedhave some buffer action.When Quercus glauca seedlings were treated by moderate acid rain and weakacidic acid rain，the comprehensive effect of acid rain had the maximum effect on promotting theirgrowth and physiological parameters（chlorophyll content, F_v/F_m, F_v/F_o, Yield）,its effect is higher thandirect effect and indirect effect，while comparing the latter two，there was no significant difference.From the aspect of3concentration gradients of simulated acid rain,severe acid rain and moderateacid rain had significant inhibitory effect on the height of Camellia sinensis seedlings,their effect isbigger than weak acidic acid rain,while comparing the former two，there was no significant difference.3 concentration gradients of simulated acid rain had significantly promoted the chlorophyll content andchlorophyll fluorescence parameters （F_v/F_m, F_v/F_o, Yield） of Camellia sinensis seedlings,whilecomparing severe acid rain and moderate acid rain，there was no significant difference,whereas thepromotion of moderate acid rain is significantly higher than the former two.When Quercus glaucaseedlings were treated by direct effect and comprehensive effect of acid rain，severe acid rain inhibitedtheir height， chlorophyll content and chlorophyll fluorescence parameters （F_v/F_m, F_v/F_o,Yield）.Moderate acid rain had significant promotion on the height，chlorophyll content and chlorophyllfluorescence parameters（F_v/F_m, F_v/F_o, Yield）of Quercus glauca seedlings，while weak acidic acid rainhad less promotion.