| The acid rain( Acid Rain, or Acid Precipitation) is an one of the global environment problems that mankind encounter now, it does not only pollute the lakes, forests and soil, endanger the living creature, but also do damage to the metals and buildings. The plant is the important part in the city ecosystem system, have a significant effect on the city ecological balance. Changsha is the central city of acid rain region in central China, the paper studied the effects of acid rain on plant photosynthesis, transpiration, growth status by using simulated acid rain in 3 different pH solutions (pH3.0, pH4.0 and pH5.0) and treating Cinnamomum camphora, Magnolia grandiflora, Osmanthus fragrans,Lor ope-talum chinense var.rubrum, Rhododendron simsii Planch, Rhododendron indicum which are the conventional greening plants in this area, and analyzed the pattern of light response curve, CO2 response curve, the net photosynthesis rate, stomatal conductance, intercellular CO2 concentration, stomatal limitation value, transpiration rate, saturated vapor pressure deficit, water use efficiency, the weight per leaf, specific leaf weight, chlorophyll content, the root/crown ratio, and total biomass in different acid rain amply, the result showed that:1?Compared to the control (63.52?mol·m?2s?1), light compensatioin point of Rhododendron indicum declined 12.45%?15.44% and 24.09% respectively at pH3.0, pH4.0 and pH5.0. Simulated acid rain of pH4.0 and pH5.0 increased light compensatioin point of Cinnamomum camphora and Rhododendron simsii Planch, but reduced that of Osmanthus fragrans and Magnolia grandiflora; and Cinnamomum camphora increased 47.17% and 53.92% compared to the control (38.67?mol·m?2s?1), and Rhododendron simsii Planch increased 42.37% and 14.77% compared to the control (63.23?mol·m?2s?1) whereas Osmanthus fragrans reduced 26.56% and 26.50% compared to the control (18.11?mol·m?2s?1) and Magnolia grandiflora only reduced 4.83% and 0.54% compared to the control (51.79?mol·m?2s?1). Light compensatioin point of Loropetalum chinense var.rubrum declined 18.99% and 45.99% compare with the control (31.70?mol·m?2s?1) at pH3.0 and pH5.0 levels.2?Simulated acid rain of pH4.0 and pH5.0 increased the apparent quantum yield of Magnolia grandiflora, Osmanthus fragrans and Loropetalum chinense var.rubrum, and Magnolia grandiflora increased 20.45% and 14.90% compare with the control (0.0396 ), Osmanthus fragrans increased 20.81% and 17.34% compare with the control (0.0173molCO2mol?1Pn), Loropetalum chinense var.rubrum increased 4.29% and 22.11% compare with the control (0.0303 molCC2mol?1Pn). Compared to the control (0.0314molCO2mol?1Pn), the apparent quantum yield of Cinnamomum camphora increased 27.07% and 22.61% at at pH3.0 and pH4.0 acid solutions. The apparent quantum yield of Rhododendron indicum declined 17.50% compare with the control (0.0280 molCC2mol?1Pn). Three kinds of acid solution had little effect on Rhododendron simsii Planch, the apparent quantum yield only declined 3.27%,5.56% and 1.96% compare with the control (0.0306 molCO2mol?1Pn).3?Three kinds of simulated acid rain all increased the dark respiration rate of Cinnamomum camphora, Magnolia grandiflora and Rhododendron simsii Planch, but decreased that of Rhododendron indicum; And Magnolia grandiflora increased 22.81%, 23.42% and 14.29% compared to the control (2.0509?mol·m?2s?1), Cinnamomum camphora increased 2.70%,80.45% and 47.55% compared to the control (1.2142?mol·m?2s?1), Rhododendron simsii Planch increased 39.57%,11.02% and 0.27% compared to the control (1.9349?mol·m?2s?1), however Rhododendron indicum decreased 9.40%,12.45% and 37.37% compared to the control (1.7785?mol·m?2s?1). The dark respiration rate of Osmanthus fragrans increased 19.69% treated by pH3.0 acid solution compare with the control (0.3133?mol·m?2s?1),hereas that of Loropetalum chinense var.rubrum delined 18.98% and 34.07% compared to the control (0.9605?mol·m?2s?1) both at pH3.0 and pH5.0 levels.4?pH3.0, pH4.0 and pH5.0 simulated acid rain increased the apparent carboxylation efficiency of Osmanthus fragrans and Loropetalum chinense var.rubrum, and Osmanthus fragrans increased 96.81%,75.16% and 31.21% compare with the control (0.0157?mol·m?2s?1/?mol·mol?1), Loropetalum chinense var.rubrum increased 149.05%?42.86%?23.33% compare with the control (0.0523?mol·m?2s?1/?mol·mol?1). However the apparent carboxylation efficiency of Cinnamomum camphora and Rhododendron indicum increased only at pH3.0 and pH4.0, and Cinnamomum camphora increased 46.33% and 28.75% compared to the control(0.0313?mol·m?2s?1/?mol·mol?1), Rhododendron indicum increased 34.33% and 3.86% compared to the control (0.0233?mol·m?2s?1/?mol·mol?1). In contrast, the apparent carboxylation efficiency of Magnolia grandiflora reduced 17.11% and 34.21% compared to the control (0.0152?mol·m?2s?1/?mol·mol?1) at pH3.0 and pH5.0, and that of Osmanthus fragrans declined 14.23% compared to the control (0.0239?mol·m?2s?1/?mol·mol?1) at pH4.0.5?Three pH levels simulated acid rain all declined the CO2 compensation point of Cinnamomum camphor a and Loropetalum chinense var.rubrum, and Cinnamomum camphora declined 3.62??9.27% and 15.39% compared to the control (44.25?mol·mol?1), Loropetalum chinense var.rubrum declined 16.97%?25.91% and 21.05% compared to the control (76.66?mol·mol?1). However the CO2 compensation point of Magnolia grandiflora and Rhododendron indicum increased at pH3.0 and pH5.0, and Magnolia grandiflora increased 49.06% and 9.22% compared to the control (88.3289?mol·mol?1), Rhododendron indicum increased 25.41% and 27.56% compared to the control (108.6910?mol·mol?1). The CO2 compensation point of Osmanthus fragrans increased 10.28% and 12.42% compared to the control (85.8471?mol·mol?1) at pH4.0 and pH5.0, but that of Rhododendron simsii Planch reduced 34.06% at pH5.0 compared to the control (30.9540?mol·mol?1).6?The diurnal variation of net photosynthetic rate in seedings of Cinnamomum camphora, Magnolia grandiflora, Osmanthus fragrans, Loropetalum chinense var.rubrum, Rhododendron simsii Planch and Rhododendron indicum treated by acid solution of different concentration in sunny day varied with a bimodal curve, the peaks occurred at 10:00 and 14:00 respectively, there was a midday depression at 12:00.7?All the three simulated acid rain increased the max stomatal conductance of Loropetalum chinense var.rubrum and Rhododendron indicum, and the former increased 119.18%,60.47% and 8.93% compared to the control (0.0683 molH2O m?2s?1), the latter increased 43.31%,29.34% and 16.51% compared to the control (0.0683 molH2O m?2s?1); whereas the three simulated acid rain decreased that of Rhododendron simsii Planch 23.64%,27.73% and 44.38% compared to the control (0.1760 molH2O m?2s?1). The max stomatal conductance of Magnolia grandiflora increased 52.86% and 48.82% compared to the control (0.0891 molH2O m?2s?1) at pH4.0 and pH5.0. And that of Cinnamomum camphora and Osmanthus fragrans increased at the pH3.0 and pH4.0, and the former increased 40.12% and 24.39% compared to the control (0.0865 molH2O m?2s?1), the latter increased 30.78% and 6.32% compared to the control (0.1202 molH2O m?2s?1). 8?Simulated acid rain of pH3.0, pH4.0 and pH5.0 all increased the diurnal changes on intercellular CO2 concentration of Osmanthus fragrans, Loropetalum chinense var.rubrum and Rhododendron simsii Planch, decreased that of Magnolia grandiflora and Rhododendron indicum, and the increments of Osmanthus fragrans were 36.37%,42.41% and 36.39%, the increments of Loropetalum chinense var.rubrum were 25.61%,29.40% and 47.09%, the increments of Rhododendron simsii Planch were 50.97%,57.74% and 28.76%; the decrements of Magnolia grandiflora were 38.74%,27.57% and 38.33%, the decrements of Rhododendron indicum were 51.22%,48.22% and 30.74%. Compared to the control (120.9?molCO2 mol-1), the diurnal changes on intercellular CO2 concentration of Cinnamomum camphor a decreased 14.49% at pH5.0.9?All the three simulated acid rain increased the minimum of stomatal limitation values of Cinnamomum camphor a, Osmanthus fragrans, Loropetalum chinense var.rubrum and Rhododendron simsii Planch, and the increments of Cinnamomum camphora were 114.56%,34.95% and 360.19%, the increments of Osmanthus fragrans were 122.45%, 141.41% and 288.11%, the increments of Loropetalum chinense var.rubrum were 231.16%, 423.91% and 210.14%, the increments of Rhododendron simsii Planch were 166.25%, 69.17% and 87.50%; the minimum of stomatal limitation values of Magnolia grandiflora and Rhododendron indicum were increased by pH3.0 and pH4.0 simulated acid rain, and the increments of Magnolia grandiflora were 170.55% and 17.67% compared to the control (0.084), that of Rhododendron indicum were 173.86% and 76.60% compared to the control (0.4556).10?Three different pH value solutions all increased the max of transpiration rate of Rhododendron indicum and Loropetalum chinense var.rubrum, reduced that of Osmanthus fragrans and Rhododendron simsii Planch, and the increments of Rhododendron indicum were 18.54%,18.60% and 37.86%, the increments of Loropetalum chinense var.rubrum were 42.92%,87.27% and 10.87%; the max of transpiration rate of Magnolia grandiflora increased 31.79% and 39.50% compared to the control (3.4480 molH2O m-2s-1) at the pH4.0 and pH5.0. However the max of transpiration rate of Cinnamomum camphora declined 27.40% compared to the control (3.502 molH2O m-2s-1) at the pH5.0.11?The diurnal changes of vapor pressure deficit of Cinnamomum camphora, Osmanthus fragrans, Rhododendron simsii Planch, Loropetalum chinense var.rubrum and Rhododendron indicum all increased at three pH levels, and the increments of Rhododendron simsii Planch were obvious,52.52%,50.75% and 32.03%. The diurnal changes of vapor pressure deficit of Magnolia grandiflora increased 45.56% and 14.13% compare with the control (2.846kPa) at the pH3.0 and pH4.0.12?Different acid solution (pH3.0, pH4.0 and pH5.0) all increased the max of water use efficiency of Osmanthus fragrans and Rhododendron simsii Planch, decreased that of Loropetalum chinense var.rubrum and Rhododendron indicum, and the increments of Osmanthus fragrans were 152.67%,464.69% and 252.06% compared to the control (3.2311?molCO2/mmolH2O), the increments of Rhododendron simsii Planch were 108.46%,74.79?and 25.10?compared to the control (4.5569?molCO2/mmolH2O); the decrements of Loropetalum chinense var.rubrum were 23.78%,68.24% and 58.94% compared to the control (40.2887?molCO2/mmolH2O), and the decrements of Rhododendron indicum were 10.96%,10.93% and 6.29% compared to the control (6.9415?molCO2/mmolH2O). The max of water use efficiency of Magnolia grandiflora increased 56.09% and 124.81% at pH3.0 and pH4.0. The pH4.0 simulated acid rain increased 101.44% of the max of water use efficiency of Cinnamomum camphora compared to the control (15.103?molCO2/mmolH2O).This paper studied the effect of simulated acid rain on the photosynthesis, transpiration, growth status, revealed the mechanism of the plant growth with acid rain, provided data and scientific basis for screening the species of trees in the construction of city forest... |
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