Effect Of Simulated Acid Rain On The Physiology,Growth Characteristics And Microbial Diversity Of Sinocalycanthus Chinensis Seeding

Acid rain pollution has become an global environmental problem which threaten the existence of human beings. Most studies focused on the damage of acide rain on plants, especially on those endemic endangered plants with reare resources. Here, the endangered plant Sinocalycanthus chinensis distributed in the typical acid rain polluted area was seleted as the study species. Acid rain pollution at high level(pH2.5), mediate level(pH 3.5) and low level(pH 4.5) was simiced and the effect on the growth, physiological traits and soil microbial characteristics were analyzed. The adaptation of S. chinensis to acid rain and the possible mechanisms were explored.These results will help to predict the population dynamics under global changes and the evolutionary potential of S. chinensis. The results were shown in the follows.1. Effect of acid rain on the seedlings’ growth and biomass allocation of S. chinensis seedlingsAfter one year treatment of rain acid at three levels, the plant height, basal diameter of S. chinensis seedlings significantly reduced. The total biomass, stem biomass and shoot biomass significantly reduced after one year treatment. Those indices were highest at low level, mediate at mediate level and lowest at high level of rain acid with significant differences among them. Root biomass of S. chinensis in the treatment of acid rain at low level were significantly higher than control, while those in the treatment at high level and mediate level were significantly lower thant those in control. Leaf biomass of S. chinensis in three treatments of acid rain with different levels was significantly lower than those in control. The root biomass ratio and root/shoot ratio of S. chinensis in the treatment of acid rain at high level and mediate level were significantly higher than those in control, while the leaf biomas ratio were significantly lower than those in control.The total leaf number were the highest in control, while that of S. chinensis in the treatment of acid rain at high level and mediate level were significantly lower than those in control. The stress of acid rain significantly reduced the total leaf area,leaf mean width and leaf mean perimeter. The leaf mean length of S. chinensis in the treatment of acid rain at high level and mediate level was significantly lower than those in control and tremant with low level. The leaf width-to-length ratio, total root length, total root surface area of S. chinensis in the treatment of high level was significantly lower than control and the other two treatments. The total root volume, root mean diameter, specific root surface area of S. chinensis in three levels of acid raion treatments were significantly lower than those in control.2. Effect of acid rain on the photosynthetic characteristics and chlorophyll fluorescence parameters of S. chinensis seedlingsThe diurnal cuve of photosynthetic rate of S. chinensis with different treatment of acid rain were shown in single curve with the highest at 14:00 PM. The stress of acid rain significantly reduced the daily mean net photosynthetic rate, maximum net photosynthetic rate of leaf with the increasing of pH value. Stress of acid rain significantly reduced the light saturated point, but significantly increased the light conpensation point and made the light utilization range narrow. Stress of acid ratin significantly reduced the apparent quantitum efficiency, but significantly increased the dark inspiration rate. Stress of acid ratin significantly reduced the manximum carboxylation rate, maximum, and triose phosphate utilization rate with the increasing of pH.The leaf chlorophyll a content and the chlorophyll b content in the leaves of S.chinensis seedlings were significantly reduced by the treatment of acid rain with three different levels. The chlorophyll a+b content in the leaves of S. chiensis seedlings in the treatment of acid ratin at high level and mediate level were singificnantly lower than those in control. The carotenoid content were significantly reduced by the stress of acid rain. The stress of acid rain significantly affected the chlorophyll fluorescence parameters. The conversion efficiency of primary light energy of PS Ⅱ and PS Ⅱ photochemical activity were significantly lower than those in control, which decreased with the increasing of pH.3. Effect of acid rain on the anti-oxidant ability of S. chinensis seedlingsAcid rain treatment significantly increased the activity of SOD and POD of S.chinensis seedlings with the increasing of pH value. The activity of CAT and APX,the glutathion content and L-Ascorbic acid content of S. chinensis seedlings in the treatment of acid rain at high level and mediate level significantly reduced. Acid rain significantly increased the content of MDA in the seedlings of S. canadensis with highest in the treatment with high level. The treatment of acid rain at high level and mediate level significantly incraed the relative permeability of plasma membrance with highest in the treatment with high level.4. Effect of acid rain on the soil enzyme activity, microbial activity and microbial community diversityAcid rain significantly inhibited the activity of soil protease and catalase and increased with the increasing of pH value. Treament of acid rain at high level significantly reduced the activity of soil phosphorase, while that at low level signficanlty incrased. Acid rain significantly reduced the activity of invertase with lowest in the treatment with low level.Acid rain significantly decreased the soil microbial biomass carbon and it decreased with the increasing of pH. Acid rain significantly reduced the soil microbial biomass nitrogen with lowest in the treatment with low level. Acid rain at high level and mediate level significantly reduced the soil microbial biomass phosphorus with highest in the treatment with high level.Acid rain significantly decreased the bacteria number and it decreased with the decreasing of pH. Compared with control, acid rain at low level significantly increased the soil fungi number while that at high level significantly decreased the soil bacteria number. All three treatments significantly decreased the soil actinobacillus number with lowest at high level. All three treatments significantly decreased the soil nitrogen-fixing bacteria number, while that in the treatment with high level and mediate level were lower than that with low level.The soil microbial evenness indices of S. canadensis in three treaments were significantly lower than those in control, with lowest in the treatment of acid rain with high level. The soil microbial Shannon-Wiener indices of S. canadensis in three treaments were lower than those in control, and only those in the treatment of acid rain was significantly. Acid rain treatment with high level and mediate level significantly reduced the soil richness indices.