| Due to extensive use of chemical raw materials such as coal and oil in themodern industry, as well as vehicle exhaust emissions, there are more and more acidgases such as sulfur and nitrogen oxides in the air, which could occurred complexreactions and then formate into SO42-and NO3-. Atmospheric precipitation’s pH valuewill be less than5.6which we call it acid rain, after the dissolution of these acidicsubstances. In the resent years, with the total of SO2emissions continue to decline andNOxemissions continue to increase, the chemical composition of rain has beentransformed to sulfuric-nitric acid.In this study, the Pakchois are chosen as the test material, which are sensitive todifferent types of simulated acid rain (Mixed acid rain, sulfuric acid rain and nitricacid rain) under different pH values. In different growth cycles, the nutritional qualityindicators (Soluble sugar and vitamin C) and physiological indicators (chlo rophyll)of pakchoi leaves will be measured. We contrast the impact of the pakchoi underdifferent types of simulated acid rain of different pH values and analyze the changesof the three indicators in pakchoi leaves in different growth periods.In mature period,fresh weight and dry weight of food, fresh weight and dry weight of root, plant height,stem length and root length are measured. We analyze the effects of growth indicatorsof pakchoi under three kinds of acid rain types.The following conclusions based on experimental results:The impact of different types of simulated acid rain on pakchoi growthindicators：fresh weight and dry weight of food, plant height and stem lengthgradually increases with the increase of the acid rain pH value. Strong acid rainsignificantly inhibited the growth of food, and compared with the control group itmake the most obvious difference. It shows that the strong acid can directlyundermine the growth of pakchoi food ministry. With the increase of pH value, thequality of food department gradually increases. When the pH value of acid rain is5.6,the indicators of food Ministry are higher than that of the control group. Theminimum of fresh weight and dry weight of root and root length appears in the acid rain treatment group which pH value is3.5. In the acid rain treatment group of samepH value, the inhibitory effect of nitric acid rain on plant growth indicators is largest.The impact of different types of simulated acid rain on soluble sugars in pakchoileaves: With the enhanced acidity of simulated acid rain, the soluble sugar content inleaves gradually decreased and is positively correlated with the pH value of acid rain.When the acid rain which pH value is5.6sprays the plant, soluble sugar content inleaves is less than that of the control group in the early growth stage. With the growthof plants, soluble sugar content in leaves with three types of acid rain-treated exceedthat of the control group in varying degrees. The results of soluble sugar content inleaves increased with time increased show that: Over time, soluble sugar content inleaves is increasing, and has a significant positive correlation with time. The solublesugar content in leaves stressed by nitric acid rain which pH2.5grew slower than thecontrol group. The growth rate of the soluble sugar content in leaves stressed by themixed acid rain and sulfuric acid rain of pH2.5was almost the same with that of thecontrol group. The growth rate soluble sugar content in leaves gradually increasedwith the weakening of the acidity. Compared with that of the control group, acid rainof pH value greater than3.5accelerated the growth of soluble sugar in leaves. Thegrowing rate of soluble sugar in leaves treated by acid rain of pH value5.6is thefastest. Compared of the effects of soluble sugar content with different types of acidrain, we fount that: Under the same pH value, soluble sugar content in leaves treatedby Sulfuric acid rain grew fastest. And its content was higher than that of the mixedacid rain treatment group, higher than that of the nitrate acid rain treatment group.The impact of different types of simulated acid rain on vitamin C in pakchoileaves, in the group treated by the same type acid rain, the stronger of the simulatedacid rain, the more inhibited of vitamin C in leaves. When pH value of simulated acidrain was5.6, the vitamin C content in the leaves was less than that of the controlgroup in the previous two measurements. But after that the content treated by threetypes of acid rain in the pH value5.6was more than that of the control group.Vitamin C content in leaves was proportional to the time in the same type ofsimulated acid rain and the same pH value. With the weakening of the acidity of simulated acid rain, the growth rate of vitamin C increased. The growth rate ofvitamin C in leaves treated by simulated acid rain of pH5.6was the fastest, farexceeding the growth rate of the control group. The growth speed of vitamin C inleaves treated by simulated acid rain of pH2.5and the pH3.5was less than that thecontrol group. Compared the results of vitamin C in cabbage leaves treated bydifferent types of acid rain of the same pH value, we fount that: When three types ofacid rain of pH value2.5treated the leaves, the difference of the growing speed ofvitamin C is not obvious, and the growing speeds were far less than that of the controlgroup. With the increase of pH value of acid rain, the growth rate of vitamin C inleaves treated by mixed acid rain was greater than that of the sulfuric acid treatmentgroup. The inhibition of nitric acid rain on vitamin C synthesis in pakchoi leaves waslarger than the other two. Vitamin C content in leaves treated by nitric acid rain wasthe lowest, and its growing speed was the slowest.The impact of different types of simulated acid rain on chlorophyll in pakchoileaves: The stronger acidity of acid rain, the greater inhibition of chlorophyllsynthesis. The acid rain of pH2.5inhibited chlorophyll synthesis largest, and thechlorophyll content in leaves had a significant difference with that of the controlgroup. Chlorophyll content increased with the increase of pH value. Difference ofchlorophyll content in leaves treated by the sulfuric acid rain treatment of weak acidicconditions and chlorophyll content in leaves treated by the control group reduced, butchlorophyll content was still less than that of the control group. The averagechlorophyll content in leaves in nitric acid rain and mixed acid rain treatment groupwas higher than that of the control group. Under the same pH value, the regularity ofthe chlorophyll increase in ee the chlorophyll in e increased gentlely, then rapidly, andat last stage, gentlely. Treated by different types of simulated acid rain, thechlorophyll relative content in nitric acid treatment group was more than that in theother two, SPAD value of chlorophyll in leaves treated by sulfuric acid rain was theminimum. |
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