Effect Of Simulated Acid Rain On Two Ground Cover Plants Of Iris Genera

In this paper, according to the main chemical compositions of natural rainfall in sichuan, compounded simulated acid rain of pH5.6,4.0,3.0,2.0, pH5.6 was contrast. The effects of different concentrations simulated acid rain and times on growth (apparent symptoms of leaf injury and leaf relative growth rate), photosynthetic characteristics(chlorophyll content and gas exchange),physiological and biochemical characteristics(Mp,MDA,SOD,POD and CAT) were studied with Iris confuse and I. pseudacorus, in order to explore these two species resistance to acid rain.The results showed.1.They all showed good stress resistance to acid rain, Iris confuse was more outstanding. After the first spraying,â… . confuse had small light injury spots at the pH2.0 acid rain,â… . pseudacorus had injuried spots at both pH2.0 and pH3.0 acid rain.With the increase of times, suffers of I. pseudacorus were significantly worse,the injuried leaves became more, the color of injury spots became darker.Result of these, the acute injury threshold value of I. pseudacorus is between pH2.0 and pH3.0,â… . confuse is in the vicinity of pH2.0.2.Both growth of leaves had been suppressed, especially in the earlier stage.These two species also growed fastly after the first treatment,but their growth rate reduced significantly after the second time.The experiment showed, the growth of plants was accelerated at low concentration acid rain,the pH4.0 group had a much higher growth rate than CK and the other groups.3.pH4.0-3.0 acid rain had a auxo-action to Chi content,Chla/b,Pn,Tr,Gs and Ci,they were all first to rise and decline with the times increasing.Ls was contrary.4.Simulated acid rain had influences on cell membranes,Mp and MDA content were both increased with the pH of acid rain reducing and times increasing.5.SOD and CAT activities at pH4.0-3.0 acid rain were higher than CK,while the other groups lower than CK,all groups were first to rise and decline with the times increasing.The changes of POD activities were more complicated, they were also first to rise and decline.In the earlier stage, POD activities increased with the pH reducing,while they reduced in the later stage,even they were higher than CK at the low concentration acid rain(pH4.0-3.0).6.Through overall evaiuation by subordinate funetion method,the results had shown that the resistance of tow species toacid rain stress could be ordered as:â… . confuse >â… . pseudacorus.