Effects Of Acid Rain On The Physiological Characteristics Of Ginkgo Biloba L.

Acid rain had been not only one of the world's environmental problems, but also the major environmental issues of China. Acid rain gave rise to the economic losses and harmed to the ecological balance and plant itself, the seriousness has become a cause for concern increasingly. In this study, Ginkgo was used to study the damage of simulated acid rain(pH2.0,3.0,4.0,5.6) on the growth and the effects of Ginkgo biloba L., leaf visible injury threshold and the sensitivity of classification. Evaluation of garden plants sensitivity reaction to acid rain for the protection of the relict plant, as well as acid-controlled areas in the future the selection of Landscape species and improving the cultivation of Ginkgo biloba L. anti-acid rain. The experimental results are as follows:(1) The third day of simulated acid rain with pH2.0 treatment, brown spots appeared on leaves, and the phenomenon became more and more serious with the increasing number of acid rain stress. New leaves had been hurt more severely than old leaves.(2) The experiment in the same nutrition resources and convergence of factors such as light conditions, the simulated acid rain on the growth of Ginkgo biloba L. created a great environmental stress, the growth of the height of Ginkgo biloba L. decreased significantly under the simulated acid rain, especially in dealing with acid rain pH≤3.0.(3) In the beginning of the simulated acid rain stress, POD, SOD activity and CAT decreased slightly, while the MDA content and membrane permeability increased. In this time, the Ginkgo biloba L. was sensitive to acid rain and had no enough time to start the various protection mechanisms in vivo, then the simulated acid rain caused a certain degree of damage. After the second simulated acid rain stress, POD, SOD activity increased sharply, CAT activity elevated slightly, MDA content and membrane permeability were decreased, it indicated that at that time antioxidant enzyme systems removed active oxygen free radicals efficiently to balance the active oxygen metabolism in the body, protect the film structure, so that Ginkgo biloba L. can tolerate a certain extent, mitigation and resistance to environmental stress. After the third simulated acid rain stress, POD, SOD activity in a high state of relatively stable, while the CAT activity, MDA content and' membrane permeability increased significantly, it indicated that Ginkgo biloba L. had made adaptive response in order to avoid being hurt, but also a large number of oxygen free radicals were generated by the simulated acid rain, and the production of oxygen free radical may have exceeded the POD, SOD, CAT and other protective enzymes in scavenging ability, it failed to remove some of the active oxygen caused by membrane, which lead to cell membrane damage. As the simulated acid rain continued, POD, SOD and CAT activity keep in a stable and high trend, MDA content also keep in a stable state after a sharp decline. At this time reactive oxygen metabolism was balance, this indicated that Ginkgo biloba L. can repair damage which was caused by simulated acid rain by its own physiological activity.(4) The content of chlorophyll decreased gradually, and Pn, Gs, Tr and intercellular CO2 concentration all had a decreasing trend while the value of chlorophyll a/b presented an increasing tendency as the intensity of stress of simulated acid rain increased, it was just opposite to the content of chlorophyll. The decreased content of chlorophyll indicated that photosynthesis of leaves of Ginkgo was partly affected, and the leaves of Ginkgo had an indication of growing old, but it was not greatly. The cause of the increased value of chlorophyll a/b was that the content of chlorophyll b decreased more quickly than that of chlorophyll a during the stress process, this showed that chlorophyll a/b value was affected mainly by the content of chlorophyll b.(5) Under the treatment of simulated acid rain pH≤3.0 to Ginkgo, the POD, SOD, CAT activity and chlorophyll content in leaves of Ginkgo biloba L. were lower than the control, and showed significant differences with the control, while the MDA content and membrane permeability were more than control, and it showed significant differences with control. In the spraying process of simulated acid rain, under the acid rain treatment of pH4.0, plants also subjected to certain injuries, but with the increasing of the number of acid rain spraying, ginkgo began to adapt to acid rain treatment of pH4.0, it imported that Ginkgo can actively repair the damage caused by the simulated acid rain and may start some acid-resistant genes of itself. Then, simulated acid rain of pH3.0 can be thought of the recessive Ginkgo biloba L. critical damage point.(6) Resistance of plant and its ability to adapt to the environment were the basis and premise of selecting plant species in the air pollution stress restoration of degraded ecosystems. In this study, a preliminary discussion of some of ginkgo resistance to acid rain pollution in physiological mechanisms, it indicated that there was a strong anti-acid rain ginkgo's ability to respond to acid rain stress quickly so that it can avoid being harm.