Study On Effects Of Simulated Acid Rain On Physiological Characters Of The Magnoliaceae Family And Myrica Rubra Family

Acid rain is a serious environmental problem with impact on agriculture, forest and water ecosystem. Many researchers have devoted much attention to forests exposed to stress, but mechanism of resistance of woody landscape plants to acid rain hasnt clearfied, especially the research for acidic tolerance of Magnoliaceae family and Myrica rubra family has been relatively limited. In this paper, the effects of simulated acid rain on characteristic of membrane lipid peroxidant, antioxidant system, chlorophyll content, photosunthetic characteristic, and diurnal course of photosynthetic parameter and chlorophyll fluorescence parameter were studied with pot-grown seedlings. The results showed:1 Study on the Resistance of Acid Rain of 4 Species in Magnoliaeeae family and 2 varieties in Myrica rubra familyThe results showed acid rain treatment at pH 5.0 are unlikely to cause significant damage to those trees, but even have obviously promotion to M. platypetala. When treated by acid rain at pH<3.5, visible foliar injury were induced, membrane lipid preoxidated and permeability increased, Chl content and the pH values of cell sap were significantly declined. Morever, Gas exchange parameters were altered by SAR treatment. However, the species(varieties)differed in their susceptibility to acid rain, so it is necessary to apply more than one index to give a comprehensive evaluation on stress resistant. In this study, acidic tolerance of four species in Magnoliaceae family and two varieties in Myrica rubra family were evaluated by applying the method of subordinate function value. The results showed the acidic tolerance of "M. platypetala"and "Myrica rubra cv. biqizhong" were the strongest, the tolerance of"Myrica rubra cv. dongkui", "Micheliafovelata"and "Paramecia lotungensis" were moderate,"Manglieta insignis"was the weakest.2 Effects of simulated acid rain on membrane lipid peroxidation and antioxidant system of Magnoliaceae tree species With the decrease of pH value of simulated acid rain, the content of glutathione(GSH)and ascorbic acid(ASA)and the activity of superoxide dismutase(SOD)and glutathione reductase(GR)were significantly declined in two species leaves with the decrease of pH value of simulated acid rain, but the activity of peroxidase(POD)increased all though in Michelia platypetala leaves, and increased then decreased rapidly in Manglieta insignis leaves. Moreover, the content of malondialdehyde(MDA)and superoxide anion(O₂^- )and membrane permeability increased obviously. On the other hand, the production of O₂^- were apparently positive correlated with the content of MDA and membrane permeability, and were remarkable negatively correlated with the activities of SOD, GR and the content of ASA. Those observations indicated that the simulated acid rain induced production of O₂^- and disordered the harmonies of antioxidant system, resulted in imbalance of activated oxygen in the production and elimination, and accelerated process of membrane lipid peroxidation. The capability of protective system against active oxygen was higher in Michelia platypetala seedlings than that ofManglieta insignis seedlings.3 Effects of simulated acid rain on photo-ecological characteristic of Magnoliaceae tree species(1) The results showed Chl content, Pn, F_v/F_m, q_p and q_Nwere significantly declined and then increased quickly in 25 days since leaves of MicheIia platypetala and Paramecia Iotungensis treated by acid rain, while Chl content, P_n, F_v/F_m, q_p and q_N obviously decreased and membrane damage increased all the time in the leaves of Manglieta insignis. Those observations indicated that the acidic resistance of Michelia platypetala and Paramecia lotungensis is stronger than Manglieta insignis; (2) The diurnal variation tapes of P_n,WUE and G_s of the three species either exposed to simulated acid rain or not were "two pesks" tape, while The diurnal variation tapes of C_i is not obvious. Besides, the diurnal variation extent of P_n,WUE and G_s of the three species had negative correlation with the pH value of simulated acid rain and the acidic resistance of the three species. However, the results showed that the diurnal curve of Pn of Manglieta insignis seedlings under strong acid rain were changed from "two peaks" tape to "one peak" tape, and had the decline trend all the time; (3) The diurnal variation tapes ofφPSΠ,F_v/Fm,q_P of the three species were "v" tape either exposed to simulated acid rain or not, while The diurnal variation tapes of q_N were "two peaks tape". Besides, the diurnal variation extent ofφPSΠ, F_v/F_m,q_p,q_N of the three species had negative correlation with the pH value of simulated acid rain and the acidic resistance of the three species; (4) Under the simulated acid rain, Maximum assimilation rate (P_max), light saturation point (LSP), apparent quantum yield (AQY), dark respiratory rate(R_d), CO₂ saturation point (CSP), carboxylation efficiency (CE) and photorespiratory rate (R_p) decreased, but light compensation point (LCP) and CO₂ compensation point (CCP) increased. Besides, the extent of the above indices increased gradually with the decrease of pH value of simulated acid rain. The results showed that simulated acid rain decreased the the ability and efficient of light and CO₂ of seedlings leaves. For the three species in Magnoliaceae family, Michelia platypetala seedlings have highest capability of efficient of light and CO₂. Manglieta insignis was the weakest.