Studies On The Effects Of Simulated Acid Rain On Camelia Japonica And Camellia Sasanqua

As the urbanization process is at a high speed, acid rain become a serious environmental problem. Many researchers have devoted much attention to the impact of acid rain on agriculture, forest and water ecosystem, but there were little research on the impact of perennial landscape plants to acid rain, especially acidic tolerance of Camellia family has been relatively limited. In this paper, the effects of simulated acid rain on characteristic of membrane permeability, antioxidant system, chlorophyll content, MAD content, morphological index and gas exchange parameters were studied with pot-grown plants of Camelia japonica and Camellia sasanqua. Investigate the mechanism of resistance of these two landscape plants, in order to provide theoretical basis and scientific reference for the choice of landscaping and vegetation constructing in the area seriously damaged by acid rain. The results showed:1,Effects of simulated acid rain on growth status and leaves visible injury of Camelia japonica and Camellia sasanquaThe results showed acid rain treatment at pH 4.0 are unlikely to cause significant damage to those trees. platypetala. When treated by acid rain at pH≤3.0, visible foliar injury were indueed, growth status were significantly inhibited. Camelia japonica showed visible injury of different degrees at pH=2.0, the damaged leaves area accout for 5%, and Camellia sasanqua showed at pH=3.0, the damaged leaves area accout for 10%. Accord to the determination method of LIR, the reselts showed that these two plants possess strong acidic tolerance, and Camelia japonica is the stronger one.2,Effects of simulated acid rain on membrane permeability and antioxidant system of Camelia japonica and Camellia sasanquaWith the increase of pH value of simulated acid rain, membrane permeability and MAD content increased in two species leaves, and they had significant positive correlation. Membrane permeability of Camelia japonica significantly higher than CK in pH=2.0, and Camellia sasanqua in pH=3.0. The MAD content of two species reached significant differences in pH=3.0. Under the acid, SOD and CAT activity of Camelia japonica generally increased first and then dropped as the pH values desersing, they reserched the hightest point in pH=3.0 and pH=4.0. POD activity showed a gradual decline in the eariy stage increased fist and then decreased in the later stage (the hightest point in pH=4.0). SOD and CAT activity of Camellia sasanqua also generally increased first and then dropped, both of them reserched the hightest point in pH=4.0. POD activity generally decreased and then increased. Those observations indisicated that low concentrations of the simulated acid rain were unlikely to cause significnnt effects, but high concentrations, as Camelia japonica at pH<3.0 and Camellia sasanqu at pH≤3.0, decreased induced production of O2- and disordered the harmomes of antioxidant system, resulted in imbalance of activated oxygen in the production and elimination, accelerated process of memberane lipid peroxidation, and MDA content. With the concentration of acid rain increasing, damage of plant were gradually increasing.3,Effects of simulated acid rain on photo-eealooral characteristic of Camelia japonica and Camellia sasanquaWith the increase of pH value of simulated acid rain, chlorophyll content of Camelia japonica had no significant changes campared to CK at pH≥3.0, but increased significantly at pH=2.0, chlorophyll content of Camellia sasanqu generally decreased first and then increased (the hightest point in pH=4.0). Pn, Gs and Ci of Camelia japonica leaves generally increased first and then decreased (the hightest point in pH=4.0). Ls decreased firstly and then increased (the hightest point in pH=4.0). Pn, Gs and Ci of Camellia sasanqu leaves generally decreased in the early stage, increased first and then decreased at later (the hightest point in pH=4.0). Ls decreased then increased. The research of Gs, Ci and Ls showed that under the heavy acid rain (pH=3.0) stress, the decraese of photosynthetic rate was mainly caused by the factors of stomata. Under the acid rain of pH=3.0, Pn of Camelia japonica leave was significantly lower than the sixth treatment CK. Pn of Camellia sasanqu leave was significantly lower than the first treatment CK. Those observations indicated that the effect of acid rain on the photosynthetic system of Camellia sasanqu was larger than Camelia japonica.Those observations indicated that the order of the Camelia japonica and Camellia sasanqua againsting acid rain capacity was Camelia japonica>Camellia sasanqu. The threshold value which Camelia japonica can be invisibly damaged was between pH=2.0-3.0, and The threshold value of Camellia sasanqu was pH=3.0.