Studies On Differential Mechanisms Of Arabidopsis Thaliana In Response To Three Types Of Simulated Acid Rain

Acid rain (AR) has become a worldwide serious environmental problem. Along with Europe and North America, China has become the third largest AR-affected area of in the world. Hence, it is of great practical significance in ecological protection and agricultural industry to study the mechanisms on how AR affects plant growth and how plants respond to AR. Currently, studies on the effects of different types of AR on plants are still limited. In this paper, we used the model plant Arabidopsis thaliana (wild type and several mutants) as the material, and treated them with pH3.0nitric-rich (N-SiAR), sulfate and nitrate mixed (SN-SiAR) and sulfuric-rich simulated AR (S-SiAR) for5days. Then we used physiological, biochemical and quantitative real-time PCR (qRT-PCR) methods to analyse the responses of A. thaliana to three types of SiAR in oxidative stress induced damages, nitrogen (N) metabolism and nitric oxide (NO) production at physiological, biochemical and gene expression levels.The major results are shown as follows:1. N-SiAR caused less damage to A. thaliana than that by SN-SiAR or S-SiAR including less necrosis percentage, lower malondialdehyde (MDA), chlorophyll, hydrogen peroxide (H2O2) and GSH content and lower superoxide dismutase (SOD), peroxidase (POD) activities.2. Among the three types of SiAR, N-SiAR treated A. thaliana had the highest N content, nitrate reducrase (NR) and nitrite reductase activity (NiR), as well as NRT1;1, NIA1, NIA2and NIR1genes expression level.3. After we assayed the NO content in A. thaliana leaves under SiAR treatment for5days, we found that in general N-SiAR treated seedlings had a higher NO content level compared to SN-SiAR or S-SiAR treated ones and NO content reached the highest at26h.4. Exogenous NO application can significantly decreased necrosis percentage and MDA content with stable NO content in vivo. 5. The application of NO scavenger cPTIO, NR inhibitor Na2WO4and NO synthetase (NOS) inhibitor L-NNA could reduce NO content while increase necrosis percentage.6. Finally, we found that NO overproducing mutant (noxl) was less injured than wild type of A. thaliana, while NO-deficient mutants (nial, nia2; Atnoal) were more injured by SiAR.Our results showed that N-SiAR induced less necrosis percentage and lower activities of antioxidant enzymes in A. thaliana than that by SN-SiAR and S-SiAR. Meanwhile, N-SiAR treated seedlings maintained an elevated N metabolism compared with SN-SiAR or S-SiAR treated ones. Besides, A. thaliana under N-SiAR treatment kept higher NO content than SN-SiAR and S-SiAR treatment. Addition of NO donor could enhance the tolerance of A. thaliana to AR, while NO synthesis inhibitors and NO scavenger resulted in more injuries to A. thaliana. Moreover, A. thaliana mutant with high NO level in vivo was less harmful than wild type A. thaliana. On the contrary, A. thaliana mutants with low NO level in vivo exhibited more necrosis percentage. Taken together, we suggested that N-SiAR induced less injury to A. thaliana than SN-SiAR and S-SiAR because of greatly enhanced N metabolism and NO content, and plants may cope with AR stress by enhancing N metabolism and NO level.