Responses To Aluminum Stress In Seedlings Of Phyllostachys Pubescens

Based on the effects of different aluminum(Al) concentrations on the seed germination, seedling root growth, SOD(superoxide dismutase), POD(peroxidase) and MDA(malondialdehyde) in Moso bamboo, this study was to determine the level of Al tolerance for Moso bamboo through the comparison with two rice varieties IR1552 (Al-sensitive)and Azucena (Al-tolerant). With cytological techniques we observed the distribution of Al in the Moso bamboo seedlings, and the influence of Al on the Moso bamboo. The results are as follows:Al concentration of 200μM did not significantly inhibit the seed germination of the Moso bamboo, while 500μM inhibited the germination rate. And the concentration of 2000μM resulted in 50% survival. With 500μM Al, the root growth was inhibited in 1d. The growth did not recover under Al stress within 3 d. While the root growth in IR1552 and Azucena would be more or less recovered within 3d. Under the Al stress for 3 d, the increase of SOD activity in root tips for Moso bamboo was insignificant (p=0.1531), while for IR1552 and Azucena were significant (p=0). The increase of POD activity was significant (p=0.018) for Moso bamboo, highly significant for IR1552 and Azucena. Moso bamboo's POD activity and MDA content in root tips were higher than those in IR1552. It concluded that Moso bamboo had a lower Al-tolerant level than IR1552 .With lumogallion staining and confocal microscopy, the localization of Al in seedling root tips of Phyllostachys pubescens was observed. The results showed that Al was mainly distributed in non-protoplasts, and most of it located in 1~2mm of the root tips. But in the meristematic zone and elongation zone, Al was found in protoplasts, especially in the nucleus. Within a certain range of Al concentrations (0~2000μM), the filtering of Al into root tips would be accelerated as the treated Al concentration increased and/or the treatment prolonged. In addition, Al could induce apoptosis in the root tips of Moso bamboo's seedlings. When the root tips were under 500μM Al for 24 h, there always appeared apoptotic bodies. Only after the Al appeared in nuclei and the apoptotic bodies would appear.