Abstract: The present study investigated the morphological and physiological responses of sorghum BTx623 seedlings under different aluminum （Al） concentrations （0， 25， 50 and 100μmol·L-1， pH=4.5）. It was shown that comparing with the control， Al stress significantly reduced the root relative growth （RRG） and root length， while the height of seedlings was not significantly influenced. The fresh weight， dry weight， chlorophyll content and root dehydrogenase activity of seedlings increased by 11.4%， 50.0%， 32.1% and 32.5% under 25 μmol·L-1 Al stress， whereas decreased under 50 and 100 μmol·L-1 Al stresses. Al accumulation， H2O2 production and MDA content of the root notably elevated as the increase of Al concentration. Further analysis revealed that the SOD and CAT activities were significantly up\|regulated by 44.5% and 33.7% under 25 μmol·L-1 Al stress， while POD activity was not significantly affected under Al stress. However， higher concentration of Al （100 μmol·L-1） could inhibit the activities of these three anti\|oxidant enzymes. In conclusion， 25 μmol·L-1 Al stress induced the up\|regulation of anti\|oxidant enzymes to alleviate the oxidative stress and increased the fresh weight， dry weight and chlorophyll content， but inhibited the root elongation of sorghum BTx623 seedlings. However， 50 and 100 μmol·L-1 Al stress had significant inhibitory effects on both above and underground parts of the seedlings.

Key words: sorghum, aluminum stress, antioxidase, H2O2 in situ detection