Abstract: The physiological responses in transgenic Bt rice expressing Cry1Ab (KMD) and in the isogenic non-transgenic rice (XSD) to elevated CO₂ (750 μL·L^-1) were studied after planting for 60 and 120 days in opentop chambers (OTC). The results showed that rice chlorophyll a, chlorophyll b, chlorophyll a+b, soluble protein content and glutamine synthetase activity increased from 60 to 120 days, while the content of free amino acids decreased significantly. The value of chlorophyll a/b significantly increased with the elevation of CO₂ level. Elevated CO₂ significantly reduced the contents of water, soluble protein, chlorophyll a and c in rice foliar tissue, and chlorophyll b content significantly increased at 60 days but significantly decreased at 120 days. The content of soluble protein decreased significantly and that of free amino acids increased significantly. Moreover, the glutamine synthetase activity wasn’t affected by elevated CO₂ at 60 days, while it was significantly reduced at 120 days. There were significant differences in soluble protein content and glutamine synthetase activity but not in contents of chlorophyll and free amino acids between transgenic Bt rice and nontransgenic rice. Compared to nontransgenic rice, the glutamine synthetase activity of transgenic rice was significantly lower under the ambient or elevated CO₂ treatments at 60 and 120 days.

Key words: alpine treeline, organic fraction, Larix potaninii, litter decomposition