Abstract: Effects of doubled CO2 on the contents of chlorophyll and carotenoid per unit fresh weight and per unit area of leaves and PS Ⅱ functions of Setaria italica (L.) Beauv. were studied. The experimental results showed that the contents of chlorophyll and carotenoid, the proportion of opened PS Ⅱ reaction center from the mature leaves at jointing stage and the mature flag leaves at grouting stage were raised with CO2 enrichment. However, qN value and the overall photochemical quantum yield of PS Ⅱ , as well as the Fv/Fo, Fv/Fro and Fd/Fs in the above-mentioned leaves both at the jointing and grouting stage in response to doubled CO2 were different. The final outcome showed that the photosynthetic functions from the leaves at jointing stage improved by doubled CO2 were better than those from the flag leaves at grouting stage.

Key words: Setaria italica, Doubled CO2 concentration, Photosystem Ⅱ functions, Efficiency of energy conversion, Photochemical quantum yield