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The diurnal variations of photosynthetic rate and water use efficiency in Setaria italica leaves

Liao Jianxiong, Wang Genxuan

State Key Laboratory of Arid Agroecology of Lanzhou University.Lanzhou 730000,Gansu

Abstract

Diurnal changes of photosynthetic rate in millet leaves were observed under low relative humidity (about 5% RH), high CO_(2) concentration (730 #mu#l CO_(2)/L) and assimilate accumulation by heat girdling of leaf sheath by CI-301 CO_(2) gas analyzer. It was found that the midday depressions of photosynthesis in nature conditions and low RH and high CO_(2) concentration treatments were significantly correlated with the accumulation of photosynthates. High CO_(2) concentration (730 #mu#l CO_(2)/L) can increase photosynthetic rate and decrease transpiration rate (E), so improve water use efficiency (WUE) greatly. Low relative humidity (5% RH) can decrease photosynthetic rate (P_(n)), but improve WUE too, it is why low RH decrease stomatal aperture and the E is more dependent on the stomata than P_(n); assimilate accumulation (heat girdling of leaf sheath) could decreased P_(n) and WUE.

Key words: Millet;Midday depression of photosynthetic rate;Water use efficiency

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Citing This Article：

Liao Jianxiong, Wang Genxuan. The diurnal variations of photosynthetic rate and water use efficiency in Setaria italica leaves. Acta Physiol Sin 1999; 51 (4): (in Chinese with English abstract).