Abstract: In order to understand the diurnal variation of photosynthetic characteristics of Zaosu and Hongzaosu pears, the diurnal variation of photosynthetic characteristics was measured by LI-6400XT portable photosynthetic measurement system. The results showed that the diurnal changes of the net photosynthetic rate(Pn) of Zaosu,Hongzaosu pears were both double-peak curve,and the mean of the Pn of Zaosu was 5.07 μmol/(m²·s),which was larger than that of Hongzaosu,4.91 μmol/ (m²·s).The diurnal variation of the Tr of Zaosu and Hongzaosu pears was a double-peak curve,and the Tr of Zaosu pear was smaller than that of Hongzaosu pear.Zaosu and Hongzaosu pears had photosynthetic “ siesta”phenomenon,and the main reason was stomatal restriction.There was little difference in WUE between Zaosu and Hongzaosu pears(2.05,2.02 μmol/mmol respectively),and the diurnal variation trend of Gs was the same.

Key words: Arid desert area, Zaosu pear, Hongzaosu pear, Photosynthesis, Diurnal variation

摘要： 为了解河西走廊早酥和红早酥梨光合作用日变化的差异，利用LI-6400XT便携式光合作用测定系统对其光合特性日变化进行测定。结果表明，早酥和红早酥梨的净光合速率（Pn）日变化均为双峰型曲线，早酥的Pn均值为5.07 μmol/(m²·s)，大于红早酥的Pn均值［4.91 μmol/(m²·s)］；早酥和红早酥梨的蒸腾速率（Tr）日变化为双峰曲线，早酥的Tr小于红早酥梨；早酥和红早酥梨均存在光合“午休”现象，原因主要为气孔限制因素。早酥和红早酥梨的日均水分利用效率(WUE)差异不大，分别为2.05、2.02 μmol/mmol，气孔导度（Gs）的日变化趋势呈相同规律。

关键词: 干旱荒漠区, 早酥梨, 红早酥梨, 光合作用, 日变化