土壤水分对山杏光合作用日变化过程的影响

在半干旱黄土丘陵区,应用CIRAS -2型光合作用测定系统,通过测定8个土壤水分梯度下山杏(Prunus sibirica L.)叶片光合生理参数的日变化过程,探讨土壤水分变化对山杏光合作用日变化过程的影响.结果表明:1)山杏光合作用日变化过程和光合午休的原因,随土壤水分的变化而明显不同,当土壤相对含水量(WT)在56.1％～66.1％之同时,山杏没有发生光合作用午休现象,但超出此土壤水分范围会发生不同程度的光合午休现象,当Wr在93.2％ ～77.0％之间时,山杏光合午休的主要原因是气孔因素限制,当Wr在49.3％ ～37.3％之间时,光合午休的主要原因开始由气孔因素向非气孔因素转变,当Wr小于37.3％后,光合午休的主要原因为非气孔因素限制,即叶肉细胞光合能力下降；2)当Wr在49.3％～77.0％之间时,山杏同时具有较高的光合速率和水分利用效率.

Effects of soil moisture on photosynthesis diurnal changes of Prunus sibirica L.

Using CIRAS-2 portable photosynthesis system,we measured the photosynthetic parameters of Prunus sibirica L.under eight soil moisture conditions in loess hilly-gully region to investigate the impact of soil moisture on the photosynthetic diurnal changes.The results showed that： 1） The reasons for photosynthetic midday depression of Prunus sibirica L.changed with different soil moisture conditions.When relative soil moisture content（Wr） was in the range of 56.1%-66.1%,the phenomenon of photosynthesis midday depression does not occur.But beyond this range,the phenomenon would occur in different soil moisture levels.When Wr was in 93.2%-77.0%,the main reason of photosynthesis midday depression was stomatal limitation.As Wr was in 49.3%-37.3%,the midday depression was changed from stomatal limitation turned to non-stomatal limitation,when Wr less than 37.3%,the main reason of photosynthesis midday depression was non-stomatal limitation,which means the photosynthetic capacity of mesophyll cells declined.2）When Wr was in the range of 49.3%-77.0%,Prunus sibirica L.had a higher photosynthetic rate and water use efficiency.