冬小麦对有限水分高效利用的生理机制

通过对不同土壤供水条件下的孕穗开花期的冬小麦叶片ＣＯ２／ Ｈ２Ｏ 气体交换参数的系统测定，研究了光合速率（Ｐｎ） 、蒸腾速率（ Ｔｒ） 、气孔导度（ Ｇｓ） 、细胞间隙ＣＯ２ 浓度（Ｃｉ） 、叶温（ Ｔｌ） 与水分利用效率（ ＷＵＥ） 间的关系．结果表明，ＷＵＥ 并不随Ｐｎ 的增长直线增长，而是呈现出二次曲线的变化趋势；只有当蒸腾达到一定程度时，Ｔｒ 才对ＷＵＥ 产生影响，而Ｔｒ 过大时Ｗ ＵＥ 则有下降的趋势；ＷＵＥ 与Ｃｉ 呈负相关，随Ｃｉ 的增加ＷＵＥ 呈递减趋势；叶温升高对光合和蒸腾都有促进作用，当超过了某种限度则表现为抑制作用，表明在一定温度范围内，Ｔｌ 升高对水分利用不利；随Ｇｓ 的增大，ＷＵＥ 增大到一定程度则不再增加，甚至出现一种回落趋势

Physiological mechanism of highly efficiency use of limited water supply by winter wheat

By determining the CO 2/H 2O gas exchange in winter wheat leaves during its earring to flowering stages under different water supply, this paper dealt with the relationships of water use efficiency (WUE) with photosynthetic rate(Pn), transpiration rate(Tr), stomatal conductance(Gs), intercellular CO 2 concentration(Ci) and leaf temperature(Tl). The WUE presented a quadratic relation with Pn. It increased to a certain degree with increasing Tr, and then decreased when Tr was higher than a certain value. It decreased remarkably with increasing Ci. The increase of Tl promoted the photosynthesis and transpiration, but when T1 was up to a certain degree, it showed an inhibitory effect on WUE, indicating that in a certain range, the increase of T1 is not beneficial to WUE. With the increase of Gs, WUE reached to a certain high level and then fall down.