冬小麦不同冠层叶片光合蒸腾和水分利用效率变化特征及对灌溉的响应

为了解冬小麦不同冠层叶片光合和蒸腾作用特征以及随水分条件的变化规律，通过田间试验，以冬小麦京冬22为试验材料，设置0 mm（T₀）、220 mm（T₁）、280 mm（T₂）3种水分处理，比较分析了冬小麦不同冠层叶片净光合速率、蒸腾速率及水分利用效率对光合有效辐射和灌溉响应的差异。结果表明，三种水分处理下，冬小麦不同冠层叶片的蒸腾速率和光合速率随光合有效辐射的增加而增加，随后趋于平缓。不同冠层叶片蒸腾速率、光合速率对光合有效辐射的响应表现为上层>中层>下层；不同冠层叶片WUE对光合有效辐射的响应表现为上中层>下层。光合有效辐射相同时，灌水处理（T₁和T₂）的叶片光合蒸腾速率均高于不灌水处理（T₀）。T₁、T₂处理下，叶片光合速率对光合有效辐射响应在整个生育期内表现为灌浆期>抽穗期>成熟期>拔节期，蒸腾速率对光合有效辐射响应在整个生育期内表现为抽穗期>灌浆期>拔节期>成熟期；T₀处理下，叶片光合速率对光合有效辐射响应在整个生育期内表现为灌浆期>拔节期>抽穗期>成熟期，蒸腾速率对光合有效辐射响应在冬小麦整个生育期内表现不显著。因此，在进行小麦叶片到单株光合蒸腾尺度拓展估算时，应考虑冠层位置和水分条件对拓展结果的影响。

Variation Characteristics of Photosynthesis, Transpiration and WUE of Winter Wheat Leaves in Different Canopy Layers and Their Response to Irrigation

In order to understand the characteristics of photosynthesis and transpiration of winter wheat leaves under different canopy conditions and their response to irrigation, field experiments were carried out with a winter wheat variety Jingdong 22 as the experimental material under three irrigation treatments:T₀ (0 mm), T₁ (220 mm) and T₂ (280 mm). The response of net photosynthetic rate, transpiration rate and water use efficiency (WUE) to photosynthesis active radiation(PAR) and irrigation in different canopy layers of winter wheat was analyzed under different water.The results showed that the photosynthesis rate, transpiration rate and WUE of the canopy leaves of winter wheat under the three irrigation treatments increased first and then stabilized with the increase of PAR.The responses of photosynthesis rate and transpiration rate of different canopy leaves to PAR ranked as upper layer> middle layer> lower layer. The response of WUE of different canopy leaves to PAR ranked as upper and middle layers > lower layer. With the same PAR, the photosynthesis rate and transpiration rate of leaves treated by irrigation (T₁ and T₂) were higher than those of leaves treated by no irrigation (T₀). Under treatments of T₁ and T₂, the response of photosynthesis rate of leaves to PAR ranked as grain filling stage > heading stage >maturity stage > jointing stage in the whole growth period. The transpiration rate response to PAR ranked as heading stage > grain filling stage >jointing stage >maturity stage during the whole growth period. Under T₀ treatment, the response of photosynthesis rate of leaves to PAR ranked as grain filling stage > jointing stage > heading stage >maturity stage. And the response of transpiration rate to PAR did not change significantly during the whole growth period of winter wheat. The effects of canopy position and irrigation conditions on the expansion results should be considered when estimating photosynthesis and transpiration rate of plant from leaf scale.