摘要:为探索宁夏北部春小麦叶片光合作用应对未来气候变化的响应机制，进一步阐明气候变暖对干旱半干旱区春小麦生长的影响。采用自动控制红外线辐射器野外增温模拟气候变化的方法，以不做增温处理的春小麦冠层温度为基础温度，设置不同增温梯度（CK：0℃、T1：0.5℃、T2：1℃、T3：1.5℃、T4：2.0℃），开展气温升高对宁夏北部春小麦全生育期叶片叶面积、光合色素含量、光合特性、叶绿素荧光参数、干物重、产量等指标的影响试验。结果表明：春小麦苗期-拔节期，温度增加0.5℃时叶片叶面积、叶绿素含量、Pn（净光合速率）、WUE（叶片水分利用效率）呈上升的趋势。温度增加1.0-2.0℃时以上指标呈下降趋势，同时Ls（气孔限制值）呈上升趋势，Ci（胞间CO₂浓度）呈下降的趋势，说明此时叶片Pn的下降主要是叶绿素含量的下降和气孔限制导致的。春小麦拔节期之后，叶片叶面积、叶绿素含量、Pn、WUE、Ls随温度的增加呈下降的趋势，而Ci随温度的增加呈上升的趋势，说明此时叶片Pn的下降则主要是叶绿素含量的下降和非气孔因素导致。叶绿素荧光参数表明在苗期-拔节期，春小麦对温度升高具有一定的抗逆性，能应对增温胁迫以热耗散的形式做出自我保护。拔节期以后，春小麦叶片光系统Ⅱ反应中心受温度胁迫可逆性失活，光合机构受到破坏。另外，春小麦干物重的变化趋势与叶面积等指标的变化趋势基本一致，产量及产量构成因素小穗数、穗粒数、千粒重随温度的增加显著降低，说明春小麦拔节期之前增温0.5℃有利于提高叶片光系统Ⅱ的潜在活性，增加叶片抗逆性，促进光合作用的进行，最终使光合产物累积量增多。增温梯度过大或增温时间过长则会使春小麦受高温胁迫，导致叶片光系统Ⅱ原初光能捕获、电子传递等效率降低，光合机构受到破坏，致使叶片Pn、WUE等数值下降，光合产物累积量减少，产量减少。



Abstract:In order to explore the response mechanism of photosynthesis of spring wheat leaves to climate change in northern Ningxia, the effects of warming on the growth of spring wheat in arid and semi-arid regions were further clarified. The effects of elevated temperature on leaf area, photosynthetic pigment content, photosynthetic characteristics, chlorophyll fluorescence parameters, and dry weight of spring wheat during the growth period in northern Ningxia were tested using automatic control infrared radiator for simulating climate change in the field. The method was based on the temperature of the spring wheat canopy temperature without treatment, and different temperature gradients were set (CK:0℃, T1:0.5℃, T2:1℃, T3:1.5℃, and T4:2.0℃). The results showed that leaf area, chlorophyll content, Pn (net photosynthetic rate), and WUE (leaf water use efficiency) of spring wheat had an upward trend when the temperature increased by 0.5℃ during seedling-jointing stage. The above indices indicated a downward trend when the temperature increased by 1.0-2.0℃, while Ls (stomatal limitation value) showed an upward trend and Ci (intercellular CO₂ concentration) showed a downward trend, indicating that the decrease of Pn in leaves was mainly caused by the decrease of chlorophyll content and stomatal limitation. However, after the jointing stage, the leaf area, chlorophyll content, Pn, WUE, and Ls were decreased when increasing temperature, while Ci increased, which indicating that the decrease of leaf Pn was mainly caused by a decrease in chlorophyll and non-stomatal limitation. Chlorophyll fluorescence parameters showed that spring wheat was resistant to temperature rise before jointing stage, and could cope with the warming stress to protect itself in the form of heat dissipation. After the jointing stage, the photosystem II reaction center of spring wheat leaves was reversibly inactivated by temperature stress, and the photosynthetic apparatus was destroyed. In addition, the change trend of dry weight of spring wheat was basically consistent with that of leaf area and other indicators. The yield and yield components, spikelet number, grains number per spike, and 1000-grain weight decreased significantly with rising temperature. When 0.5℃ rising before jointing stage, it was beneficial to increase the potential activity of leaf photosystem II, increase leaf resistance, promote photosynthesis, and eventually increase photosynthetic product. If the temperature gradient is too large or the heating time is too long, spring wheat will be subjected to high temperature stress, which leads to the reduction of the original light energy capture and electron transfer efficiency of the leaf photosystem II, and the photosynthetic mechanism is damaged. Finally, the values of Pn and WUE in the leaves of spring wheat decreased, the accumulation of photosynthetic products and the yield decreased.





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