春玉米叶片光合生理参数对土壤水分的阈值响应及其生产力分级

试验设正常灌水处理和干旱胁迫处理,讨论春玉米叶片的光合生理参数对土壤水分的阈值响应并进行生产力分级。结果表明:正常灌水处理的叶片光合速率(Pn)、蒸腾速率(Tr)和气孔导度(Gs)呈单峰曲线变化,胞间CO2浓度(Ci)和气孔限制值(Ls)对水分变化具有相反的响应变化。干旱胁迫处理下叶片的Pn、Tr在进行控水后明显下降,灌浆以前Pn下降主要是由气孔限制引起的。随着水分胁迫的加剧,光合结构受损,Pn下降,主要受非气孔因素限制。短期干旱胁迫会适当降低玉米的水分利用效率(WUE),但是下降程度不显著,WUE能达到中等水平。长期严重的水分胁迫后,WUE下降明显,与正常灌水处理相比差异极显著。以光合生理参数为指标对玉米土壤水分有效性及生产力进行分级与评价,确定当36.8%<土壤相对湿度(RWC)<42.7%时为低产低效水;42.7%

Threshold Responses of Leaf Photosynthetic Physiological Parameters of Spring Maize to Soil Moisture and Its Productivity Classification

Two modes including normal irrigation treatment and water stress treatment were designed in this experiment to discuss the threshold responses of leaf photosynthetic physiological parameters of spring maize to soil moisture and its productivity classification. The results showed that the change curves of photosynthetic rate (Pn),transpiration rate (Tr) and stomata conductance (Gs) were unimodal under normal irrigation treatment. The response of intercellular CO2 concentration (Ci) to soil moisture was opposite to that of stomata limitation (Ls). The Pnand Trvalues were significantly decreased under water stress treatment,and the reduction of Pnvalue was mainly caused by the stomata limitation before grain-filling. As the degree of water stress was aggravated and the photosynthetic structure was damaged,the reduction of Pnwas mainly caused by non-stomata limitation. Short-term water stress reduced the water use efficiency (WUE) of maize plant appropriately,which,however,was not significant,and the WUE could be reached a medium level. After a long-term and serious water stress,the WUE was decreased significantly compared to the situation under normal irrigation. Based on the photosynthetic physiological parameters,the soil moisture availability and the productivity of maize were classified and evaluated. The relative water content (RWC) ranging from 36. 8% to 42. 7% was classified as the low-yield and low-efficiency water treatment,that from 42. 7% to 60. 4% as the medium-yield and medium-efficiency one,that from 60. 4% to 77. 5% as the mediumyield and high-efficiency one,and that from 77. 5% to 80. 6% as the high-yield and high-efficiency one. It was observed that the RWC about 77. 5% was optimal.