摘要
摘要:奢侈蒸腾耗水对作物光合及产量形成贡献较低，而开花灌浆期是冬小麦产量形成的关键期，精准调控作物蒸腾耗水、明确影响奢侈蒸腾的土壤水分阈值，对提高冬小麦的水分利用效率至关重要。本研究以冬小麦品种‘石新828’为材料，在人工气候生长箱进行盆栽试验，定量研究土壤水分对作物气孔导度、光合速率和蒸腾速率的影响，明确开花灌浆期奢侈蒸腾产生的土壤水分阈值。结果表明：气孔导度与土壤水吸力关系密切，在土壤水吸力较低时，气孔导度随土壤水吸力增加而迅速降低，而土壤水吸力较高时，气孔导度降低速度变缓。光合速率随土壤水吸力增加以抛物线的形式递减，当土壤水吸力低于1.2 MPa时，光合速率接近最大值，随后土壤水吸力继续增加，光合速率逐渐降低。蒸腾速率随着土壤水吸力增加呈线性递减，降低速率为2.3 mmol·m^-2·s^-1·MPa^-1。光合速率与蒸腾速率的关系符合米氏方程，蒸腾速率低于2.179 mmol·m^-2·s^-1时，光合速率随蒸腾速率线性增加，当蒸腾速率高于此值时，单位光合速率的增加变缓，奢侈蒸腾开始产生，此值所对应的土壤水吸力为1.76 MPa，此时叶片光合速率处于较高（16 μmol·m^-2·s^-1左右）水平，叶片水平水分利用效率（WUE_L）达到最高7.3 μmol（CO₂）·mmol^-1（H₂O）。综上所述，小麦叶片奢侈蒸腾的发生始于水分利用效率从最高转向降低、光合速率处于较高水平而非最大。通过光合随蒸腾变化的米氏方程关系及蒸腾与土壤水吸力的线性关系，可以确定土壤水吸力1.76 MPa为小麦开花灌浆期叶片奢侈蒸腾发生的土壤水分阈值。
关键词:奢侈蒸腾/
水分利用效率/
水分阈值/
气孔导度/
冬小麦
Abstract:Luxury transpiration water consumption has a lower contribution to the formation of photosynthetic products and crop yield, and the flowering and filling stage is the key period for the yield of winter wheat. In order to efficiently and accurately regulate the transpiration of crops, to determine the soil moisture threshold affecting luxury transpiration is important. In this study, the winter wheat variety 'Shixin 828' was used as study material. Pot experiments were carried out in an artificial climate growth box. The effects of soil moisture on stomatal conductance, photosynthetic rate and transpiration rate of crops were quantitatively studied in order to define soil moisture threshold for luxury transpiration at flowering and filling stage. The results showed that the stomatal conductance was closely related to soil water suction. When soil water suction was low, stomatal conductance decreased rapidly with the increase in soil water suction. When soil water suction was high, stomatal conductance decreased slowly. When water suction was less than 1.2 MPa, the photosynthetic rate was close to the maximum value. Then as water suction increased, the photosynthetic rate decreased gradually in the form of a parabola. The transpiration rate decreased linearly with a reduction rate of 2.3 mmol·m^-2·s^-1·MPa^-1 as soil water suction increased. The coupling relationship between photosynthesis and transpiration was described by the Michaelis-Menten equation. When the transpiration rate was lower than K_Tr=2.179 mmol·m^-2·s^-1, the photosynthetic rate increased linearly with the transpiration rate; but when the transpiration rate was higher than K_Tr, the increase in net photosynthetic rate became slower, and luxury transpiration occurred. When soil water suction corresponded to the luxury transpiration threshold of K_Tr (1.76 MPa), the leaf photosynthetic rate was at a high level (about 16 μmol·m^-2·s^-1), and the leaf water use efficiency (WUE_L) was at the highest level[7.3 μmol (CO₂)·mmol^-1(H₂O)]. In summary, the luxury transpiration of wheat leaf started with a shift from the highest WUE_L to lower while photosynthetic rate maintaining a rather higher level. Based on the Michaelis-Menten equation, the relationship between photosynthesis and transpiration, and the linear relationship between transpiration and soil water suction, soil water suction of 1.76 MPa was found to be the soil water threshold for the start point of luxury transpiration of wheat leaves during the flowering and filling stage.
Key words:Luxury transpiration/
Water use efficiency/
Water threshold/
Stomatal conductance/
Winter wheat



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