南疆绿洲区水—盐联合胁迫下根系提水作用解析及其吐水动力学模拟

Hydraulic lift is the process of root soil system optimization and utilization of soil water resources in the root zone for water differentiation. It is a common phenomenon of many plants. However, its mechanism under water and salt stress and its regulation effect on crops are not clear. This study will take the saline soil in the oasis area of south Xinjiang and cotton as the research object, through theoretical analysis and experimental research, explore driving force and condition causing hydraulic lift, occurrence time and the lifting volume of water under the combined stresses of water and salt, analyze the differences in soil water and salt distribution induced by hydraulic lift and its effect on nutrient availability, deeply reveal the microscopic mechanism of root hydraulic conductivity change under water and salt stress and its effect on hydraulic lift, obtain the relationship among root characteristics, hydraulic lift and canopy transpiration under the condition of different water and salt stress, clear the response rule of water and salt stress on transpiration, biological traits and yield, determine water and salt dynamic threshold to stimulate root lifting water potential; quantitatively evaluate the dynamic process of crop water conductivity and the hydraulic lift in response to water and salt stress, set up the dynamic model of root system guttation under water and salt stress, and simulate and predict the change of soil moisture after hydraulic lift occurring. The research results can provide solid theoretical support for water and salt regulation research and application in the oasis area of south Xinjiang.

根系提水作用是根土系统对水分分异的根土环境中土壤水资源优化利用的过程,是许多植物所具有的一种普遍现象，但其在水盐胁迫下发生机理及对作物的调控效应尚不明确。本研究拟以南疆绿洲区盐渍土和棉花为研究对象，通过试验研究和理论分析，探讨水盐联合胁迫下根系提水作用发生的驱动力、条件、时间及提升水量，分析提水作用诱导下土壤水盐分布差异及其对养分有效性的影响，深入揭示土壤水盐胁迫引起根系导水率变化的微观机理及其对提水作用的影响，获取不同水盐胁迫条件下根系特性-提水作用-冠层气孔蒸腾之间的相关关系，明晰提水作用下作物蒸腾、生物学性状及产量对水盐胁迫的响应规律，明确能激发作物根系提水潜能的水盐动态阈值；定量表征作物水分传导与根系提水对水盐响应的动力学过程，构建土壤水盐胁迫条件下的根系吐水动力学模型，并对提水作用下土壤水分变化进行模拟预测。研究成果可为南疆绿洲区水盐高效调控研究和应用提供坚实的理论支撑。

根系提水作用是根土系统对水分分异的根土环境中土壤水资源优化利用的过程，也是易发生“上干下湿”的干旱盐渍区高效调控土壤干层的重要调节过程，对该区提高作物对深层水分的利用能力，实现农业可持续发展具有重要的意义。本研究以番茄和棉花为研究对象，通过现场试验和数值计算，研究了水盐联合胁迫下根系提水量的变化规律及根系提水作用诱导土壤干层的盐分分布特征，阐明了根系提水作用下不同水盐胁迫对番茄品质与产量的调控效应，构建了水盐胁迫条件下的根系提水动力学模型；探究了棉花生长发育、生理指标及根系提水量对不同施氮水平的响应规律，揭示了棉花在根系提水作用下的土壤水氮动态变化规律，探明了根系提水诱导下棉田产量、品质及水氮利用效率提高的响应机制。研究成果可为南疆绿洲区水盐高效调控研究和应用提供坚实的理论支撑。主要研究结论如下：.（1）番茄根系提水量随干层土壤含水率的减少而减小，随土壤盐分的增加呈先增后减的趋势，且番茄全生育期根系总根系提水量与根系最大根际导度相关。.（2）盐分和根系提水量对上层土壤电导率的影响显著，水分对上层土壤电导率影响显著，但对下层土壤电导率影响不显著。.（3）“上干下湿”条件下，适当的水盐胁迫会提高番茄品质，水分和盐分胁迫抑制了番茄产量的增加。.（4）根系提水量模拟值的变化趋势与实测值相同，达到峰值的时间也与实测值相同。在模拟土壤含水率变化时，模型RMSE和MAE均较接近于0，模拟效果较好。.（5）施氮对上部轻旱条件下的棉花根系生长有显著促进作用，重旱时能缓解根系萎缩；施氮量越大提水现象越明显，重旱时夜间提水量有显著上升。.（6）“上干下湿”条件下，施氮和根系提水均可起到明显的增产效果；施氮能够提高皮棉的上半部平均长度和伸长率。增施氮肥能提高棉花植株的氮累积量，降低氮肥回收率与氮肥偏生产力。“上干下湿”条件下棉田施氮量为 240 kg·hm-2 时水氮利用效率更高，产量更稳定。