作物水分利用效率研究方法及尺度传递研究进展

A review of progress in research and scaling-up methods of crop water use efficiency

提高作物水分利用效率(WUE)是缓解农业生产水资源匮乏压力的有效途径,而水分利用效率尺度传递是各尺度WUE相互表征、验证并应用于实际生产的基础。本文概述了作物叶片、植株、群体尺度WUE的主要观测技术,包括叶片气体交换测定、碳同位素判别、桶栽称重、涡度相关观测等,其中碳同位素判别法为研究作物水分利用的长期累积效应提供了新的思路,且适用于多个尺度;总结了各尺度WUE的影响因子及作物耗水的生理机制,阐明各尺度WUE均受气孔导度调控。讨论了叶片到植株、叶片/植株到群体的尺度传递的可行性,集中分析了尺度传递的主要限制因素,指出叶片到植株的传递研究难点集中于叶片分布和光分布的不确定性、植物夜间呼吸和蒸腾以及植物适应环境的生理调节机制等过程;而叶片/植株到群体的传递研究主要受冠层形态学差异、冠层阻力、土壤蒸发及植物同化物分配机制等限制。最后总结了尺度传递方法的现有研究成果。目前作物WUE尺度传递主要依靠模型的完善和观测手段的提高,叶片到单株的尺度传递需关注日间与夜间耗水的分离及作物各部分的光合特性;叶片/单株到群体的传递可先明确蒸散结构,了解耗水特征,再以气孔导度和冠层导度的关系为切入点,利用模型探究传递机制。

Increasing crop water use efficiency(WUE)is an effective way of alleviating agricultural water scarcity.The scaling up of water use efficiency is the basis for mutual representation,verification and application of achievements at various scales.This paper summarized the main observation technologies of leaf-scale,plant-scale and plantation-scale WUE.At present,the widely used methods include leaf gas exchange measurement,carbon isotopic discrimination,pot weighing method,eddy covariance system,etc.Carbon isotope discrimination provides a new idea for the study of long-term cumulative effects of crop water use conditions which is also available at every scale.We reviewed the impacting factors and the related physiological mechanisms of crop water use at multi-scale WUE.Crop WUE at each scale was regulated by stomatal conductance and crops usually regulated stomatal aperture to response to temperature,humidity,CO2and other interactive environmental factors.Stomatal optimization theory essentially sought optimal state of stomata under complex environmental conditions to coordinate the process of photosynthesis and transpiration of crops.Instantaneous WUE at leaf scale cannot directly represent water use status at larger spatial and temporal scales.Thus we also discussed the feasibility of scaling up WUE from leaf to plant to plantation scales and analyzed the main limiting factors at each scale transfer.We pointed out the difficulties in transfer from leaf to plant in terms of WUE.It mainly focused on three points-uncertainty in leaf and light distributions,plant nighttime respiration and transpiration,and plant physiological adjustment mechanisms.Research on leaf to plant to plantation scale transfer was mainly influenced by canopy internal resistance,boundary layer resistance,soil evaporation,night transpiration of crops,crop water use and assimilates partitioning mechanism.Finally,existing research achievements on scale transfer were summarized.At present,WUE scale transfer depended mainly on improvement of models and observation methods.The transfer from leaf to plant focused on separation of water use during day and night and photosynthetic characteristics of each part of the crop.For transfer from leaf to plant to plantation scale,studies explored efficient ways.First,studies understood the structure of evapotranspiration and confirmed the characteristics of water use.Second,studies used the relationship between stomatal and canopy conductance as breakthrough point via models to explore transfer mechanisms.Actually,several models had already been established and applied in this respect.