The University of Sydney, School of Life and Environmental Sciences, Sydney Institute of Agriculture, Sydney, New South Wales, Australia.
The University of Sydney, Plant Breeding Institute, Narrabri, New South Wales, Australia.
J Exp Bot. 2018 Jan 23;69(3):349-369. doi: 10.1093/jxb/erx415.
Yields of grain legumes are constrained by available water. Thus, it is crucial to understand traits influencing water uptake and the efficiency of using water to produce biomass. Global comparisons and comparisons at specific locations reveal that water use of different grain legumes is very similar, which indicates that water use efficiency varies over a wide range due to differences in biomass and yield. Moreover, yield increases more per millimetre of water used in cool season grain legumes than warm season species. Although greater contrasts have been observed across species and genotypes at the pot and lysimeter level, agronomic factors need to be taken into account when scaling those studies to field-level responses. Conservative water use strategies in grain legumes such as low stomatal conductance as approximated by low photosynthetic carbon isotope discrimination reduces yield potential, whereas temporal adjustments of stomatal conductance within the growing season and in response to environmental factors (such as vapour pressure deficit) helps to optimize the trade-off between carbon gain and water loss. Furthermore, improved photosynthetic capacity, reduced mesophyll conductance, reduced boundary layer, and re-fixation of respired CO2 were identified as traits that are beneficial without water deficit, but also under terminal and transient drought. Genotypic variability in some grain legume species has been observed for several traits that influence water use, water use efficiency, and yield, including root length and the temporal pattern of water use, but even more variation is expected from wild relatives. Albeit that N2 fixation decreases under drought, its impact on water use is still largely unknown, but the nitrogen source influences gas exchange and, thus, transpiration efficiency. This review concludes that conservative traits are needed under conditions of terminal drought to help maintain soil moisture until the pod-filling period, but profligate traits, if tightly regulated, are important under conditions of transient drought in order to profit from short intermittent periods of available soil moisture.
豆类作物的产量受到可用水量的限制。因此，了解影响水分吸收和利用水分生产生物量的效率的特征至关重要。全球比较和特定地点的比较表明，不同豆类作物的耗水量非常相似，这表明由于生物量和产量的差异，水分利用效率在很大范围内变化。此外，在凉爽季节的豆类作物中，每使用一毫米水，产量的增加幅度比温暖季节的物种更大。尽管在盆栽和蒸渗仪水平上已经观察到了不同物种和基因型之间更大的差异，但在将这些研究扩展到田间水平的反应时，需要考虑农业因素。豆类作物中保守的水分利用策略，如低气孔导度（近似于低光合作用碳同位素分馏），会降低产量潜力，而在生长季节内和响应环境因素（如蒸气压亏缺）时调整气孔导度有助于优化碳获取和水分损失之间的权衡。此外，提高光合作用能力、降低胞间导度、减少边界层和重新固定呼吸释放的 CO2 被认为是在没有水分亏缺的情况下有益的特征，但在终末和暂态干旱下也是如此。在一些豆类作物物种中，已经观察到了几种影响水分利用、水分利用效率和产量的特征的基因型变异，包括根长和水分利用的时间模式，但野生近缘种的变异可能更大。尽管固氮作用在干旱下会下降，但它对水分利用的影响仍知之甚少，但氮源会影响气体交换，从而影响蒸腾效率。本综述得出的结论是，在终末干旱条件下需要保守的特征来帮助维持土壤水分，直到荚果填充期，但如果受到严格调节，在暂态干旱条件下，挥霍性特征在利用短时间内可用的土壤水分方面是重要的。
