Bunce James
USDA-ARS, Crop Systems and Global Change Laboratory, Beltsville, MD 20705, USA.
Plants (Basel). 2016 Dec 11;5(4):44. doi: 10.3390/plants5040044.
Improving water use efficiency (WUE) may prove a useful way to adapt crop species to drought. Since the recognition of the importance of mesophyll conductance to CO₂ movement from inside stomatal pores to the sites of photosynthetic carboxylation, there has been interest in how much intraspecific variation in mesophyll conductance (g) exists, and how such variation may impact leaf WUE within C₃ species. In this study, the g and leaf WUE of fifteen cultivars of soybeans grown under controlled conditions were measured under standardized environmental conditions. Leaf WUE varied by a factor of 2.6 among the cultivars, and g varied by a factor of 8.6. However, there was no significant correlation (r = -0.047) between g and leaf WUE. Leaf WUE was linearly related to the sub-stomatal CO₂ concentration. The value of g affected the ratio of maximum Rubisco carboxylation capacity calculated from the sub-stomatal CO₂ concentration to that calculated from the CO₂ concentration at the site of carboxylation. That is, variation in g affected the efficiency of Rubisco carboxylation, but not leaf WUE. Nevertheless, there is considerable scope for genetically improving soybean leaf water use efficiency.
提高水分利用效率（WUE）可能是使作物品种适应干旱的一种有效方法。自从认识到叶肉导度对二氧化碳从气孔孔内移动到光合羧化位点的重要性以来，人们一直关注叶肉导度（g）在种内存在多少变异，以及这种变异如何影响C₃植物物种内的叶片水分利用效率。在本研究中，在标准化环境条件下测量了在可控条件下生长的15个大豆品种的g和叶片水分利用效率。各品种间叶片水分利用效率相差2.6倍，g相差8.6倍。然而，g与叶片水分利用效率之间没有显著相关性（r = -0.047）。叶片水分利用效率与气孔下二氧化碳浓度呈线性相关。g的值影响了根据气孔下二氧化碳浓度计算的最大Rubisco羧化能力与根据羧化位点二氧化碳浓度计算的最大Rubisco羧化能力的比值。也就是说，g的变异影响了Rubisco羧化效率，但不影响叶片水分利用效率。尽管如此，通过基因改良提高大豆叶片水分利用效率仍有很大空间。
