Abstract：
The growing demand for global food production is likely to be a defining issue facing humanity over the next 50 years. To tackle this challenge, there is a desire to bioengineer crops with higher photosynthetic efficiencies, to increase yields. Recently, there has been a growing interest in engineering leaves with higher mesophyll conductance (gm), which would allow CO2 to move more efficiently from the substomatal cavities to the chloroplast stroma. However, if crop yield gains are to be realised through this approach, it is essential that the methodological limitations associated with estimating gm are fully appreciated. In this review, we summarise these limitations, and outline the uncertainties and assumptions that can affect the final estimation of gm. Furthermore, we critically assess the predicted quantitative effect that elevating gm will have on assimilation rates in crop species. We highlight the need for more theoretical modelling to determine whether altering gm is truly a viable route to improve crop performance. Finally, we offer suggestions to guide future research on gm, which will help mitigate the uncertainty inherently associated with estimating this parameter.
摘要：
对全球粮食生产日益增长的需求可能是未来50年人类面临的一个决定性问题。为了应对这一挑战，人们希望对具有更高光合效率的作物进行生物工程改造，以提高产量。最近,人们对设计具有较高叶肉电导(gm)的叶片越来越感兴趣，这将使CO2更有效地从气孔下腔移动到叶绿体基质。然而,如果要通过这种方法实现作物产量的提高，必须充分认识到与估计gm相关的方法局限性。在这次审查中,我们总结了这些限制，并概述可能影响GM最终估计的不确定性和假设。此外，我们严格评估了预测的定量影响，提高gm将对作物物种的同化率。我们强调需要进行更多的理论建模，以确定改变转基因是否是真正提高作物性能的可行途径。最后,我们提出了指导未来转基因研究的建议，这将有助于减轻与估计此参数固有的不确定性。
