Pignon Charles P, Leakey Andrew D B, Long Stephen P, Kromdijk Johannes
Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL, United States.
Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, IL, United States.
Front Plant Sci. 2021 Feb 1;12:627432. doi: 10.3389/fpls.2021.627432. eCollection 2021.
Improving leaf intrinsic water-use efficiency (), the ratio of photosynthetic CO assimilation to stomatal conductance, could decrease crop freshwater consumption. has primarily been studied under steady-state light, but light in crop stands rapidly fluctuates. Leaf responses to these fluctuations substantially affect overall plant performance. Notably, photosynthesis responds faster than stomata to decreases in light intensity: this desynchronization results in substantial loss of . Traits that could improve under fluctuating light, such as faster stomatal movement to better synchronize stomata with photosynthesis, show significant natural diversity in C species. However, C crops have been less closely investigated. Additionally, while modification of photosynthetic or stomatal traits independent of one another will theoretically have a proportionate effect on , in reality these traits are inter-dependent. It is unclear how interactions between photosynthesis and stomata affect natural diversity in , and whether some traits are more tractable drivers to improve . Here, measurements of photosynthesis, stomatal conductance and under steady-state and fluctuating light, along with stomatal patterning, were obtained in 18 field-grown accessions of the C crop sorghum. These traits showed significant natural diversity but were highly correlated, with important implications for improvement of . Some features, such as gradual responses of photosynthesis to decreases in light, appeared promising for improvement of . Other traits showed tradeoffs that negated benefits to , e.g., accessions with faster stomatal responses to decreases in light, expected to benefit , also displayed more abrupt losses in photosynthesis, resulting in overall lower . Genetic engineering might be needed to break these natural tradeoffs and achieve optimal trait combinations, e.g., leaves with fewer, smaller stomata, more sensitive to changes in photosynthesis. Traits describing at steady-state, and the change in following decreases in light, were important contributors to overall under fluctuating light.
提高叶片内在水分利用效率（光合CO2同化与气孔导度之比）可以降低作物的淡水消耗。内在水分利用效率主要是在稳态光照条件下进行研究的，但作物冠层中的光照会迅速波动。叶片对这些波动的响应会显著影响植株的整体表现。值得注意的是，光合作用对光照强度降低的响应速度比气孔更快：这种不同步会导致内在水分利用效率的大量损失。在C4植物中，能够在波动光照下提高内在水分利用效率的性状，如气孔运动更快以使气孔与光合作用更好地同步，表现出显著的自然多样性。然而，对C4作物的研究较少。此外，虽然理论上相互独立地改变光合或气孔性状会对内在水分利用效率产生相应影响，但实际上这些性状是相互依赖的。目前尚不清楚光合作用和气孔之间的相互作用如何影响内在水分利用效率的自然多样性，以及某些性状是否是提高内在水分利用效率更易于处理的驱动因素。在这里，我们对18个田间种植的C4作物高粱品种进行了稳态和波动光照下的光合作用、气孔导度和内在水分利用效率的测量，以及气孔形态的观察。这些性状表现出显著的自然多样性，但高度相关，这对提高内在水分利用效率具有重要意义。一些特征，如光合作用对光照降低的逐渐响应，似乎对提高内在水分利用效率很有前景。其他性状则表现出权衡，抵消了对内在水分利用效率的益处，例如，对光照降低气孔响应更快的品种，预计会提高内在水分利用效率，但光合作用的损失也更突然，导致整体内在水分利用效率较低。可能需要通过基因工程来打破这些自然权衡，实现最佳性状组合，例如气孔数量更少、更小且对光合作用变化更敏感的叶片。描述稳态下内在水分利用效率以及光照降低后内在水分利用效率变化的性状，是波动光照下整体内在水分利用效率的重要贡献因素。
