Yang Qiu-Yan, Zhang Yu-Wen, Liu Ning-Yu, Sun Hu, Zhang Shi-Bao, Timm Stefan, Huang Wei
Department of Economic Plants and Biotechnology, Yunnan Key Laboratory for Wild Plant Resources, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China.
Plant Physiology Department, University of Rostock, Albert-Einstein-Straße 3, 18059 Rostock, Germany.
J Exp Bot. 2025 Jun 5. doi: 10.1093/jxb/eraf249.
Maize is one of the most important crops worldwide. Exploring the factors affecting photosynthetic efficiency alongside with the genetic variability within cultivars is fundamental to breed for high-yield maize. Despite its importance, there is limited knowledge about the variation in steady-state and dynamic photosynthetic efficiency among maize cultivars. Here, we investigated the anatomical and physiological mechanisms that contribute to the variability in photosynthetic CO2 assimilation under both, steady-state and fluctuating light conditions, respectively, in 12 high-yielding, farm-preferred maize cultivars. Under steady-state conditions, the saturating CO2 assimilation rate (Asat) varied from 50.2 to 63.1 µmol CO2 m-2 s-1. This variation was tightly related to the area ratio of mesophyll cells to bundle sheath cells, pointing out the role of leaf anatomy in determining Asat of maize. During the initial 5 minutes of light induction, we recorded a considerable range of cumulative CO2 fixation from 9.02 to 13.1 mmol m-2, with the loss of potential CO2 uptake (Closs) varying from 23% to 47% among the cultivars. This variation in Closs was primarily attributed to the kinetics of gs, which were significantly correlated to the expression of the ethylene synthesis genes ACS1 and GAD1, rather than stomatal density. Taking together, we discovered a greater degree of variation in dynamic photosynthetic efficiency compared to steady-state efficiency among the studied maize cultivars. This finding highlights the potential of manipulating gs kinetics as a valuable breeding target to enhance photosynthetic efficiency and yield in maize.
玉米是全球最重要的作物之一。探索影响光合效率的因素以及品种内的遗传变异性对于培育高产玉米至关重要。尽管其重要性，但关于玉米品种间稳态和动态光合效率的变化的了解有限。在此，我们分别研究了12个高产、受农场青睐的玉米品种在稳态和波动光照条件下，导致光合二氧化碳同化变异性的解剖学和生理学机制。在稳态条件下，饱和二氧化碳同化率（Asat）在50.2至63.1 μmol CO₂ m⁻² s⁻¹之间变化。这种变化与叶肉细胞与维管束鞘细胞的面积比密切相关，指出了叶片解剖结构在决定玉米Asat中的作用。在光照诱导的最初5分钟内，我们记录到累积二氧化碳固定量的范围相当大，从9.02至13.1 mmol m⁻²，品种间潜在二氧化碳吸收损失（Closs）从23%至47%不等。Closs的这种变化主要归因于气孔导度（gs）的动力学，其与乙烯合成基因ACS1和GAD1的表达显著相关，而非气孔密度。综合来看，我们发现与稳态效率相比，所研究的玉米品种间动态光合效率的变化程度更大。这一发现凸显了操纵gs动力学作为提高玉米光合效率和产量的有价值育种目标的潜力。
