• Past studies have established mesophyll diffusion conductance to CO₂ (g_m) as a variable and significant limitation to plant photosynthesis under steady-state conditions. However, the role of g_m in influencing photosynthesis (A) during the transient period of light induction is largely unknown.
• We combined gas exchange measurements with laser-enabled carbon isotope discrimination measurements to assess g_m during photosynthetic induction, using Arabidopsis as the measurement species.
• Our measurements revealed three key findings: (1) we found that the rate at which g_m approached steady state during induction was not necessarily faster than the induction rate of the carboxylation process, contradictory to what has been suggested in previous studies; (2) g_m displayed a strong and consistent coordination with A under both induction and steady-state settings, hinting that the mechanism driving g_m–A coupling does not require physiological stability as a prerequisite; and (3) photosynthetic limitation analysis of our data revealed that when integrated over the entire induction period, the relative limitation of A imposed by g_m can be as high as > 35%.
• The present study provides the first demonstration of the important role of g_m in limiting CO₂ assimilation during photosynthetic induction, thereby pointing to a need for more research attention to be devoted to g_m in future induction studies.

中文翻译：

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叶肉电导在光诱导过程中对光合作用产生重大限制

• 过去的研究已将叶肉对 CO ₂ ( g _m ) 的扩散电导确定为稳态条件下植物光合作用的变量和显着限制。然而，在光诱导的瞬态期间，g _m在影响光合作用 ( A ) 中的作用在很大程度上是未知的。
• 我们结合气体交换测量启用激光碳同位素歧视测量以评估克_米光合诱导期间，使用拟南芥作为测定的物种。
• 我们的测量揭示了三个关键发现：（1）我们发现在诱导过程中g _m接近稳态的速率不一定比羧化过程的诱导速率快，这与先前研究中提出的相矛盾；(2) g _m在感应和稳态设置下均与A表现出强烈且一致的协调，暗示驱动g _m - A耦合的机制不需要生理稳定性作为先决条件；(3) 我们数据的光合限制分析表明，当在整个诱导期整合时，A的相对限制由g _m可高达> 35%。
• 本研究首次证明了g _m在光合作用诱导过程中限制CO ₂同化的重要作用，从而表明在未来的诱导研究中需要更多的研究关注g _m。