Blue light induced stomatal opening has been studied by applying a short pulse (~5 to 60 s) of blue light to a background of saturating photosynthetic red photons, but little is known about steady‐state stomatal responses. Here we report stomatal responses to blue light at high and low CO₂ concentrations. Steady‐state stomatal conductance (g_s) of C₃ plants increased asymptotically with increasing blue light to a maximum at 20% blue (120 μmol m⁻² s⁻¹). This response was consistent from 200 to 800 μmol mol⁻¹ atmospheric CO₂ (C_a). In contrast, blue light induced only a transient stomatal opening (~5 min) in C₄ species above a C_a of 400 μmol mol⁻¹. Steady‐state g_s of C₄ plants generally decreased with increasing blue intensity. The net photosynthetic rate of all species decreased above 20% blue because blue photons have lower quantum yield (moles carbon fixed per mole photons absorbed) than red photons. Our findings indicate that photosynthesis, rather than a blue light signal, plays a dominant role in stomatal regulation in C₄ species. Additionally, we found that blue light affected only stomata on the illuminated side of the leaf. Contrary to widely held belief, the blue light‐induced stomatal opening minimally enhanced photosynthesis and consistently decreased water use efficiency.

中文翻译：

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C3和C4物种对蓝光分数的稳态气孔响应：与CO2浓度的相互作用。

通过在饱和光合作用红色光子的背景上施加短脉冲（约5至60 s）的蓝光，研究了蓝光诱导的气孔开放，但对稳态气孔响应了解甚少。在这里，我们报告了在高和低CO ₂浓度下气孔对蓝光的响应。C ₃植物的稳态气孔电导（g _s）随蓝光的增加渐近增加，在20％蓝光（120μmolm ^-2 s ^-1）时达到最大值。该响应在200至800μmolmol ^-1大气CO ₂（C _a）下是一致的。相比之下，蓝光仅在C _4中诱导了短暂的气孔开口（〜5分钟）C _a高于400μmolmol ^-1的物种。稳态克_小号的C ₄植物通常随着蓝色强度降低。所有物种的净光合速率下降到蓝色的20％以上，因为蓝色光子的量子产率（每摩尔吸收的光子固定的碳摩尔数）比红色光子低。我们的发现表明，光合作用而不是蓝光信号在C ₄物种的气孔调节中起主要作用。此外，我们发现蓝光仅影响叶片光照侧的气孔。与普遍认为的相反，蓝光诱导的气孔开口最小程度地增强了光合作用，并持续降低了用水效率。