Recent studies have suggested that predawn stomatal opening may enhance early-morning photosynthesis (A) and improve the relative growth rate of trees. However, the causality between night-time stomatal conductance, A, and tree growth is disputable because stomatal opening in darkness can be mediated by previous day photosynthate loads and might be a consequence of growth-related processes like dark respiration (R). To identify linkages between night-time leaf conductance (g_{l_night}), A, R, and tree growth, we conducted an experiment in hybrid aspen saplings grown under different air relative humidity (RH) conditions and previous day irradiance level (IR_{_pday}). Predawn leaf conductance (g_{l_predawn}) depended on RH, IR_{_pday} and R (P < 0.05), whereas early-morning gross A (A_{gross_PAR500}) depended on IR_{_pday} and g_{l_predawn} (P < 0.001). Daytime net A was positively related to A_{gross_PAR500} and leaf [N] (P < 0.05). Tree diameter and height increment correlated positively with g_l at the beginning and middle of the night (P < 0.05) but not before dawn. Although our results demonstrate that g_{l_night} was related to tree growth, the relationship was not determined by R. The linkage between g_{l_predawn} and A_{gross_PAR500} was modified by IR_{_pday}, indicating that daily CO₂ assimilation probably provides feedback for stomatal opening before dawn.

最近的研究表明，黎明前的气孔开放可以增强早晨的光合作用（A）并提高树木的相对生长率。但是，夜间气孔导度A和树木生长之间的因果关系是有争议的，因为在黑暗中气孔开放可以由前一天的光合产物负荷介导，并且可能是与黑暗呼吸（R）等生长相关的过程的结果。为了确定夜间叶片电导（g _{l_night}），A，R和树木生长之间的联系，我们在不同空气相对湿度（RH）条件和前一天辐照水平（IR）下种植的混合白杨树苗中进行了一项实验_{_pday}）。黎明前的叶片电导率（g _{l_predawn}）取决于RH，IR _{_pday}和R（P <0.05），而清晨的总A（A _{gross_PAR500}）取决于IR _{_pday}和g _{l_predawn}（P <0.001）。白天净A与A _{gross_PAR500}和叶片[N]正相关（P <0.05）。树木的直径和高度的升高与午夜初半和半午时的g _l正相关（P<0.05），但不是在黎明之前。尽管我们的结果表明g _{l_night}与树木生长有关，但该关系不是由R确定的。之间的联系克_{l_predawn}和甲_{gross_PAR500}通过IR改性_{_pday}，表明每日CO ₂同化可能提供了一种用于在黎明前气孔开口的反馈。