Plants developed under constant high (>85%) relative air humidity (RH) have larger stomata that are unable to close completely in response to closing stimuli. Roses (Rosa x hybrida) developed in high RH have previously been shown to have high water loss during leaf dehydration and reduced dark-induced closure resulting in a shorter postharvest life. In this study, the effect of B-light on stomatal function under high RH conditions was investigated. The ability of rose leaves developed under continuous high (90%) or moderate (60%) RH to close their stomata in response to darkness and leaf dehydration assay was studied. Moreover, the level and regulation of ABA in light and darkness in relation to B-light was measured. Our results show that increased B-light proportion improved stomatal function and dark-induced stomatal closure under high RH conditions and that was associated with increased [ABA] in general and a dynamic ABA peak during darkness. Furthermore, increased B-light during the day was associated with the presence of high β-glucosidase activity during night. This indicates that B-light is important as a signal to activate the β-glucosidase enzyme and release ABA during night. Altogether, the improved stomatal function and reduced transpiration in combination with increased [ABA] indicate that preharvest B-light plays an important role in governing stomatal functionality and ABA homeostasis under high RH and can be a useful method to improve postharvest water balance of roses.

在恒定高（> 85％）的相对空气湿度（RH）下生长的植物具有较大的气孔，无法响应关闭刺激而完全关闭。玫瑰（罗莎 X 杂种在高RH条件下开发的）先前已被证明在叶片脱水过程中具有很高的失水量，并且减少了黑暗引起的闭合，从而缩短了收获后的寿命。在这项研究中，研究了B光对高RH条件下气孔功能的影响。研究了在连续高（90％）或中（60％）RH下发育的月季叶对黑暗和叶片脱水测定的响应，以关闭其气孔的能力。而且，测量了在光和暗中ABA相对于B光的水平和调节。我们的结果表明，在高RH条件下，增加B光的比例可以改善气孔功能和暗诱导的气孔关闭，这通常与[ABA]的增加和黑暗期间的动态ABA峰有关。此外，白天增加的B光与夜间存在高的β-葡萄糖苷酶活性有关。这表明B-光作为激活β-葡萄糖苷酶并在夜间释放ABA的信号非常重要。总之，气孔功能的改善和蒸腾作用的减少以及[ABA]的增加表明，在高RH下，收获前B-light在控制气孔功能和ABA稳态方面起着重要作用，并且可以是改善玫瑰收获后水分平衡的有用方法。