Department of Plant and Environmental Sciences, Norwegian University of Life Sciences, PO Box 5003, 1432 Aas, Norway.
Plant Cell Environ. 2013 Feb;36(2):382-92. doi: 10.1111/j.1365-3040.2012.02580.x. Epub 2012 Aug 16.
Plants developed under high (90%) relative air humidity (RH) have previously been shown to have large, malfunctioning stomata, which results in high water loss during desiccation and reduced dark induced closure. Stomatal movement is to a large extent regulated by abscisic acid (ABA). It has therefore been proposed that low ABA levels contribute to the development of malfunctioning stomata. In this study, we investigated the regulation of ABA content in rose leaves, through hormone analysis and β-glucosidase quantification. Compared with high RH, rose plants developed in moderate RH (60%) and 20 h photoperiod contained higher levels of ABA and β-glucosidase activity. Also, the amount of ABA increased during darkness simultaneously as the ABA-glucose ester (GE) levels decreased. In contrast, plants developed under high RH with 20 h photoperiod showed no increase in ABA levels during darkness, and had low β-glucosidase activity converting ABA-GE to ABA. Continuous lighting (24 h) resulted in low levels of β-glucosidase activity irrespective of RH, indicating that a dark period is essential to activate β-glucosidase. Our results provide new insight into the regulation of ABA under different humidities and photoperiods, and clearly show that β-glucosidase is a key enzyme regulating the ABA pool in rose plants.
在高（90%）相对空气湿度（RH）下生长的植物以前被证明具有大的、功能失调的气孔，这导致在干燥过程中水分大量流失和减少黑暗诱导的关闭。气孔运动在很大程度上受脱落酸（ABA）的调节。因此，有人提出低 ABA 水平有助于发育不良的气孔的形成。在这项研究中，我们通过激素分析和β-葡萄糖苷酶定量研究了玫瑰叶片中 ABA 含量的调节。与高 RH 相比，在中等 RH（60%）和 20 小时光周期下生长的玫瑰植物含有更高水平的 ABA 和β-葡萄糖苷酶活性。此外，ABA 的量在黑暗中增加，同时 ABA-葡萄糖酯（GE）水平降低。相比之下，在高 RH 下生长且光照时间为 20 小时的植物在黑暗中没有增加 ABA 水平，并且β-葡萄糖苷酶活性低，无法将 ABA-GE 转化为 ABA。无论 RH 如何，连续光照（24 小时）都会导致β-葡萄糖苷酶活性降低，这表明黑暗期对于激活β-葡萄糖苷酶是必不可少的。我们的研究结果为不同湿度和光周期下 ABA 的调节提供了新的见解，并清楚地表明β-葡萄糖苷酶是调节玫瑰植物 ABA 库的关键酶。
