Kerstiens Gerhard
Institute of Environmental and Natural Sciences, Division of Biological Sciences, Lancaster University, Lancaster LAI 4 YQ, UK.
New Phytol. 1997 Nov;137(3):473-480. doi: 10.1046/j.1469-8137.1997.00847.x.
Cuticular water permeance was manipulated in Corylus avellana L., Hypericum androsaemum L. and Populus tremula L. by (1) long-term application of low doses of various systemic herbicides inhibiting biosynthesis of cuticular waxes, (2) very short-term application of organic solvents to the leaf surface, and (3) exposure to natural strong winds. Treatment effects were very variable, but increased the natural range of permeances by a factor of 10 or so in undamaged leaves. All species had hypostomatous leaves. Relative change of leaf conductance (g) in response to stepwise increases of leaf-to-air water vapour pressure difference (VPD) was measured for individual leaves (Corylus) or groups of leaves at the shoot or branch tip. Adaxial cuticular water permeance (P) was determined for the same leaves after measurement of the VPD-response. A proportional measure of relative change of g with VPD, d(log .g)dVPD, was then plotted against P. No increase in the strength of the closing response to increasing VPD was found with increasing P, as would have been expected if water loss through the cuticle was involved in stomatal response to changes in VPD via a direct effect on guard cell turgor. By contrast, high P coincided, most clearly in Corylus, with a reduced strength of the stomatal closing response to increasing VPD, i.e. less negative d(log g)dVPD. As the responses were non-linear, the value of d(log g)dVPD changed with VPD. With rising VPD, all three species and a fourth one previously studied showed a decline in the value of [d(log g)dVPD]/d(log P), reaching negative values in one species. This is interpreted in terms of two independent and antagonistic effects of increased cuticular water permeance on guard cell response to VPD, one acting by reducing the backpressure exerted on guard cells by the epidermis, and the other one possibly causing greater depression of guard cell turgor through delivery of more chemical messengers (such as abscisic acid) to the guard cells with the cuticular transpiration stream.
通过以下方式调控欧洲榛、红果金丝桃和欧洲山杨的角质层透水性：（1）长期施用低剂量的各种抑制角质层蜡质生物合成的内吸性除草剂；（2）在叶片表面极短期施用有机溶剂；（3）暴露于自然强风环境。处理效果差异很大，但在未受损叶片中，使透水性的自然范围增加了约10倍。所有物种的叶片均为气孔下生型。针对单叶（欧洲榛）或枝条或枝梢顶端的叶组，测定了叶片导度（g）对叶-气水汽压差（VPD）逐步增加的相对变化。在测定VPD响应后，测定同一叶片的近轴角质层透水性（P）。然后将g随VPD的相对变化的比例度量d(log g)/dVPD与P作图。未发现随着P增加，对VPD增加的关闭响应强度增加，而如果通过角质层的水分流失通过对保卫细胞膨压的直接影响参与气孔对VPD变化的响应，那么预期会出现这种情况。相反，高P与对VPD增加的气孔关闭响应强度降低同时出现，在欧洲榛中最为明显，即d(log g)/dVPD的负值更小。由于响应是非线性的，d(log g)/dVPD的值随VPD而变化。随着VPD升高，所有这三个物种以及之前研究的第四个物种均显示[d(log g)/dVPD]/d(log P)的值下降，在一个物种中达到负值。这可以从角质层透水性增加对保卫细胞对VPD的响应的两种独立且拮抗的效应来解释，一种效应是通过降低表皮对保卫细胞施加的背压起作用，另一种效应可能是通过角质层蒸腾流将更多化学信使（如脱落酸）输送到保卫细胞，从而导致保卫细胞膨压更大程度的降低。
