Minimum conductance in leavesーcuticle, leaky stomata, or water vapor saturation?
Minimum conductance in leavesーcuticle, leaky stomata, or water vapor saturation?
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叶角质层、气孔渗漏或水蒸气饱和度的最小电导率？
DOI：
10.1101/2020.05.28.120634
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Hanson David T.
中科院分区：
文献类型：
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作者：
Tominaga Jun;Stinziano Joseph R.;Hanson David T.
叶片的最小导度（gw，min）对陆生植物的水分关系具有重要意义。本文根据计算的和直接测量的烟草和向日葵叶气隙CO_2浓度（Ci）的差值，估算了烟草和向日葵的角质层水汽传导率（gcw）。通过一系列的光暗实验估算了气孔导度，并将气孔导度分为角质层和气孔导度。通过离体叶片模拟严重干旱，测定了光照和黑暗条件下的最小值，结果表明，光照和黑暗条件下的最小值基本一致，并成功地纠正了直接测量与计算的偏差。在黑暗条件下，气孔导度和角质层导度都对gw，min起主导作用，说明二者都能控制最小的失水量。在离体叶片中，gcw可能由于叶片气隙的不饱和而不能估算，gw，min也逐渐被低估，除角质层外，叶片水分状况也是标准气体交换模型的一个潜在缺陷。我们的技术是有用的，以研究最小的气体交换，以及完善的模型。
Minimum conductance (gw,min) in leaves is important for water relations in land plants. Yet, its regulation is unclear due to measurement constraints.Cuticle conductance to water vapor (gcw) was estimated from the difference between calculated and direct measurement of CO2concentration in the leaf airspace (Ci) of amphi-stomatous tobacco and sunflower. We estimatedgcwin a series of light and dark experiments, and partitionedgw,mininto cuticle and stomatal components. Some leaves were detached to simulate severe drought through desiccation conditions wheregw,minis generally determined.Between light and dark experiments eachgcwwas in close agreement, and successfully corrected the discrepancies of calculations from direct measurements. In the dark, either stomatal or cuticle conductance dominated thegw,min, suggesting either of them can control the minimum water loss. In the detached leaves,gcwcould not be estimated likely due to unsaturation in the leaf airspace, andgw,minwas progressively underestimated.Besides cuticle, leaf water status is a potential pitfall of the standard gas exchange model. Our technique is useful to study the minimal gas exchange as well as to refine the model.