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Minimum conductance in leaves−cuticle, leaky stomata, or water vapor saturation?
bioRxiv - Plant Biology Pub Date : 2020-05-30 , DOI: 10.1101/2020.05.28.120634
Jun Tominaga , Joseph R. Stinziano , David T. Hanson

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 CO2 concentration in the leaf airspace (Ci) of amphi-stomatous tobacco and sunflower. We estimated gcw in a series of light and dark experiments, and partitioned gw,min into cuticle and stomatal components. Some leaves were detached to simulate severe drought through desiccation conditions where gw,min is generally determined. Between light and dark experiments each gcw was in close agreement, and successfully corrected the discrepancies of calculations from direct measurements. In the dark, either stomatal or cuticle conductance dominated the gw,min, suggesting either of them can control the minimum water loss. In the detached leaves, gcw could not be estimated likely due to unsaturation in the leaf airspace, and gw,min was 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.

中文翻译:

叶片表皮,气孔渗漏或水蒸气饱和度的电导最小?

叶片中的最小电导(g w,min)对于陆地植物中的水关系很重要。然而,由于测量限制,其调节尚不清楚。通过计算和直接测量两口烟草和向日葵叶片气隙(C i)中的CO 2浓度之间的差异,可以估算表皮对水蒸气的电导率(g cw)。我们在一系列明暗实验中估计了g cw,并将g w,min分为表皮和气孔成分。通过干燥条件(g w,min通常是确定的。在明暗实验之间,每g cw都非常吻合,并且成功地校正了直接测量的计算差异。在黑暗中,任一或气孔角质层电导为主的瓦特,最小,这表明它们中的可控制的最低水分损失。在离体的叶片中,由于叶片气隙中的不饱和度,无法估计出g cw,并且逐渐低估了g w,min。除表皮外,叶片水分状态是标准气体交换模型的潜在陷阱。我们的技术对于研究最小的气体交换以及完善模型非常有用。
更新日期:2020-05-30
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