ON THE RELATIONSHIP BETWEEN TRANSPIRATION RATE AND LEAF WATER POTENTIAL
ON THE RELATIONSHIP BETWEEN TRANSPIRATION RATE AND LEAF WATER POTENTIAL
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蒸腾速率与叶水势的关系
DOI：
10.1111/j.1469-8137.1966.tb05974.x
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发表时间：
1966
期刊：
影响因子：
--
通讯作者：
P. E. Weatherley
中科院分区：
文献类型：
--
作者：
R. Tinklin;P. E. Weatherley
总结
目的是改变水培植物的蒸腾速率，并测量相应的ΔW值、叶水势下降值（= DPD =吸力）以及相对含水量（相对膨胀度）和气孔开度。根据欧姆定律类比，ΔW与蒸腾速率呈线性关系。
将蓖麻植株置于风洞中，通过改变气流的相对湿度水平来改变蒸腾速率。随着蒸腾速率的增加，ΔW急剧上升到大约6个大气压的值，在这个值下，ΔW几乎保持不变（图1）。因此，从很低的蒸腾速率到可获得的最高蒸腾速率，ΔW远不是随蒸腾速率线性增加，ΔW没有响应，相对含水量和气孔阻力也没有响应。当蒸腾作用降低到零时，叶片仍然保持约3个大气压的ΔW，而不是零，但提出了考虑该值来表示水分饱和度的理由。
植物对水分运动的主要阻力存在于根部。如果将一片叶子从一株正在蒸腾的植物上分离下来，让它以同样的速率继续蒸腾，水被自由地供应到叶柄的切断端，那么它的ΔW就从6个大气压下降到3.5个大气压（图3）。因此，抗性必须位于叶柄的“下方”。同样，它被证明位于股骨柄下方。
叶片ΔW在通过根系的水通量变化较大时保持不变，说明根系阻力随水通量的增加而减小。一个简单的水力模型，将表现在这种方式。
Summary
The aim was to vary the transpiration rate of water culture plants and to measure corresponding values of ΔW, the leaf water potential depression (= DPD = suction force), as well as relative water content (relative turgidity) and stomatal aperture. On the Ohm-law analogy ΔW and transpiration rate should be linearly related.
Ricinus communis plants were placed in a wind tunnel and the transpiration rate was varied by changing the level of the relative humidity of the air stream. With increasing rate of transpiration, ΔW rose steeply to a value of about 6 atmospheres at which it remained virtually constant (Fig. 1). Thus from very low transpiration rates to the highest obtainable, far from ΔW rising linearly with transpiration, there was no response in ΔW and similarly no response in relative water content and stomatal resistance. When transpiration was reduced to zero the leaves still maintained a ΔW of about 3 atmospheres instead of zero, but reasons are put forward for considering this value to present water saturation.
The main resistance to water movennent in the plant was shown to reside in the roots. If a leaf was detached from a transpiring plant and allowed to continue transpiration at a similar rate, water being freely supplied to the cut end of the petiole, its ΔW fell from 6 to 3.5 atmospheres (Fig. 3). Thus the resistance must lie‘below’the petiole. Similarly it was shown to lie below the stem.
The constancy of leaf ΔW in the face of large changes in flux of water through the roots, implies that the root resistance declines in step with the rise in flux. A simple hydraulic model is presented which would behave in this way.