Osonubi O, Davies W J
Department of Biological Sciences, University of Lancaster, Brilrigg, Lancs., UK.
Oecologia. 1981 Jan;51(3):343-350. doi: 10.1007/BF00540904.
First year seedlings of English oak (Quercus Cobur) and silver birch (Betula pendula) were subjected to pressure-volume analysis to investigate the water potential components and cell wall properties of single leaves. It was hoped that this rapid-drying technique would differentiate between reductions in plant solute potential resulting from dehydration and the effects of solute accumulation.Comparison of results from these experiments with those of slow drying treatments (over a number of days) with plants growing in tubes of soil, indicated that some solute accumulation may have occurred in drying oak leaves. High leaf turgor and leaf conductance were maintained for a significant period of the drying cycle. Roots of well-watered oak plants extended deep into the soil profile, and possibly as a result of solute regulation and therefore turgor maintenance, root growth of unwatered plants was greater than that of their well-watered counterparts. This was particularly the case deep in the profile. As a result of deep root penetration, water deep in the soil core was used by oak plants to maintain plant turgor, and quite low soil water potentials were recorded in the lower soil segments.Root growth of well-watered birch seedlings was prolific but roots of both well-watered and unwatered plants were restricted to the upper part of the profile. Root growth of unwatered plants was reduced despite the existence of high soil water potentials deep in the profile. Shallow rooting birch seedlings were unable to use this water.Pressure-volume analysis indicated that significant reductions of water potential, which are required for water uptake from drying soil, would occur in oak with only a small reduction in plant water content compared to the situation in birch. This was a result of the low solute potential in oak leaves combined with a high modulus of elasticity of cell walls. Deep rooting of oak seedlings, combined with these characteristics, which will be particularly important when soil deep in the profile begins to dry, mean that this species may be comparatively successful when growing on dry sites.
对英国栎（Quercus Cobur）和银桦（Betula pendula）的一年生幼苗进行压力-容积分析，以研究单叶的水势成分和细胞壁特性。希望这种快速干燥技术能够区分脱水导致的植物溶质势降低和溶质积累的影响。将这些实验的结果与在装有土壤的试管中生长的植物进行的缓慢干燥处理（持续数天）的结果进行比较，表明干燥的栎树叶中可能发生了一些溶质积累。在干燥周期的相当长一段时间内，叶片保持了较高的膨压和导度。充分浇水的栎树植物的根系深入土壤剖面，未浇水植物的根系生长可能由于溶质调节从而维持膨压，大于充分浇水的同类植物。在剖面深处尤其如此。由于根系深入，栎树植物利用土壤核心深处的水来维持植物膨压，并且在较低的土壤层中记录到相当低的土壤水势。充分浇水的桦树幼苗根系生长旺盛，但充分浇水和未浇水植物的根系都局限于剖面的上部。尽管剖面深处存在较高的土壤水势，但未浇水植物的根系生长仍受到抑制。浅根的桦树幼苗无法利用这些水。压力-容积分析表明，与桦树相比，栎树从干燥土壤中吸收水分所需的水势显著降低，而植物含水量仅略有降低。这是栎树叶中溶质势低以及细胞壁弹性模量高的结果。栎树幼苗的深根性，加上这些特性，当剖面深处的土壤开始干燥时尤为重要，这意味着该物种在干燥地点生长时可能相对成功。
