Küppers M, Neales T F, Küppers B I L, Swan A G, Myers B A
CSIRO. Division of Forest Research, GPO Bo, 4008, Canberra City, ACT 2600, Australia.Research School of Biological Sciences, The Australian National University, GPO Box 475, Canberra City, ACT 2601, AustraliaBotany School, University of Melbourne, Parkville, Victoria 3052, Australia.
Plant Cell Environ. 1987 Jan;10(1):27-37. doi: 10.1111/j.1365-3040.1987.tb02076.x.
The lignotuberous mallee Eucalyptus behriana F. Muell, had much lower predawn leaf water potentials (not higher than - 1.2MPa) than other eucalypts (as high as - 0.2MPa), even after extended rain. This led to the expectation that the lignotuber of E. behriana might have specific hydraulic characteristics. Keeping the soil around partially defoliated mallces for several days underwater did not raise the water status above the maximum leaf water potential observed under natural conditions. Digging a plant out and placing its roots in water after removal of the soil rapidly increased the water status to a level consistant with other eucalypts. This indicated that the major impedance to water uptake was a component of the soil rather than in the roots or in the lignotuber. Some of the individual mallces had only two major stems or branches. One stem or branch was kept covered throughout the experiments to prevent transpiration. The other stem was subjected to a variety of different conditions in order to modify water loss from it. The transpiring branch affected the water status of the non-transpiring plant parts. Hydraulic resistances in the shoot and root/lignotuber were determined from differences in the leaf water potential of covered and uncovered branches, at high water flow rates through the plant. Resistances in branches, including the liquid phase component of the leaf, were significantly larger than in root or lignotuber. The total plant hydraulic resistance of E. behriana was similar to that of other eucalypts, such as E. pauciflora Sieb. ex Spreng. or E. delegatensis R. T. Bak., even though its growth form was different and its natural leaf water potentials were much lower. An osmotic adjustment at the leaf level was observed in the mallee, keeping its bulk leaf turgor in the same range as compared to the other eucalypt species.
块茎状小叶桉（Eucalyptus behriana F. Muell）即使在长时间降雨后，黎明前叶水势（不高于-1.2MPa）也远低于其他桉树（高达-0.2MPa）。这使得人们预期小叶桉的块茎可能具有特殊的水力特性。将部分落叶的小叶桉周围土壤浸泡在水下数天，其水分状况并未超过自然条件下观测到的最大叶水势。挖出一株植物并去除土壤后将其根系置于水中，水分状况迅速上升至与其他桉树一致的水平。这表明水分吸收的主要阻碍是土壤成分，而非根系或块茎。一些小叶桉个体只有两个主要茎干或枝条。在整个实验过程中，一个茎干或枝条保持覆盖以防止蒸腾作用。另一个茎干则置于各种不同条件下以改变其水分散失。进行蒸腾作用的枝条影响了非蒸腾植物部分的水分状况。在高水流速率下，通过覆盖和未覆盖枝条的叶水势差异来测定枝条和根/块茎中的水力阻力。枝条中的阻力，包括叶片的液相成分，显著大于根或块茎中的阻力。尽管小叶桉的生长形式不同且其天然叶水势低得多，但其全株水力阻力与其他桉树，如少花桉（Eucalyptus pauciflora Sieb. ex Spreng.）或德利加特桉（Eucalyptus delegatensis R. T. Bak.）相似。在小叶桉中观察到叶片水平的渗透调节，使其叶片整体膨压与其他桉树种保持在相同范围内。
