Whole-plant capacitance, embolism resistance and slow transpiration rates all contribute to longer desiccation times in woody angiosperms from arid and wet habitats
Whole-plant capacitance, embolism resistance and slow transpiration rates all contribute to longer desiccation times in woody angiosperms from arid and wet habitats
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DOI：
10.1093/treephys/tpu001
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发表时间：
2014-03-01
期刊：
影响因子：
4
通讯作者：
Westoby, Mark
中科院分区：
文献类型：
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作者：
Gleason, Sean M.;Blackman, Chris J.;Westoby, Mark
木质部中的低水势可导致破坏性的空化水平，但很少有人了解哪些水力性状在干旱期间延迟水力功能障碍的发生方面影响最大。我们研究了两个不同干旱条件下11种植物离体茎干化时间延长的3个性状：（1）木质部水势下降时植物组织释放的水分量（W.）; (ii)急性水分胁迫前的最小木质部水势（定义为P-50 L;叶电导损失50%时的水势）;以及（iii）完全水合点和P-50 L点之间的综合蒸腾速率（W-时间）。物种达到P-50 L所需的时间差异很大，从1.3小时到近3天不等。W-Psi，P-50 L和W-时间都显着有助于更长的干燥时间，解释28%，22%和50%的方差所需的时间达到P-50 L。有趣的是，这三个性状几乎是相互正交的，这表明它们并不代表替代水力策略，但可能与本研究中未评估的其他生态策略进行权衡。在干燥过程中损失的大部分水分（60-91%）来自叶片，这表明当木质部水势降低到-2MPa以下时，叶电容在小型植物中起重要作用。
Low water potentials in xylem can result in damaging levels of cavitation, yet little is understood about which hydraulic traits have most influence in delaying the onset of hydraulic dysfunction during periods of drought. We examined three traits contributing to longer desiccation times in excised shoots of 11 species from two sites of contrasting aridity: (i) the amount of water released from plant tissues per decrease in xylem water potential (W.); (ii) the minimum xylem water potential preceding acute water stress (defined as P-50L; water potential at 50% loss of leaf conductance); and (iii) the integrated transpiration rate between the points of full hydration and P-50L (W-time). The time required for species to reach P-50L varied markedly, ranging from 1.3 h to nearly 3 days. W-Psi, P-50L and W-time all contributed significantly to longer desiccation times, explaining 28, 22 and 50% of the variance in the time required to reach P-50L. Interestingly, these three traits were nearly orthogonal to one another, suggesting that they do not represent alternative hydraulic strategies, but likely trade off with other ecological strategies not evaluated in this study. The majority of water lost during desiccation (60-91%) originated from leaves, suggesting an important role for leaf capacitance in small plants when xylem water potentials decrease below -2 MPa.