Hacke Uwe G, Sperry John S, Pockman William T, Davis Stephen D, McCulloh Katherine A
Department of Biology, 257S 1400E, University of Utah, 84112, Salt Lake City, UT, USA.
Department of Biology, University of New Mexico, 167 Castetter Hall, 87131-1091, Albuquerque, NM, USA.
Oecologia. 2001 Feb;126(4):457-461. doi: 10.1007/s004420100628. Epub 2001 Feb 1.
Wood density (D ), an excellent predictor of mechanical properties, is typically viewed in relation to support against gravity, wind, snow, and other environmental forces. In contrast, we show the surprising extent to which variation in D and wood structure is linked to support against implosion by negative pressure in the xylem pipeline. The more drought-tolerant the plant, the more negative the xylem pressure can become without cavitation, and the greater the internal load on the xylem conduit walls. Accordingly, D was correlated with cavitation resistance. This trend was consistent with the maintenance of a safety factor from implosion by negative pressure: conduit wall span (b) and thickness (t) scaled so that (t/b) was proportional to cavitation resistance as required to avoid wall collapse. Unexpectedly, trends in D may be as much or more related to support of the xylem pipeline as to support of the plant.
木材密度（D）是机械性能的优秀预测指标，通常被视为与抵抗重力、风、雪和其他环境力量的支撑作用相关。相比之下，我们展示了D和木材结构的变化与通过木质部管道中的负压抵抗内爆支撑作用相关的惊人程度。植物耐旱性越强，木质部压力在不发生空化的情况下就越负，木质部导管壁上的内部负荷就越大。因此，D与抗空化性相关。这种趋势与通过负压维持内爆安全系数一致：导管壁跨度（b）和厚度（t）按比例缩放，使得（t/b）与抗空化性成正比，以避免壁坍塌。出乎意料的是，D的趋势可能与对木质部管道的支撑作用和对植物的支撑作用同样相关或更相关。
