Hydraulic differences along the water transport system of South American Nothofagus species: do leaves protect the stem functionality?
Hydraulic differences along the water transport system of South American Nothofagus species: do leaves protect the stem functionality?
复制标题
DOI：
10.1093/treephys/tps054
复制
发表时间：
2012-07-01
期刊：
影响因子：
4
通讯作者：
Goldstein, Guillermo
中科院分区：
文献类型：
--
作者：
Bucci, Sandra J.;Scholz, Fabian G.;Goldstein, Guillermo
水力特性进行了研究，从南美洲（阿根廷和智利）的六个Nothofagus物种，并为这些物种的两个种群进行了研究。的主要目标是，以确定是否在茎和叶的水传导途径的性能是功能协调，并评估叶是否更容易受到空化比茎，符合水力分割理论沿着的血管系统的树木在生态系统中受到季节性干旱。对空蚀的脆弱性，茎和叶的导水率，叶水势，木材密度和叶水关系进行了研究。在不同种群和物种中，茎和叶的空化脆弱性存在很大差异，但叶始终比茎更脆弱。最大水力效率（P-50）损失50%时，各物种和种群的叶水势为-0.94 ~-2.44MPa，茎水势为-2.6 ~-5.3MPa。人口在最干燥的网站边材和树叶更容易受到空化比那些生长在最潮湿的网站。叶片导水率日变化幅度大于茎导水率日变化幅度，具有减缓茎潜在水分损失和保护茎水力免受空化作用的作用。木材密度和叶片导水率（K-叶）的种属差异进行了观察。这两个性状在功能上相关：木材密度较高的物种具有较低的K叶。其他茎和叶的水力性状的功能协调，导致在Nothofagus物种与水的有效输送到叶片。因此，在长期干旱下，可以以茎-叶连续体的可替换部分（叶）为代价来维持水分运输途径的更昂贵的木质部分的完整性。水力特性之间的补偿调整可能有助于降低栓塞形成的树木更容易受到空化的速度。
Hydraulic traits were studied for six Nothofagus species from South America (Argentina and Chile), and for three of these species two populations were studied. The main goal was to determine if properties of the water conductive pathway in stems and leaves are functionally coordinated and to assess if leaves are more vulnerable to cavitation than stems, consistent with the theory of hydraulic segmentation along the vascular system of trees in ecosystems subject to seasonal drought. Vulnerability to cavitation, hydraulic conductivity of stems and leaves, leaf water potential, wood density and leaf water relations were examined. Large variations in vulnerability to cavitation of stems and leaves were observed across populations and species, but leaves were consistently more vulnerable than stems. Water potential at 50% loss of maximum hydraulic efficiency (P-50) ranged from -0.94 to -2.44 MPa in leaves and from -2.6 to -5.3 MPa in stems across species and populations. Populations in the driest sites had sapwood and leaves more vulnerable to cavitation than those grown in the wettest sites. Stronger diurnal down-regulation in leaf hydraulic conductance compared with stem hydraulic conductivity apparently has the function to slow down potential water loss in stems and protect stem hydraulics from cavitation. Species-specific differences in wood density and leaf hydraulic conductance (K-Leaf) were observed. Both traits were functionally related: species with higher wood density had lower K-Leaf. Other stem and leaf hydraulic traits were functionally coordinated, resulting in Nothofagus species with an efficient delivery of water to the leaves. The integrity of the more expensive woody portion of the water transport pathway can thus be maintained at the expense of the replaceable portion (leaves) of the stem-leaf continuum under prolonged drought. Compensatory adjustments between hydraulic traits may help to decrease the rate of embolism formation in the trees more vulnerable to cavitation.