Divergent Hydraulic Safety Strategies in Three Co-occurring Anacardiaceae Tree Species in a Chinese Savanna.
Divergent Hydraulic Safety Strategies in Three Co-occurring Anacardiaceae Tree Species in a Chinese Savanna.
复制标题
中国稀树草原三种共生漆树科树种的不同水力安全策略。
DOI：
10.3389/fpls.2016.02075
复制
发表时间：
2016
影响因子：
5.6
通讯作者：
Cao KF
中科院分区：
文献类型：
--
作者：
Zhang SB;Zhang JL;Cao KF
脆弱性分割，即植物叶片比茎更容易受到干旱引起的空化作用的条件，可以作为一个“安全阀”，以保护茎免受液压故障。万年青，冬季落叶，干旱落叶树种共同发生在热带稀树草原，但一直没有直接的研究脆弱性分割和气孔调节的作用，在保持这三个叶物候树的水力安全。为此，我们选择了3个漆树科树种共存于中国稀树草原，万年青阿月浑子weinmanniifolia，干旱落叶Terminthia paniculata，和冬季落叶Lannea coromandelica，研究种间分化的叶和茎水力安全。结果表明，两种落叶树种的边材比导水率和叶比导水率均显著高于万年青树种。此外，两个落叶物种比万年青物种更容易受到茎空化，虽然干旱落叶物种和万年青物种都有抗旱叶片。万年青树种茎、叶具有较宽的水力安全裕度，这是通过茎、叶的抗栓塞性和等水气孔控制实现的。这两个落叶物种有有限的HSMs在茎和叶，是等水的冬季落叶物种和异水的干旱落叶物种。在导水率损失50%时，两种植物的叶与茎之间的水势差（P50叶-茎）均为正值。coromandelica，而T. paniculata表现出缺乏脆弱性分割。此外，水力结构的差异被发现与其他结构特征密切相关，即，单位面积叶质量、木材密度和边材解剖学。总体而言，冬季落叶树种表现出一种避免干旱的策略，保持水力安全的碳成本较高的茎牺牲更便宜，更脆弱的叶子，而万年青树种表现出强大的气孔调节耐旱的水力策略。与此相反，干旱落叶树种缺乏脆弱性分割和脱落的叶子在干旱高峰期顶梢的费用。这项研究表明，即使同域树种，不同的叶物候可以表现出不同的自适应水力安全策略。
Vulnerability segmentation, the condition under which plant leaves are more vulnerable to drought-induced cavitation than stems, may act as a “safety valve” to protect stems from hydraulic failure. Evergreen, winter-deciduous, and drought-deciduous tree species co-occur in tropical savannas, but there have been no direct studies on the role of vulnerability segmentation and stomatal regulation in maintaining hydraulic safety in trees with these three leaf phenologies. To this end, we selected three Anacardiaceae tree species co-occurring in a Chinese savanna, evergreen Pistacia weinmanniifolia, drought-deciduous Terminthia paniculata, and winter-deciduous Lannea coromandelica, to study inter-species differentiation in leaf and stem hydraulic safety. We found that the two deciduous species had significantly higher sapwood-specific hydraulic conductivity and leaf-specific hydraulic conductance than the evergreen species. Moreover, two deciduous species were more vulnerable to stem cavitation than the evergreen species, although both drought-deciduous species and evergreen species had drought-resistance leaves. The evergreen species maintained a wide hydraulic safety margin (HSM) in stems and leaves; which was achieved by embolism resistance of both stems and leaves and isohydric stomatal control. Both deciduous species had limited HSMs in stems and leaves, being isohydric in the winter-deciduous species and anisohydric in drought-deciduous species. The difference in water potential at 50% loss of hydraulic conductivity between the leaves and the terminal stems (P50leaf−stem) was positive in P. weinmanniifolia and L. coromandelica, whereas, T. paniculata exhibited a lack of vulnerability segmentation. In addition, differences in hydraulic architecture were found to be closely related to other structural traits, i.e., leaf mass per area, wood density, and sapwood anatomy. Overall, the winter-deciduous species exhibits a drought-avoidance strategy that maintains the hydraulic safety of the more carbon-costly stems by sacrificing cheaper and more vulnerable leaves, while the evergreen species exhibits a hydraulic strategy of drought tolerance with strong stomatal regulation. In contrast, the drought-deciduous species lacks vulnerability segmentation and sheds leaves at the expense of top shoots during peak drought. This study demonstrates that even sympatric tree species that differ in leaf phenology can exhibit divergent adaptive hydraulic safety strategies.