patial distribution of xylem embolisms in the stems of Pinus thunbergii at the threshold of fatal drought stress
patial distribution of xylem embolisms in the stems of Pinus thunbergii at the threshold of fatal drought stress
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致命干旱胁迫阈值下黑松茎木质部栓塞的空间分布
DOI：
10.1093/treephys/tpw050
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发表时间：
2016
期刊：
影响因子：
4
通讯作者：
K.
中科院分区：
文献类型：
--
作者：
Umebayashi;T.;Morita;T.;Utsumi;Y.;Kusumoto;D.;Yasuda;Y.;Haishi;T.;Fukuda;K.
尽管先前的研究表明，干旱胁迫导致的枝干枯死和整株死亡发生在茎部水力传导率损失50-88%（分别为p50和P88）的情况下，但对干旱下整株植物输水途径的灾难性失效动力学仍知之甚少。研究了3年生日本黑松（Pinus thunbergiiParl.）抗旱能力的动态变化。我们非破坏性地监测了(i)干旱引起的栓塞在茎中大于p50的空间分布和（ii）补液后栓塞的恢复情况。用低温扫描电镜观察茎干水分分布。在-5.0 MPa或更低的温度下，木质部的失水显著增加，但栓塞面积和水导损失的百分比均呈现相似的增加模式。1株导水面积损失达72%的幼苗存活，木质部水势恢复到-0.3 MPa。本研究认为，在自然条件下，日本黑松可能需要在当年木质部早期保持充满水分的管胞，以避免茎和枝顶之间的水分运动中断。为了更好地了解干旱条件下植物的生存状况，有必要确定在致死阈值点附近的栓塞的空间分布。
Although previous studies have suggested that branch dieback and whole-plant death due to drought stress occur at 50–88% loss of stem hydraulic conductivity (P50and P88, respectively), the dynamics of catastrophic failure in the water-conducting pathways in whole plants subjected to drought remain poorly understood. We examined the dynamics of drought stress tolerance in 3-year-old Japanese black pine (Pinus thunbergiiParl.). We nondestructively monitored (i) the spatial distribution of drought-induced embolisms in the stem at greater than P50and (ii) recovery from embolisms following rehydration. Stem water distributions were visualized by cryo-scanning electron microscopy. The percentages of both embolized area and loss of hydraulic conductivity showed similar patterns of increase, although the water loss in xylem increased markedly at –5.0 MPa or less. One seedling that had reached 72% loss of the water-conducting area survived and the xylem water potential recovered to –0.3 MPa. We concluded that Japanese black pines may need to maintain water-filled tracheids within earlywood of the current-year xylem under natural conditions to avoid disconnection of water movement between the stem and the tops of branches. It is necessary to determine the spatial distribution of embolisms around the point of the lethal threshold to gain an improved understanding of plant survival under conditions of drought.