Purdue Center for Plant Biology, Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana 47907.
Purdue Center for Plant Biology, Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana 47907
Plant Physiol. 2020 Jan;182(1):547-554. doi: 10.1104/pp.19.00585. Epub 2019 Oct 17.
The driver of leaf mortality during drought stress is a critical unknown. We used the commercially important tree , in which there is a large variation in the degree of drought-induced leaf death across the canopy, to test whether embolism formation in the xylem during drought drives this leaf mortality. A large range in the number of embolized vessels in the petioles of leaves was observed across the canopy of plants that had experienced drought. Despite considerable variation between leaves, the amount of embolized vessels in the xylem of the petiole strongly correlated with area of drought-induced tissue death in individual leaves. Consistent with this finding was a large interleaf variability in xylem resistance to embolism, with a 1.45 MPa variation in the water potential at which 50% of the xylem in the leaf midrib embolized across leaves. Our results implicate xylem embolism as a driver of leaf mortality during drought. Moreover, we propose that heterogeneity in drought-induced leaf mortality across a canopy is caused by high interleaf variability in xylem resistance to embolism, which may act as a buffer against complete canopy death during prolonged drought in .
在干旱胁迫下导致叶片死亡的原因尚不清楚。我们选择了一种具有商业价值的树种，该树种的树冠范围内，因干旱导致的叶片死亡程度存在较大差异，以此来检验木质部在干旱过程中形成的栓塞是否会导致这种叶片死亡。在经历干旱的植株的叶片叶柄中，观察到木质部中栓塞血管的数量存在很大差异。尽管叶片之间存在很大的差异，但叶柄木质部栓塞血管的数量与单个叶片中干旱引起的组织死亡面积强烈相关。这一发现与叶片木质部对栓塞的阻力存在很大的叶间变异性是一致的，在叶片中脉的木质部中有 50%发生栓塞时的水势存在 1.45 MPa 的变化。我们的研究结果表明，木质部栓塞是干旱导致叶片死亡的一个原因。此外，我们提出，树冠范围内因干旱导致的叶片死亡的异质性是由叶片木质部对栓塞的阻力存在很大的叶间变异性引起的，这种变异性可能在长时间干旱期间作为防止整个树冠死亡的缓冲。
