Physiological mechanisms of drought-induced tree die-off in relation to carbon, hydraulic and respiratory stress in a drought-tolerant woody plant.
Physiological mechanisms of drought-induced tree die-off in relation to carbon, hydraulic and respiratory stress in a drought-tolerant woody plant.
复制标题
DOI：
10.1038/s41598-017-03162-5
复制
发表时间：
2017-06-07
影响因子：
4.6
通讯作者：
Yazaki K
中科院分区：
文献类型：
--
作者：
Saiki ST;Ishida A;Yoshimura K;Yazaki K
与气候变化有关的干旱引起的树木死亡正在世界范围内发生，并影响森林生态系统的碳储量和生物多样性。水力衰竭和碳饥饿是干旱导致树木死亡的两种常见机制。本研究表明，在耐旱木本物种Rhaphiolepis wrightiana Maxim中，抑制小枝呼吸和土壤-叶片水力传导可能是由细胞损伤引起的，发生在水力衰竭（木质部栓塞）和碳饥饿（边材中储存的碳耗尽）之前。以总叶面积与树枝液面积之比作为干旱后的健康指标。选取6棵不同健康水平的成树和1棵枯死成树。在我们进行研究的三个月后，六棵活树中健康状况最差和第二差的两棵树死亡。土壤-叶片水力导度和叶片气体交换率随着树木健康程度的降低呈线性下降，而木质部空化和总非结构碳在小枝上保持不变，除了死树和大多数不健康的树木。随着树木健康程度的降低，边材呼吸速率和活细胞数量呈线性下降。本研究首次报道了活细胞脱水耐受性和呼吸维持的重要性。
Drought-induced tree die-off related to climate change is occurring worldwide and affects the carbon stocks and biodiversity in forest ecosystems. Hydraulic failure and carbon starvation are two commonly proposed mechanisms for drought-induced tree die-off. Here, we show that inhibited branchlet respiration and soil-to-leaf hydraulic conductance, likely caused by cell damage, occur prior to hydraulic failure (xylem embolism) and carbon starvation (exhaustion of stored carbon in sapwood) in a drought-tolerant woody species, Rhaphiolepis wrightiana Maxim. The ratio of the total leaf area to the twig sap area was used as a health indicator after drought damage. Six adult trees with different levels of tree health and one dead adult tree were selected. Two individuals having the worst and second worst health among the six live trees died three months after our study was conducted. Soil-to-leaf hydraulic conductance and leaf gas exchange rates decreased linearly as tree health declined, whereas xylem cavitation and total non-structural carbon remained unchanged in the branchlets except in the dead and most unhealthy trees. Respiration rates and the number of living cells in the sapwood decreased linearly as tree health declined. This study is the first report on the importance of dehydration tolerance and respiration maintenance in living cells.