Impact of freeze?thaw-induced pit aspiration on stem water transport in the subalpine conifer <i>Abies veitchii</i>
Impact of freeze?thaw-induced pit aspiration on stem water transport in the subalpine conifer <i>Abies veitchii</i>
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冻融诱导的坑吸气对亚高山针叶冷杉茎水分运输的影响
DOI：
10.1093/plphys/kiac388
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发表时间：
2022
期刊：
影响因子：
7.4
通讯作者：
Maruta Emiko
中科院分区：
文献类型：
--
作者：
Taneda Haruhiko;Ogasa Mayumi Y;Yazaki Kenichi;Funayama-Noguchi Sachiko;Miyazawa Yoshiyuki;Mayr Stefan;Maruta Emiko
在冬季，亚高山针叶树经历频繁的冻融循环，在干木质部，可能会导致栓塞和坑吸入由于增加的水体积在汁液到冰的过渡。本研究探讨了自然和人工茎冻结引发的冻融诱导的坑抽吸和栓塞相结合的发生和生态影响。在亚高山地区的韦奇冷杉（冷杉）树木，封闭的纹孔和栓塞管胞的比例以及电导率损失的测量，以检查纹孔抽吸及其影响。在2月和3月上旬遭受轻度干旱胁迫时，树干电导率损失70%~ 80%。冷冻扫描电镜显示，栓塞管胞<20%，但超过90%的封闭纹孔。3月下旬的严重干旱胁迫导致茎电导率损失96% ± 1.2%（平均值±标准误差），栓塞管胞比例增加到64% ± 6.6%，气孔比例下降到23% ± 5.6%。实验冻融循环也使纹孔抽吸率从7.1% ± 0.89%增加到49% ± 10%，并且封闭纹孔的比例与茎导水率的损失百分比呈正相关。结果表明，在轻度干旱和冬季重度干旱条件下，冻结诱导的纹孔抽吸是导致茎木质部功能障碍的重要因素;木质部栓塞主要抑制茎水分运输。
During winter, subalpine conifers experience frequent freeze–thaw cycles in stem xylem that may cause embolism and pit aspiration due to increased water volume during the sap to ice transition. This study examined the occurrence and ecological impacts of a combination of freeze–thaw-induced pit aspiration and embolism triggered by natural and artificial stem freezing. In subalpine Veitch’s fir (Abies veitchii) trees, the fraction of closed pits and embolized tracheids as well as conductivity losses were measured to examine pit aspiration and its effects. When trees incurred mild drought stress in February and early March, 70%–80% of stem conductivity was lost. Cryo-scanning electron microscopy indicated <20% embolized tracheids but ∼90% closed pits. Severe drought stress in late March caused 96% ± 1.2% (mean ± standard error) loss of stem conductivity, while the fraction of embolized tracheids increased to 64% ± 6.6%, and aspirated pit fraction decreased to 23% ± 5.6%. Experimental freeze–thaw cycles also increased pit aspiration from 7.1% ± 0.89% to 49% ± 10%, and the fraction of closed pits was positively correlated to the percent loss of stem hydraulic conductivity. The results indicated that freezing-induced pit aspiration is an important factor for stem xylem dysfunction under mild drought, and upon severe drought in winter; stem water transport is predominantly inhibited by xylem embolism.