Department of Renewable Resources, University of Alberta, Edmonton, AB, T6G 2E3 Canada.
Physiol Plant. 2011 Oct;143(2):154-65. doi: 10.1111/j.1399-3054.2011.01489.x. Epub 2011 Jun 28.
The relationships between the vulnerability of stem xylem to cavitation, stomatal conductance, stomatal density, and leaf and stem water potential were examined in six hybrid poplar (P38P38, Walker, Okanese, Northwest, Assiniboine and Berlin) and balsam poplar (Populus balsamifera) clones. Stem xylem cavitation resistance was examined with the Cavitron technique in well-watered plants grown in the greenhouse. To investigate stomatal responses to drought, plants were subjected to drought stress by withholding watering for 5 (mild drought) and 7 (severe drought) days and to stress recovery by rewatering severely stressed plants for 30 min and 2 days. The clones varied in stomatal sensitivity to drought and vulnerability to stem xylem cavitation. P38P38 reduced stomatal conductance in response to mild stress while the balsam poplar clone maintained high leaf stomatal conductance under more severe drought stress conditions. Differences between the severely stressed clones were also observed in leaf water potentials with no or relatively small decreases in Assiniboine, P38P38, Okanese and Walker. Vulnerability to drought-induced stem xylem embolism revealed that balsam poplar and Northwest clones reached loss of conductivity at lower stem water potentials compared with the remaining clones. There was a strong link between stem xylem resistance to cavitation and stomatal responsiveness to drought stress in balsam poplar and P38P38. However, the differences in stomatal responsiveness to mild drought suggest that other drought-resistant strategies may also play a key role in some clones of poplars exposed to drought stress.
本研究以 6 个杂交杨（P38P38、Walker、Okanese、Northwest、Assiniboine 和 Berlin）和银白杨（Populus balsamifera）无性系为材料，通过 Cavitron 技术检测木质部的抗空化能力，研究了木质部对空化的脆弱性、气孔导度、气孔密度、叶片和茎水势之间的关系。在温室中，充分供水条件下生长的植株用 Cavitron 技术检测木质部的抗空化能力。为了研究气孔对干旱的响应，通过停水 5 天（轻度干旱）和 7 天（重度干旱）来模拟干旱胁迫，并在重度干旱胁迫后分别复水 30 分钟和 2 天来模拟胁迫恢复。各无性系间的气孔对干旱的敏感性和木质部对空化的脆弱性存在差异。在轻度胁迫下，P38P38 降低了气孔导度，而银白杨无性系在更为严重的干旱胁迫条件下仍保持较高的叶片气孔导度。在重度胁迫的无性系之间，也观察到叶片水势的差异，Assiniboine、P38P38、Okanese 和 Walker 的叶片水势没有或相对较小的下降。与其余无性系相比，银白杨和 Northwest 无性系在较低的茎水势时就表现出对干旱诱导的木质部栓塞的脆弱性。在银白杨和 P38P38 中，木质部抗空化能力与气孔对干旱胁迫的响应之间存在很强的联系。然而，轻度干旱下气孔响应的差异表明，其他抗旱策略也可能在一些杨树无性系中发挥关键作用，这些无性系暴露于干旱胁迫下。
