Hölttä Teemu, Cochard Herve, Nikinmaa Eero, Mencuccini Maurizio
Department of Forest Ecology, University of Helsinki, Helsinki, Finland.
Plant Cell Environ. 2009 Jan;32(1):10-21. doi: 10.1111/j.1365-3040.2008.01894.x.
Embolisms decrease plant hydraulic conductance and therefore reduce the ability of the xylem to transport water to leaves provided that embolized conduits are not refilled. However, as a xylem conduit is filled with gas during cavitation, water is freed to the transpiration stream and this transiently increases xylem water potential. This capacitive effect of embolism formation on plant function has not been explicitly quantified in the past. A dynamic model is presented that models xylem water potential, xylem sap flow and cavitation, taking into account both the decreasing hydraulic conductance and the water release effect of xylem embolism. The significance of the capacitive effect increases in relation to the decreasing hydraulic conductance effect when transpiration rate is low in relation to the total amount of water in xylem conduits. This ratio is typically large in large trees and during drought.
栓塞会降低植物的水力导度，因此在栓塞的导管未重新充水的情况下，会降低木质部向叶片输送水分的能力。然而，由于木质部导管在空化过程中充满气体，水分会释放到蒸腾流中，这会使木质部水势瞬间增加。过去，栓塞形成对植物功能的这种电容效应尚未得到明确量化。本文提出了一个动态模型，该模型对木质部水势、木质部汁液流动和空化进行建模，同时考虑了水力导度的降低和木质部栓塞的水分释放效应。当蒸腾速率相对于木质部导管中的总水量较低时，电容效应的重要性相对于水力导度降低效应会增加。在大树和干旱期间，这个比率通常很大。
