van Ieperen Wim
Horticultural Production Chains group, Department of Plant Sciences, Wageningen University, Marijkeweg 22, 6709 PG, Wageningen, The Netherlands.
Trends Plant Sci. 2007 Apr;12(4):137-42. doi: 10.1016/j.tplants.2007.03.001. Epub 2007 Mar 23.
Although xylem provides an efficient transport pathway for water in plants, the hydraulic conductivity of xylem (K(h)) can still influence plant water status. For decades, the K(h) of functional xylem has been assumed to be constant in the short term because xylem consists of a network of dead interconnected capillary elements (conduits). Recent research has shown that K(h) can change in response to the cation content of the xylem fluid. Volume changes of pectin gel in nanometer-sized pores at inter-conduit connections are hypothesized to be the cause, and implications for xylem transport in planta are suggested. However, it seems too early to be conclusive about this phenomenon because the phenomenon has not been measured in planta with xylem fluids that realistically mimic natural xylem sap and the applied methods used to measure ion-mediated changes in K(h) have drawbacks.
虽然木质部为植物中的水分提供了高效的运输途径，但木质部的水力传导率（K(h)）仍会影响植物的水分状况。几十年来，人们一直认为功能性木质部的K(h)在短期内是恒定的，因为木质部由相互连接的死亡毛细管元件（导管）网络组成。最近的研究表明，K(h)会随着木质部汁液中阳离子含量的变化而改变。导管间连接处纳米级孔隙中果胶凝胶的体积变化被认为是其原因，并对植物体内木质部运输产生了影响。然而，关于这一现象下结论似乎还为时过早，因为尚未在植物体内使用真实模拟天然木质部汁液的木质部汁液对该现象进行测量，且用于测量离子介导的K(h)变化的应用方法存在缺陷。
