Department of Botany, University of Innsbruck, Sternwartestr. 15, A-6020 Innsbruck, Austria.
J Exp Bot. 2011 Aug;62(12):4383-90. doi: 10.1093/jxb/err157. Epub 2011 May 18.
Main resistances of the plant water transport system are situated in leaves. In contrast to angiosperm leaves, knowledge of conifer needle hydraulics and of the partitioning of resistances within needles is poor. A new technique was developed which enabled flow-meter measurements through needles embedded in paraffin and thus quantification of the specific hydraulic conductivity (K(s)) of the needle xylem. In Picea abies, xylem K(s) of needle and axes as well as in needles of different age were compared. In Pinus mugo, resistance partitioning within needles was estimated by measurements of xylem K(s) and leaf conductance (K(leaf), measured via 'rehydration kinetics'). Mean K(s) in P. abies needles was 3.5×10(-4) m(2) s(-1) MPa(-1) with a decrease in older needles, and over all similar to K(s) of corresponding axes xylem. In needles of P. mugo, K(s) was 0.9×10(-4) m(2) s(-1) MPa(-1), and 24% of total needle resistance was situated in the xylem. The results indicate species-specific differences in the hydraulic efficiency of conifer needle xylem. The vascular section of the water transport system is a minor but relevant resistance in needles.
植物水分运输系统的主要阻力位于叶片中。与被子植物叶片不同，针叶树针的水力学和阻力分配的知识还很缺乏。开发了一种新技术，该技术使我们能够通过嵌入在石蜡中的针叶进行流量计测量，从而量化针叶木质部的比水力导率（K(s)）。比较了云杉的针叶和轴以及不同年龄的针叶的木质部 K(s)。在欧洲赤松中，通过测量木质部 K(s)和叶片导度（通过“再水合动力学”测量的 K(leaf)）来估算针叶内的阻力分配。云杉针叶的平均 K(s)为 3.5×10(-4) m(2) s(-1) MPa(-1)，随着针叶年龄的增长而降低，与相应轴木质部的 K(s)相似。在欧洲赤松的针叶中，K(s)为 0.9×10(-4) m(2) s(-1) MPa(-1)，24%的总针阻力位于木质部中。结果表明，针叶树针叶木质部的水力效率具有种特异性差异。水运输系统的维管束部分是针叶中的一个小但相关的阻力。
