Chemical composition of apoplastic transport barriers in relation to radial hydraulic conductivity of corn roots (Zea mays L.)
Chemical composition of apoplastic transport barriers in relation to radial hydraulic conductivity of corn roots (Zea mays L.)
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DOI：
10.1007/pl00008138
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发表时间：
2000-01
期刊：
影响因子：
4.3
通讯作者：
H. M. Zimmermann;Klaus Hartmann;L. Schreiber;E. Steudle
中科院分区：
文献类型：
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作者：
H. M. Zimmermann;Klaus Hartmann;L. Schreiber;E. Steudle
6至8天龄玉米幼苗根部的水力传导率（Lpr）与内皮层和皮下组织（外皮层）中质外体运输屏障的化学成分以及根皮层细胞的水力传导率有关。根部有两种不同的种植方式。当在气培法中生长时，它们发育出外皮层（皮下层的凯斯帕带），而水培法的根部则缺少这种外皮层。通过用小檗碱-苯胺-蓝和苏丹-III染色观察Casparian带和木栓质片层的发育。解聚（BF3/甲醇酯交换、硫代酸解）后，使用气相色谱/质谱法对木栓质和木质素的组成进行定量和定性分析。使用根压力探头测量根 Lpr，并使用细胞压力探头测量皮质细胞 (Lp) 的水力传导率。两种栽培方法的根在以下方面存在显着差异：(i) 通过静水力学松弛预评估的 L（系数为 1.5），以及 (ii) 顶根区皮下层中木质素和脂肪族木栓质的含量。脂肪族木栓质被认为是质外体屏障具有疏水性及其相对较低的水渗透性的主要原因。基根区皮下层和内胚层中木栓质的含量没有发现差异。为了验证根 Lpr 的变化不是由膜水平水力传导率的变化引起的，还测量了细胞 Lp。两种不同方法培养的根部细胞的 Lp 值没有差异。结论是质外体的水力传导率的变化而不是细胞间路径的变化导致了观察到的根Lpr的变化。
The hydraulic conductivity of roots (Lpr) of 6- to 8-d-old maize seedlings has been related to the chemical composition of apoplastic transport barriers in the endodermis and hypodermis (exodermis), and to the hydraulic conductivity of root cortical cells. Roots were cultivated in two different ways. When grown in aeroponic culture, they developed an exodermis (Casparian band in the hypodermal layer), which was missing in roots from hydroponics. The development of Casparian bands and suberin lamellae was observed by staining with berberin-aniline-blue and Sudan-III. The compositions of suberin and lignin were analyzed quantitatively and qualitatively after depolymerization (BF3/methanol-transesterification, thioacidolysis) using gas chromatography/mass spectrometry. Root Lprwas measured using the root pressure probe, and the hydraulic conductivity of cortical cells (Lp) using the cell pressure probe. Roots from the two cultivation methods differed significantly in (i) the Lprevaluated from hydrostatic relaxations (factor of 1.5), and (ii) the amounts of lignin and aliphatic suberin in the hypodermal layer of the apical root zone. Aliphatic suberin is thought to be the major reason for the hydrophobic properties of apoplastic barriers and for their relatively low permeability to water. No differences were found in the amounts of suberin in the hypodermal layers of basal root zones and in the endodermal layer. In order to verify that changes in root Lprwere not caused by changes in hydraulic conductivity at the membrane level, cell Lp was measured as well. No differences were found in the Lp values of cells from roots cultivated by the two different methods. It was concluded that changes in the hydraulic conductivity of the apoplastic rather than of the cell-to-cell path were causing the observed changes in root Lpr.