Radial hydraulic conductivity along developing onion roots
Radial hydraulic conductivity along developing onion roots
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DOI：
10.1093/jexbot/51.344.547
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发表时间：
2000-03-01
影响因子：
6.9
通讯作者：
Steudle, E
中科院分区：
文献类型：
--
作者：
Barrowclough, DE;Peterson, CA;Steudle, E
虽然大多数研究表明，水分吸收沿着发展的根的长度变化，有没有一致的相关性，这种模式与根解剖。在本研究中，水分运动到洋葱根的三个区域的一系列微型potometers。吸收最少的是最年轻的区域（平均导水率，Lp（r）= 1.5 x 10（-7）+/- 0.34 x 10（-7）m MPa-1 s（-1）; +/- SE，n = 10根），其中内皮层仅发育凯氏带，外皮层未成熟。中间区的吸收明显更大（Lp（r）= 2.4 x 10（-7）+/- 0.43 x 10（-7）m MPa-1 s（-1）;+/- SE，n = 10根），其具有成熟的外皮层，具有凯氏带和木栓质层，在最老的区域，内皮层也发育了木栓质层，并继续保持这一水平（Lp（r）= 2.8 × 10（-7）+/- 0.30 × 10（-7）m MPa-1）。1 s（-1）;+/- SE，n = 10根）。使用细胞压力探针测量外皮层中单个细胞的水力传导率（Lp）表明，该参数在所有三个测试区域中是均匀的（Lp = 1.3 x 10（-6）+/- 0.01 x 10（-6）m MPa-1 s（-1）; +/- SE，n = 60个细胞）。最年轻的区域的脂蛋白降低氯化汞处理，表明汞敏感的水通道（水通道蛋白）的参与，水流量在老的两个根区测量的微型potometers也被氯化汞抑制，尽管表现出不渗透性的外皮层这种物质。因此，水通道的表皮和/或外皮层的较老的地区是特别重要的水流。这和以前的研究结果进行了讨论，在两个模型。第一种是描述玉米根与未成熟的外皮层，是“均匀阻力模型”，其中水力阻力均匀分布在整个根圆柱体。第二，它描述了一个成熟的外皮洋葱根，是“非均匀电阻模型”，电阻可以是可变的，并集中在一定的层（S）的径向路径。
Although most studies have shown that water uptake varies along the length of a developing root, there is no consistent correlation of this pattern with root anatomy. In the present study, water movement into three zones of onion roots was measured by a series of mini-potometers. Uptake was least in the youngest zone (mean hydraulic conductivity, Lp(r) = 1.5 x 10(-7) +/- 0.34 x 10(-7) m MPa-1 s (-1); +/- SE, n = 10 roots) in which the endodermis had developed only Casparian bands and the exodermis was immature. Uptake was significantly greater in the middle zone (Lp(r) = 2.4 x 10(-7) +/- 0.43 x 10(-7) m MPa-1 s(-1); +/- SE, n = 10 roots) which had a mature exodermis with both Casparian bands and suberin lamellae, and continued at this level in the oldest zone in which the endodermis had also developed suberin lamellae (Lp(r) = 2.8 x 10(-7) +/- 0.30 x 10(-7) m MPa-1 s(-1); +/- SE, n = 10 roots). Measurements of the hydraulic conductivities of individual cells (Lp) in the outer cortex using a cell pressure probe indicated that this parameter was uniform in all three zones tested (Lp = 1.3 x 10(-6) +/- 0.01 x 10(-6) m MPa-1 s(-1); +/- SE, n = 60 cells). Lp of the youngest zone was lowered by mercuric chloride treatment, indicating the involvement of mercury-sensitive water channels (aquaporins), Water flow in the older two root zones measured by mini-potometers was also inhibited by mercuric chloride, despite the demonstrated impermeability of their exodermal layers to this substance. Thus, water channels in the epidermis and/or exodermis of the older regions were especially significant for water flow. The results of this and previous studies are discussed in terms of two models. The first, which describes maize root with an immature exodermis, is the 'uniform resistance model' where hydraulic resistances are evenly distributed across the root cylinder. The second, which describes the onion root with a mature exodermis, is the 'non-uniform resistance model' where resistances can be variable and are concentrated in a certain layer(s) on the radial path.