Tazawa Masashi, Wayne Randy, Katsuhara Maki
Yoshida Biological Laboratory, 11-1 Takehanasotoda-Cho, Yamashina-Ku, Kyoto, 607-8081, Japan.
Laboratory of Natural Philosophy, Plant Biology Section, Cornell University, Ithaca, NY, USA.
Protoplasma. 2025 Mar;262(2):385-395. doi: 10.1007/s00709-024-02000-6. Epub 2024 Oct 23.
In the cells of Chara corallina, permeant monohydric alcohols including methanol, ethanol and 1-propanol increased the hydraulic resistance of the membrane (Lp). We found that the relative value of the hydraulic resistance (Lp) was linearly dependent on the concentration (C) of the alcohol. The relationship is expressed in the equation: Lp = ρC + 1, where ρ is the hydraulic resistance modifier coefficient of the membrane. Ye et al. (2004) showed that membrane-permeant glycol ethers also increased Lp. We used their data to estimate Lp and Lp. The values of Lp fit the above relation we found for alcohols. When we plotted the ρ values of all the permeant alcohols and glycol ethers against their molecular weights (MW), we obtained a linear curve with a slope of 0.014 M/MW and with a correlation coefficient of 0.99. We analyzed the influence of the permeant solutes on the relative hydraulic resistance of the membrane (Lp) as a function of the external (π) and internal (π) osmotic pressures. The analysis showed that the hydraulic resistance modifier coefficients (ρ) were linearly related to the MW of the permeant solutes with a slope of 0.012 M/MW and with a correlation coefficient of 0.84. The linear relationship between the effects of permeating solutes on the hydraulic resistance modifier coefficient (ρ) and the MW can be explained in terms of the effect of the effective osmotic pressure on the hydraulic conductivity of water channels. The result of the analysis suggests that the osmotic pressure and not the size of the permeant solute as proposed by (Ye et al., J Exp Bot 55:449-461, 2004) is the decisive factor in a solute's influence on hydraulic conductivity. Thus, characean water channels (aquaporins) respond to permeant solutes with essentially the same mechanism as to impermeant solutes.
在轮藻细胞中，包括甲醇、乙醇和1 - 丙醇在内的可渗透一元醇增加了膜的水力阻力（Lp）。我们发现水力阻力（Lp）的相对值与醇的浓度（C）呈线性相关。这种关系用方程表示为：Lp = ρC + 1，其中ρ是膜的水力阻力修正系数。Ye等人（2004年）表明，可渗透膜的二醇醚也会增加Lp。我们用他们的数据来估算Lp和Lp。Lp的值符合我们发现的上述醇类的关系。当我们将所有可渗透醇类和二醇醚的ρ值与其分子量（MW）作图时，得到了一条斜率为0.014 M/MW且相关系数为0.99的线性曲线。我们分析了可渗透溶质对膜相对水力阻力（Lp）的影响，它是外部（π）和内部（π）渗透压的函数。分析表明，水力阻力修正系数（ρ）与可渗透溶质的分子量呈线性相关，斜率为0.012 M/MW，相关系数为0.84。可渗透溶质对水力阻力修正系数（ρ）和分子量影响之间的线性关系可以用水通道水力传导率的有效渗透压效应来解释。分析结果表明，渗透压而非（Ye等人，《实验植物学杂志》55:449 - 461，2004年）提出的可渗透溶质的大小是溶质对水力传导率影响的决定性因素。因此，轮藻水通道（水孔蛋白）对可渗透溶质的响应机制与对不可渗透溶质的基本相同。
