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A new approach to the investigation on the tonogenic groups of root cell walls

机译：研究根细胞壁声调基团的新方法

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Acid-base properties of wheat (Triticum aestivum), lupin (Lupinus albus), and pea (Pisum sativum) root cell walls were investigated. The roots of etiolated and green plants of different age were analysed by the potentiometric method. The ion exchange capacity of root cell walls (Si) was estimated at various pH values (pHi 2 to pHi 12) and constant ion strength of the solution (10 mM). To analyse polysigmoid curves pHi = f(Si), Gregor's equation was used. It was shown that Gregor's model fits fairlywell the experimental data. The total quantities of cation-exchange (Stcat) and anion-exchange (Stan) groups were determined in the root cell walls. It was shown that the quantity of anion exchange groups is varied through a small range (60-185μmol/g dry wt.) in the plant species tested, and that the Stcat differs widely from 550 to 1300μmol/g dry weight. For leguminous plants the quantity of acidic groups (fixed anions) is nearly twice as large as that for cereals. It was found that in seedlings aswell as in plants, there are 3 cation-exchange groups and one anion-exchange group in root cell walls. The quantity of functional groups of each type (Sj) was estimated, and the corresponding values of nj and pKaj were calculated. It can be assumed thatthe groups with the pKa1～3.2 are amine groups, the ones with pKa2～5 are groups of galacturonic acid, the ones with pKa～7.5 are the carboxyl groups of the second species, and the ones with pKa4～40 are the phenolic groups. The values of dissociation constants (pKaj) and Sj indicate that the root cell walls of wheat, lupin and pea are identical in qualitative structure of ionogenic groups but vary in the quantity of each ionogenic group. It was demonstrated that the summarized quantity of carboxyl groups (S2+S3) should be connected directly with the pH gradient in the extracellular space at the membrane surface. The gradient arises from ion-exchange reactions between cations of an outer medium and protons of the ionized carboxyl groups of the cell walls.The results suggest that, Stcat and Stan allow the quantitative estimation of ion exchange properties of the cell walls. The resulting parameters (Sj, pKaj and nj) allow prediction of changes in an ionic composition of a medium that bathes the cell membrane, during the first step of mineral nutrition uptake.
机译：研究了小麦（Triticum aestivum），羽扇豆（Lupinus albus）和豌豆（Pisum sativum）根细胞壁的酸碱性质。通过电位分析法分析了不同年龄的黄化和绿色植物的根。在各种pH值（pHi 2至pHi 12）和溶液的恒定离子强度（10 mM）下，估计根细胞壁（Si）的离子交换能力。为了分析多乙形曲线pHi = f（Si），使用了Gregor方程。结果表明，Gregor的模型与实验数据吻合得很好。确定根细胞壁中阳离子交换（Stcat）和阴离子交换（Stan）基团的总量。结果表明，在所测试的植物物种中，阴离子交换基团的数量在很小的范围内变化（60-185μmol/ g干重），并且Stcat在550至1300μmol/ g干重之间有很大差异。对于豆科植物，酸性基团（固定阴离子）的数量几乎是谷物的两倍。发现在幼苗以及植物中，根细胞壁中有3个阳离子交换基团和1个阴离子交换基团。估计每种类型的官能团（Sj）的数量，并计算nj和pKaj的相应值。可以假定pKa1〜3.2的基团是胺基，pKa2〜5的基团是半乳糖醛酸基团，pKa〜7.5的基团是第二种羧基，pKa4〜40的基团是氨基。酚基。离解常数（pKaj）和Sj的值表明，小麦，羽扇豆和豌豆的根细胞壁在离子源基团的定性结构上是相同的，但是每个离子源基团的数量是变化的。结果表明，羧基（S2 + S3）的总量应与膜表面细胞外空间的pH梯度直接相关。梯度是由外部介质的阳离子与细胞壁离子化的羧基质子之间的离子交换反应引起的。结果表明，Stcat和Stan可以定量估计细胞壁的离子交换性质。最终的参数（Sj，pKaj和nj）可以预测在吸收矿物质营养的第一步期间浸入细胞膜的培养基的离子组成的变化。

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