Properties and Possible Physiological Significance of Cell Wall Calcium Binding in Etiolated Pea Epicotyls |
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Authors: | BAYDOUN, ELIAS A-H BRETT, CHRISTOPHER T. |
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Abstract: | Baydoun, E. A-H. and Brett, C. T. 1988. Properties and possiblephysiological significance of cell wall calcium binding in etiolatedpea epicotyls.J. exp. Bot. 39: 199208. The binding of 45Ca2+ ions to cell walls prepared from pea epicotylswas examined in young and old parts of the epicotyl, and wasfound to be considerably greater, on a carbohydrate basis, inthe older, non-growing cells. A similar comparison between light-and dark-grown stems showed greater binding in the dark-grownstems. The polygalacturonase-insensitive component of the bindingcontained at least three types of binding with different affinities,and had an apparent pK of 4.3. The specificity of the bindingfor calcium ions was examined and a considerable degree of specificitywas observed. The specificity of inhibition by calcium of epicotylelongation was similar to the specificity of calcium binding.A specific calcium chelator, EGTA, when present at a concentrationof above 10 mol m3, promoted the extension of matureregions of the epicotyl, while inhibiting extension of youngertissue. Key words: Cell wall, calcium, pea epicotyl |
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