Effects of Calcium and Kinetin on Growth and Cell Wall Composition of Pea Epicotyls

Kinetin and CaCl(2), in the presence of indoleacetic acid, promoted lateral expansion of epicotyls of decapitated and derooted Alaska pea seedlings (Pisum sativum L.) and inhibited their elongation. This growth response was correlated with the development of cell walls unusually rich in pectic uronic acids. Epicotyls in calcium-auxin solutions continued to enlarge and to add new wall material long after tissues in auxin only had stopped. Longitudinal enlargement, associated with the development of walls poor in pectic uronic acids, was favored by KCl, MgCl(2), and ethylenediaminetetraacetate. The last of these agents promoted the loss of (45)Ca from the epicotyls. Seedings grown in vermiculite moistened with CaCl(2), KCl, or MgCl(2) solutions did not differ in appearance or in the composition of their walls. They responded similarly to experimental treatment except that the decapitated epicotyls of the MgCl(2)-grown plants suffered an absolute loss of pectic uronate when incubated in that salt.