Developmental Features of the Primary Phloem in Phaseolus vulgaris L.

Publisher Website
Google Scholar
Abstract
Certain developmental features of the primary phloem were examined in Phaseolus vulgaris L., chiefly by the use of the pulvinus at the base of the petiole. The cells included in the study were the sieve element, the companion cell, and the tannin cell. In the sieve element, the sieve plate shows the usual sequence of conversion of plasmodesmatal canals into pores. The endoplasmic reticulum, which appears as flat cisternae associated with ribosomes in younger cells, later becomes in part stacked and in part aligned parallel with the walls as a network. The stacked ER precedes the anastornosing parietal ER in time of development, but the parietal ER persists longer. Of the two forms of P-protein characteristic of a number of Fabaceae, the crystalline body appears considerably in advance of the body composed of tubules. Neither form of P-protein disperses completely in the mature cell, although the crystalline protein may spread out into aggregates of fine fibrils. The companion cells show the typical dense protoplasts and branched plasrnodesmatal connections with the sieve elements. The vacuome of these cells is dispersed into numerous small vacuoles, many of which appear to be concerned with autophagic digestion of protoplasmic material. The tannin cells have large vacuoles in which the tannin material is located. The cells form vertical series in which the end walls become perforated.

This publication has 0 references indexed in Scilit: