Development of the Sieve Plate in Saxifraga sarmentosa L.

Publisher Website
Google Scholar
Abstract
The differentiating sieve plate in the phloem of the stolon of Saxifraga sarmentosa L. was studied with the electron microscope. Development of the pore site begins with differentiation of a pair of collar-like areas around the plasmodesma which can be seen in the youngest identifiable sieve plates. Further growth of the collars occurs by deposition of an amorphous substance, presumably caflose. Although the growth of the collars is simultaneous with the growth of the surrounding cell wall it is rapid at first and the pore sites appear asdome-shaped protuberances. It also involves deposition of callose over an increasingly wider area of the cell wall and since the thickening of the normal cell wall continues only where notcovered by callose, the collars assume a conical form. There seems to be no displacement or lysis of normal cell wall material during growth of the collars. Eventually the growth of the cell wall in thickness overtakes the pore sites so that when the growth of the cell wall is complete the pore sites appear as depressions in the sieve plate. The perforation of a pore site is accomplished by widening of the plasmodesmatal cylinder which begins at the middle lamella by removal of callose. Endoplasmic reticulum is found in close proximity to the plasmodesma andis believed to penetrate it.

This publication has 0 references indexed in Scilit: