Relationship of Cellular Organelles to the Formation and Development of the Plant Cell Wall

It has been shown that Golgi bodies, endoplasmic reticulum,and microtubules are concerned with the organization and synthesisof materials which are incorporated into the wall of the manycells making up the various tissues of a young plant. Preformedmaterial is added to the wall from vesicles which in some cellscan be inferred to be derived from the Golgi bodies. The materialis passed to the wall by a process of pinocytosis. In othercells although the same process is apparent the origin of thevesicles cannot at present be ascertained. The organization of the growth and development of the wall iscontrolled to some extent by the endoplasmic reticulum whichcan be seen to be situated in the cell at positions relativeto particular regions of cell-wall development. This is veryapparent in the formation of pit fields, sieve plates, and thesecondary thickenings of the xylem. The microtubules are organized in the cytoplasm relative towall growth and can be seen in cells in which growth is eitheroccurring uniformly along the wall or as organized annular orspiral thickenings. In the former case the microtubules arealso present all along the length of the wall whereas in thelatter cells they are found grouped in relation to the developingthickenings.