DEVELOPMENT OF THE SHOOT APEX IN ZEA MAYS

Abstract

SUMMARYIntact embryos of Zea mays have been studied by stathmokinesis and DNA labelling to find rates of cell proliferation in the regions of the developing shoot apex, and these have been compared with rates for seedlings, whose apices have to be partially uncovered for this purpose. In young embryo shoots, cells divide faster than they do in seedhngs and rates at the summit do not differ greatly from those in the rest of the apex. The tunica, which contains about half the cells in the apex, contributes a decreasing fraction of the total cell production as the embryo ages. The results are discussed in relation to the maturation of the seed and the changes in the numbers of cells in the regions of the meristem.