Cytochemical Analyses on Cellular Differentiation in the Root Tip ofAllium Cepa

Abstract

Spectrophotometry in Allium cepa root tip tissues showed that Feulgen mean absorption decreases in pericycle and protoderm cells from 500 to 1500 μ (starting from the distal end of the root cap), while in provascular cells it increases. These observations are probably consistent with the gradual accumulation of pericycle and protoderm cells in the G₁ phase of the mitotic cycle and with the ability of provascular cells to undergo chromosome endoreduplication. The collected data show that fast green absorption, when compared with Feulgen absorption in the same cell, gives an indication that DNA/histone ratio is not constant among tissues and also within one single cell line during the maturation process. The significance of these observations for studies of cell metabolism is discussed.