Abstract:One to two cm long root tips of Triticum aestivum L., after three days‘ germination at 25 ℃, each were cut into three regions--the meristem region, elongation region and mature region. The cells in different regions were stained with Hochest 33258, Pymnin G and FITC respectively. Nuclear DNA was measured by micmfluorometry with VIDAS digital image analysis system. The relative contents of RNA and protein in the cells were measured with a MPV-Ⅲ microspectrofluorometer. It was shown that the nuclear DNA content increased during root tip cell differentiation, being maximum in the mature region. The relative content of RNA was maximum in the meristem region, but decreased continuously during the growth of tissue. The relative content of protein was maximum in the elongation region, but minimum in the meristem region. The relationships among DNA, RNA, protein and cell differentiation were discussed.