NUCLEOLAR SIZE DIFFERENCES IN THE GRASS ROOT EPIDERMIS

Root tips of the festucoid grass, Festuca arundinacea, and 2 panicoid species, Chloris gayana and Panicum virgatum, were processed using 2 different staining techniques. Measurements of nucleolar size were taken on epidermal and cortical cells. Trichoblasts and hair cells of Festuca were found to contain much larger nucleoli than those in hairless initials or hairless cells. Significant nucleolar size differences between hair and hairless cells were also found in the 2 panicoid species. In contrast to Festuca, this difference between the 2 cell types was not as pronounced, and overlapping in nucleolar size occurred between adjacent hair and hairless cells. The cortex was composed of rows of cells in which nucleolar size simply decreased with cell distance from the apex. The significance of the observed nucleolar differences among cell types of the root tip is discussed briefly in relation to systematics, enzyme activity patterns, and differentiation.