Correlations Between the Dimensions of Different Zones of Grass Root Apices, and their Implications for Morphogenesis and Differentiation in Roots

Abstract

The sizes of different zones within root apices of nine species of grass were estimated, and statistically significant correlations were found between certain of them. The volume of the cap is related to the volume of the meristem of the root proper. The cortical and stelar portions of the meristem are also related, and their lengths and volumes correlate with the volume of the quiescent centre. The volume of the quiescent centre also correlates with the length of the zone in which periclinal divisions are found in the inner cortex; these divisions generate the rows of cells across the cortex. Diameter of the procambial cylinder, quiescent centre volume and vascular complexity are related, though from correlations alone it is not possible to say whether one of these characters directly influences another as has been suggested by other workers. All the zones within the root apex probably form a tightly-integrated developmental unit. Root structure seems to be independent of cell size, though cell size correlates with nuclear DNA content which is a species-specific feature.