Root hairs grow by apical growth

Develop from rhizodermal trichoblasts

Have a polar organization

A diagrammatic representation of a growing root hair (trichoblast) of radish (Raphanus sativus) from a cross-sectioned root based on transmission electron microscope observations.

The hair elongates by apical growth and large numbers of secretory Golgi vesicles are concentrated in the apex, transporting matrix polysaccharides to the growing wall region. The distribution of the cell components is polar. A zone of the highest concentrations of organelles follows the apical zone that is replaced by a zone of vacuolation. The nucleus occupies the basal portion of the cell.

The sites of adjacent rhizodermal cells without root hairs (i.e. atrichoblasts) are shown at either side as are the underlying sites of two cortex cells.