Figure 8.

A Schematic Representation of Root Hair Growth in the Wild Type and Different Vegetative Actin Mutants.

In the wild type, there are four major phases during root hair development: (I) root epidermal cell specification into trichoblast (T) and atrichoblast cells (AT); (II) root hair initiation/bulge formation in the trichoblast cells; (III) tip growth; and (IV) maturation. Root hair development is differentially affected in various single and double actin mutants. The gray arrows below the diagram indicate the stages at which root hair development is arrested. For the act7-4 single mutant and the act2-1 act7-4 and act8-2 act7-4 double mutants, the arrows are shown in dashed lines to suggest partial differentiation of root epidermal cells into trichoblast and nontrichoblast cells. This defect in cell specification reduces the number of root hairs formed compared with the wild type (act7-4 and act8-2 act7-4) or development of no root hairs (act2-1 act7-4).