ABSTRACT
The root cap covers the outermost tip of roots, from the outgrowing primary root up to the outermost branches of the root system. Whatever the developmental stage is, the root cap protects the apical meristems, senses the direction of gravity and other environmental signals, and generates the rhizosphere. In contrast to most other plant tissues, the root cap (Fig. 1), as a persisting structural entity, consists of cells determined to eventually separate from the cap tissue. Renewed by meristematic divisions, statocytes (i.e., gravityperceiving cells; Fig. 1C) develop and are transformed into mucilage producing secretion cells (Fig. 1D), which finally slough off from the cap, often as metabolically active border cells. The time for a single cell to proceed through the root cap depends on the cycle time, the size of the root cap, and the species. In general, only a few days are required to renew the cap completely, from 1 day in Zea mays to 6-9 days in Convolvulus (Barlow, 1975).
