Calcium and Polarity in Tip Growing Plant Cells

Abstract

Polarity of various plant cells is manifested most obviously by tip growth. Tip growth occurs, e.g. in some algae, fungal hyphae, moss and fern protonemata, root hairs and pollen tubes. These tubular cells are also characterized by a polar distribution of cell organelles. Golgi vesicles, produced in a certain distance from the tip, are transported vectorially into the cell apex. They accumulate there to form a “tip body” or “clear cap” and fuse with the plasmalemma, extruding matrix substances of the cell wall. Polar growth implied additionally the polar formation of cellulose microfibrils (Reiss et al., 1984b). Exogenous factors like gravity and light as well as endogenous factors, e.g. growth substances, turgor pressure, ion currents, the plasma membrane, the nucleus and cytoskeletal elements may be involved in inducing polarity and controlling tip growth. Polarity itself is based on the interrelationship of these factors (for review see Sievers and Schneft, 1981).