CELL BURST AS A MECHANISM OF PLANT-CELL INJURY .1. VISUAL OBSERVATIONAND ELECTROPHYSIOLOGICAL RECORDING OF CELL BURST INDUCED BY CA2+ DEFICIENCY

Elongating internodal cells of Nitella syncarpa and excised root tips of Trianea bogotensis with young root hairs were incubated in the pres ence of 1-10 mM EDTA. The desorption of Ca2+ from the cell surface res ulted in local ruptures of the plasmalemma and cell wall, leading to h ydrodynamic ejections of portions of the cytoplasm (cell bursts) and s ubsequent healing of the wounded regions. The electric parameters of t he plasmalemma and tonoplast (potential difference, specific resistanc e, electric-current density) continuously recorded with microelectrode s, as well as the cessation of cyclosis in the intervals between cell bursts, indicate an increase in the cytosolic Ca2+ level during cell b urst. It is suggested that cell bursts are a mechanism responsible for the injury and death of young cells under conditions of Ca2+ deficien cy. This type of injury may occur in nature under extreme mechanical t ension and upon enzymic or physical loosening of the cell wall. Tempor ary elevation of the Ca2+ concentration during a cell burst is benefic ial for wound healing; however, prolonged disturbance of Ca2+ homeosta sis (upon recurrent bursts) may result in cell death.