LIGHT-INDUCED CYTOSOLIC CALCIUM TRANSIENTS IN GREEN PLANT-CELLS - I -METHODOLOGICAL ASPECTS OF CHLOROTETRACYCLINE USAGE IN ALGAE AND HIGHER-PLANT CELLS

The fluorescent dye chlorotetracycline (CTC) has several disadvantages compared with ratio dyes like Fura-dextran. However, in many plant ti ssues the derivatives of Fura cannot be loaded. Thus, the pitfalls and possible precautions for the measurement of the light-induced changes in cytosolic free calcium concentration ([Ca2+](c)) were investigated in algae and higher plants. Eremosphaera viridis de Bary and the flow ing cytosol in whorl cells of Chain corallina Klein ex Willd. were use d as examples for possible pressure injection of Fura-dextran or bis-c arboxyethyl-carboxy-fluorescein (BCECF) dextran, illustrating the bett er calibration in absolute terms provided by these dyes. However, here it is shown that CTC works better than Fura-dextran for monitoring th e light-induced changes in [Ca2+](c) in the ectoplasm close to the pla sma membrane in Chara. Protoplasts of Solanum nigrum L. and whole inta ct leaves of Vicia faba L. and Nicotiana tabacum L. were used as examp les of cells that were too fragile for pressure injection of Fura-dext ran. The sensitivity of CTC to pH may cause artefacts when light-induc ed changes in [Ca2+](c) in intact leaves are to be measured. If some p recautions are met, this problem and others (requirement of constant t emperature, sensitivity to other ions, effect on plasma-membrane Ca2permeability) can be circumvented, thus making CTC a suitable dye for monitoring light-induced changes in [Ca2+](c) in a broad spectrum of d ifferent plant cells, tissues and species.