Axial and Transnodal Movement of14C,22Na, and36Cl inNitella translucens

Abstract

The time courses of axial movement in Nitella translucens of a number of 14C-labelled compounds and of 36C1 and 22Na have been determined together with simultaneous microscopical observations of the rates of visible protoplasmic streaming. In general, the translocation profiles suggest the irreversible absorption of tracer though there are examples of reversible absorption. The coupling between visible streaming and the front of the axial transport is weak. Light, DCMU (dichlorophenyldimethylurea), and temperature affect the translocation but visible streaming is affected only by temperature and the passage of an action potential. There is evidence, from a number of compounds, of a faster-thari-streaming translocation of small amounts of tracer in the form of ‘pulses’ which are completely detached from the main body of tracer. Either vesicles or microperistaltic packets are thought to account for this rapid moiety. Observations of transnodal transfer suggest that an active mechanism is involved in the transference of carbonate, urea, acetate, and chloride. The influxes of the various compounds have been calculated and shown to be in good agreement with existing published values. Action potentials reduce the influx of carbonate, chloride, and possibly acetate, as do lack of light and DCMU. It is suggested that the influx of these anions is coupled with the active anion pump and with loading sites on the plasma membrane which become inoperative during and immediately following an action potential.