Glucose, fructose, and sucrose influx into Nitella flexilis

Abstract

The uptake of '4C-labeled glucose, fructose, and sucrose into Nitella fiexilis has been investigated by varying concentrations of sugars, by the use of competition experiments, by the use of inhibitors, and by varying conditions of temperature. The kinetic studies and the complex interaction between the sugars were characteristic of a carrier-mediated system maintained by metabolic energy. Glucose and fructose appear to have different sites of entry thougl~ each can influence the other. It is suggested that sucrose is hydrolyzed at the plasmalemma, glucose and fructose then entering the cells.

Different Mass Transfer Rates of Labeled Sugars and Tritiated Water in Xylem Vessels and Their Dependency on Metabolism

“…Sucrose must be hydrolzyed, before entering the cell. In that case, a competitive uptake has been found between sucrose and glucose (2,24). The identical sucrose to glucose uptake ratios (2.4) during simultaneous (Table I) and successive ( Fig.…”

“…Quite recently, it also has been found in tomato roots (6). In Table I, uptake ratios for sugars in tomato internodes have been compared with the uptake ratios into tobacco leaf discs (17), into immature internodal tissue of sugarcane (2), and into Nitella flexilis cells (24). It strengthens the assumption of Goring (10), that the capability to absorb sucrose intact is proper to dicotyledons.…”

“…The sucrose to glucose uptake ratio of Saccharum resembles that of Nitella (24). Sucrose must be hydrolzyed, before entering the cell.…”

“…4). Although a Qlo as high as 2.4 is reported for a diffusiondependent sugar uptake in onion epidermis (19), it is assumed that the uptake of sucrose in tomato internodes is metabolically dependent, as generally a Qlo value higher than 2 is considered sufficient to regard uptake as such (24). In tobacco leaf veins too, sucrose uptake is determined to be metabolically dependent (4).…”

Radio-frequency rectification in electrogenic and nonelectrogenic cells ofChara andNitella

“…Since characean cells are known to take up sugars (cf Wallen, 1974 and references therein), certain amino acids (Wallen, 1973), and amines (e.g., Walker, Smith & Beilby, 1979), and since these uptakes might be presumed to be active, it is not implausible that they might also involve electrogenic hydrogen ion antiport (or, equivalently, hydroxyl symport). To examine this possibility the bathing medium was modified to contain 5 m~ glucose.…”