| Abstract: | Protoplasts were isolated from leaves of in vitro grown axenicshoots of grapevine (Vitis vinifera L. cv. Soultanina) and usedto study the characteristics of arginine transport. Uptake waslinear up to at least 60 min and the rate did not differ significantlybetween light and dark assaying conditions whereas incubationin darkness for 24 h caused a 70% reduction in uptake rate,which was probably not due to an energy dependent factor. Kineticsanalysis revealed a biphasic uptake curve. The high affinitycomponent had a Km, of 2.2 mol m–3. Optimum pH value was5.5. Two carrier systems, one for basic and neutral and onefor acidic amino acids were identified. Use of inhibitors revealedthat those associated with ATP metabolism inhibited arginineuptake; more specifically, the proton motive force appearedto be the predominant energy source. Metabolic products of labelledarginine were consistent with the operation of the Krebs-Henseleitcycle. Key words: Grapevine protoplast, grapevine tissue culture, arginine transport |
