COMPARTMENTATION AND CELLULAR CONDITIONS CONTROLLING SUCROSE BREAKDOWN IN MATURE ACID LIME FRUITS

The intracellular conditions required for acid hydrolysis of sucrose in acid lime juice cells were examined in detail with particular attention to the potential of enzymatic sucrose breakdown and the existence of acid invertase inhibitors. The decrease in acid invertase activity during fruit development was not due to the presence of an inhibitor, as measured by subjecting the tissue extract to treatments known to inactivate the inhibitor. The vacuolar pH of ca 2.1 was confirmed by microelectrode determinations using intact vesicle tissue. Additionally, compartmentation studies using the poly-L-lysine method revealed total vacuolar localization of sucrose in mature cells. We therefore confirm that the conditions necessary for in vivo acid hydrolysis of sucrose, namely a lack of enzymatic sucrose breakdown, complete vacuolar sucrose compartmentation and a low vacuolar pH, are concurrently present in mature juice cells of acid limes.