SUCROSE BREAKDOWN IN RELATION TO FRUIT-GROWTH OF ACID LIME (CITRUS-AURANTIFOLIA)

The physiological capacity for sucrose breakdown in developing juice sac cells of acid limes was estimated by assaying the activity of the three enzymes of sucrose catabolism in addition to vacuolar acid hydrolysis. The maximum potential rates of sucrose breakdown were compared with the observed rates of carbon utilization. Highest potential rates of sucrose breakdown (28.621 mmol cm-3 per hydrated active space d-1) occurred at the initial stages of fruit development where carbon utilization was highest. As the fruit developed, the potential rates of sucrose breakdown and carbon utilization declined to very low levels. At 80% of development, vacuolar acid hydrolysis became the only physiological mechanism for sucrose breakdown. The relatively low amounts of sucrose hydrolysed by acid hydrolysis at this time were just sufficient to account for the measured carbon demands. The results suggest that carbon supplied by this distinct sucrose catabolizing system is able to provide adequate levels of carbon skeletons for the observed levels of respiration and dry weight deposition early in development, but becomes a limiting factor for growth in the later stages. © 1990 Oxford University Press.