Carbohydrate metabolism in tomato (Lycopersicon esculentum L. Mill) fruitsduring ripening

A comprehensive trend in different components of carbohydrates such as star ch, sugars and cell wall polysaccharides and in the key enzymes of sucrose and cell wall hydrolysis, i.e., invertase and sucrose synthase, polygalactu ronase and cellulase in tomato (Lycopersicon esculentum L. Mill) fruits dur ing ripening was observed. Starch had almost disappeared at the ripe stage whereas, about five-fold increase was observed in total and reducing sugars from unripe to ripe stage. On the contrary, the amounts of non-reducing su gars decreased during ripening. Activity of sucrose synthase declined drama tically in parallel to the decrease in starch levels in the developing frui ts. while invertase did not exhibit parallelism with starch accumulation, w hich was spatially localized in the inner layers. whereas, the outer layers and seeds contained no starch. Total hemicellulose contents decreased cons iderably from 16% to 5.5% during ripening, whereas there were no apparent c hanges in the contents of other cell wall polysaccharides. This was also re flected in the activities of the cell wall hydrolyzing enzymes, where polyg alacturonase exhibited more than five-fold increase in activity during ripe ning. Cellulase activity, on the other hand. remained almost constant durin g ripening of tomato.