Effect of pollination on carbohydrate metabolism, in young fruits of Citrullus lanatus and Capsicum annuum

Abstract

During a 9 day period after anthesis the concentration of reducing sugars showed a 6-fold increase in fruits of Citrullus lanatus, and a 2-fold increase in those of Capsicum annuum. These increases were associated with acid invertase, the specific activity of which was high in ovaries at anthesis and which increased 5-fold in watermelon and 1.5-fold in pepper during the same period. Sucrose synthase apparently plays only a minor role in sucrose hydrolysis. Changes in sugar concentrations and both acid invertase and sucrose synthase activities were similar in fruits developed both after pollination or hormone (NAA) treatment of ovaries. In non-pollinated ovaries of watermelon there was also an increase in invertase activity up to 6 days after anthesis which paralleled the increase in activity in seeded and parthenocarpic fruits. However, there was no increase in either reducing sugars or sucrose, indicating that sucrose is not imported into non-pollinated ovaries. Utilisation of reserve starch may help prolong the life of non-pollinated ovaries for up to one week after anthesis.