Assimilate Source-Sink Relationships in Capsicum annuum L. II. Effects of Fruiting and Defloration on the Photosynthetic Capacity and Senescence of the Leaves

Abstract

The photosynthetic capacity of leaves of fruiting Capsicum plants that expanded during or shortly after anthesis remained steady throughout the growth of the fruit. The formation and growth of the fruit was associated with a reversal of the decline in photosynthetic capacity of some of the leaves that had expanded before anthesis. In deflorated plants, the photosynthetic capacity of leaves at all levels of insertion declined continuously.

The variations with age of the net CO₂ exchange of the leaf inserted one internode above the fruit were attributable almost exclusively to changes in intracellular resistance, while in the corresponding leaf of deflorated plants both leaf and intracellular transfer resistances were important determinants of photosynthesis.

Fruiting reduced the age-related loss of soluble and fraction 1 protein and of ribulosebisphosphate carboxylase activity in the leaf immediately above the fruit. The ratio of fraction 1 protein synthesis to that of other soluble proteins in fully expanded leaves showed no tendency to decline with age in plants of either type. Intracellular resistance in fruiting plants did not appear to be linked to changes in either fraction 1 protein content or ribulosebisphosphate carboxylase activity.