Regulation of Leaflet Photosynthesis by Developing Fruit in the Pea

Abstract

Abstract Changes in the net photosynthesis of leaflets of Pisum sativum L. (cv. Onward) were found to reflect closely the pattern of assimilate demand in subtended fruit during development. An early peak in leaflet photosynthesis corresponded with the rapid elongation of the fruit; a second peak with the inflation of the pod and initiation of seed growth. However, where the subtended fruit was removed at anthesis, the pattern of fluctuation in leaflet photosynthesis was altered, while leaflets at vegetative nodes maintained a lower photosynthetic rate which fluctuated little. The pattern of net photosynthesis in the fruit appears to reflect the high respiration rates associated with pod elongation and seed growth. This closely coupled system, where fruit assimilate demand modulates the photosynthesis of adjacent leaflets, provides a scope for study of source‐sink relationships with the minimum of experimental manipulation.