Photosynthetic characteristics of leaves and fruits of Hickory (Carya cathayensis Sarg.) and Pecan (Carya illinoensis K.Koch) during fruit development stages

Abstract

Fruit photosynthesis in both hickory and pecan significantly contribute to the carbon requirements of late growth stage (corresponding to seed development). Plant parts other than leaves can perform photosynthesis and contribute to carbon acquisition for fruit development. To determine the role of fruit photosynthesis in fruit carbon acquisition in hickory (Carya cathayensis Sarg.) and pecan (Carya illinoensis K.Koch), we studied changes in dry mass, surface area and CO2 exchange rate in these fruits during fruit development. Fruit development was divided into two phases: phase one involves the rapid increase of fruit size (from 0 to 59 days after pollination (DAP) for hickory; from 0 to 88 DAP for pecan); phase two involves seed development (from 59 to 121 DAP for hickory; from 88 to 155 DAP for pecan). The net photosynthetic rate (P n) in hickory leaves decreased by 48.5 % from 76 to 88 DAP, while the P n in pecan leaves decreased by 32.3 % from 88 to 123 DAP. The gross photosynthetic rate (P g) in hickory fruit was significantly greater than that of the leaf during the late stage (88 to 121 DAP) of fruit development. Pecan fruit had a significantly higher P g than leaves during ontogeny. The contribution of fruit photosynthesis to fruit carbon requirements increased during fruit development, which was estimated by the gross fruit photosynthesis divided by respiration and increased dry mass. The contribution of fruit photosynthesis to pecan carbon requirements was significantly greater than that of hickory. Fruit photosynthesis in both hickory and pecan significantly contribute to the carbon requirements of late growth stage.