The Relationship Between Photosynthesis and Translocation in a C-3 Plant PDF

Keywords

leaf, broad bean, carbon

Abstract

The basal bifoliate leaf of broad bean on separate plants was supplied with 14CO2 at four stages during the development of the species and the distribution of radiocarbon products determined quantitatively 24h later. The fed leaves retained substantial amounts of the radiocarbon they fixed initially. Determination of the dry weight of the basal bifoliate leaf at four stages of development, from a plant with two expanded leaves to one with developing pods showed no statistically significant change of leaf dry weight during this time. Whole plants of broad bean were also allowed to assimilate 14CO2 for one hour. Samples of leaf 3 were then harvested after 1h, 3h, 6h, 24h and 7 days, dried and prepared for autoradiography. The results show that the intensity of 14C in leaf 3 declined with time but with a trace of radiocarbon retained by the 7th day. A survey of published information about the loss of photosynthetically fixed 14CO2 from leaves is included. The present results do not support some previously published conclusions that the rate o export of photosynthetic products from the leaves regulates the rate of photosynthesis