AN INVITRO ASSAY OF SUCROSE UPTAKE BY DEVELOPING BEAN COTYLEDONS

An in vitro procedure, based on net rates of sucrose uptake from [14C]sucrose solutions, was developed to determine the in vivo sucrose uptake rates of French bean (P. vulgaris L.) cotyledons. Net rates of in vitro sucrose uptake exhibited saturation kinetics and temperature dependency with Q10 values in the range 1.5-2.0. Optimal rates of net sucrose uptake were obtained in unbuffered media containing sucrose alone. Under sink-limited growth conditions, where in vivo free-space sucrose concentrations saturated (90-145 mM) the sucrose uptake process, the in vitro procedure could account for in vivo gains of sucrose by the cotyledons.