Comparison of suspension cells and cotyledons of ricinus with respect to sugar uptake.

Suspension cells and cotyledons of Ricinus communis were compared as to their uptake properties for sugar and amino acids to reveal whether the previously reported sucrose-specificity of the cotyledon is a specific feature of the cotyledon or of the Ricinus cell in general. The experiments show that suspension cells have a higher hexose uptake activity at low sugar concentration than cotyledons, whereas sucrose cannot be taken up by suspension cells unless it is first hydrolyzed. Amino acids are taken up by suspension cells and by the cotyledons. It is concluded that the highly specific uptake of sucrose without hydrolysis is a special feature of certain specialized cells of the cotyledon, probably the phloem.