CONTROL OF CELL PROGRESSION THROUGH THE MITOTIC CYCLE BY CARBOHYDRATE PROVISION : I. Regulation of Cell Division in Excised Plant Tissue*

A stationary phase in the root meristem of excised pea roots was established by prolonged carbohydrate deprivation in sterile culture medium. When the stationary phase had been established, cells that had collected in the G₁ period of the mitotic cycle were induced to enter the S stage by subjection to relatively short intervals of carbohydrate provision (sucrose spurts). Progression and cycle location of the G₁ cells induced to enter S were measured with tritiated thymidine and radioautography. The results indicated that the number of G₁ cells induced to enter S increased directly with the spurt duration and that cells could be positioned and retained in the S and/or G₂ periods by varying the duration of the spurt. The data support the hypothesis that S and maybe M stages have a relatively larger dependence on carbohydrate availability, and presumably a greater energy requirement, than G₁ and G₂.