Internodal compartmentation of stem-infused [14C]sucrose in sweet and grain sorghum

Stem infusion was evaluated for quantifying downward movement, intracellular allocation, and interorgan partitioning of assimilate in sweet and grain sorghum [Sorghum bicolor (L.) Moench] stems during mid-grain fill and post-black layer. Sucrose concentration did not vary below the site of infusion with [14C]sucrose, although gradients of intracellular 80%-ethanol soluble and insoluble 14C-components were established in the stem. Variation in gradient steepness between cultivars resulted from aspects of parenchymal uptake or phloem uptake of sucrose and appears related to sucrose-concentrating ability. The introduced [14C]sucrose concentration gradient in stem tissue is useful for studying stem mechanisms that controls ink strength.