INTERNODAL COMPARTMENTATION OF STEM-INFUSED [C-14] SUCROSE IN SWEET AND GRAIN-SORGHUM

Stem infusion was evaluated for quantifying downward movement, intrace llular 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 t he site of infusion with [C-14]sucrose, although gradients of intracel lular 80%-ethanol soluble and insoluble C-14-components were establish ed in the stem. Variation in gradient steepness between cultivars resu lted from aspects of parenchymal uptake or phloem uptake of sucrose an d appears related to sucrose-concentrating ability. The introduced [C- 14]sucrose concentration gradient in stem tissue is useful for studyin g stem mechanisms that control sink strength.