%0 Journal Article
%T Compartmentation of sucrose during radial transfer in mature sorghum culm
%A Lee Tarpley
%A Donald M Vietor
%J BMC Plant Biology
%D 2007
%I BioMed Central
%R 10.1186/1471-2229-7-33
%X On the day after culm infusion of the tracer sucrose, the specific radioactivity of sucrose recovered from the intracellular compartment of growing axillary-branch tissue was greater (nearly twice) than that in the free space, indicating that sucrose was preferentially transferred through symplasmic routes. In contrast, the sucrose specific radioactivity in the intracellular compartment of the mature (ripening) culm tissue was probably less (about 3/4's) than that in free space indicating that sucrose was preferentially transferred through routes that included an apoplasmic step. In growing internodes of the axillary branch of sorghum, the tritium label initially provided in the fructose moiety of sucrose molecules was largely (81%) recovered in the fructose moiety, indicating that a large portion of sucrose molecules is not hydrolysed and resynthesized during radial transfer.During radial transfer of sucrose in ripening internodes of intact sorghum plants, much of the sucrose is transferred intact (without hydrolysis and resynthesis) and primarily through a path that includes an apoplasmic step. In contrast, much of the sucrose is transferred through a symplasmic path in growing internode (axillary branch) tissue. These results contrast with the probable symplasmic path in mature culm of the closely related species, sugarcane. Phylogenetic variability exists in the compartmental path of radial transfer of sucrose in culms of the andropogonoid grasses.The Andropogoneae tribe of grasses includes a number of large tropical grasses, several of which are widely cultivated for either their grain (sorghum [Sorghum bicolor (L.) Moench] and maize [Zea mays L.]) or for the sucrose accumulated in the culm (sugarcane [Saccharum officinarum L.] and sorghum). The examined species contain sucrose in the culms. This sucrose can support grain filling in some circumstances by buffering the supply of photoassimilate. This study contributes to improved understanding of processes of su
%U http://www.biomedcentral.com/1471-2229/7/33