High-resolution histographical mapping of glucose concentrations in developing cotyledons of Vicia faba in relation to mitotic activity and storage processes:: glucose as a possible developmental trigger

Previous studies provided evidence that the carbohydrate status triggers developmental processes in the growing cotyledons of Vicia faba. We describe here the high-resolution mapping of glucose concentrations in tissue sections of developing faba bean cotyledons by quantitative bioluminescence and single-photon imaging. Patterns of local glucose distributions are compared with tissue cell type, mitotic index and the distribution pattern of starch. During cotyledon differentiation, gradients in the glucose concentration emerge which are related to the particular cell type. Higher concentrations are found in non-differentiated premature regions of the cotyledon whereas mature starch-accumulating regions contain particularly low concentrations of glucose. In addition, glucose concentration is correlated to mitotic activity. The glucose distribution pattern is therefore related to the developmental gradient. Our data provide for the first time evidence for steep glucose gradients across developing plant embryos and favour the idea that sugar gradients may have morphogenic functions in developing cotyledons.