Are hexoses in the exudate due to selective resorption via the cut surface?
Selective resorption through the cut surface may also influence exudate composition. High hexose contents could result from intense, selective resorption of sucrose as compared with hexoses. This possibility was tested in the following series of experiments. Uptake of 0.1 and 1.0 mM [14C]glucose, [14C]fructose, and [14C]sucrose by blade-less and blade-bearing petioles of Eranthis hyemalis, Corydalis cava, and Fumaria officinalis was compared. Although the distribution profiles were unique for each single species (Table 4), species-specific uptake rates by blade-less petioles did not show significant differences between the sugars when the differences in molecular weight are taken into account (Table 4). The expectedly higher, transpiration-sustained sugar uptake rates by blade-bearing petioles were also similar for each single species (Table 4). Thus, the uptake results contradict prevalent resorption of sucrose by petiole tissues and exclude a causal relationship between selective res
