PATTERN OF FRUCTAN SYNTHESIZED IN CELL-FREE-EXTRACTS FROM LEAF BLADESOF CHILLED TRITICUM-AESTIVUM

Fructosyltransferase activities were studied with varying concentratio ns of sucrose in cell-free extracts from wheat (Triticum aestivum L.). A C18-HPLC separation method was used to quantify the synthesized com pounds individually. Hexoses and 1-kestose were the major products at all temperatures and concentrations of sucrose. 1-Kestose production w as maximal at 25-degrees-C, with an apparent K(m) of about 250 mm, but competition for sucrose by invertase affected this value. Neokestose, which is not observed in vivo, and 6-kestose were also formed in vitr o, but at a much lower rate and at lower sucrose affinity than 1 -kest ose synthesis. When extracts were incubated with a high initial concen tration of sucrose for up to 1 d, five new fructan oligomers appeared. Four of these were also accumulated early in vivo by chilled blades, whereas the fifth belonged to the neokestose series. The rates of synt hetic oligomers are compared to those in vivo. Invertase-linked artefa cts are present in wheat, but not overwhelming as they are in Lolium t emulentum.