Fructosyltransferase activity and fructan accumulation during development in wheat exposed to terminal drought.

Fructans act as storage carbohydrates in wheat (Triticum aestivum L.) stems, and published data indicate that these can account for up to 70% or more of grain dry matter under conditions of drought. The activity of enzymes involved in fructan synthesis (fructosyltransferases) in wheat was measured during development of three high-yielding wheat cultivars (cvv. Kauz, Westonia and Attila A) exposed to rainfed conditions, and one cultivar (cv.Westonia) exposed to irrigated conditions. Fructan concentration was on average 2.5-fold higher in the stems of rainfed wheat compared with irrigated samples, but average fructosyltransferase activity was similar in both. There was a weak positive correlation (r=0.35-0.38) between fructan concentration and fructosyltransferase activity across development in the stems of both rainfed and irrigated wheat. Soon after anthesis, 31% of accumulated fructans in rainfed Westonia stems were located in the penultimate internode, although fructosyltransferase activity was five times higher in the bottom two internodes than the penultimate internode.