Fructan synthesis in oat

I. Oligomer accumulation in stems during cold hardening and their in vitro synthesis in a crude enzyme extract


  • Sincere thanks are expressed to Shu-Yen Liu, Senior Research Assistant, Department of Agronomy, Pennsylvania State University for her invaluable help extracting enzymes and reviewing the manuscript.


The accumulation of fructan oligomers in cold hardened oat stems was compared to oligomer synthesis in a crude enzyme extract. Water-soluble carbohydrates were quantified at specified time intervals in three oat cultivars which had been hardened for a total of 5 wk at 2 °C. A crude enzyme extract was prepared from stems of one cultivar hardened for 6 d at 2 °C and incubated at 30 °C with 200 mM sucrose. 1-Kestose was the first oligomer to accumulate in vitro but neokestose rapidly increased after 3 h of incubation and eventually surpassed the level of 1 -kestose. Neokestose and 1-kestose accumulated at similar rates in vivo in the first week of hardening but after 1 week, 1-kestose began to decrease while neokestose remained relatively constant. The same phenomenon was observed in vitro but after only 3 h. 6-Kestose was not observed in vivo or in vitro, except for a trace before hardening began. The first tetramer to increase was 1&6G-kestotetraose but it subsequently decreased and its concentration was surpassed by that of 6G,6-kestotetraose. Similarities and differences between in vivo and in vitro patterns of fructan synthesis are discussed.