FRUCTAN SYNTHESIS IN OAT .1. OLIGOMER ACCUMULATION IN STEMS DURING COLD HARDENING AND THEIR IN-VITRO SYNTHESIS IN A CRUDE ENZYME EXTRACT

The accumulation of fructan oligomers in cold hardened oat stems was c ompared to oligomer synthesis in a crude enzyme extract. Water-soluble carbohydrates were quantified at specified time intervals in three oa t cultivars which had been hardened for a total of 5 wk at 2 degrees C . A crude enzyme extract was prepared from stems of one cultivar harde ned for 6 d at 2 degrees C and incubated at 30 degrees C with 200 mM s ucrose. 1-Kestose was the first oligomer to accumulate in vitro but ne okestose rapidly increased after 3 h of incubation and eventually surp assed 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 cons tant. 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 befor e hardening began. The first tetramer to increase was 1&6(G)-kestotetr aose but it subsequently decreased and its concentration was surpassed by that of 6(G),6-kestotetraose. Similarities and differences between in vivo and in vitro patterns of fructan synthesis are discussed.