Sulfhydryls—A New Factor in Frost Resistance. IV. Relation of GSH-Oxidizing Activity to Flower Induction & Hardiness

Abstract

GSH-oxidizing activity increases several-fold during the exposure of wheat to vernalizing conditions. This occurs equally in spring wheat that are not induced to flower by the treatment and in winter wheat that are. In general, the frost resistance rises with GSH-oxidizing activity, but only during the 2nd stage of hardening. Flower induction of short-day plants by exposure to a short photoperiod results in the same GSH-oxidizing activity as in non-induced plants exposed to a long photoperiod. The cofactor for the GSH oxidase is DHA. The increase in GSH-oxidizing activity during exposure to vernalizing conditions parallels an increase in DHA. Nearly all the non-protein SH and SS in the homogenate of the germinating wheat is in the form of GSSG. In the very early stage of germination (24 hr) some GSH and CSSC occur but these soon disappear. No free CSH was detected at any time. On the basis of the above and earlier results, hardening is proposed to take place in 3 steps.