Role of red and far-red light in frost resistance of yarovized winter wheat after thaw.

The short day in the thawing of hardened winter wheat, yarovized to a different degree, increased its frost resistance in comparison with uninterrupted illumination. Interruption of darkness of the short-day cycle by red light reduced frost resistance, far-red light had the opposite effect, but to a different degree, on the length of yarovization. Maximal resistance developed toward the end of the yarovization period. There were observed changes connected with the stabilization of the photoacceptor of the phytochrome system in the process of yarovization. The phytochrome complex participated in regulation of the movement and utilization of metabolites. There was revealed the variety specificity of winter wheat in relation to the investigated characters.