The effect of CCC and gibberellins A3 and A7 on the cold hardiness of Kharkov 22 MC winter wheat

Abstract

Continuously feeding a suitable concentration (3 × 10⁻⁵ or 3 × 10⁻⁴ M) of chlorocholine chloride (CCC) through the roots of Kharkov 22 MC winter wheat grown at both hardening (4 to 6 °C) and non-hardening (21°) temperatures induced small increases in its cold hardiness. In plants grown at 21 °C supplying 3 × 10⁻³ M CCC reduced cold hardiness. Under hardening conditions gibberellins A₃ and A₇ and under non-hardening conditions gibberellin A₃ reduced the cold hardiness of Kharkov 22 MC. CCC produced morphological changes in plants grown at 21 °C that partially duplicated those induced by growing the plants at 6 °C. In plants grown at 6 °C gibberellins A₃ and A₇ produced morphological changes that caused the plants to partially resemble those grown at 21 °C. These results are discussed in relation to the hypothesis that one of the changes accompanying cold hardening in winter wheat is a reduction of the content of endogenous gibberellins. The conclusion is reached that if a reduction in gibberellin levels occurs it can only account for a part of the change in cold hardiness produced by natural hardening temperatures.