Influence of pre-hardening duration and dehardening temperatures on varietal freezing resistance in faba beans ( Vicia faba L.)

Abstract

— Hardening response of winter faba beans at 8/2C (day/night) to pre-hardening periods at 15C of differ- ent length (3-11 days after plant emergence) and dehardening at various temperatures (7-15C) was examined in a series of experiments with 9 European varieties through detached leaf tests. Extending the pre-hardening period lower- ed the level of acquired freezing resistance (FR) in the first leaf (lowest one) and obviously shortened the phase of linear increase (AFR= 0 . 4C / day). The level of FR in the second (and third) leaf always exceeded that in the first one and differ- ences between them were most prominent under longer periods of prehardening, suggesting that the potential FR in a leaf can be attained only if hardening has already started at the onset of leaf expansion.