Cold tolerance in Arabidopsis kamchatica and related species

Abstract

Cold is a major limiting factor in the development and distribution of plants. Many plants increase cold tolerance via cold acclimation. We determined the cold tolerance strategy of Arabidopsis thaliana and A. kamchatica by comparing the extent that plants cooled below the freezing point without freezing, the supercooling capacity, to the temperatures at which 50% of freeze damage occurred (LT50). In A. kamchatica LT50 and supercooling values were similar before cold acclimation; after acclimation LT50 was much colder than supercooling, indicating non-acclimated A. kamchatica avoids freezing by supercooling but after acclimation appears to tolerate freezing. In A. thaliana, LT50 and supercooling were not different, regardless of acclimation, indicating this species avoids freezing year-round. We compared cold hardiness in populations from five Arabidopsis taxa by measuring freeze induced electrolyte leakage. There were differences among taxa; A. kamchatica, A. lyrata subspecies lyrata, and A. lyrata subspecies petraea were more cold tolerant, whereas A. thaliana and A. halleri subspecies gemmifera were less tolerant. There was no correlation between latitude of population origin and cold tolerance for any of the species we tested. Our results indicate a shared evolutionary history may be more important than latitude of origin as a predictor of cold hardiness.