ABSTRACT
As global warming progresses, plants may be forced to adapt to
drastically changing environmental conditions. Arctic-alpine plants have
been among the first to experience the effects of climate change, as
regions at high latitudes and elevations are over-proportionally
affected by rising temperatures. As a result, cold acclimation and
freezing tolerance may become increasingly crucial for the survival of
many plants as winter warming events and earlier snowmelt will cause
increased exposure to occasional frost. Studying the evolution of cold
adaptation allows us to make assumptions about the future responses of
different species to climate change. The tribe Cochlearieae from the
mustard family (Brassicaceae) offers an instructive system for studying
cold adaptation in evolutionary terms, as the two sister generaIonopsidium and Cochlearia are distributed among different
ecological habitats throughout the European continent and the far north
into circumarctic regions. By applying an electrolyte leakage assay to
leaves, the freezing tolerance of different Ionopsidium andCochlearia species was assessed by experimentally estimating
lethal freezing temperature values (LT50 andLT100 ), thereby allowing for a comparison of
different accessions in their responses to cold. We hypothesized that,
owing to varying selection pressures, geographically distant species
would differ in freezing tolerance. Despite Ionopsidium being
adapted to hot and dry Mediterranean conditions and Cochleariaspecies preferring cold habitats, all accessions exhibited similar cold
responses. Whether this phenomenon has resulted from an evolutionary
adaptation of a common ancestor of the two taxa or has evolved from
parallel evolution is yet to be investigated. The results presented in
this study may, however, indicate that adaptations to different
stressors, such as salinity and drought, may confer an additional
tolerance to cold; this is because all these stressors induce osmotic
challenges, as demonstrated via metabolomic analysis.