Colobanthus quitensis (Kunth) Bartl. (Cariophyllaceae) is distributed from Mexico to the Maritime Antarctic. It grows forming inconspicuous populations
in humid and cold sites along high elevations in the Andes Mountains. Mediterranean Andes is characterized by a wider oscillation
of diurnal and seasonal temperature, while the Maritime Antarctic is characterized by permanent low temperatures. Both places
may experience high irradiance during sunny days (reaching up to 2,000 μmol photons m−2 s−1); however, the frequency of sunny days in the Maritime Antarctica is significantly lower (less than 20% of the whole growing
season). We study whether acclimation to each environment relies on different photoprotective mechanisms. The Andean ecotype
that has a longer growing season and a higher light integral reduces light absorption by the development of smaller chloroplasts
with lower stacking granum area and down-regulation of Lhcb2. It also enhances the dissipation of the excess of absorbed energy
by higher level of de-epoxidation of xanthophylls pool. On the other hand, the Antarctic ecotype which has developed under
a shorter growing season, with lower total irradiance and continuous low temperatures, maximizes photochemical process even
at low temperatures and it has a lower light-harvesting/core complex ratio and higher level of photoprotection supplied by
an unusually high β-carotene and xanthophylls cycle pool. It resembles a well full light acclimated plant, probably due to
higher excitation pressure imposed by lower temperature even at moderate irradiance. It is suggested that the biochemical
plasticity of this species, highlighted by the development of these different strategies, is essential to cope successfully
with these particular environments.
Keywords Antarctic plants - Andean plants - Ecotypes - Low temperatures stress - High light stress - Photoprotection strategies