Responses of<Emphasis Type="Italic"> Colobanthus quitensis</Emphasis> (Kunth) Bartl. to high light and low temperature

Antarctic plants are exposed to high light and low temperature during their natural growing season. Therefore, the maintenance of an oxidative status compatible with normal metabolism is an important determinant for their survival. We hypothesized that Colobanthus quitensis, the only dicotyledonous plant from the Antarctic, has efficient energy-dissipating mechanisms, and/or high antioxidant capacity. A short time treatment (24 h) of high light and/or low temperature reduced maximum photochemical quantum yield (Fv/Fm), photochemical quenching (qP), and the quantum yield of PSII (PSII). Concomitantly, an increase in the nonphotochemical quenching (qN) was observed. Superoxide dismutase (SOD) activity increased after cold acclimation. High light and low temperature did not significantly affect SOD, ascorbate peroxidase (APx), and glutathione reductase (GR) in nonacclimated plants. Total soluble antioxidants and carotenoids decreased after cold acclimation. Thus, it is likely that the main mechanism of C. quitensis to cope with energy imbalance is heat dissipation, as evidenced by the great increase in qN.