Revista Chilena de Historia Natural 85 (4): 419-433, 2012
SPECIAL FEATURE
Antioxidant responses in two Colobanthus quitensis (Caryophyllaceae) ecotypes
exposed to high UV-B radiation and low temperature
ALEJANDRO A. NAVARRETE-GALLEGOS, LEÓN A. BRAVO, MARCO A. MOLINA-MONTENEGRO & LUIS J.
Colobanthus quitensis (Kunth) Bartl. (Caryophyllaceae) is distributed from
Mexico to the Maritime Antarctica forming colonies adapted to several micro environmental conditions along its distribution. The
Maritime Antarctica is characterized by a colder and short season with increasing radiation levels of UV-B. On the other hand, The
Andes range in Central Chile has ample thermal oscillations and a high UV-B radiation. The purpose of this study is to know the
antioxidant strategies and mechanisms adopted by the C. quitensis Antarctic and Andean ecotypes to tolerate the
damaging effects of the UV-B radiation and cold under controlled laboratory conditions. We postulate that individuals of C.
quitensis from the Central Chilean Andes (Andean ecotype), where UV-B levels are higher than in the Antarctica, would have
more effective antioxidant mechanisms than the Antarctic ecotype. Plants of the Antarctic and Andean ecotypes grown under
laboratory were subjected to three intensities of UV-B radiation (70, 35 y 3 μW cm-2), 4 and 15 ºC respectively. Antioxidant
mechanisms, such as total antioxidant activity (TAS), superoxide dismutase (SOD) activity, and leaf morphological attributes with a
putative protective role against UV-B were assessed. Finally, damaging effects of UV-B such as: malonaldialdehide (MDA)
accumulation, maximum photochemical efficiency of the PSII and photoinactivation were assessed at each treatment. Both ecotypes
showed reduced leaf area and thickening of leaf parenchyma. The Andean ecotype exhibited higher levels of TAS with high and
medium UV-B radiation. The highest SOD activity was measured in the Andean ecotype. It was detected an increase of up to eight
times of the basal level at four hours of radiation. The Antarctic ecotype exposed to UV-B and cold showed a higher damage in
membranes (MDA), also a greater degree of photoinactivation. Additionally, the accumulation a new Cu-Zn/SOD isoform, insensitive to
H2O2 was detected in UV-B treated plants. In conclusion, the Andean ecotype presents a more effective antioxidant response against
UV-B than the Antarctic ecotype.
Antarctic, antioxidants,
oxidative damage, UV-B.
