Revista Chilena de Historia Natural 80 (3): 335-343, 2007
RESEARCH ARTICLE
Photosynthetic responses to temperature and light of Antarctic and Andean populations of
Colobanthus quitensis (Caryophyllaceae)
Colobanthus quitensis (Kunth, 1831) Bartling (Caryophyllaceae) is
characterized by a wide latitudinal distribution, ranging between the tropical high Andes and the Antarctic Peninsula. Although both
habitat types are characterized by cold and freezing temperatures, important microclimatic differences exist during the growing
season. Hence, important differences in the response of the photosynthetic apparatus to abiotic factors could be expected between
Antarctic and Andean populations of C. quitensis. We studied the relationship between net photosynthesis, leaf
temperature and light intensity in two populations of C. quitensis, one from La Parva in the Andes of central
Chile and the other from King George Island, in the Maritime Antarctic. Plants from both populations were grown in the laboratory at 15
ºC under 250 µmol photons m<sup>-2</sup>s<sup>-1</sup>, with a 16/8 h light/dark photoperiod. Twenty plants
(about two months old) of each population were transferred to a 4 ºC chamber with the same light and photoperiod conditions as above
to assess the photosynthetic acclimation capacity. At 15 ºC, populations differed in their optimum leaf temperature for photosynthesis,
being 24.0 ºC in individuals from the Andes and 18.6 ºC in individuals from the Antarctic. In contrast, Antarctic individuals showed the
highest net photosynthesis rate under both temperature treatments, with the lowest light compensation and saturation points. Antarctic
individuals had higher photosynthetic activity at lower temperatures compared to individuals from the Andes. Our results suggest that
C. quitensis has adapted photosynthetic performance of individuals growing in different localities to the prevailing climatic
conditions. Differences in photosynthetic responses to temperature and light are discussed in relation to ecotypic differentiation
between two populations studied.
Key words:
photosynthesis,
Colobanthus quitensis, optimum leaf temperature, light intensity
