Alpine habitats are very stressful habitats for survival and ecophysiological performance in many plant species. Low temperatures and episodes of high light are the typical conditions of these zones and may cause photoinhibition and photodamage for plants. Nevertheless, many plant species have different strategies in order to avoid the stressful conditions. These strategies may be both morphological as physiological and may change along altitudinal gradients. In alpine habitats elevation gradients combine decreasing temperature and increasing radiation, favourable conditions for photoinhibition. Taraxacum officinale and Phacelia secunda are two of the most conspicuous plant species in the alpine habitats of central Chile and are found growing from the sea level to 3700 m. While T. officinale show not morphological variation along altitudinal gradient, P. secunda show a great morphological variation with the altitude. In the present study, we assess the hypothesis that T. officinale and P. secunda avoid the photoinhibition by high physiological and morphological adaptation, respectively. We conducted a glass-house experiment with individuals of both species from 1600 and 3600 m. In twenty-five individuals from each species and altitude we measured the photochemical efficiency, energetic dissipation mechanisms, photodamage of membrane and morphological traits under photoinhibitory conditions (5ºC and 1700 mmol m^-2s^-1).

Results/Conclusions

 Overall, T. officinale individuals from both altitudes showed not differences in the physiological traits, with high physiological performance and low levels of photodamage. On the other hand, those individuals of P. secunda from 3600 m showed significatively higher photochemical efficiency than those from 1600 m and significatively lower photodamage of membranes. Our results shown a clear differentiation in the strategies used by both species. T. officinale present a high physiological plasticity and this way can cope with photoinhibitory conditions along altitudinal gradient. On the other hand, P. secunda is morphological adapted to environment where growth, in fact individuals from 1600 m, showed photoinhibition and photodamage when were exposed to low temperature and high light intensity. Contrary, those individuals of P. secunda from 3600 m, showed not evidence of photoinhibition, suggesting that its morphology is adapted to this abiotic conditions. Finally, we concluded that T. officinale present a physiological strategy while P. secunda present a morphological strategy for cope with photoinhibitory conditions of alpine habitats. FONDECYT 1060710 and P02-051-F ICM.