Photosynthetic responses and photoprotection strategies of Phacelia secunda plants exposed to experimental warming at different elevations in the central Chilean Andes

The possible effects and implications of climate change on plant growth have not yet been studied in the central Chilean Andes, where a dry growing season differentiates this area from other mountainous areas around the world. At lower elevations, plants exposed to high temperatures and dry soil may experience severe water limitations, causing lower photosynthetic performance. At higher elevations, where water is not a limiting factor but air temperature is lower, an increase in temperature could have a positive effect on photosynthesis. We assessed whether experimental warming affects the photosynthetic performance and photoprotective mechanisms as photorespiration, Mehler reaction and cyclic electron flow in Phacelia secunda plants growing at 1600, 2800 and 3600 m elevation. Plants were exposed to a passive increase in the air temperature using open top chambers (OTC). Xylematic leaf water potential increased with elevation, and the OTC's decreased xylematic water potential at the lower elevations but not at 3600 m. While warming was associated with a decrease in the maximal carbon gain assimilation at lower elevations, it was associate with an increase at 3600 m. Photorespiration differed among elevations and was increased by warming only at 1600 m. The Mehler reaction was higher at 1600, but not affected by warming. Warming increased the cyclic electron flow only in plants at 1600 m. Plants growing inside OTCs at all three elevations exhibited lower xanthophyll pools than control plants, but similar de-epoxidation states (DEPS). Our results show that alpine plant responses to warming will most likely depend on elevation, soil moisture availability and the combination of these two factors in relation to climate change.