Response of plant physiological attributes to altitudinal gradient: Plant adaptation to temperature variation in the Himalayan region.

Plants have evolved several metabolic pathways as a response to environmental stress like low temperatures. In this perspective, it is paramount to highlight physiological mechanisms of plant responses to changing environments. To determine the impact of cold stress on the physiological attributes of high altitude plant natives, i.e. Pedicularis punctata and Plantago major, we studied the protein, sugar and proline contents, as well as abscisic acid (ABA) and indoleacetic acid (IAA) in leaves collected from three different altitudinal ranges in Himalayan region of Pakistan. Leaves were collected at the initial blooming phase from each altitudinal range i.e. 2400-2500 m, 2950-3250 m and 3500-3550 m. Temperature decreases with an increase in the altitude which induces cold acclimation. Both plant species showed significant variation in the concentrations of the ecophysiological attributes evaluated at the different collection altitudes. The concentrations of all compounds except for IAA increased as temperature decreased and altitude increased. IAA showed an opposite response, that is, the concentrations of this phytohormone decreased with decreasing temperature and increasing altitude. We showed that temperature significantly affected the physiological attributes of Pedicularis punctata and Plantago major in the Himalayan region, which works as a proxy for understanding the plant responses to climate change. As per survival and risk assessment, underlying physiological mechanisms of plant response (understory plants) to changing environments (altitude and temperature ranges) revealed adaptation in the chilling environments. Further studies are needed to completely understand how the studied plants photosynthetic characteristics are affected by altitudinal gradient.