Physiological Responses of The Leaves of a High-Altitude Plant Picrorhiza kurroa to Cold Stress

There are various plants that grow in high elevations and experience various environmental stresses, cold stress being the most prevalent one. Plants undergo biochemical, metabolic, molecular, and physiological changes under cold stress hence, they adopt various mechanisms to tolerate it. The antioxidant defense system, osmotic regulators and photosynthetic pigments in the plant provide them stress tolerance. The present study is conducted on a high-altitude plant, Picrorhiza kurroa which grows in such environmental conditions, to study the physiological parameters that provides it the coping mechanism against the cold stress. For this study, the leaves were collected from Pothivasa (2200 m asl) and Tungnath (3600 m asl) in Rudraprayag, Uttarakhand, India. The photosynthetic pigments, lipid peroxidation, antioxidant enzymes, and osmoprotectants present in the leaves were determined to visualize the impact of cold stress. It was revealed that the concentration of chlorophyll a, chlorophyll b, and carotenoids increased with increase in elevation. The activity of SOD, CAT, POD, APOX and GR were analyzed and they were observed to decrease with altitude. The MDA concentration which is an indicator of lipid peroxidation is higher in Pothivasa (2.214 mol L-1) and lower in Tungnath (1.697 mol L-1). There is a significant increase in the total protein content, total soluble sugar content and total proline content along the altitudinal gradient. Therefore, the leaves from both the sampling locations revealed the physiological changes occurred in them to adapt to the cold stress conditions.