Gas and Water Vapor Exchange Characteristics of Picrorhiza kurooa Royle ex Benth, an Endangered Alpine Medicinal Plant, at Lower Altitude

Picrorhiza kurrooa Royle ex Benth (Scrophulariaceae), commonly known as Kutki, is an important medicinal plant from the alpines of the Himalayas. This herb has been traditionally used in Ayurvedic preparations prescribed in treating liver disorders. Due to its high market value, and unscientific and uncontrolled extraction from nature, Picrorhiza kurrooa is declared endangered and listed in red data book requiring priority attention for conservation. In this regard strategies are being developed for its conservation and mass propagation at comparatively lower altitudes. In the present study, plants of Picrorhiza kurrooa were collected from its natural habitat at 3600 m above mean sea level (AMSL), grown at lower altitude (550 m AMSL) and studied for gas and water vapor exchange characteristics at different light (0, 100, 600, 900, 1200, 1500 and 2000µmol m^-2s^-1) and temperature (15, 20, 25 and 30 ^oC) conditions under the ambient (350µmol mol^-1) and elevated (700µmol mol^-1) CO₂ concentrations. The optimum temperature for photosynthesis was observed around 20 ^oC. Whereas, the rate of photosynthesis increased with light intensity up to highest level (2000µmol m^-2s^-1) tested. In general, elevated CO₂ significantly stimulated net photosynthesis (P _N), water use efficiency (WUE) and internal CO₂ concentration (C _i), and suppressed transpiration (T _R) and stomatal conductance (gCO₂) as compared to the ambient CO₂ concentration. An average increase of about 34% in net photosynthesis was observed due to elevated CO₂ as compared to ambient CO₂ concentration. The results, thus, indicate better growth potential of Picrorhiza kurooa under high light and elevated CO₂ environment.