Effect of Altitude on Photosynthetic and Biochemical Characteristics of Podophyllum hexandrum: An Alpine Endangered Medicinal Herb from Central Himalayas

Podophyllum hexandrum is a high value endangered medicinal plant from alpines of Central Himalaya. This study was conducted to explore its conservation and cultivation possibilities at comparatively lower altitudes. Seedlings of the same age, were selected from alpine medicinal crop nursery, Tungnath (3600m) and were planted at the nurseries located at 3600 and 550m altitudes. After well acclimatization at both the altitudes, plants were examined for gas exchange and biochemical characteristics during their active growth period. Our data shows that the foliage nitrogen content was higher and, P, K and C content were found lower in the plants grown at higher elevation as compared to lower altitude; however, these altitudinal variations were not found statistically significant. Chlorophyll a, Chl b, total Chl and Carotenoids were higher and Chl a/b ratio was lower at lower altitude as compared to plant grown at higher altitude. Level of protein and RUBP Carboxylase activity was higher and level of PEP Carboxylase activity was observed lower in the plants grown at high elevation as compared to their counterparts at lower altitude. Light optima for photosynthesis (PAR_opt) was observed around 2000µmolm^–2s^–1 at both the elevations in this species. A shift in optimum temperature for photosynthesis (T_opt) was observed towards higher temperature in plants grown at lower altitude as compared to higher elevation, which indicates their potential to survive in the comparatively warmer environment. T_opt was observed at 20°C in plants grown at higher altitude whereas, at lower altitude T_opt was observed at 25°C for the plants of P. hexandrum. Conductance and transpiration was found slightly higher at high altitude as compared to plants grown at lower altitude. In view of these results, it can be concluded that these species can be cultivated at lower altitudes to meet their ever-increasing industrial demand.