Altitudinal Variation in Biochemical and Photosynthetic Characteristics of Aconitum balfourii: An Alpine Endangered Medicinal Herb from Himalayas

Aconitum balfourii is an endangered medicinal plant from the alpines of the Central Himalayas. To understand its adaptability potential at lower altitudes, leaf morphology, biochemical characteristics and temperature response of photosynthesis were studied at its natural habitat (3600m) and at a comparably lower altitude 550m above mean sea level (amsl). Our results show that leaf length, width, area, accumulation of chlorophyll a (Chl a), Chl b, total Chl, carotenoids (Car) and phosphoenolpyruvate carboxylase (PEPC) activity were lower, whereas, leaf thickness, Chl a/b ratio and ribulose-1, 5-bisphosphate carboxylase/oxygenase (RuBPCO) activities were found to be higher in the high altitude grown plants of this species as compared to plants grown at the lower altitude. Optimum temperature (T _opt) for photosynthesis (P _N) was recorded at 20 ^oC at high altitude, whereas, a shift in T _opt was observed towards higher temperature (i.e. 25 ^oC) when the plants were grown at lower altitude. Transpiration (E) and stomatal conductance (g _s) increased with temperature up to highest level tested (i.e. 30 ^oC) at both the altitudes whereas, values of E and g _s were found higher in the high altitude grown plants. Mesophyll efficiency (ME) increased with the temperature and was observed higher in the plants grown at lower (550m) altitude. Similar to P _N, water use efficiency (WUE) increased with temperature up to a highest level and decreased at higher temperatures at both the altitudes, higher WUE was however, recorded in lower altitude grown plants. The shift in T _opt towards higher temperatures, higher ME together with higher WUE, when grown at lower altitude, indicates the adaptability potential of A. balfourii at a comparatively lower altitude for its conservation through cultivation.