PHOTOSYNTHETICA 44 (1): 136-139, 2006 136 BRIEF COMMUNICATION Photosynthetic response of Podophyllum hexandrum Royle from different altitudes in Himalayan ranges S.K. VATS and S. KUMAR Biodiversity/Biotechnology Division, Institute of Himalayan Bioresource Technology (CSIR), Palampur-176 061 (HP), India Abstract Plants of Podophyllum hexandrum, collected from lower, mid, and upper distribution limits in alpine Himalaya were studied under greenhouse conditions to evaluate the photosynthetic response. Net photosynthetic rates (P N ), stomatal conductance (g s ), and efficiency of carbon uptake increased with altitude. The maximum P N and g s were measured in the considered population during the 3–6 th week of development. P N and g s decreased on an average by 58 and 48 % from maximum rates reached around 4 th week to the 10 th week of growth, respectively. The photosynthetic response in the three ecotypes appeared to be genetically controlled. Additional key words: efficiency of carbon uptake; intercellular CO 2 concentration; stomatal conductance. —— Altitude influences environmental variables such as temperature and partial pressure of CO 2 (Hovenden and Brodribb 2000). A decrease in growth temperature may result in changes in leaf at the structural and biochemical level. Plants from greater elevation show higher assimi- lation rates and efficiency of carbon uptake (ECU) com- pared to plants growing at low altitudes (Körner and Diemer 1987, Friend and Woodward 1990, Hovenden and Brodribb 2000). Leaves developing at low tempera- tures exhibit higher specific activity of enzyme ribulose- 1,5-bisphosphate carboxylase/oxygenase (RuBPCO) (Björkman et al. 1978, Kumar et al. 2004), which influences ECU (Caemmerer and Farquhar 1981). How- ever, high altitude plants have higher photosynthetic rates than lowland ones (de Lillis et al. 2004), especially when grown under controlled conditions (Mächler and Nösberger 1977). The difference in photosynthetic response of mountain plants is shaped by a complex mixture of environmental and genetic influences. Some mountain plants have evolved in response to their parti- cular altitude but many of these features could occur without any genetic component (Friend and Woodward 1990). Species growing at different elevation sites and differentiating in photosynthetic characteristics such as P N and ECU could be an indicator of their respective altitude. The present study aimed to find if populations of P. hexandrum Royle, an endemic herbaceous species of the Himalayan ranges, collected from different altitudes, and grown in greenhouse differed in photosynthetic response. Gas exchange response was monitored during different developmental stages. Plants of P. hexandrum were collected from three dif- ferent elevations in the Himalayan ranges at Great Himalayan National Park (site A, GHNP; 31 o 45’N, 77 o 22’E; 2 400 m a.s.l.), and Kukumseri (site B, 32 o 42’N, 76 o 40’E; 2 800 m) and Koksar (site C, 32 o 24’N, 77 o 14’E; 3 200 m) in Indian western Himalaya (Kharakwal 2003). The plants were grown in a greenhouse (day temperature 24–28 o C, relative humidity 65–75 %) in the Institute of Himalayan Bioresource Technology at Palampur (32 06’N; 76 33’E; 1 300 m). Plants were grown in pots containing a mixture of garden soil, sand, and farmyard manure in equal proportion. Gas exchange was measured ——— Received 16 November 2004, accepted 31 March 2005. Fax: +91 1894 230433, e-mail: sk_vats@yahoo.com Abbreviations: C i – intercellular CO 2 concentration; ECU – efficiency of carbon uptake; g s – stomatal conductance; PPFD – photosyn- thetic photon flux density; P N – net photosynthetic rate. Acknowledgements: Authors are grateful to Dr. P.S. Ahuja, Director, Institute of Himalayan Bioresource Technology, Palampur for encouragement and providing necessary facilities during the course of investigation, and National Bioresource Development Board, Department of Biotechnology, New Delhi, for financial support.