Photosynthetic characteristics of Hordeum, Triticum, Rumex, and Trifolium species at contrasting altitudes

Abstract

Photosynthetic characteristics were compared between plants of low altitude (LA) grown at LA (Palampur; 1 300 m) and at high altitude, HA (Kibber; 4 200 m), and plants naturally occurring at different altitudes (Palampur, 1 300 m; Palchan, 2 250 m; and Marhi, 3 250 m). Net photosynthetic rate (P N) was not significantly different between altitudes. However, the slopes of the curve relating P N to intercellular CO2 concentration (C i) were higher in plants at Palchan, Marhi, and Kibber compared to those at Palampur, indicating that plants had higher efficiency of carbon uptake (the initial slope of P N/C i curve is an indication) at HA. They had also higher stomatal conductance (g s), transpiration rate, and lower water use efficiency at HA. g s was insensitive to photosynthetic photon flux density (PPFD) for plants naturally occurring at Palampur, Palchan, and Marhi, whereas plants from LA grown at Palampur and Kibber responded linearly to increasing PPFD. Insensitivity of g s to PPFD could be one of the adaptive features allowing wider altitudinal distribution of the plants.