Activities of some enzymes related to carbon metabolism were studied in different ecotypes of Rumex nepalensis growing at 1 300, 2 250, and 3 250 m above mean sea level. Activities of ribulose-1,5-bisphosphate carboxylase/oxygenase, phosphoenolpyruvate carboxylase, aspartate aminotransferase, and glutamine synthetase increased with altitude, whereas activities of malate dehydrogenase, NAD-malic enzyme, and citrate synthase did not show a significant difference with change in altitude. and N. Kumar ... [et al.].
In addition to other factors, high altitude (HA) environment is characterized by high photosynthetic photon flux density (PPFD). Photosynthetic characteristics of wild and cultivated plants were studied at different irradiances at Losar, India (altitude 4 200 m). Wild plants were tolerant to high PPFDs. Slopes of curve between net photosynthetic rate (PN) and intercellular CO2 concentration
(Ci) or stomatal conductance (gs) increased with increase in irradiance suggesting insensitivity or tolerance of these plants to higher PPFD. Cultivated plants, however, were sensitive to higher PPFD, their slopes of curves between PN and Ci or gs decreased with increased PPFD. Tolerance or insensitivity to higher PPFD was an important parameter affecting plant performance at HA. and N. Kumar, S. Kumar, P. S. Ahuja.
Leaf stomatal density (SD), net photosynthetic rates (PN), and stomatal conductance (gs) of Hordeum vulgare and Pisum sativum cultivars in Himalaya increased with altitude. Higher PN and leaf temperature under low CO2 partial pressure at high altitudes could evoke a higher gs and SD to allow sufficient influx of CO2 as well as more efficient leaf cooling through transpiration. and S. K. Vats, N. Kumar, S. Kumar.
Morpho-anatomical leaf traits and photosynthetic activity of two alpine herbs, Podophyllum hexandrum (shade-tolerant) and Rheum emodi (light-requiring), were studied under field (PAR>2 000 µmol m-2 s-1) and greenhouse (PAR 500 µmol m-2 s-1) conditions. Mesophyll thickness, surface area of mesophyll cells facing intercellular spaces (Smes), surface area of chloroplasts facing intercellular spaces (Sc), intercellular spaces of mesophyll cells (porosity), photon-saturated rate of photosynthesis per unit leaf area (PNmax), and ribulose-1,5-bisphosphate carboxylase/oxygenase activity decreased in the greenhouse with respect to the field and the decreases were significantly higher in R. emodi than in P. hexandrum. P. hexandrum had lower intercellular CO2 concentration than R. emodi under both irradiances. The differences in acclimation of the two alpine herbs to low irradiance were due to their highly unlikely changes in leaf morphology, anatomy, and PNmax which indicated that the difference in radiant energy requirement related to leaf acclimation had greater impact under low than high irradiance. and S. Pandey, N. Kumar, R. Kushwaha.
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 (PN) was not significantly different between altitudes. However, the slopes of the curve relating PN to intercellular CO2 concentration (Ci) 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 PN/Ci curve is an indication) at HA. They had also higher stomatal conductance (gs), transpiration rate, and lower water use efficiency at HA. gs 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 gs to PPFD could be one of the adaptive features allowing wider altitudinal distribution of the plants. and N. Kumar, S. Kumar, P.S. Ahuja.