A comparative analysis of photosynthetic characteristics of hulless barley at two altitudes on the Tibetan Plateau

To determine the photosynthetic characteristics of C(3) plants and their sensitivity to CO(2) at different altitudes on the Tibetan Plateau, hulless barley (Hordeum vulgare L. ssp. vulgare) was grown at altitudes of 4,333 m and 3,688 m. Using gas-exchange measurements, photosynthetic parameters were simulated, including the maximum net photosynthesis (P(max)) and the apparent quantum efficiency (alpha). Plants growing at higher altitude had higher net photosynthetic rates (P(N)), photosynthesis parameters (P(max) and alpha) and sensitivities to CO(2) enhancement than plants growing at lower altitude on the Tibetan Plateau. The enhancements of P(N), P(max), and a for plants growing at higher altitude, corresponding with 10 mu mol(CO(2)) mol(-1) increments, were approximately 0.20 similar to 0.45%, 0.05 similar to 0.20% and 0.12 similar to 0.36% greater, respectively, than for plants growing at lower altitude, respectively, where CO(2) levels rose from 10 to 170 mu mol(CO(2)) mol(-1). Therefore, on the Tibetan Plateau, the changes in the photosynthetic capacities and the photosynthetic sensitivities to CO(2) observed in the C(3) plants grown above 3,688 m are likely to increase with altitude despite the decreasing CO(2) partial pressure