Salinity is one of major environmental stresses that dramatically threaten plant growth, and variations in genetic structure and functional traits have important effects on the salt tolerance of perennial ryegrass (Lolium perenne L.). The objectives of this study were to: (i) assess the inter-clonal variation of functional traits of accessions among geographic groups or between wild and commercial groups in response to salt stress; (ii) develop a mathematical model to effectively assess salt tolerance of perennial ryegrass accessions originating from different geographic populations; and (iii) determine the relation between spatial genetic structure and salt tolerance in perennial ryegrass. Wide variations were found among the accessions for seven functional traits. One regression model (F = 0.49 × F1 + 0.303 × F2 + 0.207 × F3) was established to ascertain salt tolerance of each accession. The highest variation of the traits and salt tolerance were obtained for accessions from the European group. Wild accessions exhibited more variation in functional traits and salt tolerance than commercial cultivars. Both molecular marker techniques and functional traits were used to conduct phylogenetic analysis, and the majority of accessions from the same or adjacent regions were clustered into the same group or subgroup. The perennial ryegrass accessions with similar salt tolerance had a close phylogenetic background. The patterns in functional trait variations associated with salt tolerance might allow acceleration of the process for improving salt stress resistance in perennial ryegrass.

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 (α). Plants growing at higher altitude had higher net photosynthetic rates (P N ), photosynthesis parameters (P max and α) and sensitivities to CO 2 enhancement than plants growing at lower altitude on the Tibetan Plateau. The enhancements of P N , P max , and α for plants growing at higher altitude, corresponding with 10 μmol(CO 2 ) mol -1 increments, were approximately 0.20~0.45%, 0.05~0.20% and 0.12~0.36% greater, respectively, than for plants growing at lower altitude, respectively, where CO 2 levels rose from 10 to 170 μmol(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.Additional key words: altitude; apparent quantum efficiency; maximum net photosynthesis; Tibetan Plateau.