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

To determine the photosynthetic characteristics of C₃ plants and their sensitivity to CO₂ 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 CO₂ 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(CO₂) 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 CO₂ levels rose from 10 to 170 μmol(CO₂) mol⁻¹. Therefore, on the Tibetan Plateau, the changes in the photosynthetic capacities and the photosynthetic sensitivities to CO₂ observed in the C₃ plants grown above 3,688 m are likely to increase with altitude despite the decreasing CO₂ partial pressure.     

Effect of propionate and pyruvate on citrulline synthesis and ATP content in rat liver mitochondria.

Propionate inhibits citrullinogenesis when succinate (plus rotenone) or glutamate are the oxidizable substrates used. Propionate decreases the intramitochondrial concentration of carbamylphosphate by decreasing the ATP content. When the energy supply for citrullinogenesis is provided by an influx of exogenous ATP, propionate is no longer an inhibitor. Pyruvate inhibits citrullinogenesis with glutamate but not with succinate (plus rotenone) as oxidizable substrates. Propionate and pyruvate deplete mitochondrial ATP but probably by different mechanisms.     

Cytological and mapping analysis of a novel male sterile type resulting from spontaneous floral organ homeotic conversion in marigold (<Emphasis Type="Italic">Tagetes erecta</Emphasis> L.)

A male sterile line was isolated in marigold (Tagetes erecta L.) and cytological analysis determined this to be a novel genic male sterility trait (Tems). Through the use of amplified fragment length polymorphisms (AFLPs) and bulked segregant analysis (BSA), tightly linked markers of Tems were identified with a view towards a map-based cloning strategy. It was found that spontaneous homeotic conversion of floral organs was the underlying cause of the male sterility in this marigold line. Thus, petals of male sterile plants resembled sepal-like structures and the stamens were partially converted to styles, although without the full characteristics or function of the true style organs. We have constructed a fine marker-based map for the Tems gene. This is intended to provide a tool for marker assisted selection (MAS) strategies in hybrid breeding and map-based cloning strategies for the male sterility locus. We discuss the significance of this spontaneously derived genic male sterility trait relating to the homeotic conversion of floral organs in marigold.