1. The activity per unit of chlorophyll of certain carboxylases, and of other enzymes involved in photosynthesis, was determined in leaf extracts of the tropical grasses, sugar-cane, maize and sorghum, and compared with the activities for wheat, oat and silver-beet. Maximum rates of photosynthetic carbon dioxide uptake were also measured for comparison with enzyme activities. 2. Phosphopyruvate...

Phylogenetic studies of grasses (Poaceae) are advanced in comparison with most other angiosperm families. However, few studies have attempted to build large phylogenetic trees of the family and use these for evaluating patterns of diversification or other macroevolutionary hypotheses. Two contrasting approaches can be used to generate large trees: supermatrix analyses and supertrees. In this pa...

Recent evidence associates the persistence of invasive plant species with disturbance and fluctuations in distinct forms of mineral N in soils. We conducted soil and hydroponic experiments to investigate the influence of N form and availability on germination and seedling development of 2 invasive annual grasses, cheatgrass (Bromus tectorum) and medusahead (Taeniatherum caput-medusae) and 6 per...

Abiotic stresses, notably extremes in temperature, photon irradiance, and supplies of water and inorganic solutes, frequently limit growth and productivity of major crop species such as wheat (Triticum aestivum; http://www.cimmyt.org/Research/Wheat/ map/research_results/wphysio/wphysio.html). Inaddition, more than one abiotic stress can occur at one time. For example, high temperature and high ...

The present study investigates the occurrence of wild grasses at Epipalaeolithic and aceramic Neolithic sites in the Near East in order to assess their role in subsistence economies alongside the emergence of cereal cultivation. We use Chogha Golan in the foothills of the central Zagros Mountains (ca. 11.7-9.6 ka cal. BP) as a case study, where the archaeobotanical data suggest the frequent exp...

Savannas lie between the equatorial rain forests and the semi-deserts of the southern continents. From the herbivore’s viewpoint, the savanna environment is characterized by a mixture of herbaceous and woody vegetation, varying in quantity and growth stage according to the seasonal cycle of rainfall. C4 grasses (i.e. those with the C4 photosynthetic pathway) dominate the herbaceous layer, which...

Grasses are ancestrally tropical understory species whose current dominance in warm open habitats is linked to the evolution of C4 photosynthesis. C4 grasses maintain high rates of photosynthesis in warm and water stressed environments, and the syndrome is considered to induce niche shifts into these habitats while adaptation to cold ones may be compromised. Global biogeographic analyses of C4 ...