title: Responses of C4grasses to atmospheric CO2enrichment : I. Effect of irradiance.
abstract: The growth and photosynethetic responses to atmospheric CO2enrichment of 4 species of C4grasses grown at two levels of irradiance were studied. We sought to determine whether CO2enrichment would yield proportionally greater growth enhancement in the C4grasses when they were grown at low irradiance than when grown at high irradiance. The species studied were Echinochloa crusgalli, Digitaria sanguinalis, Eleusine indica, and Setaria faberi. Plants were grown in controlled environment chambers at 350, 675 and 1,000 μl 1-1CO2and 1,000 or 150 μmol m-2s-1photosynthetic photon flux density (PPFD). An increase in CO2concentration and PPFD significantly affected net photosynthesis and total biomass production of all plants. Plants grown at low PPFD had significantly lower rates of photosynthesis, produced less biomass, and had reduced responses to increases in CO2. Plants grown in CO2-enriched atmosphere had lower photosynthetic capacity relative to the low CO2grown plants when exposed to lower CO2concentration at the time of measurement, but had greater rate of photosynthesis when exposed to increasing PPFD. The light level under which the plants were growing did not influence the CO2compensation point for photosynthesis.
authors.affiliation: Duke University Phytotron and U.S. Dept Agric, Agric Res Ser, Duke University, 27706, Durham, NC, USA.
authors.forename: Nasser
authors.initials: N
authors.lastname: Sionit
authors.affiliation: Duke University Phytotron and U.S. Dept Agric, Agric Res Ser, Duke University, 27706, Durham, NC, USA.
authors.forename: David T
authors.initials: DT
authors.lastname: Patterson
keywords: C4 grasses; CO2xlight interaction; Stomatal conductance; light saturation; photosynthesis