Photosynthesis and growth rates in Salvinia molesta and Eichhornia crassipes.
Max. hourly rates of CO2 uptake measured in midsummer in well-developed communities of S. molesta and E. crassipes ranged from 20 to 23 and from 30 to 35 mg/dm2 water surface, resp. Removal of leaf laminae of E. crassipes resulted in an 88% decrease in CO2 uptake. Net CO2 uptake by day and efflux by night were fairly constant when related to unit water surface area covered by the plant community, while plant biomass/unit area had only a small effect on exchange rates. In uncrowded conditions both spp. had high RGR and short doubling times with respect to both DW and leaf area. With inter-plant competition, growth rates decreased rapidly and biomass/unit water surface area increased. It was concluded that colonizing ability as weeds was due to the free-floating habit and branched growth pattern rather than to intrinsically superior photosynthetic ability.