Gas exchanges in soybean as affected by landfill biogas atmosphere

A problem in the ecological restoration of closed landfills is the producti on of potentially toxic gases by decomposition of refuse that affects the r oot system and physiology of plants growing on these sites. The aim of the present study was to assess the effects induced by landfill biogas contamin ation on gas-exchanges of soybean [Glycine mnu (L,) Merr.]. Simulated landf ill and control gases were supplied to soybean plants under laboratory cond itions for 10 d. The composition of the simulated landfill gas used was: 16 % O-2, 8% CO2, 3% CH4, and 73% N-2; a control gas was also tested (21% O-2, 0.035% CO2, and 78% N-2). Photosynthesis and stomatal conductance were sig nificantly affected by the gas treatment after 3 d; in the course of the ex periment, biogas treatment progressively reduced A(max) in light-saturation curves. The fresh and dry weight, leaf area and leaf chlorophyll content w ere not affected by the treatment. A metabolic adaptation to the biogas in the roots of treated plants was related to the disappearance of a fraction of the protein pool.