Relationships between methane production and emission to lacunal methane concentrations in rice

We measured lacunal methane concentrations in field-grown rice plants as a correlative to both methane production and emissions. Using a gas-tight syr inge, 100-mu L samples were withdrawn from plant lacunar spaces below the w ater level and diluted to provide enough volume for analysis by gas chromat ography. Lacunal methane concentrations increased throughout the season and , for each sampling date, were usually significantly higher in the cultivar s Mars and Cypress thigh emitters) when compared with Lemont and Della (low emitters). The field site influenced lacunal methane concentrations, where in greater lacunal methane concentrations corresponded with greater methane . Methane emission rates were positively correlated with plant lacunal meth ane concentrations for each cultivar, with an improvement in the relationsh ip during the preheading season. With increases in methane production deter mined by emissions following field-induced anoxia, lacunal methane concentr ations increased accordingly. Lacunal methane concentrations also clearly i ncreased as plant biomass increased, but the relationship depended on field location, which also influenced emissions. Sampling lacunal methane concen trations of rice plants, although labor intensive, is quite flexible, using little field equipment, and may provide an effective alternative to large- scale flux measurements in areas not easily accessible.