Impacts of recent and anticipated changes in atmospheric CO2 concentrations on growth performance of weedy rice (Oryza sativa f. spontanea) biotypes in Sri Lanka

Weedy Rice (WR) competes with cultivated rice and leads to loss of yield. The differential growth responses of WR and cultivated rice to increasing CO2 are important in controlling and managing WR. The effect of changing atmospheric CO2 concentrations on growth responses of WR-biotypes and cultivated rice (CR) using three WR biotypes (Wet, Intermediate and Dry climatic zones) and cultivated rice variety Bg300 in a growth chamber with varying concentrations of CO2 (300, 400 and 500 µmol mol-1 24 hd−1) was tested. Data were collected at vegetative stage at 20, 30 and 54 Days after sowing (DAS). Destructive sampling was used for biomass determination. Differential sensitivities of WR-biotypes and CR-Bg300 to increasing CO2 concentration was observed for leaf-width, leaf-area, number of culms and number of leaves, root biomass and total biomass. Elevating CO2 significantly increased vegetative growth and biomass-accumulation in WR biotypes than Bg300 showing higher physiological plasticity in WR biotypes contributing to the wide occurrence of WR in rice fields in Sri Lanka.