Invasive potential of C3-C4 intermediate Parthenium hysterophorus under elevated CO2

Abstract

An experiment was conducted in open top chambers (OTCs) to study the growth, water-use efficiency and carbon
isotope discrimination (Δ¹³C) in Parthenium hysterophorus in response to elevated CO₂. Parthenium plants were grown
in OTCs maintained at ambient (370±20 ppm) and elevated (550±30) CO₂ levels as well as under open field conditions.
Water-use efficiency (WUE) was determined by gravimetric method. The carbon isotope discrimination (Δ₁₃C) was
determined by Isotope Ratio Mass Spectrometry (IRMS). The CO₂ enrichment enhanced both the above and below ground
biomass in Parthenium. Water-use efficiency (WUE) and Carbon isotope discrimination (Δ¹³C) were higher in plants
grown under elevated CO₂ compared to plants under ambient CO₂ conditions. The growth stimulation and increased
water-use efficiency in Parthenium indicates that this weed could become more aggressive in future if the atmospheric
CO₂ continue to rise coupled with the rise in temperature.