The Effects of Elevated CO₂ Concentration on Photosynthesis and Photosystem II Photochemistry in a Fast Growing Tree Species, Gmelina Arborea Roxb

Abstract

Sequestering atmospheric carbon and storing it in the terrestrial biosphere is one of the options to mitigate green house gas emissions. Young fast growing tree species are believed to be major potential sinks which could absorb large quantities of CO₂ from the atmosphere. The ability of plant to capture light energy, associated with the rate of CO₂ fixation per se, is crucial to understand the growth dynamics under varying environmental regimes. The role of enriched CO₂ atmosphere in the kinetics of photosynthesis and Chl a fluorescence could be an index to understand the photosystem II photochemistry associated with carbon sequestration potential. In this study, the effects of elevated CO₂ (460 μmol mol⁻¹) on diurnal courses of net CO₂ assimilation and chlorophyll a fluorescence were investigated under natural high light during summer days in a fast growing tree species, Gmelina arborea (Verbenaceae). High CO₂ atmosphere led to easy recovery from the midday photosynthetic depression in the leaves. Elevated CO₂ also enhanced the utilization of captured light energy, alleviated photoinhibition and enhanced the growth of Gmelina arborea. Data on fluorescence induction curves and JIP-test parameters also demonstrated a positive impact of elevated CO₂ on PSII photochemical performance suggesting Gmelina to be a better performer for carbon sequestration even during high irradiance regimes.