Assimilatory function and biochemical changes in Stylosanthes hamata grown under elevated CO2

Abstract

We studied the impact of 360 ± 50 µL/l (ambient) and 600 ± 50 µL/L (elevated) CO₂ on growth performance, biomass production, photosynthetic efficiency, carbon isotope discrimination, protein profile and some antioxidant enzymes on Stylosanthes hamata. This crop responded significantly to photosynthetic rate, stomatal conductance and transpiration rate under elevated CO₂. The biomass production in terms of fresh and dry was increased in elevated CO₂ by 126.81% (fresh) and 114.55% (dry) over ambient CO₂. Long term exposure to elevated CO₂ enhanced photosynthetic water use efficiency by 127.77%. The photosynthetic pigment, total chlorophyll and chlorophyll a/b ratio also increased by 220.56 and 132.86%, respectively in elevated over ambient CO₂. Around 149% increase in the soluble protein accumulation (mg/g FW) was recorded under elevated over ambient CO₂, which was also reflected in the polyacrylamide gel profile. The isoforms of superoxide dismutase and esterase isozymes showed remarkable difference under elevated as compared to ambient. Measurement of ¹³δ in different plant parts indicated a significant increase in discrimination against ¹³C when plants were grown at elevated relative to ambient CO₂. Maximum increase was recorded in roots (439.72%) followed by leaf and the stem recorded least increase in ¹³δ (119.94%) in elevated over ambient CO₂.