Enhancement of Carbon Assimilates and Macronutrients in Legumes under Elevated CO2 Concentration

Abstract

Impact  of  elevated  carbon  dioxide  (Free  Air  Carbon  dioxide  Enrichment)  was  studied  on  the  plant  chlorophyll,  plant  growth,  plant  macronutrients,  total  starch,  total  carbohydrate  and  the  activity  of  phosphoenol  pyruvate  carboxylase  (Pep  C)  enzymatic  assays  in  leaves, pods and seeds in leguminous plant Cyamopsis tetragonoloba. Plants of Cyamopsis tetragonoloba (C3) were exposed to different atmospheric CO₂ concentrations 420 ± 20 ppm (ambient) and 550 ± 20ppm (elevated). An average increase in the plant total chlorophyll (+39.17%), total starch (+43.73%, +25.44% and +26.35% in leaves, pods, and seeds), sucrose (+69.77%, +22.27% and +33.77% in leaves, pods and seed) and total carbohydrate (+58.88%, +30.54% and +28.38 % in leaves, pods and seeds) content were found in plant grown under elevated condition when compared to ambient counterpart. More over overall plant growth (+40% height and +25% biomass) increased in [CO₂] concentration. Plant total nitrogen (N) content decreased (−12.55% in leaves) under the elevated condition where as total phosphorus (P) decreased (−3.15% in leaves) along with total potassium (K) (−46.63% in leaves). In soil, total potassium (+60.23%) and phosphorous (+48.88%) were found to increase with (−16%) decrease in soil nitrogen content. In seed total nitrogen content increased (+18.15%) on an average with no significant change in total potassium and phosphorus content under e[CO2]. Phosphoenolpyruvate carboxylase  enzyme  (Pep  C)  (+139.5%  in  leaves)  activity  and  total  organic  carbon  (TOC)  (+19.12%,  +17.85%  in  leaves  and  seeds)  increases in elevated concentration thus promoting and indicating higher photosynthesis via enhanced CO₂ fixation. Thus our studies showed that [CO₂] positively promotes sugars, carbohydrates synthesis, translocation and partitioning in plant tissues and enhanced macronutrients level in leaves and seeds tissue which is contradictory to other C3 plants. Thus [CO₂] works as the boon for Cyamopsisvarieties and the seeds are nutritionally rich, healthy, balanced in proteins and carbohydrates (C/N) and so these varieties have future implication for industrial use in the agricultural country like India.