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HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

The present study is an attempt to assess the growth and biochemical responses of Pongamia pinnata grownunder elevated levels of CO2 supply. Saplings (18 months) maintained in the nursery were brought toexperimentation in two growth chambers having controlled supply of air and air- CO2 mixture, for a periodof 15 days. The control and treated chambers were retained at an average CO2 concentration of 505.28±17.39 ppm and 1053.85± 24.99 ppm respectively. Day and night fluxes of CO2 within the chambers wereanalysed daily, along with a periodic assessment of the growth and biochemical responses associated withthe plants. A standardization study, excluding plants, was also attempted to assess the resultantflux ofCO2 associated with the growth chambers. The day flux of CO2 in the control and treatedchambers wasdifferent from that of the night flux in both experimentation and standardization studies. Higher CO2assimilation by the plants in the CO2 enriched system during the day time has also resulted in increasedplant height, stem thickness, leaf area and also in the assimilation of carbohydrates, sodium and potassium.Increased Carotenoids and phenol are implications of the stress to which the plants are subjected to underelevated levels of CO2 supply. The present study confirms that, despite certain signs of stress, Pongamiapinnata can be an ideal candidate for carbon offset planting.

Rising atmospheric carbon dioxide accelerates growth and modifies physiological responses in plants. Over the last 40 years, the global scientific community had taken up initiatives to make out the role of plants in capturing and storing atmospheric carbon dioxide. This review consolidates the research of the past three decades on the responses of grass species to elevated levels of CO2. An enhancement in intercellular CO2 concentration, water use efficiency, photosynthesis, total non-structural carbohydrates, and total biomass was noticed in grass species under controlled growth systems supplied with varying levels of CO2. Each of these responses reflects the potency of grasses to survive and store ample carbon in CO2-enriched environments. Reduction in stomatal conductance, transpiration rate, and total nitrogen concentration was in effect positive responses, in connection with the acclimatization of plants at CO2-enriched environments. This review ascertains that in experimental microclimatic environments with varying CO2 regimes or varying treatment duration, grasses show positive growth responses. Thus it illustrates the efficient atmospheric carbon sequestration of grasses irrespective of their photosynthetic pathway (whether C3/C4).

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