Growth Efficiency of Greengram (Vigna radiata L. Wilczek) Under Elevated Carbondioxide Condition

The CO2 concentration in the atmosphere is rising and anticipated to be doubled by the end of the current century. Agricultural crop production is one of the key sectors that might be affected by rising atmospheric CO2 through its effect on photosynthetic rates and thus productivity. It was reported that C3 plants respond to elevated CO2 by modification of morpho-physiological traits. The crop selected for the present study was Green gram (Vigna radiate L. Wilczek). Though it is an important crop, the availability of pulses has declined. So, a study of the plant responses to high atmospheric CO2 is important since it regulates productivity and quality. Moreover information about genotypic variation of crops under elevated CO2 is lacking in legumes. The general aim of the study is test whether Green gram can adapt to such a change and to explore mechanisms underlining the adaptive response.

Six genotypes of green gram used in the study were SML1827, SML832, SML1831, PM1533, Pusa M-19-31, and Pant M-5. Three different levels of CO2 concentration namely 390ppm, 600 ppm and 750ppm under open top chambers along with an ambient concentration were maintained to assess the response of growth, physiological and yield parameters. The purpose of Open Top Chamber was to study the response of plants in high CO2 environment with precise control and regulation of desired CO2, temperature and humidity.

The results obtained for this experiment showed that elevated CO2 has a positive effect on crop growth and development. Results indicated that 600ppm CO2 enhanced some growth parameters viz. leaf area, number of branches per plant, number of effective root nodules and total biomass of plant which ultimately influenced the yield. Under 750 ppm CO2, An opposite trend was recorded where yield was significantly reduced. Genotypes like Pant M-5, Pusa M-19-31 could be considered as better genotypes when grown under elevated levels of CO2 as they have better N acquisition capability because of greater nodule formation in addition to biomass accumulation. Therefore, such genotypes may be utilized as future breeding materials for adaptation to the changed climatic condition.