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Elevated CO2: Overpowering the Growth-Retarding Effects of Ozone in Palak

Kumari, S., Agrawal, M. and Tiwari, S. 2013. Impact of elevated CO2 and elevated O3 on Beta vulgaris L.: Pigments, metabolites, antioxidants, growth and yield. Environmental Pollution 174: 279-288.
Palak (Beta vulgaris L. var Allgreen), in the words of authors Kumari et al. (2013) is "a cheap and popular leafy vegetable preferred mainly for iron content in the diet" that is "widely grown" and "suitable for all seasons in north India." Recognizing the global growth in both atmospheric CO2 (an aerial fertilizer) and tropospheric ozone (O3, and aerial pollutant) over the past two centuries, plus their anticipated future increases, Kumari et al. set out to examine the interactive effects of these two contrasting atmospheric molecules on the growth of palak. To accomplish this purpose, the three Indian researchers utilized open-top chambers at the botanical garden of Banaras Hindu University in the eastern Gangetic plains of India during December 2008 and January 2009, to measure the morphological, biochemical and yield responses of palak to ambient (A) and elevated (E) levels of CO2 and O3, alone and in combination. The atmospheric CO2 concentrations employed in the study were ambient (normal air) and 570 ppm, while the O3 concentrations utilized were ambient and ambient + 20 ppb, the elevated values of which were selected to match the predicted concentrations at the end of the century under the A1B scenario of the IPCC (2007).

As expected, the results of the analysis revealed that elevated CO2 enhanced various plant growth parameters in palak, including root length, shoot length, number of leaves, leaf area, root biomass, shoot biomass, total plant biomass, and yield (compare the ECO2 values in Table 1 with the ACO2 values), while elevated concentrations of ozone had a negative effect (compare the EO3 values in Table 1 with the ACO2 + AO3 values). When enhanced ozone and enhanced carbon dioxide were tested together, however, the growth-enhancing effects of CO2 were sufficient in every instance to overpower the growth-retarding effects of ozone for every plant parameter measured (compare the ECO2 + EO3 values in Table 1 with the ACO2 + AO3 values).

Table 1. Growth parameters of palak plants under different treatments of O3 and CO2, individually and in combination at 50 days after germination (DAG). Adapted from Kumari et al. (2013).

In discussing the various findings of their work, Kumari et al. concluded that for the IPCC-predicted atmospheric concentrations of CO2 and O3 at the end of the century, "palak is going to be benefited as biomass enhancement was more under ECO2 + EO3 compared to ACO2 + AO3." And that's great news for lovers of this popular leafy vegetable in India and elsewhere across the globe.

Additional Reference
IPCC. 2007. Climate Change 2007. The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, United Kingdom..

Archived 4 June 2013