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The Interactive Effects of CO2 and Phosphorus Supply on Two Wheat Varieties

Paper Reviewed
Pandey, R., Lal, M.K. and Vengavasi, K. 2018. Differential response of hexaploid and tetraploid wheat to interactive effects of elevated [CO2] and low phosphorus. Plant Cell Reports 37: 1231-1244.

Plant growth is often limited by the amount of nutrients available for photosynthesis and other growth-related activities. Elevated atmospheric CO2 concentrations help plants mitigate this limitation for carbon, often inducing large gains in plant biomass and yield at higher CO2 levels. Yet, there is debate that these CO2-induced growth enhancements will be reduced or altogether eliminated if other nutrients are limiting. But is such really the case?

Providing some information in this regard, Pandey et al. (2018) recently investigated the interactive effects of elevated CO2 and phosphorus (P) supply on two wheat varieties (Triticum aestivum and T. durum). The plants were grown hydroponically for 24 days in controlled-environment chambers at either ambient (390 ppm) or elevated (700 ppm) CO2 and low (5 µM) or high (500 µM) P supply.

In reporting their findings, Pandey et al. note that elevated CO2 increased the root and shoot biomass of both varieties (see Figure 1a,b), even when P was limiting in the hydroponic medium. For example, under elevated CO2 and low P conditions, shoot and root biomass increased by 73 and 145%, respectively, compared to low P and ambient CO2 conditions. Total root length, the length of the primary root, root surface area and root volume also increased under elevated CO2 levels, regardless of P supply. In addition, elevated CO2 improved total P uptake and P utilization efficiency (dry matter production per unit P uptake).

Discussing these and other findings of their paper, Pandey et al. say that the stimulation of growth and biomass accumulation of the wheat plants at elevated CO2 and sufficient P was expected. However, they did not anticipate the higher biomass production of wheat at elevated CO2 and low P compared with that observed at ambient CO2 and low P. This latter feat, however, was accomplished thanks to what they call "modifications to root traits at morphological, physiological and molecular levels due to elevated CO2," which they determined from additional analyses discussed in their paper. All in all, it would therefore appear that elevated CO2 concentrations are able to not only mitigate plant carbon limitations, but to also help alleviate the stress of low P. And that feat has great implications for the future of global agriculture, especially in regions where P is limiting on farmland soils.

Figure 1. (A) Shoot dry weight, (B) root dry weight and (C) total phosphorus (P) uptake of wheat plants grown hydroponically with sufficient (+ P 500 µM) or low (- P, 5 µM) P concentration and under ambient (AC, 390 ppm) or elevated (EC, 700 ppm) CO2 for 24 days. Adapted from Pandey et al. (2018).

Posted 24 October 2018