Paper Reviewed
Ali, S.A.M., Zain, C.R.C.M. and Latip, J. 2019. Influence of elevated CO2 on the growth and phenolic constituents production in Hibiscus sabdariffa var. UKMR-2. Jurnal Teknologi 81: 109-118.

In a revealing study, Ali et al. (2019) recently investigated the impact of elevated CO2 on the growth, yield and phenolic and antioxidant constituents of roselle (Hibiscus sabdariffa).

The work was conducted in a controlled-environment greenhouse system at the Universiti Kebangsaan Malaysia, Bangi, Malasia in 2017. Seedlings of the herbaceous shrub were grown under well-watered and fertilized conditions under either ambient (400 ppm) or elevated (800 ppm) CO2 concentrations for a period of 70 days.

The results of the analysis revealed that elevated CO2 stimulated plant height, but not the stem diameter, number of branches, or the number of leaves. However, higher levels of CO2 did increase the most important parameter in this study from an economic and medicinal perspective -- the calyces. Indeed, the roselle calyces (with seed) produced significantly higher yields in the 800 ppm CO2 treatment compared to plants growing in the ambient treatment, as fresh weights in the elevated CO2 treatment (511 g) were a factor of 4.1 greater than the fresh weights observed in the ambient treatment (123.8 g).

But perhaps the most important finding was in measurements of phenolic constituents (total phenolic and total anthocyanins) and antioxidant activity, which were significantly increased under elevated CO2 and which have important medicinal properties, including boosting immunity, controlling blood lipid levels, scavenging radicals, chelating metals and improving anti-mutagenics. Thus, it would appear that rising atmospheric CO2 concentrations will serve to improve the pharmaceutical and nutraceutical value of this key subtropical plant, which is great news for those who grow and utilize its compounds for improving human health.