Editor M. Tausz
Growth and nutritive value of cassava (Manihot esculenta Cranz.) are reduced when grown in elevated CO2
Article first published online: 6 AUG 2009
© 2009 German Botanical Society and The Royal Botanical Society of the Netherlands
Special Issue: Plant Functioning in a Changing Global Environment.
Volume 11, Issue Supplement s1, pages 76–82, November 2009
How to Cite
Gleadow, R. M., Evans, J. R., McCaffery, S. and Cavagnaro, T. R. (2009), Growth and nutritive value of cassava (Manihot esculenta Cranz.) are reduced when grown in elevated CO2. Plant Biology, 11: 76–82. doi: 10.1111/j.1438-8677.2009.00238.x
- Issue published online: 23 SEP 2009
- Article first published online: 6 AUG 2009
- Received: 4 March 2009; Accepted: 22 June 2009
- climate change;
- cyanogenic glycosides;
- food quality;
- leaf protein;
Global food security in a changing climate depends on both the nutritive value of staple crops as well as their yields. Here, we examined the direct effect of atmospheric CO2 on cassava (Manihot esculenta Cranz., manioc), a staple for 750 million people worldwide. Cassava is poor in nutrients and contains high levels of cyanogenic glycosides that break down to release toxic hydrogen cyanide when damaged. We grew cassava at three concentrations of CO2 (Ca: 360, 550 and 710 ppm) supplied together with nutrient solution containing either 1 mM or 12 mM nitrogen. We found that total plant biomass and tuber yield (number and mass) decreased linearly with increasing Ca. In the worst-case scenario, tuber mass was reduced by an order of magnitude in plants grown at 710 ppm compared with 360 ppm CO2. Photosynthetic parameters were consistent with the whole plant biomass data. It is proposed that since cassava stomata are highly sensitive to other environmental variables, the decrease in assimilation observed here might, in part, be a direct effect of CO2 on stomata. Total N (used here as a proxy for protein content) and cyanogenic glycoside concentrations of the tubers were not significantly different in the plants grown at elevated CO2. By contrast, the concentration of cyanogenic glycosides in the edible leaves nearly doubled in the highest Ca. If leaves continue to be used as a protein supplement, they will need to be more thoroughly processed in the future. With increasing population density, declining soil fertility, expansion into marginal farmland, together with the predicted increase in extreme climatic events, reliance on robust crops such as cassava will increase. The responses to CO2 shown here point to the possibility that there could be severe food shortages in the coming decades unless CO2 emissions are dramatically reduced, or alternative cultivars or crops are developed.