The Photosynthetic Response of Jicama to Elevated CO2

Paper Reviewed
Ravi, V., Pushpaleela, A., Raju, S., Gangadharan, B. and More, S.J. 2019. Evaluation of photosynthetic efficiency of yam bean (Pachyrhizus erosus L.) at saturating photon flux density under elevated carbon dioxide. Physiology and Molecular Biology of Plants 26: 189-194.

The Mexican yam bean, or jicama (Pachyrhizus erosus), is an important edible legume that originated in Latin America, but is now cultivated in tropical regions throughout the world. The plant’s roots are consumed fresh and are good sources of dietary fiber and vitamin C, calcium, zinc, iron, copper, thiamine riboflavin and niacin. The jicama is also a prebiotic and is low in saturated fat and sodium.

Surprisingly, according to Ravi et al. (2019), no study has been conducted assessing “the suitability of the yam bean for high CO2 environment.” And so to remedy this situation, the four Indian scientists set out to do just that.

Their work was performed at ICAR-Central Tuber Crops Research Institute, Sreekariyam, Thiruvananthapuram, India, in 2018, where the yam bean variety Rajendra Mishrikand-1 was grown in the field under well-watered and nutrient conditions. During the active growth period (between the 2nd and 3rd month after sowing), the researchers measured photosynthetic CO2 uptake, stomatal conductance and intercellular CO2 on leaves enclosed in the climate-controlled cuvette of a portable photosynthetic system (LICOR-6400) across a CO2 gradient from 200-1000 ppm.

And what did those measurements show?

Focusing on net photosynthesis, results indicated that, compared to ambient CO2 levels at 400 ppm, leaf photosynthesis was reduced by 54% at a CO2 concentration of 200 ppm, but increased by 19%, 21% and 23% at CO2 concentrations of 600, 800 and 1000 ppm, depicting what Ravi et al. describe as “the positive response of yam bean to elevated carbon dioxide.” Consequently, the authors conclude their short paper by indicating that their assessment of yam bean is that it is “responsive to elevated carbon dioxide and very well suited to thrive under future projected high CO2 environmental conditions.” And that is great news for those who enjoy eating jicama!

This article appeared on the CO2 Science website at http://www.co2science.org/articles/V23/apr/a2.php