Just Accepted

This article has been peer reviewed and accepted for publication. It is in production and has not been edited, so may differ from the final published form.

Evaluation of potential increase in photosynthetic efficiency of cassava plants exposed to elevated carbon dioxide

Velumani Ravi, Saravanan Raju, Sanket More

Abstract

Cassava, the most important ‘food, feed and fuel’ crop of the tropics is prone to a variety of physiological changes due to extreme climatic events. Rising atmospheric carbon dioxide concentration is one of the conspicuous characteristics of global climate change. We evaluated the short-term effect of elevated carbon dioxide concentration (ECO2) (600, 800 and 1000 ppm) on the photosynthetic efficiency of 14 cassava varieties/genotypes in comparison to ambient CO2 concentration (400 ppm). Gaseous exchange parameters viz., net photosynthetic rate (Pn), stomatal conductance (gs), intercellular CO2 (Ci) and transpiration (E) in cassava leaves in response to short-term ECO2 altered significantly (P<0.001). There were significant but varying interactive effects between ECO2 and varieties on these physiological characteristics. ECO2 i.e., 600 and 800 ppm, increased the Pn rate in the range of 13-24% in comparison to 400 ppm, followed by acclimation at the highest concentration of 1000 ppm. A similar trend was observed in the case of gs and E. Conversely, Ci increased significantly and linearly across increasing CO2 concentration. Along with Ci, a steady increase in water use efficiency [WUEintrinsic (Pn/gs) and WUEinstantaneous (Pn/E)] across various CO2 concentrations corresponded with the central role of restricted stomatal activity, a common response under ECO2. Furthermore, Pn had a significant quadratic relationship with the ECO2 (R2=0.489) and a significant and linear relationship with Ci (R2=0.227). The relative humidity and vapour pressure deficit during the time of measurements remained between 70 to 85% and ~0.9 to 1.31 kPa, respectively, at 26±2oC leaf temperature. Notably, not a single variety exhibited constant performance for any of the parameters across CO2 concentrations. The research results from the present experiment indicated that the potential photosynthesis can be increased up to 800 ppm cassava varieties with high sink capacity can be cultivated under protected cultivation to attain higher productivity.

FP23254  Accepted 22 April 2024

© CSIRO 2024