Effects of elevated atmospheric CO2 concentration on growth and photosynthesis in eddo at two different air temperatures

Future agricultural management programs should consider the responsiveness of crops to increasing atmospheric CO2 concentrations ([CO2]) and temperatures. Eddo is an important tuber crop widely grown in Asia, but its response to [CO2] and temperatures remains largely unknown. We investigated the responses of eddo and rice plants to elevated [CO2] (ambient [CO2] + 200 mu mol mol(-1)) at low and high temperatures during the early-to-intermediate growth stage in temperature gradient chambers in 2018 and 2019. The dry weights (DWs) of the eddo leaf blades, petioles, roots, and above-ground parts as well as the DWs of the rice leaf blades, leaf sheaths and stems, above-ground parts, and whole plants significantly increased under elevated [CO2]. The number of leaves, leaf area, and SPAD value of eddo significantly increased under elevated [CO2], whereas the leaf area and SPAD value of rice did not. The net photosynthetic rate of eddo and rice tended to increase under elevated [CO2]. The increasing ratio of the total DW in elevated vs ambient [CO2] was significantly higher for eddo than for rice. The result indicates that elevated [CO2] increases the eddo biomass more than the rice biomass, possibly because of the increasing eddo leaf area and SPAD value induced by elevated [CO2]. The total DW of rice increased significantly in response to the high air temperature under elevated [CO2] conditions. However, the effect of [CO2] on the total DW of eddo was similar at both temperatures, reflecting the non-significant interaction between [CO2] and temperature.