Abstract
Global warming cause due by increasing atmospheric CO<sub>2</sub> concentration, and the resulting increase in air temperature is a considerable challenge in crop production. Hence, the objectives of this study were to determine the: (a) responses of biomass and sucrose accumulation of sugarcane to elevated CO<sub>2</sub> (ECO<sub>2</sub>) and elevated temperature (ET<sub>a</sub>), both individually and together, and (b) genotypic variation of these responses. A three-factor factorial experiment considering the combination of CO<sub>2</sub> concentrations and temperatures as the main-plot factor and eight sugarcane varieties as the sub-plot factor arranged in a split-plot design in open-top chambers. Plots in open field conditions were the negative control. The main plot factor had four levels, combinations of ambient/elevated CO<sub>2</sub> concentrations (344-351/777-779 ppm) and ambient/elevated temperatures (34.9-35.6/36.6-38.4°C). Significant treatment × variety interaction effects observed on the number of shoots per hill, sucrose% (Pol), and pure obtainable cane sugar (POCS) in cane juice. Genotypic variations were significant in all variables measured. Elevated T<sub>a</sub> increased the number of shoots per hill in 4 out of 8 varieties. Biomass accumulation of sugarcane on the dry weight basis did not respond clearly to the simulated future climatic conditions. The response of Pol and POCS to ECO<sub>2</sub> and the combination of ECO<sub>2</sub> and ET<sub>a</sub> varied depending on varieties with decreased, increased, or no response. Notably, Pol and POCS in the variety SL88116, which had higher respective values at ambient and simulated future climatic conditions, were not affected by either ECO<sub>2</sub> or ET<sub>a</sub> individually or in combination. The responses and the significant genotypic variation observed in sucrose accumulation to ECO<sub>2</sub> and ET<sub>a</sub>, both individually and together, demonstrate considerable scope in sugarcane to breed varieties to maintain the stability of sugar recovery in CO<sub>2</sub>-rich warm climates.
Highlights
Increasing atmospheric CO2 concentration and resulting increase of air temperature (Ta) has variable impacts on the productivity of sugarcane depending on varieties and growing conditions (Marin et al, 2013, 2014)
Open top chambers containing elevated CO2 (ECO2) and elevated temperature (ETa) treatments, both individually and in combination, had higher air temperatures than the open top chambers (OTCs) consist of the CO2 + ambient Ta (CaTa) treatment during the daylight hours (Table 1)
Air temperatures within OTCs having elevated ECO2 and ETa treatments were higher than CaTa during the night as well (Night time data not shown)
Summary
Increasing atmospheric CO2 concentration and resulting increase of air temperature (Ta) has variable impacts on the productivity of sugarcane depending on varieties and growing conditions (Marin et al, 2013, 2014). Biomass and sucrose accumulation of sugarcane shows variable responses to elevated CO2 (ECO2) and temperature (ETa) depending on the specific growing conditions. Several studies conducted using potted plants grown in open-top chambers (OTCs) under well-watered conditions show that biomass accumulation of sugarcane increases at ECO2 (Vu et al, 2006; De Souza et al, 2008; Vu and Allen, 2009; Allen et al, 2011; Marin et al, 2013). It is likely that the magnitude of the impacts of increasing atmospheric CO2 could be different on different crops grow under varying environmental and management conditions (Chaves and Pereira, 1992; Leakey et al, 2006)
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