Soybean (Glycine max (L.) Merr.) growth and development response to CO2 enrichment under different temperature regimes

The carbon dioxide (CO2) concentration of the global atmosphere has increased during the last decades. This increase is expected to impact the diurnal variation in temperature as well as the occurrence of extreme temperatures. This potentially could affect crop production through changes in growth and development that will ultimately impact yield. The objective of this study was to evaluate the effect of CO2 and its interaction with temperature on growth and development of soybean (Glycine max (L.) Merr., cv. Stonewall). The experiment was conducted in controlled environment chambers at the Georgia Envirotron under three different temperatures and two CO2 regimes. The day/night air temperatures were maintained at 20/15, 25/20 and 30/25 °C, while the CO2 levels were maintained at 400 and 700 ppm, resulting in six different treatments. Plants were grown under a constant irradiance of 850 μmoles m−2 s−1 and a day length of 12 h; a non-limiting supply of water and mineral nutrients were provided. Five growth analyses were conducted at the critical development stages V4, R3, R5, R6 and R8. No differences in start of flowering were observed as a function of the CO2 level, except for the temperature regime 25/20 °C, where flowering for the elevated CO2 level occurred 2 days earlier than for the ambient CO2 level. For aboveground biomass, an increase in the CO2 level caused a more vigorous growth at lower temperatures. An increase in temperature also decreased seed weight, mainly due to a reduction in seed size. For all temperature combinations, final seed weight was higher for the elevated CO2 level. This study showed that controlled environment chambers can be excellent facilities for conducting a detailed growth analysis to study the impact on the interactive effect of changes in temperature and CO2 on soybean growth and final yield.