Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/7/2004
Publication Date: 1/27/2005
Citation: Caldwell, C.R., Britz, S.J., Mirecki, R.M. 2005. Effect of temperature, elevated carbon dioxide and drought during seed development on the isoflavone content of soybean [glycine max (l.)] grown in controlled environments. Journal of Agricultural and Food Chemistry. 53:1125-1129. Interpretive Summary: The effects of global climate change have become increasingly evident. Higher average summer temperatures, altered weather patterns and increased levels of carbon dioxide have been measured and these changes are likely to continue in the future. Since plant growth under elevated carbon dioxide is enhanced, many of the effects of global climate change may be benefit agricultural production by increasing the yield of crop plants. However, in many cases, the effects of global climate change on product quality has not been considered. Growing soybean under conditions that simulate current and projected environmental conditions associated with global climate change altered the levels and proportions of isoflavones in soybean seeds. A five degree increase in average temperature during seed development reduced total isoflavone content by about 70%. Since isoflavones are chemicals known to have human health benefits, the effects of long-term environmental changes on phytonutrient content need to be considered in the development of new soybean lines and agricultural practices that maximize the nutritional benefits of soy products in a changing world. Therefore, the results of this research should be of interest to soybean breeders, growers and producers of soy-based products, as well as, individuals interested in the nutritional consequences of global climate change.
Technical Abstract: The effects of elevated temperature, carbon dioxide and water stress on the isoflavone content of soybean [Glycine max (L.) Merrill] seed were determined, using controlled-environment chambers. Increasing the temperature from 18 °C during seed development to 23 °C decreased total isoflavone content by 70%. A further 5 °C increase to 28 °C decreased the total isoflavone content by 90%. Combining treatments at elevated temperature with elevated CO2 (700 ppm) and water stress to determine the possible consequences of global climate change on soybean seed isoflavone content indicated that elevated CO2 at elevated temperatures could partially reverse the effects of temperature on soybean seed isoflavone content. The addition of drought stress to plants grown at 23 °C and elevated CO2 returned the total isoflavone levels to the control values obtained at 18 °C and 400 ppm CO2. The promotive effects of drought and elevated CO2 at 23 °C on the 6"-O-malonygenistin and geneistin levels were additive. The individual isoflavones often had different responses to the various growth conditions during seed maturation, modifying the proportions of the principal isoflavones. Therefore, subtle changes in certain environmental factors may change the isoflavone content of commercially-grown soybean, altering the nutritional values of soy products.