Elevated Atmospheric Carbon Dioxide and Temperature Affect Seed Composition, Mineral Nutrition, and 15N and 13C Dynamics in Soybean Genotypes under Controlled Environments

The seed nutrition of crops is affected by global climate changes due to elevated CO2 and temperatures. Information on the effects of elevated CO2 and temperature on seed nutrition is very limited in spite of its importance in seed quality and food security. Therefore, the objective of this study was to evaluate the effects of elevated atmospheric CO2 and temperature on seed composition (protein, oil, fatty acids, and sugars) and mineral nutrition in two soybean cultivars under controlled environments. The treatments were ambient CO2 concentrations (360 μmol mol-1) and elevated CO2 concentration (700 μmol mol-1) as well as normal temperature (26/16°C) and elevated temperature (45/35°C). Plants were grown under greenhouse conditions until the R5 stage, and then, transferred to growth chambers until full maturity (R8). Elevated temperature or a combination of elevated temperature and elevated CO2 resulted in a decrease in seed protein and linolenic acid concentrations and an increase in oil and oleic acid in cultivars Williams 82 (MGIII) and Hutcheson (MG V). Seed sucrose, glucose, and fructose decreased, whereas raffinose and stachyose remained relatively stable. Minerals also decreased under elevated CO2 and temperature. Among those that decreased were N, P, K, Zn, Fe, and B. Natural abundance of 15N and 13C isotopes was altered only under high temperature, regardless of CO2 concentration, indicating that changes in nitrogen and carbon metabolism occurred at elevated temperature. The increase in oil and oleic acid and decrease in linolenic acid are desirable, as high oleic acid and low linolenic acid contribute to the stability and longer shelf-life of oil. The combination of low protein and high oil was due to the inverse relationship between them. This study showed that seed composition and seed mineral nutrients can be affected by elevated temperature alone or elevated CO2 and temperature. This information is beneficial for selecting varieties with high seed nutritional qualities and efficient mineral nutrient use and uptake, traits that are related to seed production, seed quality, and food security. Also, it provides further knowledge on the effect of climate change on seed quality.