Effects of growth temperature and carbon dioxide enrichment on soybean seed components at different stages of development

• Levels of four of five soybean seed components were maximal during early seed filling.
• Thirty-five and nine out of fifty-one metabolites exhibited treatment differences.
• Temperature and CO2 effects were mostly evident in young developing seeds.
• Treatment effects on foliar photosynthesis likely altered metabolites in young seeds.

Soybean plants were grown to maturity in controlled environment chambers and at the onset of flowering three temperature treatments were imposed that provided optimum [28/24 °C], low [22/18 °C] or high [36/32 °C] chamber air temperatures. In addition, plants were treated continuously with either 400 or 800 μmol mol−1 CO2. Seeds were harvested at 42, 53, 69 and 95 days after planting (i.e., final maturity). This study quantified 51 metabolites in developing soybean seeds, plus total lipids and proteins were measured at maturity. About 80% of measured soluble carbohydrates, amines and organic acids decreased to low levels in mature seeds, although important exceptions were raffinose, ribose/arabinose, citrate and all eight fatty acids. This suggested that the metabolism of young seeds supported lipid and protein synthesis. A total of 35 and 9 metabolites differed among temperature and CO2 treatments, respectively, and treatment effects were predominately observed on the first and second samplings. However, shikimate, pinitol and oleate were increased by high temperature treatments in mature seeds. The above results indicated that CO2 enrichment primarily altered metabolite levels during the initial stages of seed development and this was likely due to enhanced photosynthate formation in leaves.

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