Nonstructural Carbohydrates and Nitrogen of Soybean Grown under Carbon Dioxide Enrichment

Publisher Website
Google Scholar
Abstract
Carbon dioxide (CO2) concentration has been rising in the atmosphere for uver a century. This study was conducted to determine the effects of anticipated future levels of CO2 on nonstructural carbohydrates and N of soybean [Glycine max (L.) Merr. cv. Bragg]. Plants were grown at Gainesville, FL from seeding to maturity in six sunlit, controlled‐environment chambers that maintained CO2 at 330, 330, 450, 600, 800, and 800μmol (CO2) mol‐1 (air). Attached lysimeters contained Arredondo fine sand (loamy, siliceous, hyperthermic Grossarenic Paleudult). Leaflet blades were sampled five times per day at 48 and 69 d after planting (DAP). At 48 DAP, average daytime starch conc. of leaflets increased with increasing CO2 from 85 g kg‐1 of dry wt at 330 μmol mol‐1 to 205 g kg‐1 at 800 μmol mol‐1. On each date, the daytime rate of starch accumulation combined over all CO2 treatments was 6 g kg‐1 h‐1. Specific leaf weight increased significantly throughout the day both at 48 (0.64 g m‐2 h‐1) and 69 DAP (0.29 g m‐2 h‐1). Total Kjeldahl N (TKN) conc., expressed on a g m‐2 basis, showed no change over the day. Total final dry wet increased 18, 34, and 54% at 450, 600, and 800 μmol mol‐1, respectively. The TKN harvested per plant increased 25, 26, and 45% in the 450, 600, and 800 μmol mo1‐1 CO2 treatments, respectively. Plants in the 450 μmol mol‐1 CO2 treatment partitioned more biomass to seed than the other CO2 treatments. With that exception, we saw no great differences among treatment partitioning at final harvest, and thus interpret the main effect of CO2 enrichment to be enhanced photoassimilation by soybean canopies while maintaining consistent allometric relationships of the plants.