Seed Yield after Environmental Stress in Soybean Grown under Elevated CO2
1999
Ferris, Rachel | Wheeler, T. R. | Ellis, R. H. | Hadley, P.
Episodes of high temperature and drought are predicted to occur more frequently under conditions of future climate change. This study investigated whether an episode of high air temperature (HT, +15°C), water deficit (WD), or both (HTWD), for 8 d, had the same effects on the yield of soybean [Glycine max (L.) Merrill, cv. Fiskeby V] grown under either ambient (aCO₂; 360 (μol mol⁻¹ CO₂) or elevated (eCO₂; 700 μmol mol⁻¹ CO₂) CO₂ concentrations. Plants were grown in a glasshouse at either aCO₂ or at eCO₂ until 52 d after sowing (DAS). The S-d stress treatments were then imposed before the plants were returned to their original environments. Across harvests, total biomass was 41% greater under eCO₂ than under aCO₂ but reduced by HT, WD, and HTWD under both CO₂ concentrations. The relative response of total biomass to HT, WD, and HTWD episodes was the same for plants grown under either aCO₂ or eCO₂. At maturity, seed dry weight and number per plant under eCO₂ were increased by an average of 32 and 22%, respectively, compared with aCO₂. The same parameters were reduced after HTWD by 29 and 30%, respectively, in aCO₂ and eCO₂. Seed filling was earlier under HT and HTWD. The rate of change in harvest index was unaltered by CO₂ while under HTWD, it decreased. Seed number explained 85% of the variation in yield, but yield was also related linearly to photosynthesis during seed filling, suggesting both are important determinants of yields under stress.
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