Effects of increased atmospheric CO2 on varieties of oat

The effects of elevated CO₂ were investigated on seven Scandinavian varieties of oat. Three landraces (before 1920), two varieties of intermediate‐age (1920‐1940), and two recent varieties (after 1940) were exposed to two atmospheric CO2 concentrations (approx. 380 and 700 ppm). Elevated CO₂ increased the yield 7% on average but with large variation between varieties. The yield‐response was variety specific and not related to the age of the variety. The mean seed number increased about 11%, with an increase in the landraces and diverging responses within the other age groups. The mean seed weight was reduced about 5.5%, with small changes within the landraces and diverging results within the two other age‐groups. The mean dry biomass was increased about 20%; the landraees had a marked increase in dry biomass, while the response in the other varieties ranged from a large increase to a small decrease. These different responses among varieties provide a spectrum of trait‐combinations desirable in breeding oats for different purposes. The quality of the seeds was not affected by the elevated CO₂.