The growth and yield responses of Fragaria ananassa to elevated CO2 and N supply

Strawberry plants (Fragaria ananassa Duchesne var. Elsanta) were grown in pots at two concentrations of carbon dioxide (partial pressures of 39 and 56 Pa) and with three rates of nitrogen supply (0.04, 0.4 and 4 mM as nutrient solution) to study their individual and interactive effects on plant growth and fruit yield. Nitrogen deficiency reduced total dry biomass and relative growth rate (RGR), mainly through reductions in leaf area ratio (LAR) and plant N concentration (PNC), although both the net assimilation rare (NAR) and root weight ratio (RWR) increased. Elevated CO2 increased the N productivity (NP) but reduced the LAR. High CO2 increased the fruit yield by 42% at high N supply and by 17% at low N supply. The CO2 yield enhancement occurred through an increase in the flower and fruit number of individual plants. This resulted in an increase in the fruit weight ratio (FWR) of plants at high CO2. Nitrogen deficiency reduced the fruit yield by about 50% through decreases in fruit size, fruit set and the number of fruits. However, N deficiency increased the proportion of total plant dry biomass allocated to fruits. There were no significant interactions between CO2 and N supply on yield. (C) 1998 Annals of Botany Company.