Mycorrhizal effects on growth and nutrition of tomato under elevated atmospheric carbon dioxide

Arbuscularmycorrhizas are predicted to be important in de. ning plant responses to elevated atmospheric CO2 concentrations. A mycorrhiza-defective tomato (Solanum lycopersicum L.) mutant with reduced mycorrhizal colonisation (rmc) and its mycorrhizal wild-type progenitor (76R MYC+) were grown under ambient and elevated atmospheric CO2 concentrations (eCO(2)) in a controlled environment chamber-based pot study. Plant growth, nutrient contents and mycorrhizal colonisation were measured four times over a 72-day period. The 76R MYC+ plants generally had higher concentrations of P, N and Zn than their rmc counterparts. Consistent with earlier studies, mycorrhizal colonisation was not affected by eCO(2). Growth of the two genotypes was very similar under ambient CO2 conditions. Under eCO(2) the mycorrhizal plants initially had higher biomass, but after 72 days, biomass was lower than for rmc plants, suggesting that in this pot study the costs of maintaining carbon inputs to the fungal symbiont outweighed the benefits with time.