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Keywords:

  • arbuscular mycorrhiza;
  • elevated carbon dioxide;
  • root length;
  • root production;
  • root loss;
  • turnover

Abstract

  • • 
    Root responses to elevated CO2 concentrations, where nutrient demand was expected to be higher than at ambient CO2, and possible interactions with mycorrhizal symbionts are reported for pea (Pisum sativum). These are important below-ground components affecting carbon flow into the soil.
  • • 
    A video-minirhizotron system was used to study root growth in pot-grown mycorrhizal (inoculated with Glomus caledonium) and nonmycorrhizal pea plants at ambient or elevated CO2 concentrations over 9 wk. Analyses were made of root length changes, cohort size and survivorship.
  • • 
    Root length production at ambient, but not at elevated CO2, was higher in nonmycorrhizal than in mycorrhizal plants from week 4–7. Root loss began at week 5, peaking 2 wk later with 40–50% loss of the root length produced by week 8. The decline in root production and increase in root loss coincided with the onset of flowering.
  • • 
    Neither mycorrhizal inoculation nor CO2 concentration has a strong effect on pea root production and root loss, although mycorrhizal infection has a greater effect than CO2.