CO2 enrichment reduces the relative contribution of latex and latex-related hydrocarbons to biomass in Euphorbia lathyris

The hypothesis that plants grown under elevated CO2 allocate more carbon to the production of latex and C-rich secondary compounds whereas nutrient addition counteracts this effect was tested. Two similar experiments were conducted in two different experimental facilities. In both facilities seedlings of Euphorbia lathyris were exposed to factorial combinations of two CO2 concentrations and two levels of nutrient availability for 2 months. The CO2 treatments and growth conditions differed substantially between these two experiments but treatment responses to elevated CO2 and fertilizer addition were remarkably similar, underlining the robustness of our findings. Elevated CO2 increased biomass to a greater extent in fertilized than in unfertilized plants and reduced the leaf biomass fraction by accelerating leaf senescence. Concentrations of non-structural carbohydrates (NSC) increased in elevated CO2. However, this apparent carbon surplus did not feed into the whole plant latex pool. The latex harvest per leaf (-25 hydrocarbons (-20 experiments P > 0.05). Fertilization reduced NSC concentrations (-25 but neither affected latex yield per leaf nor the concentration of latex-related hydrocarbons. It is concluded that latex and related hydrocarbons in CO2-enriched plants are a negligible sink for excess carbon irrespective of nutrient status and thus, vigour of growth.