Photosynthesis and biomass allocation of radish cv. “Cherry Belle” in response to root temperature and ozone

To determine if ozone (O3) and root zone temperature (RZT) affect plant biomass allocation and photosynthesis, radish (Raphanus sativus) plants were grown in controlled environment laboratory chambers in one of four treatments: episodic O3 (average delivery 0.063 µmol mol-1) with RZT at 13°C, episodic O3 (same delivery) with RZT at 18°C, charcoal-filtered air with RZT at 13°C and charcoal-filtered air with RZT at 18°C. O3 reduced total biomass and shoot biomass of radish at 13°C RZT but had no effect at 18°C RZT. Low (13°C) RZT decreased total biomass in both O3 and charcoal-filtered air. RZT had no overall effect on biomass allocation, but O3 lowered root-to-shoot ratios for plants grown at 18°C RZT. Photosynthesis was reduced for plants grown at 18°C RZT and O3, but stomatal conductance was not affected by O3 nor RZT. These results indicate that O3 and low RZT decrease biomass, but that plant photosynthesis is decreased by O3 and warm RZT.