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

To determine if ozone (O-3) 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 O-3 (average delivery 0.063 mu mol mol(-1)) with RZT at 13 degrees C, episodic O-3 (same delivery) with RZT at 18 degrees C, charcoal-filtered air with RZT at 13 degrees C and charcoal-filtered air with RZT at 18 degrees C. O-3 reduced total biomass and shoot biomass of radish at 13 degrees C RZT but had no effect at 18 degrees C RZT. Low(13 degrees C) RZT decreased total biomass in both O-3 and charcoal-filtered air. RZT had no overall effect on biomass allocation, but O-3 lowered root-to-shoot ratios for plants grown at 18 degrees C RZT. Photosynthesis was reduced for plants grown at 18 degrees C RZT and O-3, but stomatal conductance was not affected by O-3 nor RZT. These results indicate that O-3 and low RZT decrease biomass, but that plant photosynthesis is decreased by O-3 and warm RZT. (C) 2000 Elsevier Science Ltd. All rights reserved.