Growth and maintenance respiration in leaves of bean (Phaseolus vulgarisL.) exposed to ozone in open‐top chambers in the field

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Abstract
SUMMARY: Bean (Phaseolus vulgarisL. CV. pinto) plants were grown in pots in open‐top chambers in the field and exposed to three ozone (O3) regimes at a rural site in northwestern New York state: (1) charcoal‐filtered air with O3concentrations during the day of about 40–50% ambient (CF), (2) charcoal‐filtered air with O3added to attain approximately ambient concentrations in real time (1 ×), and (3) charcoal‐filtered air with O3added to attain approximately twice ambient concentrations in real time (2×). Unifoliate leaf blade relative growth rate (RGR) and specific dark respiration rate were measured on 214 plants 12‐ to 17‐d‐old. For a given plant age, RGR was significantly reduced by increasing O3dose, and for a given RGR, specific respiration rate was significantly increased. When the specific respiration rate was mathematically partitioned into growth and maintenance components, it was found that thegrowth coefficientwas unaffected by O3but themaintenance coefficientwas significantly increased by increasing O3dose: 7.3% between the CF and 1×treatments, and 25% between the 1×and 2×treatments. These results corroborate earlier findings with plants grown in high light conditions in chambers and exposed to 10 or 90 nl O31−1, and suggest that ambient levels of O3inhibit plant growth in part by diverting respiratory substrate from growth to maintenance and repair processes.