| dc.description.abstract | The relationship of sugar levels to ozone resistance in 13-day-old primary leaves of water-stressed bean plants (Phaseolus vulgaris cv 'Pinto') was investigated. Solutions of 40%, 30%, 20%, 10%, 5%, 1%, and 0.1% (w/v) polyethylene glycol were used to induce water stress. Water stress was determined by measuring leaf diffusive resistance, osmotic potential, and water potential of 13-day-old primary leaves.
Two mechanisms for ozone resistance in bean plants were observed during the experiment, avoidance and repair of ozone injury. Plants treated with 10% and higher PEG concentrations had high leaf resistance values as compared to non-stressed plants indicating that the stressed plants closed their stomates. These plants were ozone resistant by avoidance, since ozone could not penetrate the leaf to cause damage.
Plants treated with 5% and lower PEG concentrations had open stomates as indicated by leaf resistance values. A decrease in osmotic potential and water potential was observed for all stress treatments. This indicated a rise in solute concentration of leaf cells. Subsequent ozone fumigation and sugar analysis showed that the 5% and lower PEG-treated plants were ozone resistant also and that at least a 25% rise in sugar levels over control plants occurred. Ozone resistance in these plants was considered an effect of increased sugar levels which probably allowed a repair mechanism for ozone injury to proceed. | en |
