الفهرس 
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Abstract
To document possible effects of ozone on four bean cultivars, four clover cultivars and one alfalfa cultivar, Five physiological and biochemical parameters were assessed through five experiments
Using the sensitivity screening test, clover cultivars were ranked descending as follows: Helali, Local, Serow and Giza 6. The alfalfa cultivar (Local) was highly tolerant to ozone and showed no symptoms. While bean cultivars descending ranking was: Nebrasca, Paulista, Bronco and Contender
Cell membrane damage in clover plants was higher in five weeks old compared with four weeks old. Electrolyte leakage in Helali cultivar was the highest on all the sampling times. No significant differences were observed on alfalfa cv. Local. In contrast of clover, bean plants showed higher e-leakage in four weeks old compared with five weeks old. Nebrasca showed the highest e-leakage at all the sampling time tested
Histo-chemical staining for the localization of H2O2 accumulation sites showed that clover cultivars could be ranked in order of decreasing sensitivity as follows: Helali, Local, Giza 6 and Serow. In alfalfa very few H2O2 production sites were detected. Results of bean cultivars revealed that Paulista produced more H2O2 in response to ozone treatment than Nebrasca, Bronco and Contender come third and fourth respectively in this descending order
According to the detection of O2.- accumulation on clover leaf tissue; the more sensitive cultivars Helali and Local showed the highest accumulation, whereas the intermediate cultivars Serow and Giza 6 showed less accumulation. Alfalfa cv. Local showed very few accumulation of superoxide despite showing no visible symptoms. For bean cultivars Nebrasca and Paulista were clearly the least tolerant to oxidative burst by superoxide. While Giza 6 and contender showed less sensitivity respectively
The rate of net photosynthesis was measured in all the species and cultivars under study. In clover cultivars Helali and Local showed a significant decrease in net photosynthetic activity more than Serow and Giza 6. Alfalfa cv. Local showed a significant decline in CO2 assimilation occurred immediately after the end of the fumigation session followed by a very marked recovery to the level of control. Bean plants exhibited more tolerance then clover and the highest decrease was in Nebrasca followed by Paulista, Bronco and Giza 6 respectively
These results suggest that sensitive cultivars of clover (Helali and Local) and bean (Nebrasca and Paulista) could be used as bio-indicators for O3 pollution, Tolerant and intermediate cultivars of clover, bean and alfalfa are preferred to be cultivated in areas polluted with O3 and they may be utilized for further breeding programs to improve these traits in combination with other desirable cultivars.