Stomatal mechanisms determining genetic resistance to ozone in Phaseolus vulgaris L.

Abstract

The ozone-sensitive bean cultivars 'Spurt' and 'Blue Lake Stringless' and the ozone-resistant cultivars 'Black Turtle Soup' and 'French's Horticultural' were grown from seed in a growth chamber. The resistant cultivars had 25% fewer stomata per mm2leaf area than the sensitive cultivars and exhibited partial stomatal closure following exposure to 134 pphm ozone for 1 hr, while the sensitive cultivars did not. Stomatal closure was determined to be more important than reduced stomatal frequency in providing resistance to ozone. On the basis of previously established ozone dose-response data for P. vulgaris, the stomatal mechanisms appeared to account for the difference in ozone sensitivity between the sensitive and resistant cultivars. Neither leaf area nor leaf expansion rate were correlated with genetic resistance to ozone in these cultivars.