Abstract
Nineteen bean cultivars were grown from seed in a growth chamber and exposed to 0.6 ppm ozone for 2 hr at 12 days after sowing. The degree of foliar injury of primary leaves was measured by the chlorophyll reduction percentage, and was examined in relation to sugar content, osmotic potential, transpiration rate and leaf diffusion resistance, each parameter being measured prior to ozone exposure, to clarify the main factor controlling intraspecific response to ozone.
Several cultivars exposed to ozone showed no visible injury, while other cultivars exhibited 100% leaf injury.“Wonder Crop No. 2, ”“Green processor, ”and“Bronco”were the most sensitive to ozone ; “Provider”and“Bush Blue Lake 274” were the moderately sensitive; and“Bounty, ”“Goldrush, ”and“Masterpiece improved”were the most resistant.
The sensitive cultivars had less reducing sugar content, lower osmotic potential and higher transpiration rate than the resistant cultivars. However, the obvious relationship between non-reducing sugar content and the degree of foliar injury was not detected. And, ozone injury varied from 90% to 50% with little variation of leaf diffusion resistance.
These results may indicate that, although the role of sugars for the protection of plant from ozone injury is not clear, sugars play a part of detoxication of ozone and/or antioxidation in leaf tissues. And it is considerable to use the sugar content of leaf for an indicator of the sensitivity to ozone in bean cultivars.
