Relationships between ozone absorption and leaf injury

Especially, on the relationships between differences in ozone susceptibility accompanying leaf age and ozone absorption rate

Abstract

Relationships between ozone absorption rate and degree of leaf in jury were investigated for attached leaves of tobacco, rice and corn plants.
The results obtained were as follows:
1) As for the decrease in apparent photosynthetic rate, Bel-W3 of two varieties of tobacco used for the experiment was extremely damaged by ozone, but the variety Hicks was less susceptible to ozone. Younger expanding leaves were very torelant to ozone, whereas middle or lower leaves were sensitive.
2) Ozone absorption rate of tobacco leaves calculated by the gas diffusion model was correlated linearly with that observed by assimilation chamber method. This correlation was not affected by the differences of varieties or leaf age.
3) The differences in ozone susceptibility between leaf ages were in no relation with leaf gas diffusion resistances. Threfore, it was concluded that it was not caused by ozone absorption rate of each leaf.
4) The degree of somatal closure during ozone fumigation was differed between species, varieties and leaf ages. The stomata of younger expanding leaves were more sensitive to ozone than that of the older leaves.
5) It was thought that the differnce in ozone susceptibility between two varieties of tobacco plants was considerably caused by the difference in gas diffusion resistance.