Differences in morpho-anatomical structure of ozone-sensitive and ozone-resistant tobacco cultivars.

Tropospheric ozone causes visible injuries in selected plants. Some plant species have been recognized as resistant and sensitive to ozone. Differences in the response to ozone of two kinds of plants are interesting because of practical implications. Resistant cultivars (without visible symptoms) will be more valuable for agriculture, forestry and horticulture. It is, however, necessary to find out the reason of the occurrence of the visible symptoms. The presented studies focused on selected morphological and anatomical differences between well-known ozone-sensitive (Bel W3) and -resistant (Bel B) cultivars of tobacco plants. Daily growth of the sensitive cultivar was higher than that of the resistant one. This tendency was also valid for the leaf growth which might have been the response of the sensitive cultivar to decreased photosynthetic leaf area (necrosis) caused by ozone. Morphological investigations revealed thinner upper epidermal cells in the sensitive cultivar. Moreover, a decrease of spongy mesophyll cell layers was observed. The obtained results suggest that it is the anatomical structure that may be partly responsible for ozone resistance - wider epidermal cells, more spongy mesophyll cell layers.