Effects of low concentrations of ozone on the fine structure of radish leaves

Abstract

Radish (Raphanus sativus L.) plants were fumigated with 0.1 or 0.05 μl l−l O3 for 8 or 24 h a day for 6 to 18 d and the leaf tissues examined by light and electron microscopy. Ultrastructural damage was apparent in the leaves fumigated with as low as 0.05 μl l−1 for 8 h a day for 6 d. Ozone induced an increase in both the number and size of the plastoglobules but a decrease in chloroplast dimensions. These changes in the chloroplasts developed further even after O3 fumigation had been discontinued. The plastoglobules were electron dense in the early stages of exposure to O3 but subsequently became electron translucent. Finally large plastoglobules were extruded into the vacuole, a phenomenon which may partly account for the reduction in chloroplast size. Ozone also caused disruption of the tonoplast and this was followed by collapse of the cells. Low concentrations of O3 appear to accelerate senescence of the chloroplasts. Copyright © 1989, Wiley Blackwell. All rights reserved