S. Pasqualini et al., Responses of the xanthophyll cycle pool and ascorbate-glutathione cycle toozone stress in two tobacco cultivars, FREE RAD RE, 31, 1999, pp. S67-S73
Plants of Nicotiana tabacum (O-3-tolerant cv Bel-B and O-3-sensitive cv Bel
-W3) were exposed to 150 ppb of ozone for 5 h; the fumigation produced visu
al injury in mature leaves, particularly in Bel-W3. After O-3-treatment the
pigments of the xanthophyll cycle pool decreased in both cvs, with a stron
g reduction in violaxanthin content, while antheraxanthin and zeaxanthin in
creased slightly. Under these conditions the content of leaf abscisic acid
(ABA) markedly increased, particularly in Os-sensitive cv, indicating that
the violaxanthin may have been partially converted into ABA. The control pl
ants of Bel-B showed an ascorbic acid content four times greater than Bel-W
3 and the ozone treatment did not produce significant differences in the as
corbic acid content and in the redox state. The two tobacco cvs were found
to have similar total glutathione content, however the redox state was lowe
r in O-3-sensitive cv and decreased after ozone exposure. Ozone fumigation
caused an increase in oxidized glutathione, particularly in Bel-W3, associa
ted with a reduced glutathione reductase (GR) activity and a reduced GR pro
tein content.