Involvement of oxyradicals in promotion/inhibition of expansion growth in cucumber cotyledons.

ABSTRACT

Cytokinin-induced expansion growth of cucumber cotyledons and its interaction with UV-B (280-320 nm) was studied with reference to oxyradicals. UV-B radiation enhanced the level of oxyradicals in the cotyledons measured by EPR spectroscopy. Cytokinin promoted expansion growth was inhibited by UV-B radiation. Cytokinins reduced the level of oxyradicals in dark grown cotyledons, while promoting growth. Overproduction of oxyradicals by UV-B could not be fully accounted for the inhibition of growth of cotyledons, since quenching of radicals by cytokinins did not fully restore inhibition of growth.