Action of ultraviolet-C on stilbene formation in callus ofArachis hypogaea.

The action of light on the formation of stilbenes and the induction of stilbene synthase in dark-grown and light-grown callus of peanut (Arachis hypogaea) was investigated over the wavelength range from 250 to 400 nm. Ultraviolet light of 260-270 nm had a significant and selective effect on the formation of resveratrol and isopentenylresveratrol. The callus responded by the production of stilbene synthase, with maximal activity appearing 4 h after irradiation with a fluence rate of 1 W m(-2) (270 nm) applied for 10 min. At lower fluence rates, maximal responses in enzyme activity were shifted to longer induction periods. The efficiency of the biosynthetic pathway, and the form and maxima of enzyme profiles depended on the duration of exposure. We failed to demonstrate any significant influence of red light at low energy irradiation (672 nm, 726 nm and 753 nm).