Effects of enhanced UV-B radiation on Mentha spicata essential oils

In vitro propagated plantlets representing two distinct chemotypes of Menth a spicata, viz, plants producing essential oils rich in piperitone oxide an d piperitenone oxide (chemotype I) and rich in carvone and dihydrocarvone ( chemotype II), were grown in the field under ambient or ambient plus supple mental UV-B radiation, biologically equivalent to a 15% ozone depletion ove r Patras (38.3 degrees N, 29.1 degrees E), Greece. Enhanced UV-B radiation stimulated essential oil production in chemotype II substantially, while a similar, non-significant trend was observed in chemotype I. No effect was f ound on the qualitative composition of the essential oils, whereas the quan titative composition was slightly modified in chemotype I. This is the firs t investigation reporting an improved essential oil content under UV-B supp lementation in aromatic plants under field conditions. (C) 1998 Elsevier Sc ience Ltd. All rights reserved.