Abstract
Ultraviolet B (UV-B) radiation has pleiotropic effects on plant development. There exists two types of trichomes, globular-head ones and sharp-head ones on the surface of cucumber cotyledon. Toluidine blue O stains only sharp-head trichomes. To clarify the effect of UV-B irradiation on the accumulation of polyphenolic compounds in the sharp-head trichomes, we conducted toluidine blue O staining and detection of auto-fluorescence. In connection with the cell division at the basal part of sharp-head trichomes by UV-B irradiation, the area stained by toluidine blue O expanded. In addition, toluidine blue O stained epidermal cell walls round the sharp-head trichomes. The place auto-fluorescence was detected was coincided well with the area stained by toluidine blue O. Also, UV-B irradiation increased lignin content in cucumber cotyledons. Thus, it is possible that UV-B irradiation induces polyphenolic compounds especially stress lignins in and round the sharp-head trichomes on the surface of cucumber cotyledons.
