Determination of Microgram Quantities of Stevioside from Leaves of Stevia rebaudiana Bert. by Two-Dimensional Thin Layer Chromatography

A method is described for the determination of stevioside fromleaves of Stevia rebaudiana Bert. Separation upon non-activatedsilica gel impregnated with boric acid in a two-dimensionalchromatographic system followed by clution and colorimetricassay is reported. Recuperation from chromoplates is over 95%.The observed ratio of the optical density of glucose: steviosidematches that expected theoretically so that glucose may be employedas a standard where pure stevioside is not available. Effects of the plant growth retardant, ancymidol, on the growthand morphology of the shoot system of cucumber (Cucumis sativusL. ) were investigated. Ancymidol inhibited stem elongation,reducing both number and length of internodes. Reduction inleaf area, attributable to a reduction in both cell size andnumber, was accompanied by an increase in chlorophyll per unitarea. The retardant decreased apical dominance and delayed anthesis.Gibberellic acid fully reversed ancymidol-induced inhibitionof stem elongation, internode length and production, and leafexpansion. GA_4/7 and ancymidol gave a synergistic promotionof stem elongation by increasing elongation of younger internodesand increasing internode production. Synergistic promotion ofpetiole elongation by this combination was also observed. Ancymidol,applied 7 d previously either to the shoot or root, severelyreduced the level of gibberellin-like activity in bleeding sapcollected from decapitated plants.