Photosynthetic Pigments of Tomato Plants under Conditions of Biotic Stress and Effects of Furostanol Glycosides

The adaptogenic effect of furostanol glycosides (FG) on biosynthesis of photosynthetic pigments in tomato plants (Lycopersicon esculentum Mill.) was studied under conditions of biotic stress caused by root-knot nematode (Meloidogyne incognita Kofoid et White). Treatment of plants with 5 × 10–4 M FG was accompanied by an increase in the rate of biosynthesis of pigments (particularly, chlorophyll b and carotenoids), which was observed against the background of a decrease in the relative contribution of β-carotene and an increase in the relative contribution of pigments of the violaxanthin cycle (VXC) to the overall pool of carotenoids. It was suggested that FG stimulated phytoimmunity by shifting metabolism of carotenoids toward enhanced biosynthesis of VXC pigments. These pigments play a protective role and facilitate stabilization of the photosynthetic apparatus, which is particularly important under stress conditions.