VANADIUM EFFECTS ON PHENOLIC CONTENT AND PHOTOSYNTHETIC PIGMENTS OF SUNFLOWER.

Vanadium (V) is the 21st most abundant element in the Earth's crust. If some doubt exists about the role of vanadium as a beneficial element, there is no doubt that at high levels it is dangerous to plants. In this study the effect of different concentration of V (0, 3.25, 7.5 and 15 mg L-1) was investigated hydroponically in a complete randomized design on sunflower plant. The results indicated that V at all applied concentrations significantly decreased the plant's growth, and total protein and carotenoid contents, but increased the total chlorophyll and soluble sugars contents. Also, the obvious induction in the phenylpropanoid pathway was seen in response to V application. The highest values for PAL (Phenylalanine Ammonia Lyase) activity, and lignin, tannins and flavonoids contents were observed at concentration of 15 mg L-1 of V. While, the anthocyanin content of plants showed significant increase at concentration of 7.5 mg L-1 of V. From this study it could be concluded that the applied concentrations of V were toxic for sunflower and the plant by employing the phenylpropanoid pathway efforts to overcome this stress. [ABSTRACT FROM AUTHOR]