The Effects of Fulvic Acid on Physiological and Anatomical Characteristics of Bread Wheat (Triticum aestivum L.) cv. Flamura 85 Exposed to Chromium Stress

In this study, the effects of fulvic acid (FA) were investigated on the concentrations of photosynthetic pigments, malondialdehyde (MDA) and root and stem anatomy in Triticum aestivum L. under chromium stress. Plants were grown under-controlled growth chamber conditions and then exposed to 0.10, 0.20, 0.30 or 0.50 mM chromium solution (Cr6+) and 1.5 mg/L of FA solution alone or in combination with the Cr stress for 21 days. Results indicate that the chlorophyll a, chlorophyll b, total chlorophyll and carotenoid contents were lower in the chromium-treated group than in the FA + Cr treated group, depending on the amount of chromium stress applied. The decrease levels in the ratio of the photosynthetic pigments in Cr treated groups were as follows (%): Chlorophyll a 55, chlorophyll b 72.83, total chlorophyll 44.65, total carotenoid 45.09. These levels in FA + Cr treated groups were as follows, respectively: 28.82, 53.70, 31.21 and 31.35. On the other hand, the chlorophyll a/b ratio and MDA contents were higher in the chromium-treated group in comparison to the FA + Cr treated group. The increase levels in Cr treated groups in the ratio of the chlorophyll a/b and MDA contents were as follows (%): Chlorophyll a/b 40.17, MDA 45.95. The ameliorating effect of FA was determined as 5.40% in MDA and 4.78% in chlorophyll a/b ratio. The cross-sections of plant roots exposed to Cr stress presented some anatomical changes. The stem of Cr-treated plants showed an increase in the thickness of sclerenchyma, phloem and xylem and the diameter of parenchyma cells. Significant reduction in the diameter of vessel elements in the stem were observed as a result of Cr exposure. In conclusion, FA could play an important role in reducing chromium stress in wheat plants.