Effects of Various Concentrations of Trichoderma harzianum Fungus on the Phytochemical and Antioxidative Properties of Cauliflower (Brassica oleracea.Convar.botrytis L.) in the Soils Contaminated with Lead

Background & Objective: Today, the growing rate of soil contamination is a major environmental concern. The cohabitation between microorganisms and plants hasbeen in place for millions of years, and investigationsin this regardhave become an important research area. Materials and Methods: The preset study aimed to assessthe effects of variousconcentrations of lead (0, 50, and 100 mg/l) and Trichodermaharzianumfungus (5%, 10% and 15%) on cauliflowerin a factorial design using fully randomized blocks in three replications under the climatic conditions of Dehlamavillage in Shahroud, Iran.The research was conducted during2014-2015 to measure the levels of chlorophyll a, chlorophyll b, totalchlorophyll, carotenoid, phenols, and flavonoids, as well as the antioxidant properties of cauliflower. Results: The results indicated that the highestlevels of chlorophyll a (75.723 mg/wet weight), chlorophyll b (27.378 mg/wet weight), and total chlorophyll (109.074 mg/wet weight) were associated with the interactive effects of the treatment with 5% Trichoderma and lead concentration of 0 mg/l. Furthermore, thehighest level of antioxidant properties (79.88% of free radicals) was associated with the interactive effects of lead at the concentration of 50 mg/l and treatment with 5% Trichoderma. The highest level of phenols (21.33 mg of Gaelic acid/dry weight) was associated with the interactive effects of the lead concentration of 100 mg/l and treatment with 5% Trichoderma and flavonoids(22.889 mg of quercetin/g/dry weight), as well as the interactive effects of the lead concentration of 50 mg/l and treatment with 5% Trichoderma. Conclusion: Since carotenoids are antioxidants and precursors of vitamin A, the desired levels of antioxidants were achieved with the parallel effect of other antioxidants, such as total phenols and flavonoids.