Micronutrient Fertilization Amplified the Antioxidant Capacity in Tomato Plants with Improved Growth and Yield

Micronutrients play a critical role in plant growth and development, and their deficiency can cause adverse effects on plant performance. Also, these elements can influence plant physiological processes as they incorporate in the molecular structure of enzymes as cofactors. In this study, the impacts of micronutrients solution containing manganese (125 ppm), iron (200 ppm), zinc (60 ppm), and copper (20 ppm) were investigated on growth parameters, yield, and antioxidant enzymes activity of tomato (Solanum lycopersicum) plants. Greenhouse tomatoes (cultivar Jet Star F1) were irrigated with the mentioned concentrations of elements in a completely randomized design with five independent biological replicates. The micronutrient treatment increased the specific activities of superoxide dismutase, ascorbate peroxidase, glutathione reductase, guaiacol peroxidase, catalase, phenylalanine ammonia-lyase, as well as phenols and salicylic acid contents in tomato leaves. However, malondialdehyde level and electrolyte leakage index were unaffected. Analysis of plant growth parameters revealed that micronutrients increased the stem diameter, root length, the number of leaves, stem height, and fruit’s fresh weight in the treated plants. Overall, our results indicated that micronutrients positively affected the growth and development of tomato plants without adverse effects on the health indices. Moreover, the application of micronutrients can magnify the antioxidant capacity of tomato plants through increasing enzymes activity as well as phenols and salicylic acid levels. These changes would benefit the plants under abiotic/biotic stress conditions where elevated levels of antioxidant activities are crucial.