Aqueous garlic extract stimulates growth and antioxidant enzymes activity of tomato (Solanum lycopersicum)

A glasshouse bioassay was conducted to assess the efficacy of aqueous garlic extract (AGE) as a biostimulator for the growth improvement of tomato seedlings. Application of AGE as foliar spray and/or fertigation, resulted in morphological and physiological stimulation of tomato seedlings. The plant height, leaf area, stem diameter, plant fresh/dry weight were significantly improved due to the applied treatments, however, higher concentrations applied as fertigation negatively influenced some parameters. The antioxidant enzymes superoxide dismutase (SOD) and peroxidase (POD) showed increased activity in response to variable concentrations of AGE. The highest concentration administered as fertigation resulted in increased malondialdehyde (MDA) content accumulation in the leaves indicating lipid peroxidation or possible oxidative stress in these seedlings and the effect was correlating to the hindered growth of the seedlings. Our findings provide basis for understanding the functional bioactivity of allicin containing AGE in the receiver plants' physiology. We therefore suggest AGE as a botanical for bio-priming and stimulation of an oxidative response in tomato which might be helpful in various stressful situations.