Effect of Foliar Application of Hydrogen Peroxide Macroconcentrations on Growth Parameters, Phenolic Compounds and Antioxidant Capacity in the Leaves and Seeds of Amaranthus hypochondriacus L.

Amaranth has many interesting features, both nutritional and otherwise, that make it attractive as a food crop. Plants grown in greenhouses have higher yields but lower nutritional value compared to those grown in open fields. This prompted an interest in studying viable elicitors for the production of amaranth. Small hydrogen peroxide (H2O2) concentrations for foliar spraying from 0 to 18 mM have been used in greenhouse amaranth cultivation. The objective of this work was to evaluate the effect of foliar application of H2O2 megadoses on growth parameters, total phenolic compounds, condensed tannins, anthocyanins, and the antioxidant capacity of leaves and seeds of amaranth grown in a greenhouse setting. The seed of the Amaranthus hypochondriacus L. species was used. The concentrations of H2O2 analyzed were 0, 125, 250 and 400 mM, with 11 applications throughout the growing cycle. The variable data were subjected to an analysis of variance (ANOVA), followed by a Tukey's post hoc test (95% CI, p < 0.05). The results on chlorophyll, growth parameters and proximal chemical analysis showed no statistical difference between the control group versus the treatment groups. A greater number of favorable changes in the different variables studied were observed with the 125 mM H2O2 treatment, including the increase in antioxidant capacity measured by FRAP. The seed showed a considerable increase in TFC with all treatments and responded better to the 250 mM H2O2 treatment in the case of DPPH (an increase of 30%) and TPC (an increase of 44%). A 28% increase in anthocyanin content was observed with the treatment of 400 mM H2O2. The use of H2O2 may be an appropriate strategy to enhance the production of antioxidant compounds in amaranth without affecting growth or its basic proximal chemical composition. More studies are required in this regard.