Increased drought tolerance in maize plants induced by H2O2 is closely related to an enhanced enzymatic antioxidant system and higher soluble protein and organic solutes contents

Drought stress is one of the most important agricultural problems limiting development and growth in plants. Therefore, mechanisms to alleviate drought stress have been one of the major limiting factors in production. H 2 O 2 pretreatment has emerged as a method to induce stress acclimation in plants. In this study, the effects of H 2 O 2 leaf pretreatment on plant growth, antioxidative enzymes, soluble protein, and organic solute content in maize plants under conditions of drought stress were analyzed. Results demonstrated that drought stress reduced shoot and root mass compared with the control, and H 2 O 2 leaf spraying significantly improved the growth of drought-stressed plants. In general, in drought-stressed plants, CAT, APX, GPX, and SOD activities in roots and leaves were increased by H 2 O 2 leaf spraying relative to water spraying. GPX was the main H 2 O 2 -scavenging enzyme in leaves and roots, and CAT activity was not detected in the leaves of maize plants. Increased organic solute contents (proteins, carbohydrates, soluble proline, and amino acids) were found in the leaves and mainly in the roots of H 2 O 2 -stressed plants relative to water-stressed plants. In conclusion, it was found that H 2 O 2 leaf spraying pretreatment reduced the deleterious effects of drought stress on maize plant growth. This treatment proved to be a beneficial health strategy in plants. This effect could be attributed to the ability of H 2 O 2 to induce antioxidant defense system activity, particularly GPX, and to increase organic solute (protein, carbohydrate, proline, and free amino acid) content in roots and leaves.