# Tolerance and Antioxidant Activity of Watermelon Cultivars Pre-Treated with Stress Attenuators and Subjected to Water Deficit

## TL;DR

This study examines how stress attenuators affect watermelon cultivars under water deficit, focusing on their tolerance and antioxidant activity.

## Contribution

The study identifies cultivar-specific responses to stress attenuators and water deficit, revealing novel mechanisms of tolerance and antioxidant enhancement.

## Key findings

- Crimson Sweet showed reduced oxidative stress and enhanced tolerance with GA and H2O2 treatments.
- Fairfax exhibited greater tolerance through osmotic adjustment enhanced by attenuators.
- Water deficit significantly impaired germination and seedling vigor in sensitive cultivars.

## Abstract

This study aimed to evaluate the effect of stress attenuators on the tolerance and antioxidant activity of watermelon cultivars under water deficit. The experiment was conducted in two stages, Stage I corresponding to water deficit levels (N1 = 0; N2 = −0.1; N3 = −0.2 MPa) and six watermelon cultivars. Stage II comprises two cultivars selected in Stage I (one sensitive and one tolerant) and the combination of water restriction with attenuators (T1 = 0.0 MPa (control), T2 = −0.2 MPa (water deficit), T3 = −0.2 MPa + hydropriming, T4 = −0.2 MPa + gibberellic acid, T5 = −0.2 MPa + salicylic acid, and T6 = −0.2 MPa + hydrogen peroxide). The concentration and exposure times of the attenuators were determined through preliminary tests. In Stage I, physiological and biochemical analyses were performed. In Stage II, in addition to these tests, hydrogen peroxide content, malondialdehyde levels, and the activity of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) were assessed. Water deficit impaired germination and seedling vigor of watermelon, with Crimson Sweet, Omaru, Charleston Gray, and Congo being the most sensitive cultivars, while Fairfax was the most tolerant. For Crimson Sweet, pre-germination treatments reduced oxidative stress and enhanced tolerance by stimulating antioxidant enzyme activity, with GA and H2O2 providing the most effective results. For Fairfax, greater tolerance was associated with osmotic adjustment through the accumulation of compatible solutes, a mechanism further enhanced by the use of attenuators.