# Sulfates Increase the Antioxidant Activity of Cowpea Subjected to Saline Stress

## TL;DR

Adding sulfates helps cowpea plants grow better under salty water stress by boosting antioxidants and reducing damage.

## Contribution

This study shows that calcium and potassium sulfates reduce salt stress in cowpea plants more effectively than other sulfate types.

## Key findings

- Calcium and potassium sulfates improved growth and antioxidant enzyme activity in cowpea under saline conditions.
- Ammonium sulfate worsened salt stress by increasing electrolyte leakage and lipid peroxidation.
- Potassium sulfate reduced the harmful Na+/K+ ratio in cowpea leaves.

## Abstract

Water scarcity for
irrigation presents significant challenges to
agriculture. The use of saline water from deep wells can induce salt
stress in crops, negatively impacting their growth and productivity.
Nutritional management using sulfates has emerged as a promising strategy
to mitigate the adverse effects of salinity. Therefore, this study
aimed to evaluate the effect of sulfate application as a salt stress
attenuator in cowpea plants (cv. BRS Tumucumaque). The experiment
was conducted in a greenhouse using a randomized block design in a
2 × 4 factorial arrangement, consisting of two irrigation water
electrical conductivity levels (ECw = 0.6 and 4.5 dS m–1) and four sulfate treatments: no sulfate (control), calcium sulfate,
potassium sulfate, and ammonium sulfate. Irrigation with water at
4.5 dS m–1 reduced the cowpea growth and yield.
However, it also stimulated pigment synthesis and the enzymatic activities
of catalase (CAT) and ascorbate peroxidase (APX), particularly when
combined with calcium and potassium sulfate, respectively. In contrast,
ammonium sulfate intensified salt stress, increasing electrolyte leakage
and lipid peroxidation in cowpea plants. Leaf Na+ concentrations
remained stable, while calcium and potassium sulfate increased Mg2+ and K+ levels, respectively. The Na+/K+ ratio was lower with the potassium sulfate application.
Overall, the application of calcium and potassium sulfates enhanced
cowpea performance by alleviating the detrimental effects of salinity
on growth, pigment production, yield, and antioxidant enzyme activity.