# Augmenting pH Confers to Citrus grandis the Ability to Combat Oxidative Stress Triggered by Manganese Excess

## TL;DR

Raising soil pH helps citrus plants combat oxidative stress caused by excess manganese by improving their detoxification systems.

## Contribution

New evidence on how pH augmentation improves ROS and methylglyoxal detoxification in citrus under Mn excess.

## Key findings

- Increased pH reduced ROS and methylglyoxal accumulation in citrus roots and leaves under Mn excess.
- Higher pH enhanced the coordinated detoxification of ROS and methylglyoxal in citrus tissues.
- The study supports pH adjustment as a strategy to mitigate Mn toxicity in citrus.

## Abstract

Citrus trees are mainly cultivated in acidic soils. Excessive manganese (Mn) is the second most limiting factor for crop productivity in acidic soils after aluminum toxicity. The roles of reactive oxygen species (ROS) and methylglyoxal (MG) detoxification systems in augmented pH-mediated amelioration of excessive Mn are poorly understood. ‘Sour pummelo’ (Citrus grandis (L.) Osbeck) seedlings were exposed to nutrient solution at a Mn concentration of 500 (Mn500) or 2 (Mn2) μM and a pH of 3 (P3) or 5 (P5). The increase in pH attenuated Mn500-induced increases in ROS production and MG and malondialdehyde accumulation in roots and leaves. Additionally, the increase in pH enhanced the coordinated detoxification capability of both ROS and methylglyoxal scavenging systems in these tissues under Mn500. These findings corroborated the hypothesis that augmenting pH enhances the capability of these tissues to detoxify ROS and methylglyoxal under Mn excess. Therefore, this study provided new evidence on the roles of ROS and MG detoxification systems in the augmented pH-mediated amelioration of oxidative damage in ‘Sour pummelo’ leaves and roots caused by Mn excess, as well as a basis for correcting Mn toxicity by augmenting soil pH.