# Nitric Oxide Mitigates the Deleterious Effects Caused by Infection of Pseudomonas syringae pv. syringae and Modulates the Carbon Assimilation Process in Sweet Cherry under Water Stress

## TL;DR

Nitric oxide helps sweet cherry plants resist a bacterial infection and manage water stress by improving their defense mechanisms and carbon assimilation.

## Contribution

This study demonstrates that nitric oxide mitigates Pss infection and modulates carbon assimilation in sweet cherry under water stress.

## Key findings

- Exogenous nitric oxide reduces susceptibility to Pseudomonas syringae pv. syringae in sweet cherry plants.
- Nitric oxide improves leaf membrane stability and proline content in water-stressed plants.
- Nitric oxide increases stomatal conductance and CO2 assimilation in well-watered plants.

## Abstract

Bacterial canker is an important disease of sweet cherry plants mainly caused by Pseudomonas syringae pv. syringae (Pss). Water deficit profoundly impairs the yield of this crop. Nitric oxide (NO) is a molecule that plays an important role in the plant defense mechanisms. To evaluate the protection exerted by NO against Pss infection under normal or water-restricted conditions, sodium nitroprusside (SNP), a NO donor, was applied to sweet cherry plants cv. Lapins, before they were exposed to Pss infection under normal or water-restricted conditions throughout two seasons. Well-watered plants treated with exogenous NO presented a lower susceptibility to Pss. A lower susceptibility to Pss was also induced in plants by water stress and this effect was increased when water stress was accompanied by exogenous NO. The lower susceptibility to Pss induced either by exogenous NO or water stress was accompanied by a decrease in the internal bacterial population. In well-watered plants, exogenous NO increased the stomatal conductance and the net CO2 assimilation. In water-stressed plants, NO induced an increase in the leaf membranes stability and proline content, but not an increase in the CO2 assimilation or the stomatal conductance.