# Carbon dots alleviate salinity stress and promote growth in tomato (Solanum lycopersicum)

## TL;DR

Carbon dots help tomato plants tolerate salt stress by improving growth and physiological parameters.

## Contribution

Carbon dots are shown to mitigate salt stress in tomato plants through multiple physiological and molecular mechanisms.

## Key findings

- Carbon dots increased dry weight, chlorophyll content, and relative water content in salt-stressed tomato plants.
- Carbon dots improved PSII fluorescence indices and restored K+/Na+ balance in salt-stressed plants.
- Salt-responsive genes were less induced in CD-treated plants, indicating reduced stress impact.

## Abstract

Soil salinity represents an environmental stress that substantially lowers plant performance, thereby reducing crop yield and threatening food security in many arid environments.

Here, we describe the response of tomato (Solanum lycopersicum) to high levels of NaCl, and we test the potential of carbon dots (CDs) to alleviate salt stress. Hydrothermally synthesized CDs were characterized by electron microscopy and Fourier transform infrared (FTIR) spectroscopy to identify chemical groups such as hydroxyl, carboxyl, and amine groups. Zeta potential analysis revealed a negative surface charge.

While salt stress compromised various physiological parameters in tomato plants, CD treatment of salt-stressed plants enhanced salt tolerance as indicated by increased dry weight, chlorophyll content and relative water content. CDs also decreased energy dissipation and increased PSII fluorescence indices such as the quantum yield of electron transport, and the performance index in salt-stressed plants. Furthermore, CDs enhanced the content of soluble carbohydrates and contributed to restore the K+/Na+ balance in plants under salt stress. Salt-responsive genes (SOS1, SOS2, SOS3, NHX4, and NHX2) were induced to a lesser extent when salt-stressed plants were treated with CDs, consistent with the observation that CDs protected plants against salt stress.

Taken together, these findings show that CDs can mitigate salt stress in tomato.