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

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.