# Foliar Application of Bamboo-Derived Nano-Biochar Enhances Morphological and Biochemical Responses of Lettuce (Lactuca sativa L.) Under Salt Stress

## TL;DR

Applying nano-biochar made from bamboo to lettuce plants helps them grow better and resist salt stress by improving their chemical and physical properties.

## Contribution

This study introduces bamboo-derived nano-biochar as a novel foliar biostimulant for mitigating salt stress in lettuce.

## Key findings

- Foliar application of 3.0% nano-biochar reduced sodium accumulation and improved potassium, calcium, and magnesium uptake in lettuce.
- Nano-biochar enhanced photosynthetic pigments, antioxidant enzyme activities, and reduced oxidative damage under salt stress.
- The 3.0% nano-biochar concentration showed the best overall improvements in growth and stress response in lettuce.

## Abstract

Nano-biochar (n-BC) is an emerging eco-friendly material with potential to improve crop performance under salt stress. This study aimed to evaluate the effects of foliar applications of bamboo-derived n-BC on the morphological and biochemical responses of lettuce plants under salt stress (40 mM NaCl). n-BC solutions (1.0, 3.0, and 5.0% w/v) were foliar-applied every five days until harvest. Salt stress markedly increased hydrogen peroxide (H2O2) and malondialdehyde (MDA) by 264.54% and 14.02%, disrupted Na+/K+ homeostasis, and reduced biomass. Foliar n-BC mitigated these effects by reducing Na+ accumulation by 22.24–25.11% and enhancing K+, Ca2+, and Mg2+ uptake. The treatments also improved photosynthetic pigments and increased proline, soluble proteins, and soluble sugars. Oxidative damage was alleviated, as reflected by reductions in H2O2 and MDA together with enhanced ascorbate peroxidase, catalase, and superoxide dismutase activities. Total phenolics, flavonoids, and ABTS and DPPH scavenging activities also increased under n-BC application. Among all the concentrations, 3.0% (w/v) n-BC consistently produced the greatest improvements in growth, ionic balance, and antioxidant responses. These findings demonstrate that bamboo-derived n-BC is a promising foliar biostimulant for enhancing lettuce performance under saline conditions.