# Methyl jasmonate alleviates Cd-induced lipid peroxidation in spinach by enhancing photosynthesis and the antioxidant defence system

## TL;DR

Methyl jasmonate helps spinach resist cadmium toxicity by boosting photosynthesis and antioxidant defenses.

## Contribution

This study reveals how MeJA mitigates Cd stress in spinach through physiological and biochemical mechanisms.

## Key findings

- MeJA at 25 μmol/L increased spinach growth and reduced Cd content by 24.56%.
- MeJA improved photosynthesis by enhancing chlorophyll and carotenoid levels by up to 65.78%.
- MeJA reduced oxidative stress by boosting antioxidant enzyme activity and lowering MDA content.

## Abstract

Cadmium (Cd) is a potentially harmful element that adversely affects plant growth, physiology and biochemical metabolism. In the present study, we used hydroponics with foliar spraying with the hormone MeJA to explore the mitigating effects and possible mechanisms of methyl jasmonate (MeJA) on Cd toxicity in spinach. The effects of different concentrations of MeJA (1, 5, 25 and 100 μmol/L) on growth parameters, photosynthetic characteristics, physiological functions and Cd uptake and partitioning in spinach under Cd stress (50 µmol/L) were analysed. Compared with Cd treatment, exogenous supplementation with 25 μmol/L MeJA significantly increased spinach plant height by 58.30%, root length by 58.20%, stem thickness by 58.25% and aboveground biomass by 64.94%, while reducing the Cd content of the whole spinach plant by 24.56%. Exogenous application of MeJA increased photosynthesis by increasing the net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular CO2 concentration (Ci), and transpiration rate (Tr), which decreased the stomatal limiting value (Ls) of spinach, resulting in a 15.72–65.78% increase in the chlorophyll content and a 20.98–60.23% increase in the carotenoids content. Moreover, MeJA mitigated reactive oxygen species (ROS) production by increasing peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT) activity in response to oxidative stress, which in turn reduced the malondialdehyde (MDA) content, proline content and soluble protein content in Cd-stressed spinach plants, thereby improving the stress tolerance of spinach seedlings. Therefore, the results of the present study contribute to the understanding of the mechanism by which MeJA alleviates Cd toxicity in spinach.