Unathi Dladla

University of Cape Town, South Africa

Abstract Title:

Investigating the foliar application of ecklonia maxima-derived biostimulant on tomato plants in ameliorating the effects of heat shock stress

Research Interests:

Heat shock severely impairs plant growth, viability, and productivity by disrupting cellular structures and inducing excessive production of reactive oxygen species (ROS), resulting in oxidative stress and metabolic imbalance. Solanum lycopersicum (tomato), an economically important horticultural crop, is highly susceptible to elevated temperatures. In response to increasing climate variability, sustainable strategies such as seaweed-derived biostimulants are gaining attention for their ability to enhance crop resilience. This study investigated the effect of prior foliar application of an Ecklonia maxima–derived biostimulant (AfrikelpTM) on tomato plants in mitigating heat-shock stress by examining physiological, biochemical, metabolomic, and proteomic responses. Physiological assessments included measuring chlorophyll content, chlorophyll fluorescence, and electrolyte leakage, while biochemical analyses examined ferric reducing antioxidant power (FRAP), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, lipid peroxidation, and proline accumulation. Gas chromatography–mass spectrometry (GC–MS) was employed to profile metabolites and identify pathways associated with stress tolerance. This was complemented with proteomic analysis to identify biological processes associated with stress adaptation. Biostimulant-treated plants exposed to heat shock exhibited significantly improved chlorophyll content and reduced electrolyte leakage, indicating enhanced membrane stability and photosynthetic performance. Treated plants also showed reduced lipid peroxidation and enhanced antioxidant activity, suggesting improved ROS scavenging capacity. Metabolomic analysis revealed increased accumulation of stress-associated metabolites, including amino acids (phenylalanine, isoleucine, threonine), sugars (myo-inositol, xylose), and organic acids (citric, malic, and succinic acids), which are associated with osmoprotection, metabolic regulation, and stress adaptation. Proteomic and gene ontology analyses demonstrated significant upregulation of pathways related to lignin metabolism, cell wall biogenesis, cellulose metabolism, and antioxidant defense, indicating structural reinforcement and enhanced stress tolerance. Overall, the findings demonstrate that priming tomato plants with Ecklonia maxima–derived biostimulant improved heat stress resilience through coordinated physiological, metabolic, and proteomic reprogramming, highlighting their potential as a sustainable strategy for climate-resilient agriculture.