Context-dependent responses of tomato (Solanum lycopersicum) to a Chlamydomonas reinhardtii biostimulant extract under saline and non-saline conditions

Summary

This greenhouse study used factorial design and RNA-sequencing to dissect how a Chlamydomonas reinhardtii microalgal extract interacts with salt stress in tomato. The biostimulant increased leaf area by 16% and improved hydration across both saline and non-saline conditions, but transcriptomic analysis revealed fundamentally different molecular mechanisms: under salinity, it suppressed stress-response genes to reduce energy costs of defence, whilst in non-saline conditions it triggered a 'priming' effect that upregulated temperature-response genes whilst conserving resources. The findings suggest that biostimulant efficacy is context-dependent and that tailoring application to stress conditions may enhance crop resilience.

Regional applicability

The study was conducted in a controlled greenhouse setting using standard salinity treatments (75 mM NaCl) and does not specify UK or regional growing conditions. The findings are potentially transferable to UK protected horticulture and glasshouse tomato production, particularly where salinity stress (from irrigation water or soil) is a concern; however, applicability to field conditions and regional soil types would require validation in UK-specific environments.

Key measures

Leaf area, leaf dry matter content, leaf hydration status, leaf ion content, transcriptomic profiles (RNA-seq), gene expression changes under Salt × Biostimulant interaction

Outcomes reported

The study measured vegetative growth (leaf area, dry matter content), leaf ion composition, and leaf transcriptomic profiles in tomato plants treated with Chlamydomonas reinhardtii extract under saline (75 mM NaCl) and non-saline conditions. Factorial analysis identified 138 genes with significant Salt × Biostimulant interaction, revealing context-dependent molecular mechanisms.

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