Low concentrations of ethanol can alter plant responses to drought and heat. In tomato, a 2024 study demonstrated heat-protection effects in the experimental cultivar Micro-Tom, and a 2025 study tested ethanol sprays in a PHYTOCHROME A-deficient (phyA) mutant under severe heat.
The evidence is now stronger than a single experiment, but it is still conditional. These studies do not establish ethanol spraying as a universally validated field treatment for commercial tomato cultivars.
2024: 20 mM ethanol pretreatment in Micro-Tom
In the 2024 Frontiers in Plant Science study, 16-day-old Micro-Tom seedlings were pretreated with 20 mM ethanol for three or six days before a 50°C, four-hour heat treatment. Twenty millimolar ethanol is roughly around 0.1% ethanol by volume.
Ethanol-pretreated seedlings retained more green leaf area after heat stress. In a fruit-development experiment, seedlings received a three-day ethanol pretreatment followed by 50°C for 2.5 hours and were then grown to fruiting. Ethanol-treated plants produced more fruits per plant, while fresh weight per fruit did not differ from the water-treated controls.
The result is therefore better interpreted as partial protection of reproductive development from heat damage, rather than simply “ethanol makes each tomato larger.”
Gene expression and metabolites also changed
RNA sequencing identified changes in defense, water-deprivation and reactive-oxygen-related pathways, including induction of several stress-associated genes. Metabolomics found increases in sugars such as sucrose, glucose and fructose in some tissues and treatment comparisons.
The mechanism is unlikely to be one simple switch. Stomatal behavior, sugar metabolism, stress-response networks, ROS management and the physicochemical state of cells may all contribute.
2025: spraying a phyA mutant under severe heat
The 2025 Scientific Reports study focused on a tomato phyA mutant in the Moneymaker background. This genotype lacks PHYTOCHROME A and has unusual heat-response characteristics: its vegetative heat tolerance does not fully persist through reproductive development.
Researchers applied ethanol or the plant growth regulator 4-CPA under a controlled 37°C treatment and a summer greenhouse that reached roughly 50°C during the day and 30°C at night. Ethanol-treated phyA plants showed better growth, and fruits had increased soluble-solids content and vitamin C. Heat-shock, ROS-scavenging, auxin and gibberellin-related responses also changed.
This is an important follow-up, but the genotype matters. It does not yet prove that the same spray program will improve fruit quality in every commercial cultivar.
A promising chemical-priming idea, not yet a universal farm recipe
Practical use would require cultivar-specific optimization of concentration, volume, timing and frequency, plus field-scale measurements of yield, fruit quality, cost and environmental conditions. Higher ethanol concentrations can damage plants, so the experimental results are not an invitation to improvise concentrated alcohol sprays.
Regulatory treatment of products marketed for crop protection or growth effects also varies by jurisdiction. A familiar chemical is not automatically an approved agricultural input for every claimed purpose.
As of 2026, the most defensible conclusion is that ethanol is a promising chemical-priming candidate with repeated tomato evidence, but broad field validation is still needed before it becomes a general heat-management practice.
For related context, see Can Ethanol Prime Crops Against Heat? The Evidence Is Promising, but There Is No Universal Spray Recipe.
For related context, see What Could Climate Change Do to European Hops by 2050? Re-reading the Yield and Alpha-Acid Projections.
For related context, see Barley NAC Genes Through a Pan-Genome Lens: 127–149 Genes Across 20 Genomes.
References
- Todaka D et al. Application of ethanol alleviates heat damage to leaf growth and yield in tomato. Frontiers in Plant Science. 2024;15:1325365. https://doi.org/10.3389/fpls.2024.1325365
- Ahmed RAH et al. Application of 4-CPA or ethanol enhances plant growth and fruit quality of phyA mutant under heat stress. Scientific Reports. 2025. https://doi.org/10.1038/s41598-025-17929-8
- RIKEN press releases: https://www.riken.jp/press/2024/202402191/index.html and https://www.riken.jp/press/2025/202509161/index.html
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