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Have a Drink: Ethanol Helps Crop Plants Survive Drought and Heat

Alcohol slakes the thirst of plants threatened by climate change

Few things feel worse than waking up to a nasty hangover: alcohol suppresses the release of an important hormone that keeps you from being dehydrated, leading to fatigue and headaches.

However, as counterintuitive as it sounds, alcohol has the opposite effect on plants.

A recent study published in Plant & Cell Physiology shows that pre-treating soil with ethanol significantly enhances crop plants’ drought tolerance — without genetic modification. The stakes are high for climate resilience in food systems. Some of the most economically stressed regions in the world face famine and displacement due to climate-driven heat and drought trends: weather extremes drove food insecurity for some 16 million people in 2020. Even the U.S. is not immune: In Kansas, the recent winter wheat harvest fell by over 25% due to drought; the Colorado Water Conservation Board estimates that the state could lose up to 700,000 acres of irrigated agricultural land (20%) by 2030 without better water conservation measures.

Surviving Drought

Plants produce ethanol when deprived of water, so the team, led by Motoaki Seki of the RIKEN Center for Sustainable Resource Science in Japan, hypothesized that proactively giving ethanol to plants such as wheat or rice would protect them from drought. The team grew seedlings for about two weeks with ample water. Then they treated soil with an ethanol solution for three days, followed by water deprivation for two weeks.

50 mM ethanol treatment significantly enhanced the drought tolerance of wheat (Triticum aestivum, Chinese Spring). Data was recorded 30 days after plants were rewatered. Left: Water alone. Right: Ethanol priming. (Courtesy of Plant Genomic Network Research Team, RIKEN, Japan)

Ethanol priming changed the activity of hundreds of genes. The genes caused plants to accumulate drought-tolerant amino acids and sugars, which regulate photosynthesis. Plants also closed their stomata, or leaf pores, preventing evaporation from leaves and retaining more water than plants not treated with ethanol. About 75% of wheat and rice plants treated with ethanol survived the simulated drought, compared with under 5% for untreated plants. It did not take much ethanol to show positive effects; a dilution of about 0.3% (like pouring one teaspoon of ethanol into seven cups of water) was optimal for wheat.

The team then used Arabidopsis, a non-crop plant often used for research, to learn why ethanol had these effects. They found that plants treated with ethanol released ABA, a stress hormone that tells plants to close their stomata and activate drought-related genes.

More Questions

But surviving a drought is not the same as thriving in a drought, and the study did not explore grain yields. “The mechanism used to improve survival in this paper is clear: it’s a decrease in stomatal conductance,” says François Tardieu, the Research Director of the French National Institute for Agriculture, Food, and Environment. Tardieu notes that it takes entirely different mechanisms and genes to improve survival than it does to increase grain yield.

Another question for further research is how ethanol affects plants in outdoor light. The study applied 100 μmol of light to the plants; Tardieu likens this to driving at twilight when cars’ headlights are coming on. While 100 μmol is fine for growing seedlings, a wheat field needs about 2,000 μmol of light (equivalent to full sun) to be productive. Because the amount of light strongly determines transpiration rates, ethanol could impact plants differently in bright outdoor lighting. The light question is crucial, as there is a strong association between light and crop yields.

100 mM ethanol treatment significantly enhanced the drought tolerance of rice (Oryza sativa L., Nipponbare). Data were recorded 20 days after plants were rewatered. Left: Water alone. Right: Ethanol priming. (Courtesy of Plant Genomic Network Research Team, RIKEN, Japan)

Extensive research is needed to answer such questions and to determine whether ethanol confers benefits on grain yields. “This is a major challenge, not just ‘check,’” says Tardieu. “You need to test it in many fields, with different genotypes, at least three years of work with a good budget.” A budget for this type of study can be in the millions of Euros.