Do soybean plants have a memory? Scientists think so

Plants don’t think like we do. But they might remember – in their own way. New research shows that soybean plants can pass along stress responses to their offspring.

This means if a plant survives attacks from insects or extended periods without water, its seeds may be better prepared to handle similar threats. The surprising part? None of this changes the plant’s DNA.

At the University of Arkansas System Division of Agriculture (UADA), scientists have found evidence that soybeans adapt not just in the moment but across generations.

This phenomenon, known as transgenerational plasticity, allows traits shaped by stress – such as drought or insect damage – to carry over into the next generation. And it’s all done without genetic mutation.

Making soybean plants tougher

Unlike genetic mutations, epigenetic changes don’t alter the DNA sequence. They simply adjust how the plant reads its genetic code. These changes are reversible, but their effects can be powerful.

Soybean is one of the most important crops globally. The research team discovered that both drought and insect damage can leave a lasting impression. These stressors not only influence the parent plant’s traits but also shape how their offspring grow, defend themselves, and yield.

“This gives us the opportunity where we can manipulate the degree of stress of soybean to bolster defenses early in the season without compromising the final yield of the crop,” said Rupesh Kariyat, associate professor of crop entomology.

“But there is a catch – we have yet to quantify the threshold under drought and herbivory stress that may cause more harm than good to the plants.”

This idea – that carefully timed stress could help strengthen a crop – opens up possibilities. Just like vaccines prime our immune systems, early-season exposure to mild stress could make soybean plants tougher later on.

“Memory” in soybean plants

Over the last two years, the researchers have studied how soybean looper and fall armyworm caterpillars interact with soybean plants. They looked at how drought and sequential insect attacks impact not only the plants themselves but also their offspring.

“Insects are getting bigger, and they’re going through multiple generations each year,” Kariyat said. “That leads to increased pesticide use, which isn’t sustainable.”

With climate change intensifying insect threats, soybeans that “remember” past stress might help farmers cut down on pesticide use.

This could be a game-changer – especially in regions like Brazil and Kenya, where farmers often rely on saved seeds due to the cost of commercial varieties.

What plant stress leaves behind

So, what changes when a parent plant has been stressed? Seeds from stressed plants contained more nitrogen and protein – two important indicators of plant health. The offspring also produced more flowers and had more trichomes, the tiny hairs on leaves that help defend against insects.

Interestingly, these benefits were most pronounced when parent plants were hit by both drought and insect feeding. But the news wasn’t all good.

Stressed offspring also grew less, yielded fewer pods, and produced more empty ones. And while trichomes increased early on, they declined with plant age. In short, soybeans seemed to face a trade-off: more defense, but less growth.

“It’s not that herbivory always improves the plant performance, but the type, severity and combination of stressors determine whether the responses would be beneficial or detrimental,” Kariyat said.

Insects and soybean plants

In one experiment, the team wanted to know whether insects could tell if a soybean plant had previously been through drought. The researchers built little bridges between two plants – one that had been stressed and one that hadn’t.

The soybean looper caterpillars explored both. Many paused, turned their heads, and chose to crawl back to the healthier plants.

The damage caused by caterpillars was heavier on the non-stressed plants. This supports the “plant vigor hypothesis,” which proposes that pests prefer robust hosts.

Timing changes everything

Most crop studies focus on a single stressor, but that’s not how real-life farming works. Droughts come and go. Insects swarm in waves.

Kariyat’s team studied what happens when different pests attack in a certain order. They found that timing made a major difference.

When soybean loopers attacked first, the next generation of plants had 40% higher nitrogen, more flowers, better protein, and more pods than if the order was reversed.

From this, the researchers concluded that some stress may be helpful – but only under specific conditions. For example, drought seemed to amplify the effects of insect damage.

And when drought was paired with herbivory, offspring focused more on building up internal resources (like protein and nitrogen) than on external defenses (like trichomes).

“From the research so far, while moderate or minimum biotic stress may induce resilience in soybeans – and this is also found in other systems – the combined abiotic and biotic stress may lead to exhaustive performance, triggering expensive defensive responses that often compromise yield and fitness,” said Kariyat.

Soybean plants under stress

The idea that soybean plants can “remember” stress across generations could change how we grow crops. It’s not just about surviving the current season – it’s about building stronger, smarter crops for the future.

But like Kariyat said, plant stress comes with trade-offs. Push too hard, and the plant burns out. Get the timing right, and you might have a tougher, more resilient crop.

That’s the challenge ahead: figuring out just how much stress soybeans can take – and when to apply it – without tipping the scales from help to harm.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–