Maize plants signal neighbors when it's time to boost defenses

Maize does not stand quietly when fields get crowded. New work shows that plants packed close together release linalool – an airborne cue that prompts neighbors to change what their roots release, reshaping soil life and stiffening defenses against pests.

The response comes with a catch. Stronger defense can shave off growth, so the same chemistry that deters attackers can also slow the plant itself.

Maize signals neighbors

The research team reports that a dense canopy raises linalool in the air to a threshold that neighboring plants notice. Once that signal lands, roots ramp up jasmonate signaling, which is a well studied stress pathway in plants.

“High planting density boosts crop yields but also heightens pest and pathogen risks,” wrote study lead author Dongsheng Guo of Zhejiang University.

The team’s coordinated experiments linked signals above ground to changes below ground in a simple chain, ran field plots at different densities, then tracked the chemistry in the air and the soil.

Roots change soil microbes

After jasmonate switches on in roots, plants exude more benzoxazinoids, a class of indole-based defense metabolites that maize makes naturally.

These molecules leak into the soil zone around roots, the rhizosphere microbiome, where they can favor some microbes and sideline others.

One key benzoxazinoid in this story is HDMBOA-Glc. It is a major member of the benzoxazinoid family in maize roots and exudates that has been tracked for more than a decade.

Microbial communities do not change randomly. Prior work has shown that benzoxazinoids help assemble specific root bacteria and fungi, and those communities then echo back into plant traits in the next growth cycle.

Stronger defense makes plants smaller

The dense inner rows of the field plots suffered less herbivore damage than edge plants, but they also stayed smaller. That trade is consistent with a long line of studies showing that investment in immunity can pull resources away from growth when conditions demand it.

Plants juggle these priorities through hormone cross-talk. Jasmonate tends to organize responses to chewing insects and tissue damage, while salicylic acid often coordinates responses to biotrophic pathogens. The two pathways can compete or reinforce each other depending on context.

The study shows that the microbial shift in linalool-conditioned soils pushes subsequent plants toward stronger salicylic acid signaling. This pattern matches the classic growth defense tension documented across species under stress.

Speed and specificity

Timing matters in fields where pests can spike quickly. A related perspective notes that the high-density response emerged after only three days of maize growth, which is fast enough to matter for early herbivore pressure. 

The experiments also showed breadth. Soils conditioned under dense maize reduced not only insect damage but pressure from nematodes and pathogens in later plantings. This finding indicates a broad-spectrum tilt in defensive readiness that outlived the first crop.

The authors pinpointed the sequence from airborne cue to root exudate to microbial shift to hormone state. The sequence sets a clear set of targets for breeding and management without assuming one silver bullet.

What this means for farmers 

Farmers have leaned on denser planting to drive yield per acre, but density can make a field more vulnerable to outbreaks. Using an internal warning cue like linalool to pre-set defenses could help reduce losses without heavy chemical inputs if the growth costs can be managed.

There is a second lever in the soil legacy. Field studies show that benzoxazinoid-conditioned soils can lift the yield of the next crop under the right conditions, even when overall fertilizer inputs remain unchanged.

“A yield increase of 4 percent may not sound spectacular, but it is still significant considering how challenging it has become to enhance wheat yields without additional inputs,” explained Matthias Erb, professor at the University of Bern.

Future of plant defense research

Plant breeders could select lines that tune linalool output at useful thresholds, or lines that change root exudation patterns with minimal penalties.

Microbial inoculants that mimic the linalool legacy effect are another route already being explored in other crops.

Agronomists will need to map when the costs outweigh the benefits. Heat, water stress, and pathogen loads can all shift how salicylic acid and jasmonate signals interact, so prescriptions will likely be seasonal and region specific rather than one size fits all.

For now, the study offers a clear lesson. Packed fields are not just noisier in scent, they are also busier below ground, and that bustle can be steered toward resilience when we understand who sends which signal and when it lands.

The study is published in the journal Science.

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