Corn communicates with its neighbours by releasing a gas that prompts nearby plants to alter their soil, a new study has found.
And when corn is densely planted, that can boost defences against pests and predation. But emission of the volatile gas – called linalool – can also reduce maize growth.
The international team of scientists who discovered this mechanism says it offers clues on how the release of linalool could be optimised to combat pests and increase yield.
The researchers from Zhejiang University, Chinese Academy of Sciences, Leiden University in the Netherlands and the University of Bern in Switzerland published their findings in the peer-reviewed journal Science last week.
To investigate whether planting density affects plant growth and defence through interactions between plants, the team conducted a survey in four maize fields in the southern Chinese island province of Hainan last winter.
“Field surveys revealed that maize plants in the inner rows of densely planted fields suffered less herbivore damage than those at the edges, but that they also had reduced growth,” the researchers said.
“Laboratory soil-transplantation experiments confirmed that soils conditioned by high-density plantings decreased plant biomass while enhancing resistance to insects, nematodes and pathogens,” they said.
“Harnessing this natural defence pathway through breeding, microbial inoculants, or synthetic biology could enable the development of crops that are more resilient and require fewer chemical inputs.”
The team found that when the level of linalool was concentrated enough to trigger a chemical response, the roots of neighbouring maize plants would release plant hormones, which then led to the release of plant metabolites called benzoxazinoids into the soil.
These compounds change the composition of the soil microbiome, providing protection against pests but also resulting in reduced plant growth.
“High-density planting is key for increasing crop yields, but it also raises the risk of pests and diseases,” said first author Guo Dongsheng, a doctoral candidate at Zhejiang University.
“Pathogens and pests spread more easily among closely spaced plants, threatening both crop yield and quality,” he added.
“Our study reveals a new mechanism by which plants have evolved to sense their environment. By detecting the concentration of volatile compounds released by leaves, they can sense how dense the environment is and adjust their growth-defence balance in response to density.”
Guo said the findings could help to determine the ideal amount of linalool that should be released in response to disease in fields.
“In areas with severe pest problems, releasing linalool externally or adjusting planting density to enhance gas accumulation can boost pest resistance,” he said.
“On the other hand, in regions with lighter pest pressure, reducing linalool accumulation can further increase yields.”
Plant genomics researchers Claude Becker and Niklas Schandry from the Ludwig Maximilian University of Munich, who were not involved in the study, said in a commentary also published in Science that the most surprising finding was the speed of plant-soil communication – occurring after only three days of maize growth at high density.
“This bet-hedging by the plant has implications for agriculture, because high-density planting, despite its inherent risks, generally results in higher yield,” they said.
“Plants with higher baseline linalool production might be better suited for dense growth in areas with a higher risk of pathogen or herbivore attacks because they would allocate more resources into primed defences.
“Conversely, low linalool production would allow higher resource allocation for growth and seed production when pathogen and herbivore pressures are low,” they wrote, adding that further studies were needed before the findings could become guidelines for agricultural practices. - SOUTH CHINA MORNING POST
