Plants “Scream” When Stressed: Study
Sun, April 11, 2021

Plants “Scream” When Stressed: Study

For the first time, researchers have detected plants emitting airborne sounds when they’re stressed / Photo by: lovelyday12 via Shutterstock

 

For the first time, researchers have detected plants emitting airborne sounds when they’re stressed.

The study, which appeared in the preprint server for Biology bioRxi, was done by Israeli scientists who shared that they have recorded tobacco and tomato plants producing sound frequencies. The way plants “scream” when they’re stressed may not be heard by humans but can be heard by animals or other plants.

 

How Plants Respond to Stress

Plant stress is caused by various factors such as natural disasters and problems in the soil. One significant abiotic factor is water stress. When plants are stressed, researchers said that they exhibit changes in their phenotypes (characteristics). They will change visually both in shape and color. Stressed plants also emit volatile organic compounds VOCs (gases) into the air. These chemical substances are supposedly released to defend plants against parasites and herbivore insects and also serve as signals to neighboring plants. Altogether, plants can produce tactile, chemical, and visual cues.

However, it has not been sufficiently explored by studies that plants can also emit airborne sounds that can be heard by other organisms too. 

Emitting Airborne Sounds

The researchers added that when plants are deprived of water, they will experience cavitation. This is a process where air bubbles will form, gradually expand, and explode in the xylem. As a result, vibrations occur as a way of plants to vocalize their pain.

The team detected the sounds by placing microphones around 10 centimeters or four inches away from tomato and tobacco plants. On average, tomato plants make 35 sounds per hour when exposed to drought environment and tobacco plants produce 11 sounds. When researchers cut the stems of the plants, the tomato plants made 25 sounds per hour and tobacco plants emitted 15. These “screams” can be heard by insects and some mammals a few feet away though and not just limited to the team's location of microphones. 

They further tested the plants’ acoustic behavior in two settings: the acoustic box and the greenhouse. They also made sure to first construct a greenhouse noise library by first recording an empty greenhouse without a plant inside so that their convolution neural network model can differentiate sounds of plants and natural greenhouse noises.  The acoustic manifestation of the plants’ dehydration process was recorded for 10 consecutive days. 

The researchers added that when plants are deprived of water, they will experience cavitation. This is a process where air bubbles will form, gradually expand, and explode in the xylem / Photo by: CLICKMANIS via Shutterstock

 

Use of Machine Learning Models

The team's use of machine learning models helped them distinguish the difference between control, cut, and drought-stressed plants based on the sounds they emit. The results showed the potential of the machine learning models in studying phytoacoustics (sound perception in plants).

 

Paving the Way for Precision Agriculture

Researchers said that their findings can change the way people think about the Plant Kingdom, considering that it has always been considered as silent. Although their test was limited to tobacco and tomato plants, the authors believe that other plants could also produce sounds. Their findings may likewise have important implications for those in the agriculture industry. For instance, it would offer a new way of monitoring the water state of crops.

The findings can likewise help achieve a more accurate irrigation system, potentially increasing yield and saving 50% water expenditure. The authors highlighted the importance of efficient water use for ecology and food security as more areas are now exposed to climate change.

If the experiment is replicated in wide applications, farmers are better equipped to determine drought-stressed plants based on their sounds. This also results in greater environmental production and sustainability, higher productivity, and economic benefits.

If the experiment is replicated in wide applications, farmers are better equipped to determine drought-stressed plants based on their sounds. This also results in greater environmental production and sustainability, higher productivity, and economic benefits / Photo by: IvanRiver via Shutterstock

 

Global Industry Trends: Precision Farming Market

Stock market and business news site MarketWatch shared last September that the precision farming market is estimated to reach a 12% CAGR from 2017 to 2023 and will be valued at $7 billion by 2023. The biggest driver for market growth is the high adoption of market techniques by farmers from around the world to improve their yields. Other factors that will contribute to the growth of the precision farming market include a rise in the population, growing demand for food, a focus on conserving resources, and a lack of arable land.

North America is forecasted to dominate the precision farming market because of its adoption of recent farming methods. Major players, including Canada and the US, are also found in the continent. Europe is second in rank because Germany, France, and the UK have adopted precision farming technologies. These techs use remote sensing and location tracking to manage the crops.

Meanwhile, collaborative effort International Assessment of Agricultural Knowledge, Science and Technology for Development (IAASTD) initiated by the World Bank and the United Nations reported that one-third of the economically active population in the world is obtaining its livelihood from agriculture. In 2017, an estimated 866 million people are working in the agricultural sector, 148.4 million of which were located in Eastern Asia, 292.2 million in Southern Asia, and 215.7 million in sub-Saharan Africa.

Farming is indeed becoming more scientific with data analytics, GPS, and remote sensing in the farming market. As growers will be equipped with information about the sounds that plants emit, it will help improve agricultural productivity and reduce plant losses in the near future.