New research found stressed plants emit airborne sounds.

The study, published in Cell journal, found that stressed plants emit airborne sounds that resembling clicking and popping which can be recorded from a distance and classified.

The researchers used microphones to record healthy and stressed tomato and tobacco plants and found that stressed plants emit more sounds than unstressed plants. They stressed the plants by not watering them for several days and by cutting their stems.

While the frequency of these noises is too high for human ears to detect, the sounds may potentially trigger a response in nearby organisms like insects or small mammals or other plants.

Queensland Alliance for Agriculture and Food Innovation's Dr Alice Hayward told ACM that nearby animals may use this indicator of the plants' condition for their own benefit.

"Small mammals like mice and bats can technically hear at that same range of noise or sound. So it's possible that they could be detecting those noises from plants, and then altering their behaviour," she said.

"That could be to avoid eating a plant that is in stress, because it's not as healthy as one that's juicy and flush and maybe a bit more nutritious, or it could be moths avoiding laying their eggs on a plant that's just about to die as opposed to one that can support their young when they hatch."

Plants have previously demonstrated their capacity to respond to noise. The same researchers proved in a 2019 study that the buzzing of bees can cause plants to produce sweeter nectar.

The researchers trained a machine learning algorithm to differentiate between unstressed plants, thirsty plants, and cut plants.

Dr Hayward said this function could have significant benefits for plant cultivators and farmers.

"If a machine can learn that from those sounds you can imagine potentially being able to put microphones or devices in areas of a field, getting them detect how the plants are going in that area, and tailoring your watering regime specifically for that section of the field," she said.

"So you're not just randomly spraying water, you're actually tailoring it to what it needs. You would be wasting less."

Increasing the precision of irrigation can save up to 50 per cent of the water expenditure and increase the yield, with dramatic economic implications and water conservation potential.

Closer to home, Dr Hayward's team at the University of Queensland are working to improve the resiliency of Australian crops by using plant genes to produce plants.

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The system can produce up to 500 plants from a single shoot tip in culture within eight to 12 months.

"A lot of the tropical species, not just native ones, but the crops we rely on for food like our avocados and our mangoes, the crops that make us happy, are all at risk of environmental change," she said.

"So if there is a severe weather event, or disease outbreak, or increasing temperatures or major changes due to climate change, that could be impacting their ability to survive because they need certain temperatures to flower.

"All these kinds of things could either obviously impact the plant itself if it's not getting enough water or things like that, but also impact its ability to reproduce."

Her team, led by Professor Neena Mitter, created the world's first tissue-culture production system for avocado plants.

These innovations are a sustainable and cost-effective way to produce plants that are under threat from climate change.