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While pollen is known to seed the next generation of trees and plants, a new study has suggested that it might also seed clouds.

The tiny grains, about a millionth of an inch across, might cause rain by helping clouds to collect water, say scientists.

The findings suggest that these wind-carried capsules of genetic material might affect our planet's climate in an unknown way.

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A University of Michigan-led study claims that pollen (stock image shown on a mature tuft of grass) can cause rain. It was thought that pollen was too big to influence clouds. But they found when causing allergies, pollen is broken into fragments. The same process could also seed clouds with rain

The research, by the University of Michigan and Texas A&M and published in Geophysical Research Letters, highlights a fresh link between plants and the atmosphere.

In experiments, a spray of moist pollen fragments was sent into a cloud-making chamber.

The team found that pollen of different types began to pull in moisture and form clouds.

The researchers tested pollen from oak, pecan, birch, cedar and pine trees, as well as ragweed - the most common sources of wind-driven pollen in the US.

'What we found is when pollen gets wet, it can rupture very easily in seconds or minutes and make lots of smaller particles that can act as cloud condensation nuclei, or collectors for water,' said Dr Allison Steiner, U-M associate professor of atmospheric, oceanic and space sciences.

She added: 'It's possible that when trees emit pollen, that makes clouds, which in turn makes rain and that feeds back into the trees and can influence the whole growth cycle of the plant.'

Until now, pollen has been largely ignored by atmospheric scientists who study aerosols - particles suspended in the air that scatter light and heat and play a role in cloud formation.

'The grains were thought to be too large to be important in the climate system, too large to form clouds or interact with the sun's radiation,' Dr Steiner said

'And also the large particles don't last in the atmosphere. They tend to settle out relatively quickly.'

But Dr Steiner and her colleagues weren't sure that was the whole story, so they looked to the medical community.

Hayfever sufferers beware! Studies reveal pollen may make clouds

'What we found is when pollen gets wet, it can rupture very easily in seconds or minutes and make lots of smaller particles that can act as cloud condensation nuclei, or collectors for water,' said Dr Allison Steiner, U-M associate professor of atmospheric, oceanic and space sciences

Pollen causes seasonal allergies, which affect between 10 and 20 per cent of US residents, when it breaks up into tiny pieces and triggers an allergic response.

'When we were looking in the allergy literature we discovered it is pretty well known pollen can break up into these tiny pieces and trigger an allergic response,' said Dr Steiner.

And when they found that moisture can break pollen down, they speculated that clouds might be affected by such pollen fragments.

In experiments, a spray of moist pollen fragments was sent into a cloud-making chamber. The team found that pollen of different types began to pull in moisture and form clouds. It may mean that some rain on Earth (stock image in Sydney shown) is driven by pollen

'What happens in clouds is one of the big uncertainties in climate models right now,' Dr Steiner said.

'One of the things we're trying to understand is how do natural aerosols influence cloud cover and precipitation under present day and future climate.'

As next steps, they plan to conduct similar studies in the field and, through computer simulations, model the potential feedback between the plant life and the atmosphere.