Nav: Home

The journey of the pollen

August 20, 2019

For allergy sufferers, the pollination period is a tough time, whereas for plants it is the opportunity to reproduce: in addition to the wind, insects, in particular, carry the pollen from one flower to another to pollinate them. During this transport, the pollen must repeatedly attach to and detach from different surfaces. To date, the underlying adhesive mechanisms have hardly been studied so far. Now, scientists from the Zoological Institute at Kiel University have discovered that the mechanisms are far more complex than previously assumed. They differ depending on the duration of the contact and the microstructure of the surfaces. In their study presented in the current issue of the Journal of the Royal Society Interface, they found a unique pollen gripping mechanism on the receptive female part of plants for the first time. The results could provide important knowledge for the transport of medicinal substances, and also - in light of the alarming decline in insect populations - for the development of alternative strategies in agriculture and food production.

Pollen: an all-round adhesive talent

Itchy nose, red eyes, constant sneezing - materials scientist Shuto Ito suffered from a severe pollen allergy. To learn more about the process of pollen dispersal he left his hometown in Japan to study the adhesive properties of pollen under Professor Stanislav Gorb at Kiel University. Bionics researcher Gorb and his working group "Functional Morphology and Biomechanics" investigate the special abilities of plants and animals, and how these can be imitated artificially.

"If pollen is transported by insects from flower to flower, it encounters three different types of surfaces to which it must attach itself and then detach again. We want to find out which adhesive mechanisms enable this," explained Gorb. Doctoral researcher Ito investigates these mechanisms using as a model species Hypochaeris radicata, also known as common cat's-ear (or false dandelion). This species within the family of the composite plants blooms from spring to late autumn in the entire northern hemisphere. As with many other plants, the pollen on their yellow flowers is covered with an oily substance known as pollenkitt. "Until now, scientists believed that pollenkitt has a central adhesive function. But we have found out that under certain conditions it behaves in exactly the opposite way. We must consider the adhesive mechanisms in a much more differentiated manner," Ito summarised the findings thus far. Accordingly, pollen adhesion is influenced by a complex interplay of the age of the pollen, the humidity and the respective surfaces for adhesion.

Examining the starting and ending points of the pollen's journey

In their current study, the scientists concentrated on the two parts of the plant, which are most important for the pollination. They represent the starting and ending points of the pollination: on the style of a flower, the pollen grain is presented before it is rubbed off by an insect. On the upper end of the style, the incoming pollen grains land on the stigma.

With an atomic force microscope, the scientists measured how strongly the pollen adhered to both the style and the stigma in Hypochaeris radicata. They discovered that both parts of the plant have very distinct adhesive properties, which change during the course of the pollination. Thus, the pollen adhesion on the stigma increases, while that on the style is rather restrained. The adhesion force of fresh pollen on the stigmatic surfaces exhibited a dramatic increase over the contact time of 180 seconds by a factor of 11.9, while the adhesion force of fresh pollen on the stylar surfaces yielded an increase only by a factor of 2.7.

Optimal adjustment during the course of evolution

"We assume that during the course of evolution, the two parts of the plant have developed different functions, in order to optimize the pollination process," explained Ito. If the adhesion increased on the style as the starting point of pollination, then the pollen grains could not be detached. In contrast, the stigma has increased its adhesive properties and keeps hold of pollen grains once they come into contact with it. "The newly found pollen gripping mechanism on the stigma is likely to assure the reproduction of plants by anchoring pollen on the stigma until fertilization occurs" Ito continued.

The scientists suggest that the different properties of the two parts of the plant are due to their different surface structures and the presence or absence of secreted liquid on the surface, which can be seen at the resolution of an electron microscope. They examined shock frozen samples of the plants with a Cryo scanning electron microscope. In this condition, the samples retain their original structure, and even fluids such as the secreted liquid on the stigma can be observed in high-resolution images.

New insights into coating processes and transporting medicinal substances possible

"If we can discover the mechanisms by which such interactions of microparticles and surfaces could be controlled, we could potentially draw conclusions for coating and printing processes, the transport of medicinal substances, or the treatment of respiratory diseases," suspects Gorb. And maybe one day special filters for pollen allergy sufferers.
Original publications:

Ito S, Gorb SN. 2019, Attachment-based mechanisms underlying capture and release of pollen grains. J. R. Soc. Interface 20190269.

Ito S, Gorb SN. 2019, Fresh "Pollen Adhesive" Weakens Humidity-Dependent Pollen Adhesion. ACS Appl. Mater. Interfaces 2019, 11, 24691-24698 DOI 10.1021/acsami.9b04817

Photos are available to download:

Caption: Insects carry pollen grains from blossom to blossom. Scientists from Kiel University have studied what happens with the pollen during the pollination process.

© Pixabay

Caption: Shuto Ito (left) and Professor Stanislav Gorb and investigated how pollens stick to a flower on the basis of the Hypochoeris radicata, also known as common cat's-ear or false dandelion.

© Julia Siekmann, Kiel University

Caption: Colored cryo-SEM image of stigma of Hypochaeris radicata. It embraces the successful pollen that have completed their journey of pollination.

© Shuto Ito


Professor Stanislav N. Gorb
Working Group "Functional Morphology and Biomechanics"
Zoological Institute at Kiel University
Tel.: +49 (0)431/880-4513

Shuto Ito
Tel. +49-157-36280789

Julia Siekmann
Science communication
Priority research area Kiel Nano, Surface and Interface Science (KiNSIS)
Kiel University
Tel.: +49 (0)431/880-4855

More information about the priority research area KiNSIS:

Details, which are only a millionth of a millimetre in size: this is what the priority research area "Kiel Nano, Surface and Interface Science - KiNSIS" at Kiel University has been working on. In the nano-cosmos, different laws prevail than in the macroscopic world - those of quantum physics. Through intensive, interdisciplinary cooperation between physics, chemistry, engineering and life sciences, the priority research area aims to understand the systems in this dimension and to implement the findings in an application-oriented manner. Molecular machines, innovative sensors, bionic materials, quantum computers, advanced therapies and much more could be the result. More information at

Kiel University

Press, Communication and Marketing, Dr Boris Pawlowski, Postal address: D-24098 Kiel, Germany, Telephone: +49 431 880-2104, Fax: +49 (0)431 880-1355

E-mail: Internet: Twitter: Facebook: Instagram:

Kiel University

Related Science Articles:

75 science societies urge the education department to base Title IX sexual harassment regulations on evidence and science
The American Educational Research Association (AERA) and the American Association for the Advancement of Science (AAAS) today led 75 scientific societies in submitting comments on the US Department of Education's proposed changes to Title IX regulations.
Science/Science Careers' survey ranks top biotech, biopharma, and pharma employers
The Science and Science Careers' 2018 annual Top Employers Survey polled employees in the biotechnology, biopharmaceutical, pharmaceutical, and related industries to determine the 20 best employers in these industries as well as their driving characteristics.
Science in the palm of your hand: How citizen science transforms passive learners
Citizen science projects can engage even children who previously were not interested in science.
Applied science may yield more translational research publications than basic science
While translational research can happen at any stage of the research process, a recent investigation of behavioral and social science research awards granted by the NIH between 2008 and 2014 revealed that applied science yielded a higher volume of translational research publications than basic science, according to a study published May 9, 2018 in the open-access journal PLOS ONE by Xueying Han from the Science and Technology Policy Institute, USA, and colleagues.
Prominent academics, including Salk's Thomas Albright, call for more science in forensic science
Six scientists who recently served on the National Commission on Forensic Science are calling on the scientific community at large to advocate for increased research and financial support of forensic science as well as the introduction of empirical testing requirements to ensure the validity of outcomes.
World Science Forum 2017 Jordan issues Science for Peace Declaration
On behalf of the coordinating organizations responsible for delivering the World Science Forum Jordan, the concluding Science for Peace Declaration issued at the Dead Sea represents a global call for action to science and society to build a future that promises greater equality, security and opportunity for all, and in which science plays an increasingly prominent role as an enabler of fair and sustainable development.
PETA science group promotes animal-free science at society of toxicology conference
The PETA International Science Consortium Ltd. is presenting two posters on animal-free methods for testing inhalation toxicity at the 56th annual Society of Toxicology (SOT) meeting March 12 to 16, 2017, in Baltimore, Maryland.
Citizen Science in the Digital Age: Rhetoric, Science and Public Engagement
James Wynn's timely investigation highlights scientific studies grounded in publicly gathered data and probes the rhetoric these studies employ.
Science/Science Careers' survey ranks top biotech, pharma, and biopharma employers
The Science and Science Careers' 2016 annual Top Employers Survey polled employees in the biotechnology, biopharmaceutical, pharmaceutical, and related industries to determine the 20 best employers in these industries as well as their driving characteristics.
Three natural science professors win TJ Park Science Fellowship
Professor Jung-Min Kee (Department of Chemistry, UNIST), Professor Kyudong Choi (Department of Mathematical Sciences, UNIST), and Professor Kwanpyo Kim (Department of Physics, UNIST) are the recipients of the Cheong-Am (TJ Park) Science Fellowship of the year 2016.
More Science News and Science Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

Why do we revere risk-takers, even when their actions terrify us? Why are some better at taking risks than others? This hour, TED speakers explore the alluring, dangerous, and calculated sides of risk. Guests include professional rock climber Alex Honnold, economist Mariana Mazzucato, psychology researcher Kashfia Rahman, structural engineer and bridge designer Ian Firth, and risk intelligence expert Dylan Evans.
Now Playing: Science for the People

#540 Specialize? Or Generalize?
Ever been called a "jack of all trades, master of none"? The world loves to elevate specialists, people who drill deep into a single topic. Those people are great. But there's a place for generalists too, argues David Epstein. Jacks of all trades are often more successful than specialists. And he's got science to back it up. We talk with Epstein about his latest book, "Range: Why Generalists Triumph in a Specialized World".
Now Playing: Radiolab

Dolly Parton's America: Neon Moss
Today on Radiolab, we're bringing you the fourth episode of Jad's special series, Dolly Parton's America. In this episode, Jad goes back up the mountain to visit Dolly's actual Tennessee mountain home, where she tells stories about her first trips out of the holler. Back on the mountaintop, standing under the rain by the Little Pigeon River, the trip triggers memories of Jad's first visit to his father's childhood home, and opens the gateway to dizzying stories of music and migration. Support Radiolab today at