pollen

using-pollen-to-make-paper,-sponges,-and-more

Using pollen to make paper, sponges, and more

Paper, pollen, Science, sponges, syndication / /

Softening the shell

To begin working with pollen, scientists can remove the sticky coating around the grains in a process called defatting. Stripping away these lipids and allergenic proteins is the first step in creating the empty capsules for drug delivery that Csaba seeks. Beyond that, however, pollen’s seemingly impenetrable shell—made up of the biopolymer sporopollenin—had long stumped researchers and limited its use.

A breakthrough came in 2020, when Cho and his team reported that incubating pollen in an alkaline solution of potassium hydroxide at 80° Celsius (176° Fahrenheit) could significantly alter the surface chemistry of pollen grains, allowing them to readily absorb and retain water.

The resulting pollen is as pliable as Play-Doh, says Shahrudin Ibrahim, a research fellow in Cho’s lab who helped to develop the technique. Before the treatment, pollen grains are more like marbles: hard, inert, and largely unreactive. After, the particles are so soft they stick together easily, allowing more complex structures to form. This opens up numerous applications, Ibrahim says, proudly holding up a vial of the yellow-brown slush in the lab.

When cast onto a flat mold and dried out, the microgel assembles into a paper or film, depending on the final thickness, that is strong yet flexible. It is also sensitive to external stimuli, including changes in pH and humidity. Exposure to the alkaline solution causes pollen’s constituent polymers to become more hydrophilic, or water-loving, so depending on the conditions, the gel will swell or shrink due to the absorption or expulsion of water, explains Ibrahim.

For technical applications, pollen grains are first stripped of their allergy-inducing sticky coating, in a process called defatting. Next, if treated with acid, they form hollow sporopollenin capsules that can be used to deliver drugs. If treated instead with an alkaline solution, the defatted pollen grains are transformed into a soft microgel that can be used to make thin films, paper, and sponges. Credit: Knowable Magazine

This winning combination of properties, the Singaporean researchers believe, makes pollen-based film a prospect for many future applications: smart actuators that allow devices to detect and respond to changes in their surroundings, wearable health trackers to monitor heart signals, and more. And because pollen is naturally UV-protective, there’s the possibility it could substitute for certain photonically active substrates in perovskite solar cells and other optoelectronic devices.

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with-fewer-pollinators,-plants-are-cutting-back-on-nectar-production

With fewer pollinators, plants are cutting back on nectar production

Biology, pansies, plant biology, pollen, pollinators, reproduction, Science / /

I can handle this myself —

Fewer pollinators means more self-pollination, less food for bees.

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Image of a field of multi-colored flowers.

In a striking experiment, scientists from the French Centre Nationale de la Recherche Scientifique (CNRS) and the University of Montpellier have observed the impact of selective pressure on a flowering plant. By comparing the pansy flower variety of today that grows in the Paris region to those regrown from the seeds of the same variety collected in the 1990s and 2000s, the researchers have observed notable differences.

According to the study’s co-author, Pierre-Oliver Cheptou, the plant’s evolution over this period has resulted in a 25 percent increase in self-pollination (or selfing) in modern two plants. “We also noticed a 10 percent decrease in the flower size and a 20 percent reduction in the nectar production, which suggests the decrease in rewards for pollinators such as bumblebees,” he said.

To confirm this outcome, Cheptou and his colleagues conducted behavioral tests involving bumblebees “which preferred the ancestor plants,” Cheptou said.

He added that the study showed the impact of pollinators’ decline on the reproductive system in these plants.

When mom and dad are the same plant

Elaborating on the experiment techniques, the study’s lead author, Samson Acoca-Pidolle, said the researchers used “resurrection ecology,” which involved using plant seeds from the 1990s and 2000s that were picked from the fields in the Paris region and stored in fridges in two botanical conservatories. “In 2021, we went to the same fields to collect the seeds of the descendants of the same flowering plant,” he said. For the study, all the plants were cultivated in a greenhouse at the same time of year to ensure consistency.

Cheptou said that to determine the selfing rates of the ancestor and descendant varieties, the team used a classical molecular technique that involved measuring the frequency at which individual plants had stretches of chromosomes with identical versions of genes. This happens often in selfing since the maternal and paternal copies of a chromosome come from the same individual.

According to Acoca-Pidolle, the research team was surprised at the rapidity of the plant’s evolution in the natural environment. “It seems that the pollinators’ decline is already strong, and there is already selective pressure on this species. The other significance of the result is that we are currently observing the breakdown in the plant-pollinator interaction for this species,” he added.

Acoca-Pidolle said the study suggests that the decline of pollinators could become self-reinforcing. “If plants produce less nectar, we can predict that pollinators will have less food and this could increase the pollinator decline,” he said.

Everything is a trade-off

This adaptation may not necessarily turn out to be beneficial for the plant. “It depends on the time scale we are considering this adaptation as an answer to the selective pressure. In the long term, we know that selfing species have a higher extinction rate than out-crossing species,” he said.

Although this study was restricted to a single plant species, Cheptou suspects a similar evolutionary adaptation could be taking place in other species, too. “For plants that can practice at least a little selfing, we should expect this result. But this has to be checked by experiments,” he said.

According to Cheptou, future research should investigate if a similar pattern exists in this plant species elsewhere in Europe and see if a similar adaptation has occurred in other species.

“The other interesting aspect would be to see if plants’ future evolution could be reversible, which will again make them more attractive to the pollinators and practice less selfing,” Acoca-Pidolle said.

New Phytologist, 2023. DOI: 10.1111/nph.19422

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