After it is released from a flower’s anther, a pollen grain walks a humidity tightrope. It dries up a bit as it travels through the air, the cellular material inside becoming dormant so it survives until it reaches the humid environment of another flower’s stigma. But it can’t become so dry that the material dies.
A scanning electron micrograph of a dehydrated Lily pollen grain.
Pollen grains achieve the proper state of desiccation by folding in on themselves as they dry, which reduces the rate of water loss (and also accommodates the reduced volume of water, making the grain smaller). It’s an elegant trick, and the structure of the pollen grain wall determines how it occurs, according to research published in The Proceedings of the National Academy of Sciences.
Eleni Katifori, previously at Harvard and at Rockefeller University, and colleagues studied the folding of pollen from lilies and other flowers (a video of folding grains is at nytimes.com/science). The walls of pollen grains have weaker, more flexible sections called apertures, and Dr. Katifori said those sections guide the folding process. Like origami, in which paper stretches only at the creases, pollen grains deform at the apertures “so the rest can fold without stretching,” she said.
“It’s like pulling the air out of a beach ball,” she said. “Parts of the wall have to comply to accommodate the change of volume.”
Dr. Katifori said the goal of the research was to discover the basic principles by which the folding occurs as a way of understanding some of the functional demands that drive the great diversity of pollen grain structures in nature. But she said that the work might also prove useful to those who design structures. “I could imagine that engineers could get inspiration from just looking at pollen grains,” she said.
Henry Fountain, New York Times
Full article and photo: http://www.nytimes.com/2010/04/27/science/27obpollen.html