Leaf veins loopy for a reason

Circular networks are best for getting around a bad spot, varying load

Tree branches have inspired efficient transit networks, but a new study finds inspiration in leaves. The curvy, connected leaf veins found in some plants are an efficient way to circumvent damaged areas and channel nutrients, report researchers led by Eleni Katifori of the Rockefeller University in New York City.

AVOIDING A BAD SPOT Veins’ looped network allows water and nutrients to flow around an injury (green dot) on the main vein of a lemon leaf. E. Katifori et al/PRL 2010

“It’s obvious that if you look at leaves, they have a lot of loops,” Katifori says. To find out how the looped networks may be beneficial for the plants, the researchers created a computer model to compare how efficiently different branching patterns could do the job of leaf veins, which move water and nutrients around. “The question we’re asking is, what’s the best network we can build?” Katifori says.

In the simulations, the looped network performed better than nonlooped ones in several important ways, the team reported January 29 in Physical Review Letters. Damage from hungry insects, cold weather or parasites can interrupt leaves’ normal venation patterns. Connected circular veins allowed the flow of water and minerals to circumvent areas where veins were destroyed, the team shows. The looped network also allowed leaves to easily adjust the flow rate of water through veins, which can help leaves conserve water on a hot day, Katifori says.

Loop networks aren’t found just in tree leaves. Blood vessels in the retina, structural veins in insect wings and the architecture of certain corals are all based on loops, the researchers write. Understanding the benefits of such networks might lead to more efficient man-made network designs.

Leaf loop networks from Science News on Vimeo.

A bright yellow dye visualizes a leaf’s nutrient flow network as it moves past and around an injury to the main leaf vein.

Credit: E. Katifori et al/PRL 2010

Laura Sanders is the neuroscience writer. She holds a Ph.D. in molecular biology from the University of Southern California.

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