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WHAT KEEPS SEEDS VIABLE FOR SO LONG?

June 23, 2014

WHAT KEEPS SEEDS VIABLE FOR SO LONG?

The hot and humid tropical forest floor voraciously decomposes virtually anything that is biodegradable

The hot and humid tropical forest floor voraciously decomposes virtually anything that is biodegradable. So it came as a bit of a surprise when Jim Dalling, a professor at the University of Illinois, demonstrated that seeds from some pioneer tree species can retain their ability to germinate for up to four decades in forest topsoil.

His research, published in The American Naturalist in 2009, inspired Venus Kuo, an undergrad at UI, to find out what keeps seeds viable. She suspects soil fungi. “Do they play some kind of a protective, mutually beneficial role for the seeds?” asked Kuo, as she hiked to the 50-hectare forest plot on Panama’s Barro Colorado Island where the seeds for the original study were collected.

Pioneer trees are the first to emerge when a forest regenerates. But they need a lot of light and this is in low supply in the understory. Not until a tree falls and opens a gap will pioneers have a chance to grow into reproductive adults.

Kuo will collect seeds from Dalling’s sites as well as other spots in the 50-hectare plot where tree census data suggest pioneer species rained seeds on the forest floor decades ago. She will test the seeds for viability and diversity of endophytic fungi, and compare her findings with younger seeds. She expects fungal diversity will be lower in older seeds, pointing to which fungi may promote long-term seed dormancy.

“I think it can probably lead to some interesting questions about how we can predict tree emergence and canopy composition over time,” said Kuo.

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