Sweetheart in the mud

Seeds of supposedly extinct plants remained in the mud for over 100 years

Germinating plant seeds - some species can survive in the mud for 100 years. © GeorgeManga / iStock
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Hidden reservoirs of biodiversity: In sludge soils, plant seeds can last much longer than previously thought - more than 100 years. Researchers discovered this when looking for pollen-able seeds from ponds in the muddy ground. They even found intact seeds of plants that were long considered extinct at these sites. Sludge soils are therefore an important seed bank of biodiversity.

Whether cherry, nut or tiny flower seeds: The fruits and seeds of plants are used for their reproduction, but are also persistence artists. Protected in the ground, they can survive even unfavorable weather periods or the cold winter and then germinate again under more favorable conditions. The seeds of some wild herbs can stay in the soil undamaged even for years.

How long do seeds last?

But true long-term endurance among the plant seeds was previously considered rare: biologists knew, for example, in northwestern Europe only 14 plant species, mostly arable weeds, which can survive more than 100 years in the soil. But are they really so few? To find out, Peter Poschlod from the University of Regensburg and his team have now studied a special soil habitat: muddy soils in wetlands and ponds.

For their study, the researchers took mud samples from 108 fish ponds in Bavaria and Baden-Württemberg. In the lab they examined how many and which plant seeds were in the mud and tested if they were still germinable.

Thousands of seeds in the mud

The result: In the pond mud hid an amazing amount and variety of plant seeds. The researchers found up to 3, 000 seeds per liter of sediment. Many of the plant seeds found came from endangered species: "In all ponds except three, we found species from the national or regional Red List, " the researchers report. In some ponds, even eleven different endangered species were preserved in the form of their seeds. display

The sludge soils act as an important reservoir for biodiversity - as a kind of seed bank in the mud. This is important, among other things, if an area is to be renatured or if you want to reintroduce rare species, as the scientists explain. Because the muddy reservoir could then be used to selectively sow such plant species again.

Germinable even after 100 years

Surprising, too: Most of the plant seeds discovered in the mud soils germinated in the soil even after 50 to more than 100 years. Among these "resurrected" species were many that were previously considered lost, extinct or non-existent at these sites, as Poschlod and his colleagues report.

"Red Lists should revise their entries and write 'potentially extinct' for species with very long-lived seeds: 'extinct', " the researchers said. This hidden diversity needs more attention in the future. (Biological Conservation, 2018; doi: 10.1016 / j.biocon.2018.06.024)

Source: University of Regensburg

- Nadja Podbregar