[Science News] - A six-year experiment reveals the secrets behind the germination of creeping marshwort

Heliosciadium repens or creeping marshwort
grows in moist grasslands and requires a very specific management such as grazing by horses. In Flanders, only a few populations are left, the largest of which occurs in Vrijbroekpark

in Mechelen. It is a rare plant listed in national Red Lists of all countries where it occurs and in the European
Habitats Directive. The creeping marshwort

has a particular life cycle, reproducing both asexually

and sexually, with seeds that can form a persistent soil seed bank. To improve conservation measures for maintaining the few viable populations, Meise Botanic Garden researchers studied the germination requirements of this species and the behaviour of the seeds in the soil seed bank, which was not very well known.

To detect which signals trigger the germination of creeping marshwort

, we carried out a series of laboratory experiments simulating the conditions that seeds experience in a natural environment. The experiments revealed that seeds dispersed from the mother plant are dormant and require a period of after-ripening to germinate. Once the dormancy was broken, seeds could germinate at a wide range of temperatures given that light was present. The fact that light acts as a signal for the seeds to germinate plays a crucial role in the formation of a soil seed bank in this species. An additional experiment was performed where seeds
creeping marshwort

were buried in small nylon bags in the Botanic Garden and retrieved every two months for over 6 years. The results showed that even after more than 6 years, seeds were still not germinating in the soil, but they were still viable!




. Once these seeds were exposed to light in the laboratory, they germinated

. Light is an important signal, which can provide the seed with information about how deep it is buried and how much competing vegetation is present.

Considering the rareness and decline of creeping marshwort

populations, knowledge about how seeds behave in the soil seed bank is critically important when considering habitat management as well for possible reintroductions in the future.

Source:

Ronse A, Van de Vyver A, Vandelook F. Seed germination requirements of the rare Helosciadium repens (aka Apium repens) determine persistence of seeds in the soil seed bank. Plant Biol (Stuttg). 2024 Jul 9. https://doi.org/10.1111/plb.13681