In 1879, a botanist buried 20 bottles containing the seeds of 23 different types of weeds. The aim is to dig one up every five years and determine how long the seeds remain viable. It is now 144 years later and the experiment has recently managed to surprise researchers again.
This can be read in the magazine American Journal of Botany. The research article reveals the latest discoveries within it Beal Seed Experimentan experiment that has been running since 1879, making it one of the longest-running plant experiments in the world (see box).
Beal Seed Experiment
In 1879, botanist William J. Beal buried 20 small bottles, each filled with sand and 50 seeds of 23 different species of weeds. He intends to dig one up every five years to check whether the seeds are still germinating. The aim is to find out how long weed seeds remain viable. Beal retired in 1910. But his experiment was taken over by a colleague who decided in 1920 to extend the experiment by digging up a bottle not every five, but every ten years. Decades pass and the unearthed seeds continue to germinate. And in 1980 it was therefore decided to bring out a bottle every 20 years from now on. The last time that happened was in 2021. At this point, four vials are still buried, meaning the experiment won’t come to completion until around the year 2100.
Some 141 years after Beal carefully buried the vials, researchers – in 2021 – unearthed the sixteenth vial. The seeds were carefully removed, after which the researchers made the seeds as comfortable as possible in the hope of encouraging them to germinate. And sure enough, the seeds germinated. “For me, the biggest surprise was that the seeds sprouted again,” says researcher Frank Telewski. “It’s amazing that something so old can still grow.”
Hybrid
But it doesn’t stop there. Because for the first time since this experiment began 144 years ago, researchers have also sequenced the DNA of the plants. And that results in a remarkable discovery. For example, seeds from a hybrid appear to have accidentally ended up in the bottle. It is a cross between Berbascum blattaria (mothweed) and I’ve got a bunch of Spanish (mullein). “Beal stated that he only seeds from I’ve got a bunch of Spanish used, so something must have gone wrong during the preparation of the vials,” says researcher Grace Fleming.
New research methods
The researchers already suspected that there was a hybrid among the emerged seedlings based on external characteristics. But DNA testing was needed to confirm that. Beal – who died in 1924 – would undoubtedly have been surprised by the latest findings within ‘his’ experiment. Because in his time DNA – at least as a carrier of genetic information – was still unknown. “When Beal buried these seeds, we didn’t even know what DNA was,” emphasizes researcher Frank Telewski. “Technology has changed so much.” And that makes the fact that this experiment has been running for so long even more valuable. As time passes, new research methods emerge and even questions can be answered that did not even occur to Beal a century and a half ago.
And so this long-term experiment can continue to surprise us. Of course, what remains remarkable is that every time a bottle is taken out and seeds are planted, something always comes up. This is also the case this sixteenth time, more than 140 years after Beal hid the bottles. But not all seeds germinate; a large proportion of weed species appear to have given up and are no longer viable in the first sixty years of the experiment (see box). However, one species never disappoints the researchers and actually always emerges and that is Berbascum blattaria. And other species from this genus also appear to be still willing to germinate after more than 140 years in the soil. It is unclear why these plants are still so vibrant after more than a century – while others no longer seem viable.
Viable
When plants drop their seeds, they rarely all germinate at the same time. Some remain in the soil and germinate – if conditions are favorable – at a later time. These seeds are also collectively referred to as a seed bank; they are present in the ground, do not actively participate in life in the moment above, but ‘sleep’ (often a little deeper in the ground) until conditions change. Beal wondered how long such a seed bank of different types of weeds remains viable, or in other words, within how many years these seeds have to ‘wake up’ in order to germinate. It is assumed that with this knowledge he encouraged the farmers – who in his time could only tackle sprouting weeds armed with a hoe. And this by being able to tell them when they no longer had to fear those ‘dormant’ seeds and – assuming they removed emerging weeds before the seed produced – could expect that the weeds in their field would decrease.
Relevance
In 2023, weeds still grow in fields, but farmers have more options for combating them. The modern farmer is probably not sitting on the edge of his seat while awaiting the results of Beal’s experiment. Yet the research is still extremely relevant, as the researchers working on it today explain. For example, the question of how long seeds remain viable is relevant for the recovery of ecosystems that have been seriously disturbed by fire, floods or other disasters. For example, the research indicates that the original vegetation in such an area can be restored from the seed bank deep in the ground.
2040
In the meantime, the main question Beal asked remains – how long do seeds remain viable? – for many of the seeds he put in the bottles still unanswered. Because more than 140 years after the start of his experiment, seeds are still germinating. And so it remains unclear how long it will take before those specimens also lose heart. There is only one way to find out: by continuing Beal’s experiment. And that is certainly what researchers intend to do. The next bottle will be brought out around 2040. “I’m looking forward to seeing if we can wake up even more seeds,” said researcher David Lowry.
Lowry does not rule out that after successful germination in 2040, it will be decided to extend the period between excavations – and thus also the experiment – again. For example, by digging up a bottle every 30 years instead of every 20 years. In that scenario, scientists could still be working on Beal’s experiment in the 22nd century. And who knows what conclusions could be drawn by then – with all kinds of research methods that are still unthinkable –
