National Evolutionary Synthesis Center (NESCent)
Sprouts. Seeds that sprout as soon as they're
planted may be good news for a garden. But wild plants need to be more careful.
Seeds that sprout as soon as they're planted may be
good news for a garden. But wild plants need to be more careful. In the wild, a
plant whose seeds sprouted at the first warm spell or rainy day would risk
disaster. More than just an insurance policy against late frosts or unexpected
dry spells, it turns out that seed dormancy has long-term advantages too: Plants
whose seeds put off sprouting until conditions are more certain give rise to
more species, finds in a team of researchers working at the National
Evolutionary Synthesis Center in North Carolina.
When they first emerge from the soil, plant
seedlings are very vulnerable, said co-author Rafael Rubio de Casas of the
Universidad of Granada in Spain. "They're like babies. They don't have
protective thorns or woody tissue any of the other defenses that are more
typical of adult plants yet."
The tiny embryos of many plants can lie huddled
inside their seed coats in a state of suspended animation
for years before finally springing to life. The oldest known was a date palm
that sprouted from a 2000-year-old seed recovered from the ruins of a fortress
Taking advantage of data compiled over more than
forty years by University of Kentucky seed scientists Jerry and Carol Baskin,
who were also co-authors on the study, researchers analyzed seed dormancy data
for more than 14,000 species of trees, shrubs, vines and herbs from across the
When the researchers mapped the data onto the seed
plant family tree, they found that plants with the ability to regulate the
timing of germination in response to environmental cues were more likely to spin
off new species.
"Having the capacity to fine-tune their development
to the environment seems to be crucial for diversification," de Casas said.
Seed dormancy may help plants colonize new
environments by preventing new arrivals from sprouting under conditions or at
times of year when the probability of seedling survival is low.
The strategy is as ancient as seeds themselves. "Our
results suggest that even the earliest seeds had this ability," de Casas said.
Plants whose seeds have since lost the ability may
be more prone to extinction under future climate change, especially if the
timing of sprouting is no longer in tune with their environment, he added.
The study appears in the journal New Phytologist.
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