Seeds found germinating in 40 million-year-old pine cone trapped in amber
Phenomenon caused by a rare botanical disease called early germination
CORVALLIS, Ore. (KOIN) – Researchers at Oregon State University have discovered seeds sprouted from a pine cone covered with amber.
The phenomenon is caused by a rare botanical condition called early germination in which seeds germinate before leaving the fruit, according to the university.
George Poinar Jr. with the Oregon State College of Science published an article in Historical Biology describing a pine cone – about 40 million years old – enclosed in a Baltic amber, where several embryonic stems emerge.
âCreating for the development of all plants, seed germination usually occurs in the soil after a seed has dropped,â Poinar said. “We tend to associate viviparity – embryonic development while still inside the parent – with animals and forget that this sometimes happens in plants.”
He added that typically these events involve angiosperms. They directly or indirectly provide most of the food that people eat, have flowers, and produce seeds enclosed in fruits.
âSeed germination in fruits is quite common in plants that lack seed dormancy, such as tomatoes, peppers and grapefruits, and it happens for a variety of reasons,â Poinar said. “But it’s rare in gymnosperms.”
According to the university, gymnosperms – like conifers – produce “naked” or unenclosed seeds.
Early sprouting of pine cones is so rare, Poinar said, that only one natural example of this disease, dating from 1965, has been described in the scientific literature.
“This is in part what makes this find so intriguing, even beyond it is the first fossil record of plant viviparity involving seed germination,” he noted. “I find it fascinating that the seeds of this little pine cone can start to germinate inside the cone and that the shoots can grow so far before they perish in the resin.”
Poinar said the tips of the sprouts include clusters of needles, some in packs of five. This links the fossil to the extinct pine species Pinus cembrifolia, which was previously derived from Baltic amber.
Pine cones in Baltic amber are not common, he added.
“The ones that appear are prized by collectors and because the scales on the cones are hard, they are generally very well preserved and appear lifelike,” the university said.
Viviparity in plants usually manifests in two ways, but early germination is the more common of the two, Poinar explained, such as when a bulbil emerges directly from the flower head of a mother plant.
âIn the case of the seed viviparity in this fossil, the seeds produced embryonic stems which are quite evident in amber,â he said. âIt is not known if these stems, called hypocotyls, appeared before the cone was covered with amber. However, from their position, it appears that some, if not most, growth occurred after the pine cone fell into the resin.
Research on viviparity in existing gymnosperms suggests the condition may be linked to winter frosts, cited OSU. Poinar said slight frosts would have been possible if the Baltic amber forest had a humid and warm temperate environment, as has been argued.
“This is the first fossil record of seed viviparity in plants, but this condition probably occurred a little earlier than this Eocene record,” he added. “There is no reason why vegetative viviparity could not have occurred hundreds of millions of years ago in ancient spore plants like ferns and lycopods.”
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