CORVALLIS, O.R. (KOIN) — Researchers with Oregon State University have discovered seeds sprouting from an amber-encased pinecone.
The phenomenon is caused by a rare botanical condition called precocious germination in which seeds sprout before leaving the fruit, according to the university.
George Poinar Jr. with the Oregon State College of Science published a paper in the Historical Biology that described a pinecone – about 40 million years old – encased in a Baltic amber, where several embryonic stems make an appearance.
“Crucial to the development of all plants, seed germination typically occurs in the ground after a seed has fallen,” Poinar said. “We tend to associate viviparity — embryonic development while still inside the parent — with animals and forget that it does sometimes occur in plants.”
He added that typically, those occurrences involve angiosperms. They directly or indirectly provide most of the food people eat, have flowers and produce seeds enclosed in fruit.
“Seed germination in fruits is fairly common in plants that lack seed dormancy, like tomatoes, peppers and grapefruit, and it happens for a variety of reasons,” Poinar said. “But it’s rare in gymnosperms.”
According to the university, gymnosperms, such as conifers, produce “naked,” or non-enclosed seeds.
Precocious germination in pinecones is so rare, Poinar said, that only one naturally occurring example of this condition, from 1965, has been described in the scientific literature.
“That’s part of what makes this discovery so intriguing, even beyond that it’s the first fossil record of plant viviparity involving seed germination,” he noted. “I find it fascinating that the seeds in this small pinecone could start to germinate inside the cone and the sprouts could grow out so far before they perished in the resin.”
Poinar said that the sprouts’ tips include needle clusters, some in bundles of five. That associates the fossil with the extinct pine species Pinus cembrifolia, which was previously derived from Baltic amber.
Pinecones in Baltic amber are not commonly found, he added.
“The ones that do appear are prized by collectors and because the cones’ scales are hard, they’re usually very well preserved and appear lifelike,” the university said.
Viviparity in plants typically shows up in one of two ways, but precocious germination is the more common of the two, explained Poinar, such as when a bulbil emerges directly from the flower head of a parent plant.
“In the case of seed viviparity in this fossil, the seeds produced embryonic stems that are quite evident in the amber,” he said. “Whether those stems, known as hypocotyls, appeared before the cone became encased in amber is unclear. However, based on their position, it appears that some growth, if not most, occurred after the pinecone fell into the resin.”
Research on viviparity in extant gymnosperms suggests the condition could be linked to winter frosts, cited OSU. Poinar said light frosts would have been possible if the Baltic amber forest had a humid, warm-temperate environment as has been posited.
“This is the first fossil record of seed viviparity in plants, but this condition probably occurred quite a bit earlier than this Eocene record,” he added. “There’s no reason why vegetative viviparity couldn’t have occurred hundreds of millions of years ago in ancient spore-bearing plants like ferns and lycopods.”