Evidence of Sexual Reproduction in a Flowering Plant Discovered in 100-Million-Year-Old Amber

The oldest evidence of sexual reproduction in flowering plants has been discovered in an ancient piece of amber that dates back to nearly 100 million years, according to a latest finding.

A team of researchers at the University of Oregon State has discovered a 100-million-year-old flower fossil from the Cretaceous period showing evidence of sexual reproduction in a cluster of nearly 18 well-encased small flowers. One of the flowers is in the process of forming new seeds.

Discovered from the amber mines in the Hukawng Valley of Mynamar, the newly described genus and species of flower was named Micropetasos burmensis.

This currently extinct plant serves as a good example of a flowering plant from the mid Cretaceous period. The fossilized reproduction process is similar to the one exhibited by angiosperms or flowering plants in current times.

This finding is remarkable as the 18 tiny flower clusters represent one of the most complete amber ever discovered and the flowering plants in this period appear to be quite small. What is even more interesting is the microscopic image of the pollen tubes growing out of two grains of pollen and entering into the stigma of the flower. This sets the stage for fertilization of the egg. If this reproductive act was completed it would further initiate the process of seed formation.

"In Cretaceous flowers we've never before seen a fossil that shows the pollen tube actually entering the stigma. This is the beauty of amber fossils. They are preserved so rapidly after entering the resin those structures such as pollen grains and tubes can be detected with a microscope," George Poinar, Jr., a professor emeritus in the Department of Integrative Biology at the OSU College of Science, said in a statement.

Poinar further explains that, the pollen of the trapped flowers appeared to be sticky, indicating it was carried by a pollinating insect. This feature throws light into the biodiversity and biology of life in this distant era. Also during that era, the plant life was mostly made of conifers, ferns, mosses and cycads. The evolution of such plants triggered a great change in the biodiversity of life on Earth, mainly the tropics and subtropics. Though dinosaurs continued to dominate earth, flowering plants were beginning to emerge.

"New associations between these small flowering plants and various types of insects and other animal life resulted in the successful distribution and evolution of these plants through most of the world today," he said. "It's interesting that the mechanisms for reproduction that are still with us today had already been established some 100 million years ago."

The findings were published in the Journal of the Botanical Institute of Texas.