January 3, 2014
Flowers In Amber Show Earliest Evidence Of Pollination
Brett Smith for redOrbit.com – Your Universe Online
Like many other plants and insects preserved in amber, the flowers are essentially frozen in time with nearly every detail appearing as it had millions of year ago. The preservation process began with flowing tree sap covering the flowers. Eventually, the sap hardened into a fossilized, semi-precious gem.
The flower cluster came from a time when many of the flowering plants on Earth were still fairly small. During the Cretaceous, flowering plants started to emerge, providing increased biodiversity and food. Until the Cretaceous, plant life on Earth was composed entirely of conifers, ferns, mosses, and cycads.
The remarkable amount of preservation allowed the OSU scientists to capture microscopic images of pollen tubes emerging from two grains of pollen and entering the flower’s stigma, direct evidence of sexual reproduction. The pollen tubes allow for the fertilization of the egg within the stigma and the eventual formation of a seed.
“In Cretaceous flowers we’ve never before seen a fossil that shows the pollen tube actually entering the stigma,” said study author George Poinar, Jr., a professor of integrative biology at OSU. “This is the beauty of amber fossils. They are preserved so rapidly after entering the resin that structures such as pollen grains and tubes can be detected with a microscope.”
The biologist said the pollen of these flowers appeared to be sticky – an indication that it was transported by a pollinating insect. During the Cretaceous, a few mammals and birds, other potential pollinators, were beginning to appear.
“The evolution of flowering plants caused an enormous change in the biodiversity of life on Earth, especially in the tropics and subtropics,” Poinar said.
“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 added. “It’s interesting that the mechanisms for reproduction that are still with us today had already been established some 100 million years ago.”
A study released in November revealed that amber could also be used to provide details about the ancient Earth’s atmosphere. According to the study, the atmosphere of the Cretaceous had relatively low oxygen content – making previous theories about high-oxygen atmosphere severely flawed.
“Compared to other organic matter, amber has the advantage that it remains chemically and isotopically almost unchanged over long periods of geological time,” said study author Ralf Tappert, from the University of Alberta. “During photosynthesis plants bind atmospheric carbon, whose isotopic composition is preserved in resins over millions of years, and from this, we can infer atmospheric oxygen concentrations.”