Origin of Flowers and Angiosperms

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#1)  Origin of Flowers and Angiosperms

Postby edfrank » Thu Oct 21, 2010 3:24 pm

Insight Into Evolution Of First Flowers
ScienceDaily (May 19, 2009)
http://www.sciencedaily.com/releases/2009/05/090518172453.htm

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The flower is one of the key innovations of evolution, responsible for a massive burst of evolution that has resulted in perhaps as many as 400,000 angiosperm species. Before flowering plants emerged, the seed-bearing plant world was dominated by gymnosperms, which have cone-like structures instead of flowers and include pine trees, sago palms and ginkgos. Gymnosperms first appeared in the fossil record about 360 million years ago.  The new study provides insight into how the first flowering plants evolved from pre-existing genetic programs found in gymnosperms and then developed into the diversity of flowering plants we see today.  


Researchers don't know exactly which gymnosperms gave rise to flowering plants, but previous research suggests some genetic program in the gymnosperms was modified to make the first flower, Soltis said. A pine tree produces pine cones that are either male or female, unlike flowers, which contain both male and female parts. But a male pine cone has almost everything that a flower has in terms of its genetic wiring. Continued...


1.Chanderbali et al. Transcriptional signatures of ancient floral developmental genetics in avocado (Persea americana; Lauraceae). Proceedings of the National Academy of Sciences, 2009; DOI: 10.1073/pnas.0811476106

Mutation Over 100 Million Years Ago Led Flowers to Make Male and Female Parts Differently
ScienceDaily (Oct. 19, 2010)
http://www.sciencedaily.com/releases/2010/10/101018163100.htm

Research by University of Leeds plant scientists has uncovered a snapshot of evolution in progress, by tracing how a gene mutation over 100 million years ago led flowers to make male and female parts in different ways.

In a number of plants, the gene involved in making male and female organs has duplicated to create two, very similar, copies. In rockcress (Arabidopsis), one copy still makes male and female parts, but the other copy has taken on a completely new role: it makes seed pods shatter open. In snapdragons (Antirrhinum), both genes are still linked to sex organs, but one copy makes mainly female parts, while still retaining a small role in male organs -- but the other copy can only make male.


1.Chiara A. Airoldi, Sara Bergonzi, Brendan Davies. Single amino acid change alters the ability to specify male or female organ identity. Proceedings of the National Academy of Sciences, 2010; DOI: 10.1073/pnas.1009050107

Flowering Plants Evolved Very Quickly Into Five Groups
ScienceDaily (Nov. 27, 2007)
http://www.sciencedaily.com/releases/2007/11/071126170900.htm

Based on the Soltises' and their collaborators' research in previous years, it was known that flowering plants split into three branches shortly after they appeared about 130 million years ago. That process was relatively gradual, at least compared with the rapid radiation that happened next. The details of that radiation have long been murky. The latest research clears the picture by showing that all plants fall into five major lineages that developed over the relatively short period of 5 million years, or possibly even less.  



South Pacific Plant May Be Missing Link In Evolution Of Flowering Plants
ScienceDaily (May 17, 2006)
http://www.sciencedaily.com/releases/2006/05/060517181205.htm

A new University of Colorado at Boulder study involving a "living fossil plant" that has survived on Earth for 130 million years suggests its novel reproductive structure may be a "missing link" between flowering plants and their ancestors.

[url]The Amborella plant, found in the rain forests of New Caledonia in the South Pacific, has a unique way of forming eggs that may represent a critical link between the remarkably diverse flowering plants, known as angiosperms, and their yet to be identified extinct ancestors, said CU-Boulder Professor William "Ned" Friedman.

"The study shows that the structure that houses the egg in Amborella is different from every other flowering plant known, and may be the potential missing link between flowering plants and their progenitors."

In basic terms, Amborella has one extra sterile cell that accompanies the egg cell in the female part of its reproductive apparatus known as the embryo sac, according to the study. The discovery of the unique configuration of the egg apparatus, which is thought to be a relic of intense evolutionary activity in early angiosperm history, "is akin to finding a fossil amphibian with an extra leg," according to a May 18 Nature perspective piece accompanying Friedman's article.[/url]

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