Magazine article Science News

Floral Shocker: Blooms Shake Roots of Flowering-Plant Family

Magazine article Science News

Floral Shocker: Blooms Shake Roots of Flowering-Plant Family

Article excerpt

Imagine discovering a mammal without mammary glands or an insect with eight legs. Aquatic herbs in the genus Hydatella pose a similar paradox--they lack a defining developmental feature of flowering plants, raising questions about their evolution and rampant speciation during the past 135 million years.

Evolutionary biologists group together organisms that share unique traits, such as mammary glands or fur, which presumably emerged in a common ancestor. In the flowering plants--the angiosperms--these features include bearing true flowers and key events that occur during fertilization and development.

One such event is double fertilization. The plants' sperm cells each have two nuclei containing genetic material. One partakes in normal fertilization by joining with the egg cell to make an embryo. The other sperm nucleus fuses with two of mom's nuclei to make a starchy tissue called endosperm that, like a placenta, nourishes the developing plant. This second fertilization and its timing are hallmarks of angiosperm evolution. "These are the great rules of flowering plants,' says botanist William Friedman of the University of Colorado at Boulder, whose new study of Hydatella was published online March 19 in Nature.

Friedman's analysis finds that Hydatella doesn't make proper endosperm--it provides nutritive tissue made only from mom's cells. And this starchy plant food starts developing before fertilization has even taken place.

"This is very unusual--putting down a payment irrespective of whether there is an embryo to invest in," says Friedman. …

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