Hot Dates in the Plant
World
You know
about the birds and the bees, but what have you heard about the
"dating life" of daffodils and daisies? You'd probably
guess that the closest a flower ever gets to a "date"
is becoming part of a corsage on prom night.
Recent discoveries, however, suggest that plants may not be as passive as we thought. Although they still don't pull up their roots and head for the party, they don't just hang out in the garden waiting for the first bit of pollen that drifts by, either. They're actually pretty fussy about mates. In fact, cross fertilization from species to species is the exception rather than the rule. That realization has led scientists to ask some pretty interesting questions about plant reproduction, such as
- Do plants select their mates? If so, how?
- How do flowers "decide" what is "the right kind" of pollen?
- What consitutes a hot date in the plant kingdom?
Like many scientists who study plant hybrids, Daphne Preuss and Greg Zinkl of the University of Chicago wondered why plants accept some mating crosses, but not others. They wanted to know how quickly the flower makes a "to mate or not to mate" choice.
Greg, a student in Preuss' lab, brushed the stigmas of Arabidopsis flowers with a variety of pollen. Next he washed the stigmas (Yes--he even used detergent!) and spun them in a centrifuge machine. Then he counted the pollen grains that were still clinging to the stigma. Most of the pollen grains had fallen off. Just one kind was left--Arabidopsis pollen.
The experiment raised a new question. Was this Love at First Sight between Arabidopsis stigma and pollen or was Arabipopsis pollen just the "cutie" of the plant world? To find out, Greg brushed Arabidopsis pollen on the stigma of a different kind of flower--a petunia. When he repeated the detergent/centrifuge abuse, the pollen fell off. Arabidopsis just didn't have "the right stuff" for the petunia. Apparently the flower stigmas were making some pretty snappy mating decisions. It seems there's not much chance for a second date in the plant world. It's Love at First Sight or be blown away.
Now researchers want to know how the flower's stigma snags the right kind of pollen. Under an electron microscope, Preuss and Zinkl could not see any of the usual hooks and loops that often work as snares in the plant world. Said Preuss, "Whatever it is has to be very small--some kind of molecular Velcro."
For more information, visit these sites:
International
Association for Sexual Plant Reproduction Research
http://www.iasprr.org/
Interview
with Daphne Preuss
http://www.nsf.gov/bio/pubs/arabid/inter-dp.htm
The Preuss Lab
Visit Dr. Preuss's lab at the University of Chicago and read more about cell-cell interactions during pollination.
In the News
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