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BIRDS, BEES & TREES
By Sean Henahan, Access Excellence
CHICAGO- Researchers at the University of Illinois have now begun using PCR, RFLP and related DNA profiling techniques to observe the sex lives of trees. Beverly Dow, a graduate student in ecology, conducted a unique genetic study of oak tree progeny on an abandoned farm in Harvard, Ill. Dow first collected fresh leaves and acorns from 150 burr oak trees on the farm and from each tree and froze them in liquid nitrogen. Using a variety of DNA analysis techniques, she obtained microsatellites- visual representations of repeating patterns of DNA- for every tree, sapling and acorn. Comparing the DNA of each acorn with that of adult trees allowed her to determine who the "father" tree was for each and how far its pollen had traveled. "Most people don't think about trees having sex. It's a complicated thing, actually, because plants are rooted in place," notes Dow. All oak trees produce male and female flowers. The male flowers release pollen that is carried to receptive female flowers -- sometimes on the same tree, but usually on other trees -- by an intermediary like a bee or the wind. Once a female flower is pollinated, it develops an acorn. Dow's genetic analyses showed that ten percent of acorns collected from one of the "mother" oaks was fathered by a tree far away, i.e. one not even living in the same stand of trees. "That's not what I expected to find," says Dow, whose research will be published in the Journal of Theoretical and Applied Genetics. "I thought more offspring would come from nearby trees, because studies of wind-carried pollen have shown that the density of pollen decreases rapidly with distance from the father tree." Interestingly, two of the adult trees on the abandoned farm did not contribute pollen to any of the acorns or saplings in the area. Dow hypothesized that these trees may have been infertile for some reason. This is the first study to use DNA profiling to study a natural population of plants. The research should ultimately benefit forest preservation and the study of wind pollination and other plant mating systems, she said. Transmitted: 95-03-08 16:30:18 EST
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