Plants adapt to the local weather and soil conditions in which they grow, and these environmental adaptations are known to evolve over thousands of years as mutations slowly accumulate in plants' genetic code. But a University of Rochester biologist has found that at least some plant adaptations can occur almost instantaneously, not by a change in DNA sequence, but simply by duplication of existing genetic material.
Justin Ramsey's findings are published in the current Proceedings of the National Academy of Sciences.
While nearly all animals have two sets of chromosomesone set inherited from the maternal parent and the other inherited from the paternal parentmany plants are polyploids, meaning they have four or more chromosome sets. "Some botanists have wondered if polyploids have novel features that allow them to survive environmental change or colonize new habitats," says Assistant Professor Justin Ramsey. "But this idea had not been rigorously tested."
Plant breeders have previously induced polyploidy in crop plants, like corn and tomato, and evaluated its consequences in greenhouses or gardens. Such an experimental approach had never been taken in wild plant species, Ramsey said, so it was unknown how polyploidy affected plant survival and reproduction in nature.
Ramsey decided to perform his own test by studying wild yarrow (Achillea borealis) plants that are common on the coast of California. Yarrow with four chromosome sets (tetraploids) occupy moist, grassland habitats in the northern portion of Ramsey's study area; yarrow with six sets of chromosomes (hexaploids) grow in sandy, dune habitats in the south.
Ramsey transplanted tetraploid yarrow from the north into the southern habitat and discovered that the native hexaploid yarrow had a five-fold survival advantage over the transplanted tetraploid yarrow. This experiment proved that southern plants are intrinsically adapted to dry conditions; how
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