Toronto, Ontario, Canada
July 22, 2008
Environmental factors can
transform the ratio of females to males in plant populations
according to new research out of the
University of Toronto.
The study conducted by Ivana Stehlik, a lecturer, Jannice
Friedman, a PhD candidate, and Spencer Barrett, a professor,
involved a novel approach using genetic markers (known DNA
sequences) to identify the sex of seeds. The team investigated
six natural populations of the wind-pollinated herb Rumex
nivalis in the Swiss Alps and mapped the distance between
females and neighbouring males. They then measured the amount of
pollen captured by female flowers and collected seeds from the
plants when they were mature.
"The plant has strongly female-biased flowering sex ratios in
these populations. We wanted to find out the mechanism causing
the bias," said Barrett. "We found that where there were more
males surrounding females, females captured more pollen, matured
more seed and produced more strongly female-biased offspring."
The authors suggest that when females capture large amounts of
pollen, female-determining pollen tubes out-compete
male-determining pollen tubes to fertilize the single ovule in
each flower.
Barrett leads a world-renowned research group working on the
genetics and evolution of plant reproduction. His pioneering
work has had a profound influence on the understanding of
biological invasions, weed management strategies and
conservation biology. "Our results demonstrate for the first
time that demographic aspects of the mating environment of
plants can influence the sex ratios of plants females produce,"
added Barrett.
The study findings are published in the current edition of the
Proceedings of the National
Academy of Sciences. |
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