Focus
on Research
Penn State Intercom......April
25, 2002
Weed reveals plant-pollination secrets
By Barbara Kennedy
College of Science
The
research group of Andy Stephenson, professor of biology, recently has
begun studying the horse-nettle plant, a major weed in agricultural fields
in Pennsylvania and other states, which is in the same "Solanaceae" family
as tomato, potato, eggplant, tobacco and petunia 
plants.
"Horse nettle is a particularly damaging weed because any pesticides that kill the weed also kill the economically important plants in the Solanaceae family," Stephenson said.
Until the Stephenson group began its research, the horse nettle was thought to be unable to fertilize itself -- an unusual trait for a weed. "We have found evidence that after 20 to 40 flowers on a horse-nettle plant have failed to set fruit because there is no pollen around from other plants of its species, the plant does become partially able to pollinate itself," Stephenson said. "The plant's first several clusters of flowers appear to strongly reject that plant's own pollen; however, if those flowers do not produce any fruits the plant will begin to make just a few fruits by self-pollination that have a relatively small number of seeds. If there continues to be no 'cross' pollen around from other horse-nettleplants, more and more fruits will form with more and more seeds as a result of self-pollination."
The group uses its electric toothbrush -- modified by replacing the brush with a flower-support loop -- to remove pollen from the flowers and collect it in miniature test tubes made from half a pharmaceutical gel cap. "The electric toothbrush vibrates at the same frequency as the wings of a bee that is shaking pollen out of these flowers," Stephenson explained. The researchers are selectively pollinating their 30 sets of horse-nettle plants -- each group genetically identical to one of the 30 wild parent plants they collected from fields near the University -- by dipping the female parts of the flowers into the miniature test tubes to coat them with a particular plant's pollen.
A plant that cannot
fertilize itself recognizes its own pollen cells as "incompatible" and
uses 
biochemical
means to prevent them from growing -- thereby preventing the plant from
making seeds containing the pollen's genes. "We are studying how plants
naturally control inbreeding by looking at the molecular, genetic, population
and environmental factors that affect the growth of the pollen tube during
the fertilization process," Stephenson said. "The horse nettle is a particularly
useful species for these studies."
The University's Teh-Hui Kao, professor of biochemistry and molecular biology, is one of the worldwide leaders in fertilization molecular biology in the entire family of plants that includes the horse nettle. "By making use of the molecular biology that Teh-Hui Kao already has worked out, we now have more time and resources to focus on the ecological and evolutionary questions we really want to answer concerning mating and breeding systems in these plants," Stephenson explained.
"We hope to answer such questions as what are the consequences of inbreeding, what effects does the environment have on the breakdown of self-incompatibility, what can we do to overcome those environmental factors, and what are the genes that modify the strength of incompatibility," Stephenson said. "Mostly I'm interested in how plants regulate which pollen grains actually achieve fertilization and what impact does that selection process have for the genetics and the evolution of a plant species."
"One important reason to study this plant is to learn how to control it, especially since it is becoming an increasingly prevalent pest in Pennsylvania," he said.
Stephenson said he also hopes his team's research with the horse nettle will help to reveal how to control other invasive species of native and non-native plants, and will develop new knowledge about the basic biology of the interactions between plant cells during fertilization that could benefit breeders of hybrid crops.
Barbara Kennedy can be reached at bkk1@psu.edu.
Groundwater expert
urges people to take
drought seriously
As the drought of 2001-2002 worsens, a water resources extension specialist in the College of Agricultural Sciences worries that people are not taking a critical situation seriously.
"So far, this has been an invisible drought," said Bryan Swistock. "It has been a water supply drought -- in much of Pennsylvania, the really dry weather started last fall after the growing season was over. Wells are going dry across the state. In many places, we have a groundwater crisis. But they can't see groundwater, so most people aren't concerned.
"People really need to begin conserving water. Groundwater levels are so low that a rainstorm or two won't make much of a difference. But rain changes people's perception. Even if the rain makes no difference in the water situation, people let down their guard. That's the biggest hurdle we face -- people no longer take drought seriously."
Swistock pointed out that groundwater levels under much of the state never recovered from the drought of 1999. "Unless we get considerably more than average precipitation in a short time -- between now and early May -- this drought will be worse on a water-supply basis than the drought of '99," he said.
In Pennsylvania, average precipitation over the year averages to just over 3 inches a month. "But my sense is that we will need considerably more than that to end this drought," he said.
Swistock offers these suggestions to save water:
* Replacing an old toilet with a new
.6 gallon-per-flush model could save a typical household from 7,900 to 21,700 gallons of water per year;
* Placing a plastic jug filled with water or small rocks in older toilet tanks can cut down on the amount of water needed for each flush and save more than 1,000 gallons per year;
* Repairing dripping faucets and leaking toilets can save more than 10 gallons of water per person per day. A faucet dripping at one drop per second wastes 2,700 gallons per year;
* Wash clothes and dishes only when you have a full load. When replacing an older machine, consider high-efficiency models, which use an average of 30 percent less water and 40 percent to 50 percent less energy, saving about nine gallons per washing machine cycle and 7.5 gallons per dishwasher cycle; and
* Installing a water-efficient showerhead can save one to 7.5 gallons per minute. Taking a quick shower can save an average of 20 gallons of water.