Genome duplication encourages rapid adaptation of plants

ScienceDaily (May 3, 2011) — 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 were recently published in the Proceedings of the National Academy of Sciences.
While nearly all animals have two sets of chromosomes -- one set inherited from the maternal parent and the other inherited from the paternal parent -- many 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; however, it was unclear if the change in chromosome number, per se, was responsible. Over time, natural hexaploid populations could have accumulated differences in DNA sequence that improved their performance in the dry habitats where they now reside.
To test that idea, Ramsey took first-generation, mutant hexaploid yarrow that were screened from a tetraploid population, and transplanted them to the sandy habitat in the south. Ramsey compared the performance of the transplanted yarrows and found that the hexaploid mutants had a 70 percent survival advantage over their tetraploid siblings. Because the tetraploid and hexaploid plants had a shared genetic background, the difference of survivorship was directly attributable to the number of chromosome sets rather than the DNA sequences contained on the chromosomes.
Ramsey offers two theories for the greater survivorship of the hexaploid plants. It may be that DNA content alters the size and shape of the cells regulating the opening and closing of small pores on the leaf surface. As a result, the rate at which water passes through yarrow leaves may be reduced by an increase in chromosome set number (ploidy). Another possibility, according to Ramsey, is that the addition of chromosome sets masks the effects of plant deleterious genes, similar to those that cause cystic fibrosis and other genetic diseases in humans.
"Sometimes the mechanism of adaptation isn't a difference in genes," said Ramsey, "it's the number of chromosomes." While scientists previously believed polyploidy played a role in creating gene families -- groups of genes with related functions -- they were uncertain whether chromosome duplication itself had adaptive value.
Now, Ramsey says scientists "should pay more attention to chromosome number, not only as an evolutionary mechanism, but as a form of genetic variation to preserve rare and endangered plants."
Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Rochester.

Journal Reference:
J. Ramsey. From the Cover: Polyploidy and ecological adaptation in wild yarrow. Proceedings of the National Academy of Sciences, 2011; 108 (17): 7096 DOI: 10.1073/pnas.1016631108
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Miniature power plants for aircraft bodies

ScienceDaily (June 14, 2011) — Sensor networks are supposed to pervade the body shell of airplanes in the future -- much like a nervous system. Thanks to a joint research project of EADS Germany and the Vienna University of Technology, these sensors do not require any external power supply.

Aircraft maintenance can be time consuming and expensive. It is much simpler if the airplane itself reports, where maintenance is required. The best solution is a sensor system, which even has its own power supply and is therefore independent of electrical wiring -- and this is what has now been developed by EADS Germany, in cooperation with the Institute of Sensor and Actuator Systems at Vienna University of Technology (TU Vienna). For each individual sensor, electricity is produced by a thermoelectric generator with a small water tank, storing thermal energy. The electricity is simply generated from the temperature difference between the icy cold air in high altitudes and the air close to the ground. This new sensor technology could not only facilitate aircraft maintenance, but also increase comfort for travelers.

Energy from the "Energy Harvester Module"

Even small collisions can easily lead to damage in the body of the aircraft. On aluminum bodies, a slight dent may be visible -- but on modern carbon materials, it is much harder to detect damage. Tiny, invisible cracks may appear, which are very hard to detect. With suitable sensors connected directly to the body of the aircraft, this could be constantly monitored. "A major problem with these sensors is the energy supply. Wiring up hundreds of sensors in the aircraft body is complicated and expensive," professor Ulrich Schmid from the Institute for Sensor and Actuator Systems at TU Vienna explains. For this reason, he -- together with Dominik Samson and professor Thomas Becker (EADS Germany) -- developed the idea of the "thermoelectric energy harvester" as an energy source, in order to be completely independent of batteries and wiring.

Electrical Current from Differences in Temperature

When an airplane rises to an altitude of thousands of meters, the exterior wall cools down. "From the temperature difference between the exterior and the interior, we can harvest energy for the sensor element, using a thermoelectric generator," Dominik Samson explains. In the energy-harvester module, there is a little water tank which can store the ground temperature for a while. Water is especially well suited for this task, because it can store large quantities of energy in terms of heat. The inner part of the module with the water tank is connected to the cold exterior wall via the thermoelectric generator. Therefore, a gradient in temperature arises at the generator, which can be used to create electrical voltage. During landing, it works the other way around: The plane heats up again, whereas the inner part of the module is still cold -- and again, electricity can be produced.

Whenever there is no thermoelectric current, for instance right after takeoff and during the landing, sophisticated electronics controls storage and transfer of electrical energy. The electronics and the components which create electricity only take up very little space: They fit on the palm of a hand and can easily be integrated into the aircraft body. The size can be adjusted for the individual energy demand of different applications.

No Wires, no Batteries

The data collected by the sensor can be transmitted wirelessly. Wireless technology does not only make maintenance easier, it also minimizes potential causes of defect and it reduces the weight of the airplane. During one flight, the energy harvester can provide the energy of eight to ten milliwatt hours -- which is sufficient for a wireless sensor. "A plane has a durability of roughly thirty years. If the sensors were operated with batteries, each of them would use up about one hundred batteries during this time," Dominik Samson estimates. Using a large number of sensors, this would not only require costly maintenance but it would also create unnecessary amounts of waste.

The concept of generating electricity in the airplane by utilizing differences in temperature could also be used for other purposes. Sensors could monitor whether the passengers have fastened their seatbelts or whether the tables are in an upright position. At the push of a button, a wireless signal could be transmitted to the flight attendants -- without expensive and complicated wiring, just powered by the body heat of the passengers. "The first and most important step has been taken. We are confident that this wireless sensor technology will travel on board of many airplanes soon," Ulrich Schmid says.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Vienna University of Technology, TU Vienna, via AlphaGalileo.

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Miniature power plants for aircraft bodies

ScienceDaily (June 14, 2011) — Sensor networks are supposed to pervade the body shell of airplanes in the future -- much like a nervous system. Thanks to a joint research project of EADS Germany and the Vienna University of Technology, these sensors do not require any external power supply.

Aircraft maintenance can be time consuming and expensive. It is much simpler if the airplane itself reports, where maintenance is required. The best solution is a sensor system, which even has its own power supply and is therefore independent of electrical wiring -- and this is what has now been developed by EADS Germany, in cooperation with the Institute of Sensor and Actuator Systems at Vienna University of Technology (TU Vienna). For each individual sensor, electricity is produced by a thermoelectric generator with a small water tank, storing thermal energy. The electricity is simply generated from the temperature difference between the icy cold air in high altitudes and the air close to the ground. This new sensor technology could not only facilitate aircraft maintenance, but also increase comfort for travelers.

Energy from the "Energy Harvester Module"

Even small collisions can easily lead to damage in the body of the aircraft. On aluminum bodies, a slight dent may be visible -- but on modern carbon materials, it is much harder to detect damage. Tiny, invisible cracks may appear, which are very hard to detect. With suitable sensors connected directly to the body of the aircraft, this could be constantly monitored. "A major problem with these sensors is the energy supply. Wiring up hundreds of sensors in the aircraft body is complicated and expensive," professor Ulrich Schmid from the Institute for Sensor and Actuator Systems at TU Vienna explains. For this reason, he -- together with Dominik Samson and professor Thomas Becker (EADS Germany) -- developed the idea of the "thermoelectric energy harvester" as an energy source, in order to be completely independent of batteries and wiring.

Electrical Current from Differences in Temperature

When an airplane rises to an altitude of thousands of meters, the exterior wall cools down. "From the temperature difference between the exterior and the interior, we can harvest energy for the sensor element, using a thermoelectric generator," Dominik Samson explains. In the energy-harvester module, there is a little water tank which can store the ground temperature for a while. Water is especially well suited for this task, because it can store large quantities of energy in terms of heat. The inner part of the module with the water tank is connected to the cold exterior wall via the thermoelectric generator. Therefore, a gradient in temperature arises at the generator, which can be used to create electrical voltage. During landing, it works the other way around: The plane heats up again, whereas the inner part of the module is still cold -- and again, electricity can be produced.

Whenever there is no thermoelectric current, for instance right after takeoff and during the landing, sophisticated electronics controls storage and transfer of electrical energy. The electronics and the components which create electricity only take up very little space: They fit on the palm of a hand and can easily be integrated into the aircraft body. The size can be adjusted for the individual energy demand of different applications.

No Wires, no Batteries

The data collected by the sensor can be transmitted wirelessly. Wireless technology does not only make maintenance easier, it also minimizes potential causes of defect and it reduces the weight of the airplane. During one flight, the energy harvester can provide the energy of eight to ten milliwatt hours -- which is sufficient for a wireless sensor. "A plane has a durability of roughly thirty years. If the sensors were operated with batteries, each of them would use up about one hundred batteries during this time," Dominik Samson estimates. Using a large number of sensors, this would not only require costly maintenance but it would also create unnecessary amounts of waste.

The concept of generating electricity in the airplane by utilizing differences in temperature could also be used for other purposes. Sensors could monitor whether the passengers have fastened their seatbelts or whether the tables are in an upright position. At the push of a button, a wireless signal could be transmitted to the flight attendants -- without expensive and complicated wiring, just powered by the body heat of the passengers. "The first and most important step has been taken. We are confident that this wireless sensor technology will travel on board of many airplanes soon," Ulrich Schmid says.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Vienna University of Technology, TU Vienna, via AlphaGalileo.

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Climbers leave rare plants' genetic variation on the rocks

ScienceDaily (May 3, 2011) — Rock climbers are having a negative impact on rare cliff-dwelling plants, ecologists have found. Writing in the British Ecological Society's Journal of Applied Ecology they say that in areas popular with climbers, conservation management plans should be drawn up so that some cliffs are protected from climbers.

The Northern Franconian Jura and the Swabian Alb are two of Germany's most important climbing areas but also the last European stronghold of the rare yellow whitlowgrass (Draba azoides) -- a small plant that lives on limestone cliffs where it forms cushion-like rosettes.

To find out how climbing in the area was affecting the plant, Frank Vogler and Christoph Reisch of the University of Regensburg compared the number and distribution of D. azoides on eight cliffs that had been climbed for at least the past 50 years with eight pristine, unclimbed cliffs of similar size and aspect. They also tested the plants' DNA to find out how climbers affected its genetic variation.

They found that on climbed cliffs, the plants were smaller and fewer in number on cliff faces but more frequent on the scree -- the broken rock fragments at the base of the cliffs.

According to Dr Reisch: "Climbing adversely affects these plants in a direct way. Abrasion by climbing ropes and using cracks and ledges as hand and footholds obviously lead to a decline in the species' abundance."

Genetic fingerprinting showed that compared with climbed cliffs, there were greater genetic differences between plants living at different heights on the pristine cliffs, meaning that by displacing plants the climbers are also moving their genes down the cliff. These genetic changes could, in the long-term, affect the plants' fitness to survive in an environment it has spent thousands of years adapting to.

"Seed dispersal is presumably enhanced by rock climbers. But climbers also remove and drop individual plants from cliff faces, causing a downward shift in population structure. This shift reduces the genetic differences between the plant populations living at different heights on the cliff," says Dr Reisch.

Because of their inaccessibility, cliffs are among the few ecosystems to be relatively unaffected by humans over the last centuries. Cliffs harbour a multitude of rare and endangered plant species and make a major contribution to regional biodiversity, so more effort needs to be made to conserve them.

"In mountain regions popular with climbers, conservation management plans should always ensure that some cliffs are out-of-bounds to climbers so that the native vegetation is protected," he concludes.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Wiley-Blackwell, via EurekAlert!, a service of AAAS.

Journal Reference:

Frank Vogler, Christoph Reisch. Genetic variation on the rocks - the impact of climbing on the population ecology of a typical cliff plant. Journal of Applied Ecology, 2011; DOI: 10.1111/j.1365-2664.2011.01992.x

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here