Plants play larger role than thought in cleaning up air pollution

Poplars, aspens, other trees provide extensive "ecosystem services."
Credit: USDAChemicals known as oxygenated volatile organic compounds (oVOCs) affect environment, human health

Vegetation plays an unexpectedly large role in cleansing the atmosphere, a new study finds.

The research, led by scientists at the National Center for Atmospheric Research (NCAR) in Boulder, Colo., uses observations, gene expression studies, and computer modeling to show that deciduous plants absorb about a third more of a common class of air-polluting chemicals than previously thought.

Evolution caught in the act

Different mutants of Arabidopsis thaliana. Image: Detlef WeigelUS-German team measures how quickly genomes change

Mutations are the raw material of evolution. Charles Darwin already recognised that evolution depends on heritable differences between individuals: those who are better adapted to the environment have better chances to pass on their genes to the next generation. A species can only evolve if the genome changes through new mutations, with the best new variants surviving the sieve of selection.

Shedding light on microscopic flower petal ridges

Scanning electron microscope view of plant cell nanoridges. Photo: John OhlroggeMicroscopic ridges contouring the surface of flower petals might play a role in flashing that come-hither look pollinating insects can't resist. Michigan State University scientists and colleagues now have figured out how those form.

The result could help researchers learn to enhance plants' pollination success and even could lead to high-grip nanomaterials and "green chemical" feedstocks."Surprisingly, our work on plant surface biochemistry became a birds and bees and flowers story," said John Ohlrogge, MSU University Distinguished Professor of plant biology.

How the daisy got its spots

Photo:Meredith Murphy ThomasDevelopment and morphology of insect-mimicking spots on the flower petals of a South African beetle daisy

Dark spots on flower petals are common across many angiosperm plant families and occur on flowers such as some lilies, orchids, and daisies. Much research has been done on the physiological and behavioural mechanisms for how these spots attract pollinators. But have you ever wondered what these spots are composed of, how they develop, or how they only appear on some but not all of the ray florets?

Fertiliser use not always helpful in re-vegetation efforts

Photo:Danielle Langlois/WikimediaPlants in subarctic Quebec community don't always benefit from application of fertiliser

Companies and communities trying to restore vegetation on damaged northern landscapes should think twice about using fertiliser to stimulate growth according to new research published in the November issue of Arctic, Antarctic and Alpine Research.Not all plants benefit from the use of fertilisers. In fact, some do worse.

How did flowering plants evolve to dominate Earth?

Photo:John O'Neill/WikimediaSuperior 'leaf plumbing' gave flowering plants evolutionary advantage

To Charles Darwin it was an 'abominable mystery' and it is a question which has continued to vex evolutionists to this day: when did flowering plants evolve and how did they come to dominate plant life on earth? A study in Ecology Letters reveals the evolutionary trigger which led to early flowering plants gaining a major competitive advantage over rival species, leading to their subsequent boom and abundance.

When camouflage is a plant's best protection

Photo: Matthew R. KloosterA rare woodland plant uses 'cryptic coloration' to hide from its predators

It is well known that some animal species use camouflage to hide from predators. Individuals that are able to blend in to their surroundings and avoid being eaten are able to survive longer, reproduce, and thus increase their fitness (pass along their genes to the next generation) compared to those who stand out more. This may seem like a good strategy, and fairly common in the animal kingdom, but who ever heard of a plant doing the same thing?

The cause behind the characteristic shape of a long leaf revealed

By stretching a foam ribbon and dissecting leaves, a mathematical model emerges

Applied mathematicians dissected the morphology of the plantain lily (Hosta lancifolia), a characteristic long leaf with a saddle-like arc midsection and closely packed ripples along the edges. The simple cause of the lily's fan-like shape – elastic relaxation resulting from bending during differential growth – was revealed by using an equally simple technique, stretching foam ribbons.

New discoveries showing how crops survive drought

Breakthrough research done earlier this year by a plant cell biologist at the University of California, Riverside has greatly accelerated scientists' knowledge on how plants and crops can survive difficult environmental conditions such as drought.

Working on abscisic acid (ABA), a stress hormone produced naturally by plants, Sean Cutler's laboratory showed in April 2009 how ABA helps plants survive by inhibiting their growth in times when water is unavailable – research that has important agricultural implications.

Plants prefer their kin, but crowd out competition

Forest Starr, Kim Starr/WikimediaPlants don't mind sharing space with their kin but when they're potted with strangers of the same species they start invigorating their leaves, a study by McMaster University reveals.

The research, which appears in the current issue of the American Journal of Botany, suggests non-kin plants will not only compete underground for soil nutrients, but will attempt to muscle out the competition above ground in the ongoing struggle for light.

How plant stem cells guard against genetic damage

This is a confocal laser scanning micrograph of an Arabidopsis root tip in which the cell outlines are marked in green by a fluorescent protein. The orange region marks stem cells that died after treatment with a drug that damages DNA. Image: John Innes CentreScientists at the John Innes Centre in Norwich, UK, have shown how plants can protect themselves against genetic damage caused by environmental stresses. The growing tips of plant roots and shoots have an in-built mechanism that, if it detects damage to the DNA, causes the cell to 'commit suicide' rather than pass on its defective DNA.

Plants have, at the very tips of their roots and shoots, small populations of stem cells, through which they are able to grow and produce new tissue throughout the plant's life. These stem cells are the precursors to producing plant tissues and organs.

Common plants can eliminate indoor air pollutants

Hemigraphis alternata, or purple waffle plant, one of the highest rated ornamentals for removing indoor air pollutants. Photo: Dr. Stanley KaysAir quality in homes, offices, and other indoor spaces is becoming a major health concern, particularly in developed countries where people often spend more than 90 per cent of their time indoors. Surprisingly, indoor air has been reported to be as much as 12 times more polluted than outdoor air in some areas. Indoor air pollutants emanate from paints, varnishes, adhesives, furnishings, clothing, solvents, building materials, and even tap water.

A long list of volatile organic compounds, or VOCs [including benzene, xylene, hexane, heptane, octane, decane, trichloroethylene (TCE), and methylene chloride], have been shown to cause illnesses in people who are exposed to the compounds in indoor spaces.

Acute illnesses like asthma and nausea and chronic diseases including cancer, neurologic, reproductive, developmental, and respiratory disorders are all linked to exposure to VOCs. Harmful indoor pollutants represent a serious health problem that is responsible for more than 1.6 million deaths each year, according to a 2002 World Health Organisation report.

Stanley J. Kays, Department of Horticulture, University of Georgia, was the lead researcher of a study published in HortScience that tested ornamental indoor plants for their ability to remove harmful VOCs from indoor air. According to Kays, some indoor plants have the ability to effectively remove harmful VOCs from the air, and not only have the ability to improve our physical health, but also have been shown to enhance our psychological health. Adding these plants to indoor spaces can reduce stress, increase task performance, and reduce symptoms of ill health.

The ability of plants to remove VOCs is called "phytoremediation". To better understand the phytoremediation capacity of ornamental plants, the research team tested 28 common indoor ornamentals for their ability to remove five volatile indoor pollutants. "The VOCs tested in this study can adversely affect indoor air quality and have a potential to seriously compromise the health of exposed individuals," Kays explained.

"Benzene and toluene are known to originate from petroleum-based indoor coatings, cleaning solutions, plastics, environmental tobacco smoke, and exterior exhaust fumes emanating into the building; octane from paint, adhesives, and building materials; TCE from tap water, cleaning agents, insecticides, and plastic products; and alpha-pinene from synthetic paints and odorants."

During the research study, plants were grown in a shade house for eight weeks followed be acclimatisation for twelve weeks under indoor conditions before being placed in gas-tight glass jars. The plants were exposed to benzene, TCE, toluene, octane, and alpha-pinene, and air samples were analysed. The plants were then classified as superior, intermediate, and poor, according to their ability to remove VOCs.

Of the 28 species tested, Hemigraphis alternate (purple waffle plant), Hedera helix (English ivy), Hoya carnosa (variegated wax plant), and Asparagus densiflorus (Asparagus fern) had the highest removal rates for all of the VOCs introduced. Tradescantia pallida (Purple heart plant) was rated superior for its ability to remove four of the VOCs.

The study concluded that simply introducing common ornamental plants into indoor spaces has the potential to significantly improve the quality of indoor air. In addition to the obvious health benefits for consumers, the increased use of indoor plants in both ''green'' and traditional buildings could have a tremendous positive impact on the ornamental plant industry by increasing customer demand and sales.

Plant fossils give first real picture of earliest Neotropical rainforests

Photo: WikimediaA team of researchers including a University of Florida palaeontologist has used a rich cache of plant fossils discovered in Colombia to provide the first reliable evidence of how Neotropical rainforests looked 58 million years ago.

Researchers from the Smithsonian Institution and UF, among others, found that many of the dominant plant families existing in today’s Neotropical rainforests – including legumes, palms, avocado and banana – have maintained their ecological dominance despite major changes in South America’s climate and geological structure.

The study, which appears this week in the online edition of the Proceedings of the National Academy of Sciences, examined more than 2,000 megafossil specimens, some nearly 10 feet long, from the Cerrejón Formation in northern Colombia. The fossils are from the Paleocene epoch, which occurred in the 5- to 7-million-year period following the massive extinction event responsible for the demise of the dinosaurs.

“Neotropical rainforests have an almost nonexistent fossil record,” said study co-author Fabiany Herrera, a graduate student at the Florida Museum of Natural History on the UF campus. “These specimens allow us to actually test hypotheses about their origins for the first time ever.”

Herrera said the new specimens, discovered in 2003, also provide information for future studies that promise to provide an even stronger understanding of the plants that formed the earliest Neotropical communities.

Many previous assumptions and hypotheses on the earliest rainforests are based on studies of pollen fossils, which did not provide information about climate, forest structure, leaf morphology or insect herbivory.

The new study provides evidence Neotropical rainforests were warmer and wetter in the late Paleocene than today but were composed of the same plant families that now thrive in rainforests. “We have the fossils to prove this,” Herrera said. “It is also intriguing that while the Cerrejón rainforest shows many of the characteristics of modern equivalents, plant diversity is lower.”

The site, one of the world’s largest open-pit coal mines, also yielded the fossil for the giant snake known as Titanoboa, described by UF scientists earlier this year.

“These new plant fossils show us that the forest during the time of Titanoboa, 58 million years ago, was similar in many ways to that of today,” said Florida Museum vertebrate palaeontologist Jonathan Bloch, who described Titanoboa but was not part of the rainforest study. “Like Titanoboa, which is clearly related to living boas and anacondas, the ancient forest of northern Colombia had similar families of plants as we see today in that ecosystem. The foundations of the Neotropical rainforests were there 58 million years ago.”

Megafossils found at the Cerrejón site made it possible to use leaf structure to identify specimens down to the genus level. This resolution allowed the identification of plant genera that still exist in Neotropical rainforests. With pollen fossils, specimens can be categorised only to the family level.

Researchers were surprised by the relative lack of diversity found in the Paleocene rainforest, Herrera said. Statistical analyses showed that the plant communities found in the Cerrejón Formation were 60 per cent to 80 per cent less diverse than those of modern Neotropical rainforests. Evidence of herbivory also showed a low diversity level among insects.

The study’s authors say the relative lack of diversity indicates either the beginning of rainforest species diversification or the recovery of existing species from the Cretaceous extinction event.

The researchers estimate the Paleocene rainforest received about 126 inches of rainfall annually and had an average annual temperature greater than 86 degrees. The Titanoboa study, which used different methods, estimated an average temperature between 89 and 91 degrees. Today the region’s temperatures average about 81 degrees.

Herrera is now comparing fossils from the Cerrejón site to specimens from other Paleocene sites in Colombia to see how far the early rainforest extended geographically. He is also examining fossils from a Cretaceous site to determine differences in composition before and after the extinction event.

Writer: Bill Kanapaux

Plants' response to fire tested

There was a fire this summer Tietar Valley (Ávila). Photo: SINC

A team from the National Institute for Agricultural and Food Research and Technology (INIA) has developed a new method for identifying the flammability of plant species by using a device that measures how construction materials react to fire. The technique, being presented this week at the Fifth Spanish Forestry Congress, can be used to improve fire risk maps.

A group of researchers from the Forest Fires Laboratory (CIFOR-INIA) has applied a "mass loss calorimeter", a device used to study how construction materials respond to fire, to forestry samples. "This allows us to study the flammability of plant species", Javier Madrigal Olmo, one of the study's authors, tells SINC.

The flammability trials measure the speed at which combustion starts and develops, as well as the amount of heat emitted by the sample during the process.

In order to measure these data, the researchers first put the plant sample in a special basket, "which is unique in the world", and which simulates natural conditions. The material heats up "constantly and uniformly" with a conical heater, and the gases rise up through a chimney, with a "thermopile" at the end, which registers the heat emitted.

Researchers have tested plants' response to fire. Photo: Laboratorio de incendios forestales (CIFOR-INIA)/ SINC"This methodology gives a very good reflection of how combustion takes place in conditions more like those found in the field, which is why we suggest it could be used to improve the classification systems (league tables, risk indices and flammability maps used in the Spanish autonomous regions), which to date have been based on tests that provide less information, or on those carried out in laboratory conditions far removed from reality", Madrigal tells SINC. "This would allow forestry managers to prioritise their preventive actions according to the tree species in the area".

The creators of this technique, which is being presented in Ávila this Thursday at the Spanish Forestry Congress, have shown that flammability varies according to the humidity of the sample and the type of species. For example, it is higher for the Aleppo pine (Pinus halepensis) than the Maritime pine (Pinus pinaster), while the flammability of this species is higher still than that of the Kermes oak (Quercus coccifera).

Madrigal says that one of the investigation strands within climate change research focuses on how global temperature increase will affect plant physiology, "and this is influenced by factors such as humidity, and related to flammability".

The research has been published recently in the Journal of Fire Sciences and has been carried out as part of the EU's Sixth Framework Programme FIRE PARADOX project, which is backing the development of new methods to prevent and extinguish forest fires using "innovative and integrated" approaches.

Woody plants adapted slower to past climate change

If evolutionary history repeats itself, woody plants may have a harder time than herbaceous plants keeping pace with global warming. Photo: Yoshikazu Hara/Wikimedia CommonsIf past is prelude, trees and shrubs may have a harder time keeping pace with global warming

Can we predict which species will be most vulnerable to climate change by studying how they responded in the past? A new study of flowering plants provides a clue. An analysis of more than 5000 plant species reveals that woody plants – such as trees and shrubs – adapted to past climate change much more slowly than herbaceous plants did. If the past is any indicator of the future, woody plants may have a harder time than other plants keeping pace with global warming, researchers say.

In a new study, biologists at the National Evolutionary Synthesis Centre and Yale University teamed up to find out how flowering plants adapted to new climates over the course of their evolution. By integrating previously published genealogies for several plant groups with temperature and rainfall data for each species, they were able to measure how fast each lineage filled new climate niches over time.

When they compared woody and herbaceous groups, they found that woody plants adapted to new climates 2 to 10 times slower than herbs. "Woody plants eventually evolved to occupy about the same range of climates that herbaceous plants did, but woody plants took a lot longer to get there," said lead author Stephen Smith, a postdoctoral researcher at the National Evolutionary Synthesis Center in Durham, NC.

The researchers trace the disparity to differences in generation time between the two groups. Longer–lived plants like trees and shrubs typically take longer to reach reproductive age than fast–growing herbaceous plants, they explained. "Some woody plants take many years to produce their first flower, whereas for herbs it could take just a couple months," said co-author Jeremy Beaulieu, a graduate student at Yale University.

Because woody plants have longer reproductive cycles, they also tend to accumulate genetic changes at slower rates, prior research shows. "If genetic mutations build up every generation, then in 1000 years you would expect plants with longer generation times to accumulate fewer mutations per unit time," said Smith.

This could explain why woody plants were slower to adapt to new environments. If genetic mutations provide the raw material for evolution, then woody plants simply didn't accumulate mutations fast enough to keep up. "If woody and herbaceous plants were running a race, the herbs would be the hares and the woody plants would be the tortoises," said Beaulieu.

By understanding how plants responded to climate change in the past, scientists may be better able to predict which groups will be hardest hit by global warming in the future. Unlike the tortoise and the hare, however, in this case slow and steady may not win the race. "Woody groups are obviously at a disadvantage as the climate changes," Beaulieu explained.

Does this mean that ecosystems dominated by trees – such as rainforests – will be more likely to disappear? Possibly. "If we look to the past for our clues, chances are trees will continue to respond much slower than herbs – as much as 10 times slower," Smith said. "But if the rate of climate change is 100 times faster, then they could all be in trouble. The kind of change we're experiencing now is so unprecedented," he added. While this study focused on long-term change over the last 100 million years, most climate models predict significant warming in the next century, the researchers explained. "That time frame may be too quick for any plant," Beaulieu said.

Tamarisk to invade Northwestern US

Models show habitat of the aggressive invasive plant likely will expand as temperature warms

If the future warming trends that scientists have projected are realised, one of the country's most aggressive exotic plants will have the potential to invade more US land area, according to a new study published in the current issue of the journal Invasive Plant Science and Management. The study found that tamarisk, prevalent today in some parts of the region, but generally limited to warm and dry environments, could expand its range into currently uninvaded areas.

"Results of our study suggest that a little over 20 per cent of the Northwest east of the Cascade Mountains supports suitable tamarisk habitat, but less than one per cent of these areas is currently occupied by the species," said Becky Kerns, a research ecologist with the Western Wildland Environmental Threat Assessment Center (WWETAC) who led the study. "That means the remainder is highly vulnerable to invasion right now with the situation potentially getting worse as favorable conditions for tamarisk may expand under climate change."

These findings translate into a two- to ten-fold increase in highly suitable tamarisk habitat in Oregon, Washington, and Idaho by the end of the century.

Tamarisk, also known as "saltcedar," is a deciduous shrub or small tree that grows quickly, reproduces profusely, and tolerates drought and salty conditions, making it capable of easily displacing native species. It also sheds flammable leaves that serve as potential fuel, significantly increasing an area's wildfire risk. The plant was intentionally introduced to the West in the 1800s as an ornamental, windbreak, shade, and erosion control species and today can be found growing prolifically in the Northwest in the central Snake River Plain, Columbia Plateau, and Northern Basin and Range.

"Tamarisk is not a newcomer to the Northwest," Kerns said. "But most people are surprised that it is found here and that it forms extensive stands along certain portions of our arid waterways."

In the study, Kerns and her Forest Service and Oregon State University colleagues compiled distribution data for all species of tamarisk in the region and used the information to develop habitat suitability maps, which helped identify those areas most susceptible to invasion. They then projected differences in habitat resulting from a changing climate to determine how the plant's habitat and distribution may change in the future.

Their projections indicated that, although most of the region maps as low habitat suitability for tamarisk, suitable and unoccupied habitat prone to invasion exists. Large, relatively uninvaded areas, including the Columbia, Okanagon, Yakima, upper John Day, Deschutes, lower Salmon, upper Owyhee, and lower Snake Rivers and their tributaries, appear to be especially vulnerable to infestation from adjacent populations.

"It's important to acknowledge that considerable uncertainty exists surrounding future climate change," Kerns said. "But our results provide a useful starting point for discussing the emerging threat of this highly invasive species in relation to climate change."

The slow and steady race of carnivorous plants

The trap of a Venus fly trap, showing trigger hairs.Photo by: Noah ElhardtFindings advance understanding of how complete food webs function

Like the man-eating plant in Little Shop of Horrors, carnivorous plants rely on animal prey for sustenance. Fortunately for humans, carnivorous plants found in nature are not dependent on a diet of human blood but rather are satisfied with the occasional fly or other insect. The existence of carnivorous plants has fascinated botanists and non-botanists alike for centuries and raises the question, "Why are some plants carnivorous?"


A recent article by Drs. Jim Karagatzides and Aaron Ellison in the September issue of the American Journal of Botany addresses this question. As Ellison stated, "The general answer to this is that in environments that have few nutrients (such as bogs, where we study carnivorous plants), carnivory allows these plants to capture nutrients 'on the wing'.

But if it's so good to be a carnivorous plant in these kinds of environments, why aren't there more carnivorous plants? Knowing how much it 'costs' a carnivorous plant to make a trap is a key piece of information needed to understand why there aren't more carnivorous plants."

Elllison and Karagatzides simultaneously measured both costs and benefits for traps, leaves, roots, and rhizomes of 15 different carnivorous plant species, including pitcher plants and the Venus fly trap. By measuring the construction cost of carbon needed to create these plant structures and comparing it to the payback time – the amount of time the structure takes to photosynthesise to recoup the carbon used in its construction – Ellison and Karagatzides were able to determine how beneficial a trap might be to a plant.

Contrary to expectations, the average cost to create a trap was actually significantly lower than the cost to create a leaf. Ellison said, "The most interesting result is that carnivorous traps are 'cheap' to make (at least compared with leaves). Models of the evolution of carnivory in plants have suggested that traps should be 'expensive' structures – they take a lot of carbon and nutrients to make, and so only when they can't recover these costs in any other way should carnivory be adaptive (or evolutionarily favored). But because carnivorous plants have very low rates of photosynthesis, it still takes a very long time for the plants to 'pay' for them (by accumulating new carbon through photosynthesis)."

Understanding how carbon and mineral nutrients are allocated among different plant organs, different species, and vegetation of different biomes is one of the major goals of the field of plant ecology. Carnivorous plants are a model organism to study these carbon and mineral nutrient tradeoffs because the plants inhabit open environments where light and water are not limiting but nutrients are in extremely short supply, and therefore it is relatively easy to separate out experimentally the effects of nutrient limitation from effects of limitation of light or water.

Ellison and Karagatzides's findings advance our understanding of how complete food webs function. Ellison stated, "Nicholas Gotelli [from the University of Vermont] and I, along with our students and colleagues, have spent more than 10 years developing this micro-ecosystem as a model for how complete food webs – including the plant as both producer and habitat, and the aquatic food web that lives in the pitchers as both detritivore and mutualist – and aquatic ecosystems actually work.

These studies have provided new insights into population dynamics and extinction, the importance of food webs for persistence of top predators, and now how organisms allocate nutrients to better control and modulate energy and nutrient fluxes across ecosystem boundaries."

Secrets in a seed: Evolution of the first flowers

Flowering individuals of Trithuria submersa (Hydatellaceae) from Western Australia, 1998. Each “flower” is a compact head of multiple flowers. Photo: Dennis Stevenson, New York Botanical Garden.Researchers work on part of Darwin's 'abominable mystery'

Approximately 120-130 million years ago, one of the most significant events in the history of the Earth occurred: the first flowering plants, or angiosperms, arose. In the late 1800s, Darwin referred to their development as an "abominable mystery." To this day, scientists are still challenged by this "mystery" of how angiosperms originated, rapidly diversified, and rose to dominance.

Studies of key features of angiosperm evolution, such as the evolution of the flower and development of the endosperm, have contributed to our current understanding of relationships among the early families of flowering plants. Examining the development of seeds and embryos among early angiosperms may help to improve our understanding of how flowering plants evolved from the nonflowering gymnosperms.

A recent study by Dr. Paula Rudall and colleagues published in the September issue of the AJB explores a piece of this mystery: the microscopic anatomy of seed development in Trithuria, a genus in the plant family Hydatellaceae, thought to be one of the earliest families of angiosperms – the so-called "basal angiosperms."

Rudall and colleagues' observations of the development of the embryo and endosperm (tissue that surrounds the embryo and provides nutrition) in Trithuria suggest that double fertilisation occurs. Double fertilisation is a unique feature of flowering plants where one sperm nucleus unites with the egg, producing the embryo, while another sperm nucleus unites with a separate nucleus from the female, producing the endosperm. The endosperm is divided into two regions – the micropylar and chalazal regions.

In Trithuria, the cells of the micropylar region divide many times to form the multi-celled endosperm. However, the chalazal region forms a single-celled haustorium, a structure that absorbs nutrients and ultimately degenerates to form an empty space in the seed. This situation is broadly similar to that of some waterlilies and some monocots but differs from that of many other early-diverging angiosperms such as Amborella, in which the endosperm is formed from the chalazal region.

One of the current hypotheses is that the endosperm originated as a monstrous proembryo that fails to develop into a plant. Rudall and colleagues' observations support this theory.

"Comparative studies of early endosperm development in extant 'basal' angiosperms (including Trithuria) tend to support this theory," Rudall said, "because there are similarities in early development of embryo and endosperm. In both cases, the first cell division produces two distinct domains that differ in their subsequent development." In the embryo, divisions of the chalazal cell produce most of the embryo.

The micropylar cell develops into a stalk that attaches the embryo to the seed coat. In the endosperm of Trithuria, the chalazal haustorium may regulate early endosperm development of the micropylar region, in addition to facilitating transfer of nutrients from the perisperm, maternally derived nutritive tissue, to the embryo.

Rudall and colleagues' findings shed some light on the possible role of the endosperm in early angiosperms. "The endosperm of Trithuria, though limited in size and storage capacity, is relatively persistent," Rudall stated. "Coupled with the well-developed perisperm that occurs in Trithuria, this could indicate that the ancestral role of endosperm was to transfer nutrients from the perisperm to the embryo, rather than as a storage tissue."

Indoor plants release volatile organic compounds

Snake Plant (Sansevieria trifasciata Prain), a popular houseplant, was found to emit VOCsStudy shows need for further research to determine environmental, health impacts

Potted plants add a certain aesthetic value to homes and offices, bringing a touch of nature to indoor spaces. It has also been shown that many common house plants have the ability to remove volatile organic compounds, gases or vapors emitted by solids and liquids that may have adverse short- and long-term health effects on humans and animals, from indoor air.

But take heed when considering adding some green to your environment; in addition to giving off healthy oxygen and sucking out harmful VOCs, a new study shows that some indoor plants actually release volatile organic compounds into the environment.

A research team headed by Stanley J. Kays of the University of Georgia's Department of Horticulture conducted a study to identify and measure the amounts of volatile organic compounds (VOCs) emitted by four popular indoor potted plant species. The study, published in the American Society for Horticultural Science journal HortScience, also noted the source of VOCs and differences in emission rates between day and night.

The four plants used in the study were Peace Lily (Spathiphyllum wallisii Regel), Snake Plant (Sansevieria trifasciata Prain), Weeping Fig (Ficus benjamina L.), and Areca Palm (Chrysalidocarpus lutescens Wendl.). Samples of each plant were placed in glass containers with inlet ports connected to charcoal filters to supply purified air and outlet ports connected to traps where volatile emissions were measured. The results were compared to empty containers to verify the absence of contaminants. A total of 23 volatile compounds were found in Peace Lily, 16 in Areca Palm, 13 in Weeping Fig, and 12 in Snake Plant. Some of the VOCs are ingredients in pesticides applied to several species during the production phase.

What are VOCs?
“Volatile organic compound” or VOC is the name given to a substance that contains carbon and that evaporates (becomes a vapor) or “off-gases” at room temperature.

Some examples of VOCs include benzene, methylene chloride, hexane, toluene, trichloroethane, styrene, heptane, and perchloroethylene.

What are the health effects?
The ability of VOCs to cause health effects varies greatly. As with other chemicals, the effects of VOC exposure depends on several factors including the type of VOC, the amount of VOC and the length of time a person is exposed.

Exposure to elevated levels of VOCs may cause irritation to the eyes, nose, and throat. Headaches, nausea, and nerve problems can also occur. Some people do not appear to have any kind of reaction to fairly “low” amounts of VOCs, while other people are fairly sensitive.

Studies of animals have shown that breathing some types of VOCs over a long period of time can increase the risk of getting cancer.

Source: Vermont Department of Health

Ficus benjamina, a popular houseplant, was found to emit VOCs. Photo: Stanley J. KaysOther VOCs released did not come from the plant itself, but rather the micro-organisms living in the soil. "Although micro-organisms in the media have been shown to be important in the removal of volatile air pollutants, they also release volatiles into the atmosphere", Kays stated. Furthermore, 11 of the VOCs came from the plastic pots containing the plants. Several of these VOCs are known to negatively affect animals.

Interestingly, VOC emission rates were higher during the day than at night in all of the species, and all classes of emissions were higher in the day than at night. The presence of light along with many other factors effect synthesis, which determines the rate of release.

The study concluded that "while ornamental plants are known to remove certain VOCs, they also emit a variety of VOCs, some of which are known to be biologically active. The longevity of these compounds has not been adequately studied, and the impact of these compounds on humans is unknown."

Wild ginseng smuggling racket busted in Russia

The roots were bound for China

Three plastic bags with 385 wild ginseng roots weighting 3.5 kilos were confiscated from a Russian citizen by Far Eastern Operative customs officers. The precious plant has been listed in the Russian Red List of threatened species and in Appendix II of CITES (the Convention on International Trade in Endangered Species of Wild Fauna and Flora). A criminal case has been filed against him.

All roots were in good salable condition. "The packaging method indicates that the roots were prepared for rapid transportation and were meant to be taken to the other side of the border. We believe he was just a part of a well-organised smuggling ring," said Sergey Aramilev, WWF Amur branch biodiversity conservation programme co-ordinator.

Apart from wild ginseng roots, Amur tiger and Far Eastern leopard parts are smuggled through such channels.

Last year, the organiser of a smuggling ring to China was jailed for for smuggling 3142 wild ginseng roots (29 kilos).

"Illegal harvesting of big packages of wild ginseng causes great damage to the nature," said Pavel Fomenko, WWF Amur branch biodiversity conservation programme co-ordinator.

"Despite these facts as well as appeals of Russian Academy of Science and WWF Russia to the government, administrative agencies never took enough measures for effective protection of this rare plant."