December 2009 Archives

Plant Releases Toxic Chemicals Into Soil

A team led by Harsh Bais has determined that Phragmites employs a strategy known as allelopathy, in which plants release toxic chemicals into the soil to deter other plants from growing close to them.

Phragmites australis, ranks as one of the world's most invasive plants.

The invasive strain, which hails from Eurasia, overtakes its "native" cousin, which has lived in North America for the past 10,000 years, ironically by provoking the native plant to "take itself out," through a combination of microbial and enzymatic activity in the soil.

Phragmites Reeds in Wetlands

In soil studies at the Delaware Biotechnology Institute, a center for life sciences research at UD, scientists discovered that invasive Phragmites produces elevated levels of a benign compound, a precursor of gallic acid known as gallotannin, relative to its native cousin.

However, when this gallotannin, a polymeric phenol, is attacked by tannase produced through enzymatic activity by native plants and rhizospheric microbes, toxic gallic acid is produced and released in the root zone, exacerbating the invasive Phragmites' noxiousness.

"The tannins are like partners in crime in the process," Bais said.

He noted that Hanson and Kumar collected microbes present on the root surface of the plants and revealed that the "bugs" cleave the polymer (gallotannin) to release the monomer (gallic acid) because the microbes are using the tannins as a carbon source.

"It's like a two-way highway," Bais said, "the plant is working with bacteria to secrete gallic acid into the soil."

Bais says that the microbial population is the same in the native versus the invasive Phragmites. The invasive variety simply secretes more gallotannins into the soil than its native cousin, putting the native plant at a disadvantage in turf battles between the two strains.

Phragmites has overtaken millions of acres of wetlands in the United States, thanks to the aggressive, invasive strain of the plant that came on the scene some 200 years ago from Eurasia.

The exotic species has displaced the non-aggressive native variety of the plant, relegating the native strain to isolated patches and wetland margins along the Atlantic coast.

"Now we have a way to remedy the sick soil," Bais said. "After years of research, we have identified a mechanism that may lead to a solution to the Phragmites invasion."

The research was supported by the University of Delaware Research Foundation (UDRF). Gurdeep Bains's involvement in the study was made possibly by a BOYSCAST Fellowship from the Department of Science and Technology, India.

SOURCE: Newswise

"Killer spices" provide eco-friendly pesticides for organic fruits and veggies

Rosemary, thyme, clove, and mint are well-known spices that are emerging as organic agriculture's key weapons against insect pests.

Scientists in Canada are reporting new research on these so-called "essential oil pesticides" or "killer spices." These pesticides have added to the crop-preserving arsenal of organic growers and offer several advantages over their counterparts -- they're readily available and don't require lots of regulatory approval.

And they're safer for gardeners and farm workers, who are at high risk for pesticide exposure.

Murray Isman, Ph.D., of the University of British Columbia is developing these pesticides.

So, just what is it exactly about these spices that allow them to work their magic outside the kitchen? Here's Dr. Isman again:

"It turns out that some of these oils and some of the chemical constituents in the oils are neurotoxic to many types of insects. At least one of their actions, and we're not certain about all of their actions, one of their actions is they interfere with a neuromodulator in insects called octopamine. It's sort of an internal valium for insects, it sort of calms them down so their nervous systems
don't get overstimulated by external stimuli. If you remove that octopamine, which is what
some of these oils do, they get hyperexcited and eventually die."

These pesticides, usually a combination of spices diluted with water, have added to the crop-preserving arsenal of organic growers and offer several advantages over their counterparts. First, they are readily available and don't require lots of regulatory approval. Also, insects exposed to the spices are less likely to evolve resistance to the toxins. And, they're safer for farm workers, who are at high risk for pesticide exposure. 

"Some of these oils, as some other people have mentioned, are very good antimicrobials,
so they could be very useful against food spoilage organisms, for example. They are useful
against certain plant pathogenic fungi and bacteria, and they do have this phytotoxic effect
on plants, so at high concentrations they can be used as natural herbicides."

 

Don't you love this idea?  I can just see this as a rose garden :-)


In the heart of a residential neighborhood there is a wonderful community garden with some amazing surprises. Community gardens are very special for a multitude of reasons. They provide small growing plots to people who may not have access to any other planting area. They are popping up all over urban and suburban centers all over the United States . In place of debris, abandoned neglected vacant lots, greenery, flowers and vegetables are sprouting. People are taking pride in their new gardens and neighborhoods improve because of them. New friendships bloom. Going green, producing your own locally grown food and being politically correct: it's all great!

Read more about urban gardening at Robert's Tropical Paradise Garden