#nitrogen fixers

[gardenthrives]

Nitrogen Fixers in Your Organic Garden will Preserve the most Important Resource.

stop wasting your garden's potential

[gr33nguys]

Vetch and pea in bloom.

[tattooed-alchemist]

January 6, and the pea vines are still hanging in there.  We’ve got predicted freeze with maybe-snow starting around the 13th, so I’m just going to leave the vines and nature will take care of them finally/soon.

We’ve only bumped up against freezing temps overnight so far here in Seattle, and what’s coming could genuinely be close to freezing during the day and down to about 27˚F overnight and that really should be the end of these vines.

[indefenseofplants]

The Nitrogen-Fixing Abilities of Cycads

Long before the first legumes came onto the scene, the early ancestors of Cycads were hard at work fixing atmospheric nitrogen. However, they don't do this on their own. Despite being plentiful in Earth's atmosphere, gaseous nitrogen is not readily available to most forms of life. Only a special subset of organisms are capable of turning gaseous nitrogen into forms usable for life. Some of the first organisms to do this were the cyanobacteria, which has led them down the path towards symbioses with various plants on many occasions. 

Cycads are but one branch of the gymnosperm tree. Their lineage arose at some point between the Carboniferous and Permian eras. Throughout their history it would seem that Cycads have done quite well in poor soils. They owe this success to a partnership they struck up with cyanobacteria. Although it is impossible to say when exactly this happened, all extant cycads we know of today maintain this symbiotic relationship with these tiny prokaryotic organisms. 

The relationship takes place in Cycad roots. Cycads don't germinate with cyanobacteria in tow. They must acquire them from their immediate environment. To do so, they begin forming specialized structures called precoralloid roots. Unlike other roots that generally grow downwards, these roots grow upwards. They must situate themselves in the upper layer of soil where enough light penetrates for cyanobacteria to photosynthesize.

The cyanobacteria enter into the precoralloid roots through tiny cracks and take up residence. This causes a change in root development. The Cycad then initiates their development into true coralloid roots, which will house the cyanobacteria from that point on. Cycads appear to be in full control of the relationship, dolling out carbohydrates in return for nitrogen depending on the demands of their environment. Coralloid roots can shed and reform throughout the lifetime of the plant. It is quite remarkable to think about how nitrogen-fixing symbiotic relationships between plants and microbes have evolved independently throughout the history of life on this planet.

Photo Credits: [1] [2]

Further Reading: [1] [2]

[indefenseofplants]

Of Gunnera and Cyanobacteria

Nitrogen is a limiting resource for plants. It is essential for life functions and yet they do not produce it on their own. Instead, plants need to get it from their environment. They cannot uptake gaseous nitrogen, which is a shame because it makes up 78.09% of our atmosphere. As such, some plants have developed very interesting ways of obtaining nitrogen from their environment. Some, like the legumes, produce special nodules on their roots, which house bacteria that fix atmospheric nitrogen. Other plants utilize certain species of mycorrhizal fungi. One family of plants, however, has evolved a symbiotic relationship that is unlike any other in the angiosperm world.

Meet the Gunneras. This genus has a family all to itself - Gunneraceae. They can be found in many tropical regions from South America to Africa and New Zealand. Some species of Gunnera are small while others, like Gunnera manicata, have leaves that can be upwards of 6 feet in diameter. Their leaves are well armed with spikes and spines. All in all they are rather prehistoric looking. The real interesting thing about the Gunneras though, is in the symbiotic relationship they have formed with cyanobacteria in the genus Nostoc.

Gunnera produce specialized glands that house these cyanobacteria. The glands are filled with a special mucilage that not only attracts the cyanobacteria, but also stimulates it to grow. Once inside the glands, the cyanobacteria begins to grow into the plant, eventually fusing with the Gunnera cells. From there the cyanobacteria earn their keep by producing copious amounts of usable nitrogen and in return, the Gunnera supplies carbohydrates. This relationship is amazing and quite complex. It also offers researchers an insight into how such symbiotic relationships evolve.

Photo Credit: Fluffymuppet (http://bit.ly/1QARvXm) and Lotus Johnson (http://bit.ly/1QEBegP)

Further Reading: http://www.sfbotanicalgarden.org/garden/bloom_07_09.shtml

http://bit.ly/1U8SUHr

http://bit.ly/1q2cNDt

http://bit.ly/1UkBvvF

http://bit.ly/1MCgnsE

[theemperorsfeather]

In a new global theory of land-biome evolution, researchers suggest that plants are not passive features of their environments, but may instead actively behave in ways that determine the productivity and composition of their ecosystems. The theory was developed to explain why trees known as "nitrogen fixers," which produce their own fertilizer from atmospheric nitrogen, flourish in nitrogen-rich tropical soils, but are short-lived in the nitrogen-poor soils of boreal or temperate forests. The aerial photo above shows a rainforest in Panama in which nitrogen-fixing trees are abundant (about 10 percent of all trees), diverse, and persist in both young and old forests. The researchers found that tropical nitrogen fixers evolved to stop producing nitrogen in order to compete with neighboring trees.

It's easy to think of plants as passive features of their environments, doing as the land prescribes, serving as a backdrop to the bustling animal kingdom.But what if the ecosystems of the world take their various forms because plant "decisions" make them that way? A new theory presented by Princeton University researchers in the journal Nature Plants suggests that in some cases that may be exactly what happens. In one of the first global theories of land-biome evolution, the researchers write that plants may actively behave in ways that not only benefit themselves but also determine the productivity and composition of their environs.

. . .

Benjamin Houlton, an associate professor of terrestrial biogeochemistry at the University of California-Davis, said that the work "shows that it's possible to consider evolution at the scale of entire ecosystems and their functioning." 

[mindyourdirt]

It’s been one week since I sowed the seeds for soil repair. I’ve been watching closely hoping for some green sprout to push its way through the rich dark top soil. Get your machete and your local trail guide ready, because the brush is getting thick my gentle readers!

Planting a Winter Garden: Status Report It's been one week since I sowed the seeds for soil repair. I've been watching closely hoping for some green sprout to push its way through the rich dark top soil.