All Life depends upon the chemical element nitrogen.
An atom of nitrogen lies at the heart of all amino acids, which are not only the building blocks of protein of which muscles and many other of the body’s parts are made, but also the basic constituent of DNA, which carries the genetic code for all living things.
Nitrogen atoms are also present in the molecules which enable energy transfer during photosynthesis. Without nitrogen, life as we know it would not exist.
Though about 78% of the Earth’s atmosphere is nitrogen, plants and animals don’t necessarily have an easy time getting all the nitrogen they need. Green plants can’t use the nitrogen that’s free in the atmosphere. Nitrogen must be “fixed” before it is usable by most living things.
The process of chemically altering unusable, free atmospheric nitrogen into a form usable by organisms is referred to as nitrogen fixation. In nature, there are two main ways of “fixing” nitrogen:
FIRST WAY: Lightning. If you’ve ever been close to a lightning flash and right afterwards smelled an ammonia-like odor, that was lightning-fixed nitrogen you smelled. Only a relatively small percentage of nitrogen gets fixed in this way, however. Nature’s main nitrogen fixers are…
SECOND WAY: Special microorganisms living mostly in soil and water.
Nitrogen-fixing microorganisms, existing abundantly but practically invisibly nearly everywhere, include a few forms of bacteria, the blue-green algae, and some fungi. Some nitrogen-fixing bacteria live in nodules, or small, bag-like growths on the roots of certain plants, especially members of the Bean Family.
NITROGEN-FIXING NODULES ON BACKYARD CLOVER
In many backyards, nodules can be seen on the fine, wiry roots of clover, a member of the Bean Family, and considered a weed by those who don’t know its importance.
The image below is a much-magnified section of the roots of the clover in the above photo. The brown, baglike things hanging on the larger roots are nitrogen-fixing nodules.
USABLE NITROGEN, STEP BY STEP
Typically, nitrogen-fixing microorganisms do not fix free atmospheric nitrogen to a usable form in one step. Usually one set of organisms converts free nitrogen(N2) to ammonia (NH3). This ammonia is accompanied by its ammonium ion (NH4+), which some plants can use. However, most flowering plants need nitrogen in yet another form, which microorganisms provide by converting the ammonia to usable nitrate (NO3-).
Already you see that various organisms must work together to accomplish this profoundly important job. However, it’s even more complex than what’s described above! The process of converting ammonia to nitrate, callednitrification, is usually accomplished by two different sets of bacteria working one after the other.
POINT TO PONDER
The point of all this is not to convince you that nitrogen is wonderful stuff, although it is. The point is that nature is composed of a huge number of interrelated parts, and nitrogen with all of its jobs is just one tiny, usually ignored part.
When we dump toxic chemicals (insecticides and oil pollution,for instance) into the Earth’s air, water, and soil, we are upsetting vital life-enabling processes by killing organisms that are profoundly important to the continuance of Life on Earth.
- Nitrogen Fixation (sundayfarmer.wordpress.com)