Proteins, some hormones, and even our DNA contain nitrogen. Every living organism needs nitrogen to grow. Nitrogen is also essential for plants: if they absorb too little nitrogen, they will grow less well and produce less. For this reason, farmers feed their plants with nitrogen in the form of fertilizer. But some plants do not need fertilizers thanks to the presence of special microbes in their roots.
Although the air is composed of 78% nitrogen, this nitrogen is in the form of the extremely stable, biologically unusable dinitrogen (N2). In the early twentieth century, Fritz Haber and Karl Bosch developed a process to “fix” dinitrogen from the air; That is, converting dinitrogen into ammonia (NH3). This ammonia is biologically usable and is used in fertilizers. The Haber-Bosch process was a revolutionary discovery for which the two gentlemen were awarded the Nobel Prize. Because thanks to fertilizers made through this process, agricultural productivity has exploded in most regions of the world: scientists estimate that about fifty percent of the world's population is fed today thanks to fertilizers. But fertilizers are not harmful. After heavy rains, fertilizer is washed off the field and large amounts of nitrogen end up in our waterways. Excess nitrogen in the water causes algae blooms. When these algae eventually die, oxygen levels in the water can drop to critical levels, killing fish and other aquatic animals. In addition, the Haber-Bosch process requires an enormous amount of energy: approximately 2% of global energy use annually goes to fertilizer production, which contributes to global warming.
Solidarity
This is what makes it so special that the same reaction has been occurring in nature for billions of years. Some microbes can fix nitrogen themselves. One of the most prominent of these microbes is undoubtedly Rhizobia. These bacteria are found freely in the soil, but can also settle in the root nodules of plants of the butterfly family (members of this family include beans, peas, clover, etc.).
And in those root nodules that Rhizobia Nitrogen repair. They give most of this fixed nitrogen to the plant, which in turn provides the bacteria with food (in the form of carbohydrates or sugars) and protection (the root nodules provide shelter for the bacteria). Win-win situation! In this way of working together – also called symbiosis – both partners make themselves extremely vulnerable. The plant allows a foreign organism to enter its roots, and even into its cells. The bacteria then have to trust the plant that they will not simply consume it. That's why they exchange many signals to choose the right partner. The plant maintains a “passport check” at the root hairs: only bacteria that can deliver the correct molecules are allowed into the plant's root and can then settle in the root nodules. But in biology it's never all roses and sunsets. Both parties do not trust their spouse. This is what scientists think Rhizobia It secretes certain molecules that prevent the plant's immune system from attacking the cells Rhizobia Turns. The plant then produces substances that help germs multiply Rhizobia To restrict.
Scientists have conducted research to better understand this collaboration for more than a century. The butterfly flower family contains important agricultural crops. In addition, scientists have an ambition to expand the collaboration to include crops outside this family, such as corn. The goal is to make agriculture less dependent on synthetic fertilizers to reduce the impact on the environment and climate.
