Plant Chemistry

You don’t have to understand chemistry to learn how to grow plants. The earth, rain, atmosphere and sun work together and you just need to plow, fertilize, sow, and tend the plants at the right time. But learning a little chemistry is necessary to learn how plants grow.

In atomic theory, atoms are the smallest building blocks of matter. They are called the elements and are made of a proton and neutron surrounded by electrons orbiting around their core like planets around the sun. If the outer orbit of electrons is incomplete, in other words it is missing electrons, then the element is reactive and wants to join with another element which also has an incomplete outer orbit of electrons. These electrons are available to be paired with other available electrons.

An example is water. “H” stands for hydrogen and “O” stands for oxygen. A hydrogen atom has only one electron, and oxygen has two available electrons. So two hydrogen atoms readily join with an oxygen atom. When this happens water is formed and it is called H2O, because it takes 2 hydrogen atoms for every one oxygen atom. Hydrogen and oxygen readily form bonds with many elements.

Hydrogen was discovered in 1766, and oxygen was discovered in 1774. In 1772, nitrogen was discovered. Nitrogen’s outer orbit needs three electrons to complete it, and readily finds them in another nitrogen atom, forming N2. “N” stands for nitrogen.

Our atmosphere is 78% N2, which is an inert gas so strongly bonded to itself it is extremely difficult to break free. It must be free, as plain N, so it can react with other elements to grow plants. Bacteria, living organisms in the soil, can do this and are called nitrogen fixing microbes. Other soil organisms, called protozoa, eat these microbes and excrete N that plants can use.

Carbon was discovered a few years later in 1789. It is written as “C”, and has four unpaired electrons. Together with hydrogen and oxygen, carbon forms all life as we know it. We are carbon-based life forms on this planet.

Carbon dioxide, CO2, in the air joins with water, H2O, to form carbohydrates in plants. This happens in a leaf when the sun shines, and is called photosynthesis. These carbohydrates (carbo- for carbon, -hydro for hydrogen, and -ates for oxygen) feed the plant and go down a tube in the plant called a phloem. They exit the plant’s roots, called a root exudate, and become food for the microbes living nearby.

In addition to nitrogen, soil microbes also supply the plant with minerals, which are always in combination with oxygen. Water and these nutrients go back up the plant in different tubes, called xylem. Fungi, the non-flowering plants that make mushrooms, have roots underground that stretch throughout the soil and connect to soil particles.

Besides bacteria, fungi, and protozoa, many other microscopic animals live in the soil and help plants grow. The grains of soil are coated with a waxy, black substance called humus, which is where most of these microbes live, get food for and from the plant, and reproduce.

Sulfur, S, was known to ancient people and is the “brimstone” of the Bible. It evaporates from the ocean as a gas produced by phytoplankton, providing a dilution of sulfur in rainfall everywhere. Sulfur has four unpaired electrons and joins with oxygen to form SO4 in the soil.

This dissolves in water and brings oxygen to the surface of soil particles, where the humus and microbes are. Sulfur makes the soil elements more available and is the catalyst for biological activity.

Hydrogen, the smallest element and first on the periodic table, makes up 98% of the universe and is what the sun is made of. Oxygen (oxy- means acid and -gen mean “maker of”) is the basis for acids in chemistry and joins with the soil’s elements in living organisms. Nitrogen is the basis for our DNA, our nervous system, and protein formation. Carbon provides the structural framework for the forms of all life. Sulfur, in much smaller quantities, helps get the air with these other four elements into the soil’s life processes. H2O, N, C, and S are provided for freely from the atmosphere for plant growth.