All plants require 17 elements to complete their life cycle. Carbon, hydrogen and oxygen are obtained from the air and water. Plants derive the remaining 14 elements from the soil, which is often enriched with fertilizers and amendments. Plant growth and development largely depend on the combination and concentration of available mineral nutrients.
About half of the essential elements are considered macronutrients: carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. Carbon is required to form carbohydrates, proteins, nucleic acids, and many other compounds making it an essential component of all macromolecules (molecules made through the joining of smaller subunits). On average, the dry weight (that is, excluding water) of a cell is 50 percent carbon, making it a key part of plant biomolecules. There are four major classes of biological macromolecules — carbohydrates, lipids, proteins, and nucleic acids. These store energy and act as chemical messengers.
The second-most-abundant element in plant cells is nitrogen. This is why we place value on the carbon:nitrogen ratio. Nitrogen is part of proteins and nucleic acids, and is also used in the synthesis of some vitamins. Hydrogen and oxygen are part of many organic compounds and also form water. Oxygen is necessary for cellular respiration as plants use oxygen to store energy in the form of ATP. Adenosine 5′-triphosphate, or ATP, is the principal molecule for storing and transferring energy in cells. Plants capture and store the energy they derive from light during photosynthesis in ATP molecules. It is often referred to as the energy currency of the cell and can be compared to storing money in a bank. ATP can be used to store energy for future reactions, i.e. be withdrawn to pay for reactions when energy is required by the cell.
Phosphorus is necessary to synthesize nucleic acids and phospholipids. As part of ATP, phosphorus enables food energy to be converted into chemical energy through oxidative phosphorylation, the final stage of cellular respiration or light energy being converted into chemical energy. Sulfur also plays a role in photosynthesis as part of the electron transport chain that’s key for conversion of light energy into ATP. Potassium is important because of its role in regulating stomatal opening for gas exchange, helping to maintain a healthy water balance.
Magnesium and calcium are also important macronutrients. Calcium regulates nutrient transport and supports many enzyme functions. Magnesium is important to the photosynthetic process.
In addition to macronutrients, organisms require various elements in small amounts. These micronutrients, or trace elements, are present in very small quantities. The seven main micronutrients are boron, chlorine, manganese, iron, zinc, copper, and molybdenum. Iron, for example, is essential for plant growth and development and is required as a cofactor for proteins that are involved in a number of important metabolic processes, including photosynthesis and respiration.
The overall theme here is that we need these elements to help perform two major functions for delivering maximum plant health. First and foremost is to amplify photosynthesis, the energy factory for the plant. Second, they are needed for the ATP process, to store and transfer the energy that’s being created through photosynthesis. Deficiencies in any of these micronutrients impacts these key processes, resulting in less-than-optimal plant growth.