Nitrogen (N) is responsible for vegetative growth. Nitrogen assimilation into amino acids is the building block for protein in the plant. It is a component of chlorophyll and is required for several enzyme reactions.
Phosphorus (P) is essential for all living organisms. Plants must have phosphorus for normal growth. Phosphorus plays a role in photosynthesis, respiration, energy storage and transfer, cell division, cell enlargement, and several other processes in plants.
Potassium (K) is found in the plant cell solution and is used for maintaining the turgor pressure of the cell (meaning it keeps the plant from wilting). In addition, potassium plays a role in the proper functioning of stomata (cells located on the bottom of the leaf that open and close to allow water vapor and waste gases to escape) and acts as an enzyme activator.
Calcium (Ca), in the form of calcium pectate, is responsible for holding together the cell walls of plants. When calcium is deficient, new tissue such as root tips, young leaves, and shoot tips often exhibit distorted growth from improper cell wall formation. Calcium is also used in activating certain enzymes and to send signals that coordinate certain cellular activities.
Magnesium (Mg) is required by many enzymes in order to perform properly. The most important role of magnesium is as the central atom in the chlorophyll molecule. Chlorophyll is the pigment that gives plants their green color and carries out the process of photosynthesis. It also aids in the activation of many plant enzymes needed for growth and contributes to protein synthesis.
Sulfur (S) is acquired by plants from the growing medium as sulfate (SO4=). Plant metabolism reduces sulfate and sulfur dioxide to forms that can be used to build organic molecules. Sulfur is a vital part of all plant proteins and certain plant hormones.
Boron (B) is used with calcium in cell wall synthesis and is essential for cell division (creating new plant cells). Boron requirements are much higher for reproductive growth so it helps with pollination, and fruit and seed development. Other functions include translocation of sugars and carbohydrates, nitrogen metabolism, the formation of certain proteins, regulation of hormone levels, and transportation of potassium to stomata (which helps regulate internal water balance). Since boron helps transport sugars, its deficiency causes a reduction of exudates and sugars from plant roots, which can reduce the attraction and colonization of mycorrhizal fungi.
Chloride (Cl) is needed in small quantities and aids in plant metabolism, photosynthesis, osmosis (movement of water in and out of plant cells), and ionic balance within the cell.
Cobalt (Co) has not been proven essential for higher plant growth, however, modulating bacteria need it for fixing atmospheric nitrogen in some plant species.
Copper (Cu) activates some enzymes in plants that are involved in lignin synthesis and it is essential in several enzyme systems. It is also required in the process of photosynthesis, which is essential in plant respiration and assists in plant metabolism of carbohydrates and proteins. Copper also serves to intensify the color in flowers.
Iron (Fe) is involved when a plant produces chlorophyll, which gives the plant oxygen as well as its healthy green color. This is why plants with an iron deficiency, or chlorosis, show a sickly yellow color to their leaves. Iron is also necessary for some enzyme functions in many plants.
Manganese (Mn) is a contributor to various biological systems including photosynthesis, respiration, and nitrogen assimilation. Manganese is also involved in pollen germination, pollen tube growth, root cell elongation, and resistance to root pathogens.
Molybdenum (Mo) is an essential component in two enzymes that convert nitrate into nitrite (a toxic form of nitrogen) and then into ammonia before it is used to synthesize amino acids within the plant. It is also needed by symbiotic nitrogen-fixing bacteria in some plant species to fix atmospheric nitrogen. Plants also use molybdenum to convert inorganic phosphorus into organic forms in the plant.
Zinc (Zn) activates enzymes that are responsible for the synthesis of certain proteins. It is used in the formation of chlorophyll and some carbohydrates, conversion of starches to sugars, and its presence in plant tissue help the plant to withstand cold temperatures. Zinc is essential in the formation of auxins, which help with growth regulation and stem elongation.