A catalyst is a substance that increases the rate of a chemical reaction without undergoing any permanent chemical change itself. One group of catalysts is found in every garden and provides countless benefits to plants. These catalysts are enzymes. Enzymes are highly selective catalysts made up of amino acids, proteins, or RNA (ribonucleic acid). Enzymes are biological molecules responsible for numerous chemical reactions which help to sustain all life. They differ from other catalysts in their selective nature as enzymes only react with their specific, predetermined substrate. The role an enzyme plays in these reactions is unique because the enzyme itself is not responsible for the reaction, but rather, the speed at which it occurs. Essentially, enzymes become a biological regulatory system for many of the chemical reactions that affect plant life and are an important connection between minerals, microbes, and biological creatures.

(For additional information on enzymes and gardening, check out Enzyme Energy or How Enzymes Work.)

Enzyme Reactions are Specific

Much like a puzzle piece, enzymes take on a certain shape to ensure only particular reactions will occur. The place on the enzyme where the reaction occurs is called the active site. This active site is like a keyhole and will only bind to a specific mineral or substrate that fits perfectly. The enzyme remains unchanged throughout the entire reaction process. After the reaction has occurred and the resulting chemical reactions have taken place, the enzyme is ready for a new reaction.

Increasing the Rate of Reactions

Like other catalysts, enzymes can increase the rate of chemical reactions by lowering the activation energy required for the given reaction. In other words, the presence of enzymes is what makes particle reaction happen at a faster rate. This is one of the reasons why enzyme formulas and products that indirectly add enzymes to a grow medium have become so popular among horticulturists. By supplementing specific enzymes or microorganisms that produce enzymes, horticulturists ensure they are maximizing the rate at which nutrient absorption can occur and helping protect the plants from pathogens.

Temperature and pH Effect on Enzymes

Enzymes, and the microorganisms that produce them, do not do well in extreme temperature conditions. Extremely hot or cold conditions will have a negative effect on enzymes and microorganisms. Many prepackaged soils are inoculated with beneficial microorganisms in the hopes they will produce the enzymes needed to accelerate chemical reactions in the soil. However, when the soil is shipped or stored in hot or cold conditions, the microorganism population can be negatively affected, thus adversely affecting their ability to produce beneficial enzymes. Some soil manufacturers have rectified this by adding moisture protectants in prepackaged soils to preserve the valuable microorganisms and the enzymes they produce.

The pHof a soil or medium has little effect on the enzymes themselves as they can withstand a wide pH range. However, the pH of a soil or medium will limit a plant’s ability to uptake particular nutrients. Although the enzymes will still be able to carry out their functions, the plant itself may not be able to reap the rewards because of a pH range falling outside of the range for nutrient absorption.

Supplementing Enzymes in the Garden

A horticulturist can supplement enzymes into a garden either directly or indirectly. There are specific enzyme formulas containing isolate enzymes. These are an example of direct enzyme supplementation. In some cases, an enzyme formula is comprised of a single isolated enzyme or a combination of multiple enzymes. Most of the isolated enzyme formulations are targeted at a plant’s root zone and aid in breaking down dead root matter while reducing the likelihood of pathogens, such as root rot.

Beneficial Microorganisms Provide Enzymes

An example of indirect enzyme supplementation is the use of beneficial microorganisms. Supplementing beneficial microorganisms into a medium or nutrient solution will indirectly increase the number of enzymes since the beneficial microorganisms produce the enzymes.

Mycorrhizae are very popular beneficial microorganisms to be supplemented in a garden. The enzymes (including some hydrolytic enzymes) produced by mycorrhizae fungi are what makes them such assets to their synergistic plant partner. It is the enzymes released by mycorrhizae that help make some of the hard-to-capture nutrients — such as organic nitrogen, phosphorus, and iron — available.

Trichoderma is another beneficial microorganism supplemented by horticulturists. As with mycorrhizae, the benefits derived are directly linked to the specific enzymes released. The enzymes released by trichoderma are called chitinase enzymes and their main role is to break down chitin. Chitin is the main component of fungal cell walls, which means the enzymes created by trichoderma can help protect a plant from pathogenic fungi. In fact, it is the chitinase enzymes produced by trichoderma that are responsible for trichoderma’s reputation in warding off pathogens. When pathogenic fungi exist in the soil, trichoderma will increase chitinase production, which, in turn, will attack the pathogen. Many indoor horticulturists are adding trichoderma as extra insurance against root-borne pathogens.

Trichoderma also produces cellulase enzymes, which break down cellulose. Cellulases enzymes can add another level of protection for plants. The cellulase enzymes can penetrate the cells in the plant’s root system, instantly triggering the plant’s natural defenses and stimulating the plant’s metabolism. No real harm is done to the plant and the heightened response helps protect the plant from other pathogens.

Whether a horticulturist supplements an isolated enzyme formula or the microorganisms producing the enzymes, the benefits of enzymes in the garden are undeniable. Considering nutrient uptake is dependent on multiple chemical reactions in the soil, and enzymes are the catalyst to increase the rate of those reactions, it is no wonder so many growers are relying on enzyme supplementation. As more is discovered about enzymes and how they can assist gardeners, the horticultural industry is sure to see even more enzyme-specific additives, fertilizers, and pest control products emerge in the future.