Endophytes

Endophytes are tiny heroes of the garden.

You rarely see them with the naked eye, but most of these tiny organisms work hard to protect our plants.

Beneficial endophytes (threadlike structures) seen in tall fescue plant cells (Nick Hill) Public Domain

What are endophytes?

The word ‘endophyte’ literally translates as ‘in the plant’ (‘endo’ = within; ‘phyte’ = plant). Endophytes are tiny organisms that live inside plants, for at least part of their life, without causing disease. In most cases, they provide a benefit to the host. The plant returns the favor by providing the endophytes with carbon [sugar]. Endophytes can be fungal, bacterial, or viral, or they can be other plants. Endophytes are everywhere and they can occur in any place within a plant.

Some endophytes grow between plant cell walls, while others live inside plant cells, and they tend to grow at the same rate as their host. Researchers have learned that plants and their endophytes use chemical signals to communicate with each other. These communications determine which helpful chemicals and what quantities are needed by both sides of the arrangement.

The science behind endophytes is relatively new. Because of this, the definitions are still being sorted out. Some scientists include parasitic and pathogenic organisms as endophytes, while others focus on the beneficial, or mutualistic forms. That’s where I stand, for now. There are several different ways that endophytes help their host plants.

Nutrient acquisition

Certain endophytes help plants get the food they need. The rhizobium bacteria that helps legumes fix atmospheric nitrogen is a type of endophyte. Other endophytes break down rock phosphate within the soil, making it absorbable to plant roots. Some scientists categorize mycorrhizae, or root fungi, as a type of endophyte, while others do not. [Isn't it exciting, being on the crest of new scientific research?]​

Pest and disease resistance

Some endophytes produce chemicals as secondary metabolites, that taste bad to certain insects or grazers. The ergot that grows on wheat and rye is an endophyte that deters grazers, such as cattle and humans. Other endophytes produce natural insecticides, while other generate chemicals that deter insects from laying eggs on the host plant. Research has shown that the Tagetes spp. of marigold, for example, can deter harmful nematodes from entering the root systems of nearby plants. Other endophytes populate areas within plants to the degree that there is simply no physical room for pathogens.

Ergot growing on wheat (Wikipedia) CC BY-SA 2.5

Other benefits

Endophytes have been shown to enhance overall plant growth. They do this by improving a plant’s tolerance of abiotic stresses, such as drought, heat stress, water stress, salinity, and poor soil. When allowed to grow naturally, these mutually beneficial arrangements make both parties stronger. Unfortunately, the use of fungicides interferes with endophyte development. Also, the use of fertilizers reduces a plant’s reliance on its resident endophytes. This is, theoretically, fine, as long as the fungicides and fertilizers continue to be supplied. As soon as these artificial treatments are withdrawn, however, host plants are left with less food and protection.

Commercial agriculture is slowly coming around to the long term benefits associated with these natural arrangements, but you can take advantage of it in your own garden right away by avoiding the use of chemical fertilizers and fungicides.

Did you know that when you inoculate legumes, you are putting endophytes to work for you in the garden? Now you know!