An Introduction to Mycorrhizae

BIOTECHNOLOGY can be defined as the controlled use of living organisms or their components for the benefit of mankind. One aspect of biotechnology involves the special relationships formed between certain fungi and plants, called mycorrhizae, which have been shown to dramatically enhance the establishment, growth, development and survival of plants. The term mycorrhiza (pl. mycorrhizae or mycorrhizas), means "fungus root" and can be defined as a beneficial symbiotic association between plant roots and specific soil fungi. In the mycorrhizal relationship, the fungus penetrates secondary roots during periods of active root growth. The anatomy of the root is changed, and a new organ, "the mycorrhiza," is formed (Hacskaylo 1972). Mycorrhizal organs can exist in many forms, their morphology is determined by the characteristics of each partner involved and by the specific plant-fungus combination (Harley & Smith 1983). During the infection process, the fungus invades the root epidermis and cortex (Figure 1), but does not enter the vascular cylinder (specialized tissues that transport food and water) or the meristem (region of cell division) that is covered by the root cap.