Mycorrhizae: when roots cooperate with fungi
Olive roots can cooperate with mycorrhizal fungi. Plants provide food; fine fungal hyphae extend the area explored for nutrients.
A partnership beneath our feet
Mycorrhiza describes a fungus–root symbiosis. Plants supply photosynthesis-derived carbon compounds, primarily sugars, and also transfer lipids. Root exudates contain sugars, amino acids and other compounds serving as food and chemical signals. Fungi develop networks of fine hyphae and help supply nutrients. Communication is influenced by plant nutritional status and regulates the partnership: in this sense roots signal their needs.
How phosphorus reaches roots
Exchange occurs at arbuscules, microscopic tree-like fungal structures within root cells. Hyphae extend beyond root surfaces into smaller pores, exploring more soil and transporting phosphorus despite its slow movement through soil water.
Benefits do not always appear as greater growth. The mycorrhizal pathway can supply phosphorus without increasing biomass. We therefore examine colonisation, nutrition and growth together.
Research on olives
A 2013 Greek greenhouse study followed young Koroneiki, Kothreiki and Chondrolia Chalkidikis plants for six months in three soils. All varieties formed mycorrhizae, with differences between varieties and soils. Establishment depends on the cultivar and root environment.
A 2022 pot experiment found that inoculating young olive trees with mycorrhizal fungi improved growth. Some local fungal mixtures also improved phosphorus uptake. Researchers called for field monitoring of long-term effects after transplanting.
Cover and olive grove management
A ten-year study in a Mediterranean high-density olive grove compared permanent cover with shallow tillage. Roots were colonised in both systems, but cover-cropped soil had greater capacity to establish symbiosis in an assessment bioassay. Management matters for conserving fungi already present.
Observation starts with roots
Appropriate fine-root samples require preparation and staining to make fungal structures visible and record colonisation. A hypha in soil or compost alone does not confirm a mycorrhizal partnership with an olive tree. The root itself must be examined.
Our field work
We aim to study mycorrhizal symbiosis in our olive groves through appropriate root examination and monitoring of applications.
Sources and further reading
- USDA–NRCS, Soil Health Glossary
- Smith, Jakobsen, Grønlund & Smith, Roles of Arbuscular Mycorrhizas in Plant Phosphorus Nutrition
- Colonization of Greek olive cultivars’ root system by arbuscular mycorrhiza fungus
- Arbuscular mycorrhizal fungi enhanced the growth, phosphorus uptake and Pht expression of olive plantlets
- Protective green cover enhances soil respiration and native mycorrhizal potential compared with soil tillage in a high-density olive orchard in a long term study
- A starting guide to root ecology
- Arbuscular Mycorrhizal Symbiosis Triggers Major Changes in Primary Metabolism Together With Modification of Defense Responses and Signaling in Both Roots and Leaves of Vitis vinifera
- Mycorrhiza-induced resistance: more than the sum of its parts