Mycorrhiza is the symbiotic association between root system of higher plants and _______

✅Explanation:
-Mycorrhizae is a symbiotic association between a fungus and roots of higher plants.
-Mycorrhizal fungi allow plants to draw more nutrients and water from the soil.
-They also increase plant tolerance to different environmental stresses.
-They play a major role in the soil aggregation process and stimulate microbial activity. 
-Mycorrhizae play a vital atmospheric nitrogen fixation
Important Points  

• Mycorrhiza is of two types:
-Ectomycorrhiza – In this, the fungus forms a covering around the plant's roots. In this way, a layer like structure is formed on the surface of the roots, which is called peudoparenchymatous sheath. Ex – Pinus, Abies, Eucalyptus and Oak
-Endomycorrhiza – In this the fungus does not form a layer on the roots of plants. They enter intracellularly in the roots. Intracellular fungal hyphae form branched structures in cells of roots called ''arubscule'' and unbranched structures called vesicles so these are also called Vesicular arbuscular mycorrhizal (VAM). Ex – Orchids