Question

Choose the correct answer from the alternatives given.
 Ectotrophic mycorrhiza is found in
A. Pinus
B. Orchids
C. Riccia
D. Ocimum

Answer 1

Hint: Mycorrhiza is the symbiotic association between fungi and the roots of some higher plants. It is a mutually beneficial system in which the fungus gets the products of photosynthesis as food from the plant and the roots of plants are facilitated with easy absorption of water and nutrients from the soil by the fungi. It also boosts the disease resistance of the plants.

Complete answer:
Mycorrhiza is classified mainly into two categories based on the site of living of fungus - ectomycorrhizae and endomycorrhizae. If the fungi is incorporated inside the root, it is called endomycorrhiza and if the fungi is living outside the roots, it is called ectomycorrhizal. The ectotrophic mycorrhiza are different where the fungus grows outside the roots and forms a special type of network around the roots of the plant called hartig net. They are usually found in plants like pinus. A mantle or mesh of fungal hyphae is formed around the small roots. The morphology of the roots changes, resulting in increased branching. The fungi involved in ectotrophic mycorrhiza belongs to Actinomycetes and Basidiomycetes. Both the organisms get nutritional benefit from this association. Establishment of ectotrophic mycorrhiza helps the environment soil and forestry as the roots of the plants and trees are more efficient in absorbing minerals. Orchid mycorrhiza is seen in orchids which is the symbiotic relation between fungi and roots of plants in the family Orchidaceae. Mycorrhiza is absent in Riccia. Riccia lacks true roots and has roots like rhizoids. In ocimum, vesicular arbuscular mycorrhiza is seen. In arbuscular mycorrhiza, they make arbuscules for nutrient exchange. Arbuscule is a hair-like branched structure of cilia.
The correct answer is Option A - Pinus.

Note:
Different types of mycorrhizal relationships exist between fungus and plants like arbuscular mycorrhiza, ericaceous mycorrhiza, arbutoid mycorrhiza, ectotrophic mycorrhiza and endomycorrhiza. Plants of the order Ericales form ericaceous mycorrhiza. Arbutoid mycorrhiza is a form of endomycorrhiza in which cortical cells of plants are being invaded. As the mycorrhizal hyphae are very thin, it helps efficient absorption of nutrients and minerals.