Q. 49 Arbuscules are highly branched structures, formed by
(A) ectomycorrhizae
(B) endomycorrhizae
(C) arbutoid mycorrhizae
(D) monotropoid mycorrhizae
Arbuscules are specialized, highly branched fungal structures vital for nutrient exchange in plant roots. They form exclusively in endomycorrhizae, making option (B) the correct answer for this biology MCQ.
Correct Answer
Arbuscules are highly branched structures, formed by (B) endomycorrhizae. These tree-like formations develop inside root cortical cells of host plants, enabling efficient exchange of phosphorus, carbon, water, and nutrients between fungus and plant.
Option Breakdown
Ectomycorrhizae (A)
Ectomycorrhizae form a fungal mantle around root tips and a Hartig net between cells but do not penetrate cortical cells to create arbuscules. They associate mainly with trees like pines, lacking intracellular branching structures.
Endomycorrhizae (B)
Endomycorrhizae, particularly arbuscular mycorrhizae (AMF) from Glomeromycota, produce arbuscules by penetrating root cells. These structures maximize contact area for nutrient transfer, found in 80% of vascular plants like grasses and crops.
Arbutoid Mycorrhizae (C)
Arbutoid mycorrhizae, a subtype in Ericaceae (e.g., Arbutus), combine ecto- and endomycorrhizal traits with some intracellular hyphae but no true arbuscules. They feature Hartig nets and limited cell penetration.
Monotropoid Mycorrhizae (D)
Monotropoid mycorrhizae occur in chlorophyll-lacking plants (e.g., Monotropa in Ericaceae), forming parasitic associations with ectomycorrhizal fungi. They lack arbuscules, relying on fungal hyphae for carbon without mutualistic branching.
Mycorrhizae Significance
Mycorrhizae boost plant growth, soil health, and stress resistance. Arbuscules in endomycorrhizae exemplify symbiotic efficiency, key for agriculture and ecology studies in exams like NEET or CSIR NET.
