Question

These seeds cannot germinate and establish without the presence of mycorrhizae are

• A. Cycas
• B. Gnetum
• C. Ephedra
• D. Pinus

Hint:

Pinus is a classic example of a gymnosperm showing ectomycorrhizal association that greatly aids seedling establishment and nutrient absorption.

Answer 1

The Correct Option is D

Concept: Mycorrhiza is a mutualistic association between fungi and plant roots. The fungal partner enhances water and mineral absorption, especially phosphorus uptake, while receiving carbohydrates from the plant. Certain gymnosperms are highly dependent upon mycorrhizal associations for successful establishment.

Step 1: Understand mycorrhizal dependence. In some plants, seedlings fail to establish properly unless mycorrhizal fungi colonize their roots. This association significantly improves nutrient acquisition from poor soils.

Step 2: Examine Pinus. Pinus develops ectomycorrhizal associations with fungi. The fungal mantle surrounds the roots and assists in nutrient uptake. Seedlings of Pinus often fail to establish successfully in the absence of mycorrhiza.

Step 3: Compare with other options. Cycas possesses coralloid roots associated with cyanobacteria. Gnetum and Ephedra are not characteristically dependent upon mycorrhiza for seed establishment. Therefore these options are incorrect.

Step 4: Final conclusion. The seeds that require mycorrhizal association for successful germination and establishment belong to: \[ \boxed{\text{Pinus}} \] Hence option (D) is correct.