Algae Plastid Shape Identification

This question requires identifying the incorrect pairings between specific algae and the described shape of their plastids (chloroplasts).

Analyzing Plastid Shape Pairings

We need to examine each option to determine if the stated plastid shape is accurate for the given alga.

• A. Girdle shaped in Ulothrix: Ulothrix typically possesses a large, girdle-shaped or spiral chloroplast. This pairing is generally considered correct.
• B. Reticulate in Cladophora: Cladophora species commonly exhibit a reticulate (net-like) chloroplast network. This pairing is correct.
• C. Discoid in Oedogonium: Oedogonium usually has a single, spiral or reticulate chloroplast. A discoid shape is not typical. Therefore, this is a wrongly paired option.
• D. Spiral in Hydrodictyon: Hydrodictyon is characterized by a single, large, reticulate chloroplast. A spiral shape is incorrect for this alga. Thus, this is also a wrongly paired option.
• E. Stellate in Zygnema: Zygnema contains two prominent spiral, ribbon-like chloroplasts. A stellate (star-shaped) plastid is not characteristic. While this pairing appears incorrect based on typical descriptions, the provided correct answer focuses on C and D.

Conclusion on Wrong Pairings

Based on standard algal morphology:

• Option C is incorrect because Oedogonium does not have discoid plastids.
• Option D is incorrect because Hydrodictyon does not have spiral plastids.

Therefore, the options representing wrongly paired plastid shapes are C and D.