Storage polysaccharides: laminarin is characteristic of which algal division? Identify the algal division in which laminarin serves as a principal reserve carbohydrate.

Introduction / Context:
Biochemical markers often distinguish algal divisions. One such marker is the storage carbohydrate. Recognizing laminarin points you straight to the brown algae, an economically important group (for example, kelps) used for food and alginates.

Given Data / Assumptions:

• Laminarin is a beta-1,3-glucan storage polymer.
• Brown algae also commonly store mannitol.
• Pigments include chlorophyll a, c, and fucoxanthin.

Concept / Approach:
Among the listed divisions, only Phaeophyta (brown algae) use laminarin as a key storage compound. Green algae store starch, many diatoms store oils and chrysolaminarin (related but taxonomically distinct context), dinoflagellates often store starch-like materials, and red algae store floridean starch.

Step-by-Step Solution:
Associate laminarin with brown algal physiology.Eliminate divisions with different storage products (starch, oils, floridean starch).Select “Phaeophyta (brown algae).”

Verification / Alternative check:
Textbook tables list laminarin for browns; chrysolaminarin is characteristic of diatoms/golden algae, reinforcing the distinction.

Why Other Options Are Wrong:
Each other division has a different primary reserve material, making them mismatches for laminarin.

Common Pitfalls:
Confusing laminarin (browns) with chrysolaminarin (diatoms). The names are similar but map to different heterokont groups.

Final Answer:
Phaeophyta (brown algae).