Answer: (3) starch

Hydrom sheath cells in Polytrichum (haircap moss) store starch as energy reserves, surrounding the central hydrom cylinder to support water conduction in this advanced bryophyte’s stem.

Option Analysis

• (1) Oils: Incorrect. Oils/lipids are minimal in bryophyte conducting tissues; hydrom sheath prioritizes carbohydrates over hydrophobic storage for water conduction support.

• (2) Proteins: Incorrect. While structural proteins exist in cell walls, hydrom sheath cells are not protein-rich; their role is storage, not metabolic activity.

• (3) Starch: Correct. Called the “amylom sheath,” these cells contain abundant starch grains in dark-brown suberized walls, providing reserves near hydroids (water-conducting cells).

• (4) Chlorophyll pigments: Incorrect. Stem tissues lack photosynthesis; chlorophyll localizes to leaf lamellae, not internal hydrom sheath.​

Polytrichum hydrom sheath cells starch is essential botany knowledge for competitive exams testing bryophyte anatomy and conducting tissue differentiation.

Hydrom Sheath Function

In Polytrichum stems, the amylom (hydrom) sheath forms a 1-2 layered zone around the hydrom cylinder. These starch-laden cells with suberized walls store carbohydrates, aiding the moss’s endohydric water transport via hydroids (xylem analogs) and leptoids (phloem analogs).

Structural Context

• Central hydrom cylinder: Stereids (support) + hydroids (conduction)

• Surrounding amylom sheath: Starch reserves for metabolic support

• Outer leptom mantle: Food conduction

This organization enables Polytrichum’s exceptional height (up to 20 cm) among mosses.​

Exam Relevance

Questions distinguish storage (starch) from conduction (hydroids empty) or photosynthesis (chlorophyll in leaves). Starch confirms the sheath’s nutritive role, not primary conduction.​