Equisetum Hydrophytic Feature Analysis

The question asks to identify a feature of Equisetum that indicates its adaptation to wet environments (hydrophytic nature).

Analyzing the Options

• Option 1: Presence of ridges and groves on the stem: While characteristic of Equisetum stems, this feature primarily relates to stem structure and surface area, not directly indicating hydrophytic adaptation.
• Option 2: Presence of sunken stomata: Sunken stomata are adaptations for reducing water loss, typically found in xerophytes (plants adapted to dry conditions). This contradicts hydrophytic adaptation.
• Option 3: Vallecular canal and central pith cavity: Large internal cavities, like the vallecular canals (running beneath the ridges) and the large central pith cavity (often forming a hollow lacuna), are significant adaptations for hydrophytes. These structures facilitate gas exchange (aeration) and provide buoyancy in waterlogged or aquatic environments.
• Option 4: Presence of well developed sclerenchymatous hypodermis: A strong hypodermis usually provides mechanical support, which is less critical for submerged or partially submerged plants and more common in plants exposed to stress or dryness.

Conclusion on Hydrophytic Nature

The presence of extensive internal air spaces, namely the vallecular canal and the large central pith cavity, are key anatomical features enabling Equisetum to thrive in wet habitats. These spaces improve aeration and buoyancy.

Therefore, option 3 correctly identifies a feature indicating the hydrophytic nature of Equisetum.