Question

Endodermis is characterized by the presence of ____.

• A. Pits
• B. Casparian strips
• C. Plasmodesmata
• D. Stomata

Hint:

Think of the endodermis as a "security checkpoint" at a gate. The Casparian strips block the open side paths, forcing all incoming molecules to go straight through the security guards (the living cell protoplast) for inspection!

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
The endodermis is the innermost cellular layer of the cortex in plant roots, serving as a biological checkpoint regulating selective nutrient transport into the central vascular cylinder.

Step 2: Detailed Explanation:
The tangential and radial walls of the endodermal cells feature a band-like deposition of a water-impermeable, waxy material called suberin. This specialized structural feature is called a Casparian strip. Because water cannot cross this suberin layer passively, it forces water and dissolved minerals to travel through the living protoplast of the cell membrane (symplastic pathway) instead of passing between cells (apoplastic pathway), acting as a natural cellular filter.

Step 3: Final Answer:
The endodermis is characterized by the presence of Casparian strips.

Answer 2

The endodermis has one very specific structural feature that sets it apart from other cell layers, so working through each option against what the endodermis is actually known for will identify the correct structure.

1. Pits: are thin, unthickened regions in secondary cell walls (common in xylem cells) that allow water and substances to pass between adjacent cells; they are a general wall feature found in several tissue types, not something unique to the endodermis.
2. Casparian strips: are band-like deposits of suberin, a waterproof waxy substance, found specifically on the radial and tangential walls of endodermal cells. This waterproof band forces water and minerals to pass through the cell's cytoplasm instead of around it, acting as a selective checkpoint. This feature is found only in the endodermis, making it the defining structure of this layer.
3. Plasmodesmata: are microscopic cytoplasmic channels connecting adjacent plant cells across their walls; these are present throughout most plant tissues generally and are not a feature unique to the endodermis specifically.
4. Stomata: are pores found in the epidermis, mainly of leaves, that regulate gas exchange and water loss; they belong to a completely different tissue (the epidermis) and layer of the plant, not the endodermis.

Since only one of these structures is a specialised, defining feature found exclusively in the endodermal cell layer, that is the correct choice.

Therefore, the correct answer is Casparian strips.