Q.47 Which one of the following statements on Casparian strips is correct?
(A) Casparian strips are specific to vascular plants found in epidermal cells.
(B) Casparian strips are modifications mostly found in shoot tissue.
(C) Casparian strips act as a cellular barrier to allow selective nutrient uptake and
exclusion of pathogens.
(D) Casparian strips are common in root endodermal cells of non–vascular plants.

The correct answer is (C) Casparian strips act as a cellular barrier to allow selective nutrient uptake and exclusion of pathogens.​

Casparian strips form a lignin-impregnated band in the radial and transverse walls of root endodermal cells in vascular plants, creating an impermeable apoplastic barrier that forces water and solutes through the symplast for selective absorption. This structure regulates ion homeostasis and prevents uncontrolled diffusion into the stele.​

Option Analysis

Option (A): Incorrect. Casparian strips occur exclusively in the endodermis of roots, not epidermal cells, and characterize vascular plants (ferns and seed plants).​

Option (B): Incorrect. They primarily develop in root endodermal cells, with rare occurrences in some stems or leaves but not “mostly” in shoot tissue.​

Option (C): Correct. The barrier blocks apoplastic flow, enabling plasma membrane-mediated selective nutrient uptake while excluding pathogens and toxins from the vascular cylinder.​

Option (D): Incorrect. Non-vascular plants like mosses and liverworts lack Casparian strips; the structure defines vascular plant roots.​

Casparian strips function as a critical apoplastic barrier in the root endodermis of vascular plants, ensuring controlled water and nutrient movement. Named after Robert Caspari, these lignin-suberin bands form in anticlinal walls, sealing intercellular spaces and forcing symplastic transport through selective cell membranes.​

Structure and Location

• Band-like thickenings in radial/transverse endodermal cell walls behind the root tip.​

• Composed of lignin (primary) and suberin, with plasma membrane tightly adhered.​

• Absent in epidermis, pericycle, or non-vascular plants; root-specific in most species.​

Biological Role

Casparian strips function by blocking passive diffusion, promoting active nutrient uptake via ion channels and excluding Na+, heavy metals, and pathogens. Under stress like salinity, they form closer to the tip, enhancing ion regulation.​

Exam Relevance

For CSIR NET Life Sciences, recognize Casparian strips function matches option (C) in MCQs testing plant anatomy and transport. Mutants lacking functional strips show stele ion leakage, confirming barrier necessity.​