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Endodermal Regulation
MCQ questions and answers.
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MCQ Questions
1. Which layer of the root regulates the movement of water and minerals into the vascular tissues?
A.
Epidermis
B.
Endodermis
C.
Root cap
D.
Cortex
Correct Answer:
Endodermis
Explanation:
The endodermis forms a selective boundary around the vascular tissues and regulates the entry of water and minerals into them.
2. What is the main function of the Casparian strips in endodermal cells?
A.
They increase photosynthesis
B.
They block uncontrolled apoplastic movement
C.
They produce root hairs
D.
They store starch in the root cap
Correct Answer:
They block uncontrolled apoplastic movement
Explanation:
Casparian strips contain a waterproof material that blocks the apoplastic pathway, forcing water and dissolved minerals through the endodermal cells.
3. The Casparian strip is mainly made of which substance?
A.
Lignin and suberin
B.
Chlorophyll and cellulose
C.
Starch and protein
D.
Pectin and glucose
Correct Answer:
Lignin and suberin
Explanation:
Casparian strips are impregnated mainly with suberin, often along with lignin, making the endodermal cell walls less permeable to water.
4. Because of the Casparian strips, water must pass through which route while crossing the endodermis?
A.
Only through air spaces
B.
Through the symplastic pathway
C.
Only through the root cap
D.
Through the stomata
Correct Answer:
Through the symplastic pathway
Explanation:
The Casparian strips block the apoplastic route, so water must enter the cytoplasm of endodermal cells and move through plasmodesmata by the symplastic pathway.
5. How does the endodermis help regulate mineral ion entry into the xylem?
A.
By allowing every ion to enter freely
B.
By selectively controlling ions crossing its cells
C.
By converting ions into sugars
D.
By preventing all water movement
Correct Answer:
By selectively controlling ions crossing its cells
Explanation:
Endodermal cells contain selective transport systems that control which mineral ions move into the vascular tissues.
6. What would happen if the endodermis did not contain Casparian strips?
A.
Water and ions could move freely through cell walls
B.
The root would stop absorbing oxygen
C.
Root hairs would turn into leaves
D.
Photosynthesis would increase in the root
Correct Answer:
Water and ions could move freely through cell walls
Explanation:
Without Casparian strips, the apoplastic pathway would remain open, allowing less-regulated movement of water and dissolved substances toward the xylem.
7. Which structure acts as a selective barrier between the cortex and the vascular tissues of a root?
A.
Pericycle
B.
Endodermis
C.
Root hair
D.
Epidermal cuticle
Correct Answer:
Endodermis
Explanation:
The endodermis forms the innermost layer of the cortex and selectively regulates the passage of water and minerals into the vascular cylinder.
8. How can endodermal regulation contribute to the development of root pressure?
A.
It helps control ion movement into the xylem
B.
It stops all solute movement in the root
C.
It removes water from the xylem
D.
It prevents the formation of root hairs
Correct Answer:
It helps control ion movement into the xylem
Explanation:
Selective movement of ions through the endodermis into the xylem can help create a concentration difference that draws water into the xylem and contributes to root pressure.
9. Which pathway is directly restricted by the waterproof Casparian strips?
A.
Apoplastic pathway
B.
Symplastic pathway
C.
Phloem pathway
D.
Transpiration pathway
Correct Answer:
Apoplastic pathway
Explanation:
Casparian strips seal the cell walls of endodermal cells, thereby restricting the movement of water through the apoplast.
10. Why is the endodermis important for mineral absorption by roots?
A.
It provides selective control over mineral entry
B.
It produces sunlight for mineral absorption
C.
It carries sugars from leaves to root hairs
D.
It forms the outer protective covering of the root
Correct Answer:
It provides selective control over mineral entry
Explanation:
The endodermis regulates mineral entry into the vascular tissues, helping the root control which ions reach the xylem.
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Endodermal Regulation
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