Apoplasmic transport barrier
noun phrasePronunciation: /ˌæpəˈplæzmɪk ˈtrænspɔːrt ˈbæriər/
The physical and chemical modifications of cell walls and intercellular spaces that restrict movement of ions and water through the apoplasm, particularly in roots at the endodermis and exodermis. This barrier regulates nutrient and contaminant uptake under various stress conditions including salinity and heavy metal exposure.
Plain English
Physical barriers in plant cell walls that prevent unwanted substances from moving freely through tissues and reaching the plant interior.
Etymology & History
Usage
"Salt-stressed plants strengthen the apoplasmic transport barrier through Casparian strip development and suberin deposition, preventing excessive sodium accumulation in shoots."
Style guide notes: Use technical terminology precisely; may require definition or explanation in non-specialist contexts.
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Frequently Asked Questions
Where is the apoplasmic transport barrier located in roots?
The primary barrier exists at the endodermis with the Casparian strip, with secondary barriers at the exodermis in mature roots.
How does salt stress affect the apoplasmic barrier?
Plants increase suberin and lignin deposition in endodermis and exodermis, strengthening barrier function to exclude excess sodium and chloride.
Why Test Candidates on This?
Specialized concept tested in advanced plant physiology and root physiology courses focusing on ion transport mechanisms.
Required skill level: Senior