Apoplast vs Symplast
The difference between apoplast and symplast is that apoplast and symplast in plants make two different pathways to pass water and ions from root hair through root cortex to xylem elements. These pathways may occur either separately or simultaneously, and have different transport rates. The concept of these two paths was first presented by Munch in 1980. Let’s see these two pathways and the difference between them in more detail, in here.
What is Apoplast?
Apoplast is the space outside the plasma membrane, comprising of the cell wall and intercellular spaces. It does not include the protoplasm within the plant tissues, hence considered as the non-living part of the plant. Apoplast creates a main pathway called apoplastic pathway or apoplasty that helps to transport water and ions from the soil through root to xylem elements.
In the plants with secondary growth, the major portion of water is transported by apoplasty in the root cortex as cortical cells are loosely packed and have low resistance to the water flow. The apoplastic way is blocked by the Casparian strip of endodermal cells. Thus, the symplastic pathway is used to transport water and ion beyond the cortex. The apoplastic pathway is much faster than the symplastic pathway. Since the apoplast is made up of non-living parts, apoplastic pathway is not affected by the metabolic state of the root.
What is Symplast?
Symplast comprises of the network of cytoplasm of all the plant cells, which are interconnected by plasmodesmata. Symplast does not include the cell wall and intercellular spaces, thus considered as the entire living part of the plant tissue. The water and ion pathway creates by symplast is called symplasty or symplastic pathway. Symplastic pathway creates resistance to the water flow, because selectively permeable plasma membrane of the root cells control the water and ion intake. In addition, symplasty is also affected by the metabolic states of the plant root. In the plants with secondary growth, symplastic pathway occurs mainly beyond the endodermis.
What is the difference between Apoplast and Symplast?
• Comprises Of:
• Apoplast comprises the cell wall and intercellular spaces.
• Symplast comprises the protoplasm.
• Living Parts vs Non-living Parts:
• Apoplast has non-living parts, whereas symplast has living plants.
• Apoplast makes the apoplastic pathway.
• Symplast makes the symplastic pathway.
• Rate of the Pathways:
• Apoplastic pathway is faster than symplastic pathway.
• Metabolic State:
• Metabolic states interfere the movement of water in symplastic pathway unlike in apoplastic pathway.
• In the plants with secondary growth, more water and ion are transported via apoplastic pathway in the cortex.
• Beyond cortex, water and ion are mainly transported through symplastic pathway.
Images Courtesy: The apoplast pathway and the symplast pathway via Wikicommons (Public Domain)
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