iGCSE Biology Notes Transport in plants

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[h] iGCSE Biology Notes Transport in plants

[q] How do plants transport things? 

What do plants use to transport things? 

[a] 

[q] Xylem

[a]

• Xylem transports water and minerals up a plant (only up).
• They also help support the plant as they are strengthened with lignin.

[q] Phloem 

[a]

• Phloem transports nutrients like sucrose and amino acids.
• Glucose must be turned into sucrose before being transported in the phloem

[q] How do plants transport things? 

What do plants use to transport things?

[a] 

• You need to know the structure of the vascular bundle in roots, stems and leaves.
• In the stem and root, remember the xylem is always on the inside.
• In a lead, xylem is on top.

[q] How do plants transport things? 

What do plants use to transport things?

[a] 

• We need to know how plants absorb water
• We already know that root hairs provide a large surface area for osmosis.
• The water is absorbed into the root hair cells, then moved into the root cortex cells, then into the xylem vessels, then is transported up through the stem to the mesophyll cells in the leaf.

[q] What is transpiration? 

What do plants use to transport things?

[a] 

• Transpiration is the evaporation of water from leaf mesophyll cells then the diffusion of this water vapour out of the stomata.
• Water exhibits something called cohesion, where molecules of water tend to attract each other
• When water evaporates from the leaves, it pulls up the water in the xylem with it (transpiration pull), creating a gradient of water potential.

[q] How can transpiration be affected by the weather? 

What do plants use to transport things? 

[a] 

• If the temperature is higher, particles have more kinetic energy and diffuse faster out of the stomata, so transpiration increases.
• If the humidity is higher, there is more water around the leaf so there’s less of a concentration gradient of water between the inside of the leaf and the outside so transpiration decreases

[q] What is translocation? 

What do plants use to transport things? 

[a] 

• Translocation is completely different.
• Translocation is the movement of nutrients like sucrose and amino acids in the phloem.
• These substances move from a source (where they are produced, usually the leaves)
• To storage like in the roots
• Or to a sink where the nutrients are used up, like for respiration or growth.

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