Phosphorous Cycle
Biology: AQA A Level, topic 5.4.2
Mycorrhizae
Mycorrhizae are fungi that form symbiotic relationships with the roots of plants. Mycorrhizae help plants absorb inorganic ions and water from the soil.
Structure
- The fungi associate with the roots using hyphae.
- Hyphae are long strands that extend from the cell body.
Function
- Hyphae increase the surface area of the plant root system.
- This helps plants take up ions that are in short supply (e.g. phosphorus) and water at a faster rate.
Phosphorus Cycle
The phosphorus cycle shows how phosphate ions (PO43-) are transferred between organisms and their ecosystem and how micoorganisms influence each step.
Uptake of phosphate ions
- Phosphate ions are assimilated by plants because of the symbiotic relationship between the plant roots and mycorrhizae.
- Mycorrhizae help to increase the rate of phosphate ion uptake.
Breakdown of phosphate ions
- As phosphate ions are transferred through the food chain, they are lost as waste products or when an organism dies.
- Saprobionts decompose waste and dead organisms through extracellular digestion.
- Phosphate ions are released into the soil and can be recycled for reuse in the cycle.
Test yourself on Phosphorous Cycle
What type of relationship is formed between mycorrhizae and the roots of plants?
What is the role of saprobionts in the phosphorus cycle?
Which of the following statements about the phosphorus cycle are true?
Stages in the Phosphorus Cycle
Which of these statements is NOT true about the role of mycorrhizae in the phosphorus cycle?