Mycorrhiza promote plant growth by?

Step 1: Analyze the question The question asks how mycorrhiza promote plant growth. First, recall what mycorrhiza are.

Step 2: Explain the concept Mycorrhiza (singular: mycorrhiza, plural: mycorrhizae) is a symbiotic association between a fungus and the roots of a higher plant.

• The fungal hyphae extend far into the soil, much further than root hairs can reach.
• They greatly increase the surface area for absorption.
• They absorb water and mineral ions, especially phosphate (and also nitrate, potassium, zinc) and pass them to the plant.
• In return, the plant supplies the fungus with carbohydrates (sugars) from photosynthesis.

Step 3: Evaluate the options

• A. Absorbing inorganic ions from the soil: Correct. This is the main role of mycorrhiza: improved uptake of phosphates and other mineral ions.
• B. Protecting it from infection: Mycorrhiza can give some protection against root pathogens, but this is a secondary benefit, not the main way they promote growth.
• C. Helping it to utilize atmospheric nitrogen: This describes nitrogen-fixing bacteria such as Rhizobium in the root nodules of legumes, not mycorrhiza.
• D. Serving as a growth regulator: Growth regulators are hormones like auxins and gibberellins. Mycorrhiza are not hormones.

Step 4: Answer

Exam tip: Link the words to their functions:

• Mycorrhiza = fungus + root, giving mineral/water absorption.
• Rhizobium = bacteria + legume root nodules, giving nitrogen fixation.

JAMB often tests this contrast, so remember it.