Read the passage and answer the following questions:
Mutualism is an interaction that benefits both species involved. One example of mutualism is the lichen, an intimate association between a fungus and photosynthesising algae or cyanobacteria, which rely on each other for survival. The fungus provides a protected environment and absorbs water and nutrients, while the photosynthetic partner conducts photosynthesis and produces energy-rich carbohydrates that benefit both organisms. Another example is mycorrhizae, where fungi form associations with the roots of higher plants. The fungi assist the plants in absorbing essential nutrients from the soil, such as phosphorus, in exchange for receiving energy-yielding carbohydrates produced by the plants through photosynthesis. In plant-animal relationships, mutualism is evident in the process of pollination and seed dispersal. Plants rely on animals, such as bees, butterflies, and birds, to transfer pollen between flowers, facilitating reproduction. In return, plants offer rewards to the pollinators, such as pollen and nectar, which serve as a source of food for the animals. Similarly, when animals consume fruits and disperse seeds through their excretion or by carrying them to new locations, they benefit from the nutritional value of the fruits, while the plants benefit from the dispersal of their seeds. Not all mutualistic interactions involve direct rewards. Some orchids, like the Mediterranean orchid Ophrys, employ "sexual deceit" to achieve pollination. One petal of the flower resembles the female bee in size, colour and markings, attracting male bees that attempt to mate with the flower. During this process, the bee gets covered in pollen, and when it visits another flower, it transfers the pollen, facilitating pollination.
How do mycorrhizae benefit plants?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → By aiding in the absorption of essential nutrients from the soil
The passage states that in mycorrhizae, fungi form associations with the roots of higher plants and “assist the plants in absorbing essential nutrients from the soil”, such as phosphorus. In return, the plant gives the fungi energy-yielding carbohydrates made in photosynthesis.
Option (1) By providing carbohydrates to the plants — Incorrect. It is the other way round. The plant supplies carbohydrates to the fungi, because the fungi cannot make their own food.
Option (2) By aiding in the absorption of essential nutrients from the soil — Correct. The fungal partner helps the roots take up essential nutrients from the soil. This is the plant’s gain from the association.
Option (3) By protecting the plants from herbivores — Incorrect. Protection from herbivores is not part of the mycorrhizal association. The fungi work below ground, at the roots.
Option (4) By pollinating the plants — Incorrect. Pollination is done by animals such as bees, butterflies and birds. Fungi at the roots play no part in it.