Question

Mycorrhiza does not help the host plant in
A. Enhancing its phosphorus uptake capacity
B. Increasing its tolerance to drought
C. Enhancing its resistance to root pathogens
D. Increasing its resistance to insects

Answer 1

Mycorrhiza is a symbiotic relationship between a fungus and a green plant. Through photosynthesis, the plant creates organic molecules like sugars and supplies them to the fungus, and the fungus supplies the soil with plant water and mineral nutrients, such as phosphorus.

Complete Answer:
In areas where the soil does not contain enough nitrogen and phosphorus, as well as in areas where water is not readily available, mycorrhiza associations are especially beneficial. Since mycorrhizal mycelia are much thinner and smaller in diameter than roots and root hairs, the surface area for water, phosphorus, amino acids, and nitrogen absorption is greatly increased, almost like a second collection of roots.

In areas where soils are deficient in water and certain nutrients - conditions that are found in the desert - mycorrhizae are important. Even if a nutrient is necessary, it can not be readily available to the plant. A significantly larger root system (or mycorrhizae) allows extra moisture and nutrients to be accessed by the plant. This is especially important as phosphorus, one of the most important nutrients needed by plants, is absorbed.

Plants are less susceptible to water stress when mycorrhizae are present. Not only do the fungal threads help bring water and nutrition into the plant, but when rainfall is scarce and temperatures are high, they can also store them for use. Mycorrhizae are important in making their nutrients accessible when organic matter (compost) is applied to boost the soil. The organic residual matter and the hyphae strengthen the soil structure.

Resistance to disease: Mycorrhizae also allows other fungi and even bacteria to avoid infection by the plant. This may be because the plant is healthier and has more resistance to the invader, becoming better nourished. It may also be that one fungus's large physical presence impedes contamination by others. Another possibility is that compounds that resist infection by pathogens are formed by either the plant or the fungus.

Interaction with other soil bacteria, a beneficial cycle: In the soil, desert plants communicate with other species. By "fixing" nitrogen, which is then available for plant growth, many of these microorganisms fertilise plants. The number and vitality of these nitrogen fixers increases when mycorrhizae are present. As a consequence, the health and vigour of the plant is improved, as is the health and vigour of the beneficial fungi.

The correct Answer is option (D) Increasing its resistance to insects.

Note: There is no sure-fire way to ensure natural mycorrhizal populations, but a few simple rules are followed in order to maximise the number of fungi. When planting a native desert, make sure the native soil is present in the root ball. This is where the mycorrhizal fungi reside; no interactions will occur without the fungi.