Question

VAM is important for
(a) Breaking of dormancy
(b) Phosphate nutrition
(c) Water uptake
(d) Retarding flowering
(e) Decrease in yield

Answer 1

Hint: It is a symbiotic association between the mycelium of fungi and the roots of plants. This interaction gives benefits to both the interacting species.

Complete answer:
The main benefits of vesicular-arbuscular mycorrhizal (VAM) involve the increased uptake of nutrients especially phosphorus and transport them to the host plant. Vesicular arbuscular mycorrhizal fungi belong to the class zygomycetes and are responsible for improving the growth of host plant species. The benefits in plants involve increased nutrient uptake, production of growth-promoting substances, tolerance to drought, salinity, etc. VA mycorrhizae get carbon from their plant hosts. This symbiosis played a vital role in the initial colonization of land by plants and the evolution of the vascular plants.

Additional information:
1. VAM association may also increase the phytoavailability of micronutrients such as copper and zinc.
2. Some arbuscular mycorrhizal (AM) associations can activate organically bound nitrogen, which the plants can't assimilate.
3. The flavonoids secreted from plants regulate activities of soil microbes at micromolar concentrations.
4. AM fungal hyphae possess a high surface-to-volume ratio that makes their absorptive ability greater than that of plant roots.
5. AM fungi utilize the products of the plant host's photosynthesis as hexoses which are monosaccharides. This hexose is converted into trehalose and glycogen inside the mycelium.
6. Transfer of carbon from plant to fungi may take place through the arbuscules or intraradical hyphae.

So, the correct answer is ‘phosphate nutrition’.

Note:
1. The spores of the AM fungi are thick-walled and multi-nucleated structures.
2. Lipid biosynthesis also takes place in the intraradical mycelium of fungi.
3. Arbuscular mycorrhizal fungi are present in 80% of plant species.