Q. Mycorrhizal biotechnology has been used in rehabilitating degraded sites because mycorrhiza enables the plants to

1. resist drought and increase absorptive area
2. tolerate extremes of pH
3. resist disease infestation

Select the correct answer using the codes given below.

• 1 only
• 2 and 3 only
• 1 and 3 only
• 1, 2 and 3

Answer: (d) 1, 2 and 3

Mycorrhiza

• Mycorrhiza are symbiotic associations between plant roots and certain soil fungi which play a key role in nutrient cycling in the ecosystem and also protect plants against environmental and cultural stress.
  • The plant makes organic molecules by photosynthesis and supplies them to the fungus in the form of sugars or lipids, while the fungus supplies the plant with water and mineral nutrients, such as phosphorus, taken from the soil.
  • Mycorrhizas are located in the roots of vascular plants, but mycorrhiza-like associations also occur in bryophytes.
• They greatly increase the efficiency of nutrient and water uptake, enhance resistance to pathogens, and buffer plant species against several environmental stresses and drought resistance. Mycorrhizae also improve plant growth and survival in soils contaminated by heavy metals.
• Mycorrhiza fungi act as a bio-fertilizer and help in maintaining soil biology and chemistry. These are of 2 types:​
  • Endo mycorrhizae – Example with orchids.
  • Ecto mycorrhizae – Example with pines, mushrooms, etc.

Fungus

• A fungus is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms.
  • These organisms are classified as one of the traditional eukaryotic kingdoms, along with Animalia, Plantae and either Protista or Protozoa and Chromista.
• A characteristic that places fungi in a different kingdom from plants, bacteria, and some protists is chitin in their cell walls. Fungi, like animals, are heterotrophs; they acquire their food by absorbing dissolved molecules, typically by secreting digestive enzymes into their environment. Fungi do not photosynthesize.
• Growth is their means of mobility, except for spores (a few of which are flagellated), which may travel through the air or water. Fungi are the principal decomposers in ecological systems.
  • Many fungi are free-living in soil or water; others form parasitic or symbiotic relationships with plants or animals.
• Fungi are heterotrophic organisms; therefore, they rely on photosynthetic carbon to produce energy, and some species get this carbon from plant root exudates. Together, plants and fungi perform a process called soil carbon sequestration, capturing carbon from the atmosphere and storing it into the soil for decades if not hundreds of years.
  • This important process not only improves soil fertility as it can also help reduce the excess carbon human activities have put into the atmosphere.
• Importance of fungi
  • Together with bacteria, fungi are responsible for breaking down organic matter and releasing carbon, oxygen, nitrogen, and phosphorus into the soil and the atmosphere.
  • Fungi are important contributors to the soil carbon stock. They play a major part in the carbon cycle through the soil food web.
  • Fungi have been found to help degrade various pollutants from the environment, such as plastic and other petroleum-based products, pharmaceuticals and personal care products, and oil.
  • Fungi are essential to many household and industrial processes, notably the making of bread, wine, beer, and certain cheeses.
  • Fungi are also used as food; for example, some mushrooms, morels, and truffles are epicurean delicacies, and mycoproteins (fungal proteins), derived from the mycelia of certain species of fungi, are used to make foods that are high in protein.