From UPSC perspective, the following things are important :
Prelims level : Wood wide web
Mains level : Not Much
Plants appear to be simple enough in their organization. Whether small shrubs or tall trees, all they seem to be made up of is leaves, flowers, fruits, stems, and roots. But simple they are not. Being rooted in one spot has required very special personality traits.
Wood Wide Web
- Trees in the forest share resources by using an underground network.
- A scientist from the University of British Columbia, Dr. Suzanne Simard, revealed this network and called it the wood wide web.
- In the wood wide web, mycorrhizal fungi colonize the plant roots, and their tiny fungal filaments, or mycelia, connect hairy root tips of different trees together.
- Mycorrhizal fungi refer to the role they play in the plant’s root system—as symbionts.
- These root-associated fungi are harmless to plants. Instead, they form harmonious symbiotic relationships with plants.
An ancient association
- The association between plants and fungi is ancient.
- Fossils of plants from about 400 million years ago show the first evidence of roots, and these roots are fungus associations – rhizoids – suggesting that roots co-evolved with fungi.
- One good example is species of Penicillium, the fungus from which Alexander Fleming isolated the antibiotic penicillin.
- Fungus–root associations, called mycorrhizae, appear at first glance to be simple mutualisms that are beneficial to both.
- The root-invading fungus gains nutrients made by the plant, and the plants get difficult-to-find minerals like phosphorus from the microbe. But the association is deeper.
How does it work?
- The wood wide web works by offering a win-win situation for all parties: mycorrhizal fungi and trees.
- The fungal filaments transport nitrogen, phosphorous, water, and other hard-to-capture nutrients from the soil to the trees, in exchange for carbon-rich sugars made by the plants.
- The fungi also help deliver substances from one tree to its neighboring trees.
- By using the network, mature trees feed their seedlings with nutrients to boost their survival.
- When a plant is sick or dying, it can allocate its nutrients to the other plants nearby through the wood wide web.
- Bacteria that associate with roots are called rhizobacteria, and a very wide range of these species are plant growth promoters.
- Like the fungi, mutualism operates in these relationships too. In exchange for sugars, these bacteria offer plants a wide range of benefits.
- They may help plants ward off pathogens that cause diseases of the root. They may even trigger systemic resistance to a pathogen throughout the plant.
Back2Basics: Symbiotic Relationship
- It is a type of interaction between two species that results in damage and harm to one member and benefit to another member.
- Ex. As in the case of the tick-host relationship, the tick gains benefit by sucking blood while the host is harmed as it loses blood.
- In this type of relationship one species benefits without affecting the other.
- Barnacles growing on the back of the whale, orchids growing as an epiphyte on some mango branch, cattle egret and grazing cattle in close association, Sea anemone, and the Clown Fish are some of the classic examples of Commensalism.
- In this relationship, one species is harmed while the other is neither harmed nor benefitted and remains unaffected.
- When an organism excretes the chemicals as a part of the normal metabolism of its own, but which may severely impact other nearby species, this kind of relationship is seen.
- In this type of relationship both the partners benefit from one another. When similar interaction occurs within a species, it is known as cooperation.
- Lichens a mutual relationship between algae and fungus. In this mutual cooperation, fungus gives protection and raw material for the preparation of the food while Green Algae synthesizes the food for both.
- In this kind of biotic interaction, certain organisms live on dead and decaying organic matter.
- Dung Beetles, Vultures, Fungi, Bacteria, Protozoa are the example of Saprophytism.
- In this type of biological interaction, a predator feeds upon its prey and in this type of relationship, one species is benefitted while the other is harmed.
- In this type of interaction both the species compete with each other for the resources like food, shelter, mating, and both the species get harmed out of the process of competition.