plant diet ....Q AND A

Notes : chapter 2 plant diet

Q. what is symbiosis? Explain with an example.

Ans : Symbiosis is the phenomenon by which two organisms maintain relationship with each other to be mutually benefitted. In symbiotic mode, organisms develop a special relationship with certain other organisms to obtain nourishment. Organisms involved in this type of relationship are called as symbionts.

·                     e.g. Rhizobium bacteria and Leguminous plants are symbionts exhibiting symbiosis. Plants cannot utilise atmospheric nitrogen directly. Hence, leguminous plants establish a symbiotic relationship with bacteria like Rhizobium. Both the organisms of symbiotic relationship are mutually benefited. Leguminous plant provides shelter and nourishment for the bacteria and in turn bacteria fix atmospheric nitrogen to the plant.

Q2 Write short notes on the following topics

1.  Mycorrhizae  2. Lichens 3. Total parasites 4. Partial parasites

1.Mycorrhizae

   It is a Plant and Fungi association

• The fungal partner grows on the surface of plant roots of the host plant increasing the surface area for water uptake and also supplies the plant with phosphate and other minerals from the soil
• In return the plant provides fungus with sugar.

2. Lichens

•      Symbiotic relationship between  autotrophic algae and heterotrophic fungi

•      The fungus helps alga in absorption of minerals and water from the soil

•      Algae prepares food which is shared with fungus

3. Partial parasites

•      Some parasitic plants are photosynthetic .

•      They depend on host for only water and minerals so called as partial parasites

•      Example- Mistletoe

3. Total parasites

•      These plants completely depend on the host plant  for sugar, water and minerals eg. Cascuta

•      Cuscuta shows modified roots haustoria for sucking food from the host plant .

Q3. What are insectivorous plants ?

Ans

Insectivorous plants :- These are plants which feed on insects. They generally grow in nutrient deficient soil.  Eg:- Pitcher plant. The leaf of the pitcher plant is modified into a pitcher. The end of the pitcher has a lid which can open and close. When an insect enters the pitcher, the lid closes. The insect is then digested by digestive juices inside the pitcher.

Q 4.How nutrients are replenished in the soil ?

Ans :   Plants absorb nutrients from the soil. So the nutrients in the soil decreases. So farmers add manures and fertilisers to the soil to increase the nutrients in the soil.

  The bacterium called rhizobium which lives in the roots of leguminous plants like grams, peas, beans etc. converts nitrogen from the air into soluble form in the soil and makes the soil rich in nitrogen. In return the plant provides food and shelter to the bacteria. So they have a symbiotic relationship.