NCERT Class 11-Biology: Chapter –12 Mineral Nutrition Part 4

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Question 4:

Name the most crucial enzyme found in root nodules for fixation? Does it require a special pink coloured pigment for its functioning? Elaborate.

Answer:

1. Nitrogenase is the crucial enzyme found in root nodules for N2 fixation it converts the free nitrogen in the air to Ammonia or other nitrogenous compounds.

2. Yes, it requires a special pink coloured pigment for its functioning called Leg Haemoglobin, present in the root nodules of a legume. It is also considered as oxygen molecule scavenger because it combines with the oxygen molecule and helps in it’s removal. Thus helping enzyme nitrogenase in nitrogen fixation, which only works in absence of molecular oxygen.

Question 5:

How are the terms ‘critical concentration’ and ‘deficient’ different from each other in terms of concentration of an essential element in plants? Can you find the values of ‘critical concentration’ and ‘deficient’ for minerals & .

Answer:

The concentration below which plant growth is retarded is called critical concentration for an essential element. Any concentration below the critical concentration is called deficiency

Element Critical Concentration Deficient
Element Critical concentration Deficient

Element

Critical concentration

Deficient

Question 6:

Carnivorous plants exhibit nutritional adaptation. Citing an example explain this fact.

Answer:

Carnivorous plants exhibit nutritional adaptation because they have green leaves which shows they are Autotrophic but they grow in nitrogen deficient soil. So, to meet the nitrogen need these plants feed on insects to fulfil their nutritional requirement?

Example: In case of Pitcher Plant it is assumed that during the course of evolution the leaf folded inwards to form the inside of the pitcher .Now, this plant grows in nitrogen deficient soil and traps insects. These insects are digested inside the pitcher which has a digestive liquid and meet its nitrogen need.

Question 7:

A farmer adds/ supplies and regularly to his field and yet he observes that the plants show deficiency of and. Give a valid reason and suggest a way to help the farmer improve the growth of plants.

Answer:

A farmer adds/ supplies Na, , Mg and Fe regularly to his field and yet he observes that the plants show deficiency of , Mg and Fe because:

1. If the soil pH is not maintained, that is the soil is too alkaline or too Acidic the plant is unable to take up the nutrients from the soil. Example: Too alkaline pH can lead to Iron deficiency.

Preventive Measure: Maintaining the pH and use of good quality fertilizers

2. Manganese Toxicity: Excess of Manganese in the soil competes with Ca, Mg and Fe for uptake leading to their deficiency in the plant.

Preventive Measure: Excess Manganese should not be used.

Long Answer Type Questions

Question 1:

It is observed that deficiency of a particular element showed its symptoms initially in older leaves and then in younger leaves.

a. Does it indicate that the element is actively mobilized or relatively immobile?

b. Name two elements which are highly mobile and two which are relatively immobile.

c. How is the aspect of mobility of elements important to horticulture and agriculture?

Answer:

(a) If it is observed that deficiency of a particular element showed its symptoms initially in older leaves and then in younger leaves than this indicates that the element is actively mobilized. It is because, the immobile elements are first transported to the tip level of the plant and mobile elements to the base.

(b) Highly Mobile elements: Nitrogen and Magnesium

Relatively Immobile elements: Calcium and Boron

(c) If it is observed that deficiency of a particular element showed its symptoms initially in older leaves and then in younger leaves than this indicates that the element is actively mobilized. This information is used by agriculturist and horticulturist to understand the deficiency of a particular element. For example Sulphur is an immobile element so it’s deficiency is seen in younger leaves first.

Question 2:

We find that Rhizobium forms nodules on the roots of leguminous plants.

Also Frankia another microbe forms nitrogen fixing nodules on the roots of non-leguminous plant Alnus.

a. Can we artificially induce the property of nitrogen fixation in a plant – leguminous or non-leguminous?

b. What kind of relationship is observed between Mycorrhiza and pine trees?

c. Is it necessary for a microbe to be in close association with a plant to provide mineral nutrition? Explain with the help of one example.

Answer:

(a) Yes, the property of nitrogen fixation in a plant – leguminous or non-leguminous can be artificially induced by genetic engineering. It involves the introduction of a specific genes in the plant to produce nitrogenase enzyme which is involved in nitrogen fixation.

(b) Mycorrhiza and Pine trees show symbiotic relationship. In this type of relationship both the organisms benefit from each other.

(c) Yes, It is necessary for a microbe to be in close association with a plant to provide mineral nutrition. The most common association is in the form of nodules. The nodules has all the necessary biochemical such as enzymes .For example the rod shaped Rhizobium has such relationship with several legumes like sweet pea, lentils, garden pea etc.

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