Question

Assertion: A mangrove tree growing in marshy place has pneumatophores.
Reason: Pneumatophores help in a better anchorage in marshy soil.
(a) Both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
(b) Both Assertion and Reason are correct and Reason is not the correct explanation of Assertion.
(c) Assertion is correct but Reason is incorrect
(d) Both Assertion and Reason are incorrect

Answer 1

Hint: A marshy place is characterized by its oxygen-deficient sub-soil environment. It poses a problem for underground structures of plants whose cells also need oxygen to respire. Pneumatophores are upright structures emerging from the ground at short intervals.

Complete answer:
Pneumatophores are also known as respiratory roots which is a characteristic of plants growing in marshy regions. It is a transitional water zone between freshwater and saltwater. Mangroves grow well in such areas due to certain adaptations in their root system helping them to survive an oxygen- deficient and salt- rich environment. In mangroves, the traditional root system spreads horizontally but cannot obtain enough oxygen for their survival due to the anaerobic conditions underground. This leads to the development of upright aerating roots or pneumatophores at short intervals. The apical region of pneumatophores bears pneumatophores or lenticels for storage and exchange of air. Thus, a mangrove tree growing in a marshy place has pneumatophores for the exchange of gases. E.g. Sonneratia and Avicenia.
Other modifications of roots include:
- Storage of food: In the tap root system, the base of the root becomes fleshy and conical after storing food. This is followed by the emergence of secondary roots from the fleshy basal part.E.g Carrot.
- Nitrogen fixation: In families of Legumes, there are numerous small irregular swellings known as root nodules or tubercles. It develops in the secondary and tertiary roots. Such nodulated roots is a harbor for nitrogen- fixing bacteria like Rhizobium. They pick up the free nitrogen from the atmosphere and convert into useful nitrogenous compounds for the plants. E.g. Pisum sativum.
So, the Assertion is correct and the Reason is incorrect.

Note:
Mangroves represent an important ecosystem for the earth due to the following Reasons:
- The thick forests act as a natural barrier against any cyclones or floods.
- They represent the rich biodiversity of plants and animals. It is a home of endangered animals like the American alligator and Green sea turtle.
- Resources like hard, durable, and water- resistant wood are extracted to build furniture, boats, etc.