Assertion Reason Questions for Biology Chapter 12 Mineral Nutrition

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Directions: In the following questions, a statement of assertion is followed by a statement of reason.
Mark the correct choice as:
(a) If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
(b) If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
(c) If Assertion is true but Reason is false.
(d) If both Assertion and Reason are false.

Q.1. Assertion : Hydroponics is used for solution culture.
Reason : A balanced nutrient solution contains both essential and nonessential elements.

Answer Answer: (c) Solution culture is being used for raising flowers and vegetables at home. This soilless production of plants is called hydroponics. A solution having all the essential elements in proper proportion is called normal or balanced nutrient solution.

Q.2. Assertion : In solution culture of plants, iron is added in the form of Fe-EDTA.
Reason : Hydroponics setup is costly.

Answer Answer: (b) In solution culture, iron is added as Fe- EDTA. The agent which keeps metals in the soluble state is called chelating agent or ligand. Fe-EDTA complex is called chelate. The soilless production of plants is called solution culture or hydroponics. The cost of setting up a hydroponic system is very high.

Q.3. Assertion : Hydroponics requires purified water and mineral nutrient salts.
Reason : Purified water and mineral salts are always not essential for the growth of hydroponics.

Answer Answer: (c) Due to exposure of the plant roots to a limited amount of the solution, there are chances that the concentrations of oxygen and other minerals in the plant roots would reduce. That’s the reason that purification of water and nutrient salts are essential for hydroponics, so as to maintain an optimum growth of the plants.

Q.4. Assertion : Every plant can grow in a suitable mineral solution only (i.e., without soil).
Reason : Hydroponics does not help in the identification of essential elements and deficiency symptoms of the plants.

Answer Answer: (c) Hydroponics is a technique of growing plants in a nutrient solution. After that, a number of improvised methods have been employed to determine the mineral nutrients essential for plants. After a series of experiments in which the roots of the plants were immersed in nutrient solutions and an element was added/removed or given in varied concentration, a mineral solution suitable for the plant growth was obtained. By this method, essential elements were identified and their deficiency symptoms were discovered.

Q.5. Assertion : Manganese is an activator of enzyme nitrite reductase.
Reason : Manganese deficient cells prefer ammonia over nitrate.

Answer Answer: (a) Manganese plays an important role in nitrate reduction. Manganese acts as an activator for the enzymes nitrite reductase and hydroxylamine reductase. The preference of ammonia over nitrate as a nitrogen source by the manganese – deficient cells supports the above mentioned analysis of the role of manganese.

Q.6. Assertion : Calcium is a constituent of cell wall.
Reason : Calcium is required in mitotic division.

Answer Answer: (b) Calcium is a constituent of cell walls in the form of calcium pectate. Calcium in small amounts is necessary for normal mitosis. Calcium may be involved in chromatin or mitotic spindle organization.

Q.7. Assertion : Plants absorb sulphur in the form of sulphate ions.
Reason : Sulphur bacteria are required for the formation of sulphate. [AIIMS 2007]

Answer Answer: (a) Sulphur is a constituent of amino acids (cystein and cystine and methionine). Sulphur is present in the soil in the form of oxides. Sulphur bacteria convert them into sulphate ions.The plants absorb sulphur in the form of sulphate ions.


Q.8. Assertion: Plants absorb calcium from soil in the form of calcium ions (Ca2+).
Reason: Calcium is required by meristematic and differentiating tissues.

Answer Answer: (b) Plants absorb calcium from the soil is absorbed by plants in the form of calcium ions (Ca2+). Calcium is required by meristematic and differentiating tissues. During cell division it is used in the synthesis of cell wall, particularly as calcium pectate in the middle lamella. It is also needed during the formation of mitotic spindle. It activates certain enzymes and plays an important role in regulating metabolic activities.

Q.9. Assertion: Certain essential elements are called structural elements of cells.
Reason: These essential elements are the components of certain biomolecules.

Answer Answer: (a) Some essential elements play a structural role in plants. These essential elements are carbon, hydrogen, oxygen and nitrogen. They are the building blocks of macromolecules that form the bulk of plant body. Carbon and hydrogen are components of all organic substances. Many of them also contain oxygen. Nitrogen is a constituent of amino acids, proteins, nucleic acids, chlorophyll, auxin, cytokinins and vitamins.

Q.10. Assertion: The main constituent of several coenzymes, vitamins and ferredoxin is sulphur.
Reason: Sulphur is present in two amino acids – valine and cysteine.

Answer Answer: (c) Sulphur is an important macroelement of plants. Plants obtain sulphur in the form of sulphate (SO4 2–). Sulphur is present in two amino acids –cysteine and methionine and is the main constituent of several coenzymes, vitamins (thiamine, biotin, coenzyme A) and ferredoxin.

Q.11. Assertion: Plants obtain molybdenum in the form of molybdate ions (MoO4 2+).
Reason: Molybdenum is a component of pollen germination, cell elongation and cell differentation.

Answer Answer: (d) Plants obtain molybdenum in the form of molybdate ions. It is a component of several enzymes, including nitrogenase and nitrate reductase both of which participate in nitrogen metabolism.

Q.12. Assertion : Iron is a microelement.
Reason : Microelements are required in traces only, less than 1mg/gm of dry matter.

Answer Answer: (a) Micro elements are those essential elements which are required by plants in traces only, less than 1 mg/gm of dry matter. Iron occurs in the concentration of less than 1 mg/gm.

Q.13. Assertion : Magnesium is important in photosynthesis and carbohydrate metabolism.
Reason : Mg++ is involved in the synthesis of nucleic acids.

Answer Answer: (b) Magnesium is a constituent of the chlorophyll molecule, without which photosynthesis would not occur. Many of the enzymes involved in carbohydrate metabolism require magnesium as an activator. Magnesium is also an activator for those enzymes involved in the synthesis of nucleic acids (DNA, RNA) from nucleotide polyphosphate.

Q.14. Assertion: The technique of growing plants in a nutrient solution is known as hydroponics.
Reason : Hydroponics is used for commercial production of vegetables such as tomato, seedless cucumber and lettuce.

Answer Answer: (b) The production of plants without soil is called hydroponics. Solution culture is used for raising soilless flowers and vegetables. Plants are raised in small tanks of concrete or metal. The upper covering has supports for plants. The narrow tanks are provided with nutrient solution. A pump circulates air as well as nutrient solution. Roots of the plants are, therefore, regularly provided with aerated nutrient solution. Hydroponics is useful in areas having thin, infertile and dry soil.

Q.15. Assertion : Some essential elements can alter the osmotic potential of a cell.
Reason : Osmotic potential can be regulated by potassium.

Answer Answer: (a) Some essential elements can alter the osmotic potential of a cell. Potassium plays an important role in the opening and closing of the stomata.

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