Important Questions Class 11 Biology Chapter 12 Mineral Nutrition
Plants absorb a variety of mineral elements and obtain inorganic nutrients from the soil, air, and water. However, not all the mineral elements absorbed by them are required. Those that are required in larger quantities are called macronutrients while elements that are needed in lesser quantities are termed as micronutrients. Deficiency of these elements results in deficiency symptoms such as stunted growth, impaired cell division, chlorosis, etc. Nitrogen is very essential for the nourishment of plants. As they cannot directly use atmospheric nitrogen, nitrogen fixation is carried out by the microbes present in the soil. Continue reading to discover more about mineral nutrition.
Q.1. Give the name of a plant that accumulates silicon.
A.1. Triticum aestivum and Oryza sativa
Q.2. How do entities in a mutualistic association benefit from each other as seen in mycorrhiza?
A.2. A mycorrhiza is a symbiotic association between the roots of vascular plants and a fungus. This association provides the fungus with a constant supply of carbohydrates. Plants in return procure the benefit of the mycelium of the fungus which promotes its absorptive capacity of minerals and water provided the large surface area of mycelium.
Q.3. Why is nitrogen fixation observed in prokaryotes and not eukaryotes?
A.3. Eukaryotes do not contain the enzyme – nitrogenase, required to fix nitrogen which is possessed by prokaryotes such as Rhizobium.
Q.4. Name the nutrients obtained by carnivores such as venus flytrap and Nepenthes. Where do they obtain them from?
A.4. They grow in nitrogen-deficient soil hence make up for their deficiency by trapping insects for which they develop special adaptations.
Q.5. Name a plant that lacks chlorophyll. How does it fulfil its nutritional requirements? Give an example.
A.5. Monotrapa, commonly known as ghost plant
Q.6. Write the name of an insectivorous angiosperm.
Q.7. Name the mineral element that is restored with the addition of Azotobacter culture to the soil.
A.7. To enhance the nitrogen element in the maize field through nitrogen-fixation
Q.8. In the root nodule of a legume, what are the conditions posed by a leghaemoglobin?
A.8. It is responsible for initiating anaerobic conditions in the root nodules. They serve as oxygen scavengers thereby protecting enzyme nitrogenase to come in contact with oxygen thus aiding in their proper functioning(nitrogen fixation)
Q.9. In the context of the mode of nutrition, what do the following share in common? Nepenthes, Drosera, Utricularia
A.9. These are carnivorous(insectivorous) plants.
Q.10. Zinc-deficient plants exhibit reduced biosynthesis of?
Q.11. Deficiency of what is indicated by yellowish edges in leaves?
Q.12. Which is that macronutrient that is a component of all organic compounds but is not obtained from the soil?
Q.13. List one prokaryote that is non-symbiotic and fixes nitrogen.
Q.14. Name an important greenhouse gas produced by rice fields.
Q.15. For reductive amination, write the following equation.
Q.16. Why does an excess of Mn in soil lead to a deficiency of Ca, Mg and Fe?
A.16. When absorbed in higher amounts by plants, Manganese becomes toxic which is expressed in the form of brown spots surrounded by chlorotic vein. Due to:
The decline in the uptake of iron and manganese.
Hinderance of binding of manganese to particular enzymes
Hinderance of calcium translocation in the shoot apex
Hence excess of manganese causes a lack of magnesium, calcium, and iron.
Q.1. What is the importance of sulphur in plants? Name the amino acids which contain it.
A.1. It is an important macronutrient in plants which is absorbed by plants as an ion. It primarily functions as a component of proteins, vitamins(thiamine, biotin), coenzyme-A, amino acids (methionine, cysteine), etc. Also, it is a necessary component of ally sulphide (garlic, onion) and sinigrin(mustard). Sulphur-deficiency can cause chlorosis in young leaves, the formation of hard and woody stems, extensive root growth, etc. It also results in a reduction of juice content of citrus fruits and yellow disease of tea. Sulphur is found in amino acids methionine, cysteine, etc.
Q.2. What is the significance of Pseudomonas and Thiobacillus in the nitrogen cycle?
A.2. They are denitrifying bacteria which carry our denitrification in the nitrogen cycle, wherein under anaerobic conditions, nitrate present in the soil is reduced back to nitrogen oxides thereby contributing to the atmospheric nitrogen.
Q.3. Observe the diagram and answer the following questions:
a) What is the technique demonstrated in the figure? Name the scientist who demonstrated it for the first time.
b) List any three plants on which this technique can be applied for commercial purposes.
c) State the importance of feeding funnel and aerating tube. A.3. a) Hydroponics. Scientist – Julius Von Sachs
A.3. b) Hibiscus asculentus (ladies finger) Solanum Lycopersicum (tomato) Solanum melongena (brinjal)
A.3. c) Feeding funnel is used to add nutrients and water. Aerating tube supplies with oxygen for the proper growth and development of the roots nurturing in the liquid solution.
Q.4. Which is the most important enzyme present in root nodules for fixation? For its functioning, does it require the pink coloured pigment? Explain.
A.4. Its Nitrogenase, that catalyzes the conversion of atmospheric nitrogen to ammonia. Leghaemoglobin is the pink coloured pigment. Yes, it is required as it creates anaerobic conditions for the functioning of the nitrogenase enzyme.
Q.5. In association with the concentration of an essential element in plants, differentiate between ‘critical concentration’ and ‘deficient’. Find the ‘critical concentration’ and ‘deficient’ values for – Fe and Zn.
A.5. Critical concentration is a concentration of a nutrient that is measured in tissue, just below the level that gives maximum growth. Example – K, P, and N are critical elements whereas deficient is the concentration below the critical concentration and the lack of nutrient element can lead to an eventual drop in the plant growth.
Q.6. Explain the following with an example – Carnivorous plants exhibit nutritional adaptation.
A.6. Carnivorous or insectivorous plants are usually found in nitrogen deficient soil. To make up for this deficiency, they have developed an insect trapping mechanism in which leaves adapt to the shape of a pitcher having insect digesting proteolytic enzymes. They absorb nitrogen received from them and trap insects.
Q.1. What are the essential elements for plants? State criteria for their essentiality. Give the classification of minerals basis the amount in which they are required by plants.
A.1. An element is said to be essential to a plant if it is required for maintaining its normal growth and reproduction. This requirement needs to be specified and cannot be replaced by any other element in the soil and should be directly involved in plant metabolism. Following are the criteria for essentiality:
Essential elements are further subdivided into:
Q.2. What will it be beneficial to plants if they are supplied with excess nutrients? If no, why and if yes, how? A.2. No, it is not beneficial as higher doses of micronutrients may become toxic. Toxic concentration is any concentration that reduces the dry weight of tissue by 10%. However, critical concentration differs for various micronutrients and different plants. For instance, beyond 600μ is toxic for soybean and beyond 5300 μfor sunflower. These toxic effects can be either due to interference in the absorption and functioning of nutrients or due to the excess of the micronutrient. Example – Toxicity in manganese can be due to:
Q.3. Most of the crops are still cultivated on land despite hydroponics being a successful technique to grow plants. Why?
A.3. Hydroponics is a solution culture that is utilized to raise plants in a soilless medium. However, there are various disadvantages of these techniques, such as:
Regular root aeration for normal growth of plants is required.
For maximum growth, the solution needs to be replaced frequently.
Undesirable pH changes due to the loss of certain ions that are quickly absorbed.
It is an expensive technique. The handling and settling of this technique needs much more investment than soil-based production.
There are chances of these methods spreading water-borne diseases.
Due to lack of knowledge, it is not practised by traditional farmers.
Q.4. What are the essential elements? Explain macro and microelements with examples? A.4. Roots are the underground part of all vascular plants are mainly responsible for absorbing the chemicals present in their surrounding soil. Among all the available elements only 14 of the absorbed elements are necessary for plant growth and these are called as the essential elements. The essentials elements required in larger amounts and are called the macronutrients. The essentials elements required in lesser amounts are the micronutrients. Macronutrients are absorbed from both the air and soil. It includes calcium, carbon, hydrogen, magnesium, nitrogen, oxygen, potassium, phosphorus, and sulfur. Macronutrients are absorbed from the soil. It includes iron, boron, chlorine, manganese, zinc, copper, molybdenum, and nickel. Further Reading:
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