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Class 11 Biology Chapter 12 Mineral Nutrition
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Chapter – 12
VERY SHORT ANSWER TYPE QUESTIONS
Q.1. What are the basic needs of all living organism ?
Ans :- Living organism require macromolecule like carbohydrate, protein and fat and water, minerals for growth and development.
Q.2. Who and when demonstrated ‘hydroponics’ ?
Ans :- Julies von sachs, in 1860 demonstrated hydroponics.
Q.3. What is the technique of hydroponics ?
Ans :- The technique of growing plants in a nutrient solution is known as hydroponics.
Q.4. Give few examples of vegetable grown through hydroponics ?
Ans :- Vegetable such as tomato, seedless cucumber and lettuce are grown through hydroponics.
Q.5. What are macronutrients ?
Ans :- Macronutrients are the nutrients present in large amount in plant tissues.
Q.6. Write the name of few macronutrients ?
Ans :- Example of macronutrient are carbon, hydrogen, oxygen, nitrogen, phosphorus, sulphur, potassium, calcium and magnesium etc.
Q.7. From where are carbon, hydrogen and oxygen taken in plants ?
Ans :- Carbon, hydrogen and oxygen are taken in plants from Co₂ and H₂O.
Q.8. What are micronutrients ?
Ans :- The nutrients which are required in very small amount are called micronutrient. e.g iron, copper, zinc, boron etc.
Q.9. Give few examples of beneficial elements required by higher plants.
Ans :- Sodium, silicon, cobalt and selenium are the beneficial element required by higher plants.
Q.10. Which element plays an important role in the opening and closing of stomata ?
Ans :- Potassium.
Q.11. In which form is nitrogen absorbed in plants ?
Ans :- Nitrogen is absorbed in plants in the form of nitrates (NO₃).
Q.12. In what form is phosphorus absorbed in plants ?
Ans :- Phosphorus is absorbed from the soil in the form of phosphate ion (HPO₄²).
Q.13. What is the main function of potassium ?
Ans :- Potassium helps to maintain an anion-cation balance in cells and is involved in protein-synthesis, opening and closing of stomata etc.
Q.14. Which element is required to maintain ribosome structure ?
Ans :- Magnesium is required to maintain ribosome structure.
Q.15. Write the name of amino acids in which sulphur is present ?
Ans :- Sulphur is present in two amino acids cysteine and methionine.
Q.16. Which element is required for the formation of chlorophyll ?
Ans :- Iron is required for the formation of chlorophyll.
Q.17. When is an element said to be deficient ?
Ans :- An element is said to be deficient when present below the critical concentration.
Q.18. What are the kinds of deficiency symptom seen is plants ?
Ans :- The kind of deficiency symptom shown in plants are chlorosis, necrosis, stunted plant growth, premature leaf fall and bud fall and inhibition of cell division.
Q.19. Write the name of elements whose deficiency leads to chlorosis.
Ans :- The deficiency of N, K, Mg, S, Fe, Mn, Zn, and Mo are responsible for chlorosis.
Q.20. Write the name of elements whose deficiency causes necrosis.
Ans :- The deficiency of Ca, Mg, Cu, K causes necrosis.
Q.21. When is a micronutrient considered toxic ?
Ans :- When the mineral ion concentration in tissue reduces the dry weight of tissue by about 10 percent, then micronutrient is considered toxic.
Q.22. Which term is used for the movement of ions ?
Ans :- Flux is the term used for the movement of ions.
Q.23. Which term is used for the movement of ions ?
Ans :- The process of conversion of nitrogen (N₂).
Q.24. Write the name of the bacterium responsible for oxidising ammonia to nitrite ?
Ans :- Nitrosomonas or Nitrococcus bacterium.
Q.25. Which microorganism carries the denitrification process in plants ?
Ans :- Pseudomonas and Thiobacillus.
Q.26. Write the enzyme present in prokaryotes, capable of nitrogen reduction.
Ans :- Enzyme nitrogenase is capable of nitrogen reduction.
Q.27. Give the names of any two cyanobacteria that are nitrogen-fixer ?
Ans :- Anabaena and Nostoc.
Q.28. What are nodules ?
Ans :- Nodules are small outgrowths on the roots which are centrally pint due to the presence of leg haemoglobin.
Q.29. What is the first stable product of nitrogen fixation ?
Ans :- Ammonia.
Q.30. Name the important amides found in plants ?
Ans :- Asparagine and glutamine are the important amides found in plants.
SHORT ANSWER TYPE QUESTIONS
Q.1. Write explanatory note on hydroponics.
Ans :- Hydroponics is a method of growing plants in nutrient enriched water without soil the plants are grown in large tanks containing nutrient solution. The tanks are provided with the solution with regulating and pumping system and are placed in green house under controlled environment Hydroponics is also known as tank farming.
Hydroponics is used for growing herbaceous vegetables, flowers etc.
Q.2. Classify elements into its categories.
Ans :- Elements are classified into two categories
Macronutrients are present in plant tissues in large amounts e.g. carbon, hydrogen, oxygen, nitrogen, sulphur etc.
Micronutrient are needed in very small amounts. These include iron, manganese, capper, zinc, boron etc.
Q.3. Write the chief functions of nitrogen and phosphorus.
Ans :- Nitrogen is the essential nutrient element required by the plants in greatest amount. It is required by the meristematic tissue and the metabolically active cells. It is one of the major constituent of protein, nucleic acid, vitamin and hormone.
Phosphorus is absorbed by the plants from the soil in the form of phosphate ions. Phosphorus is a constituent of cell membrane, proteins, all nucleic acids and nucleotide and is required for all phosphoryl action reaction.
Q.4. Write the function of calcium in plants.
Ans :- Calcium is absorbed from the soil in the from of calcium ions. (Ca2+) Calcium is required by meristematic and differentiating tissues. During cell division it is used in the synthesis of cell wall. It is also needed during the formation of mitotic spindle. It activates certain enzymes and plays an important role in regulating the metabolic activities.
Q.5. Mention the functions of iron ?
Ans :- Iron is taken in ferrie ions forms by plants. It is an important constituent of protein involved in the transfer of electrons like ferredoxin and cytochromes. It activates catalase enzymes and is required for the formation of chlorophyll.
Q.6. Name at least five deficiency symptoms observed in plants.
Ans :- The plants in the absence of any particular element show certain morphological changes. These changes are indicative of certain element deficiencies and are called deficiency symptoms.
The deficiency symptoms are –
i) Chlorosis :- Loss of chlorophyll leads to yellowing of the leaves is termed as necrosis.
ii) Necrosis :- The localised death of leaf tissues which may spread to entire leaf is called necrosis.
iii) Mottling :- The appearance of patches of green and non-green areas in leaves is called mottling.
iv) Leaf curl :- This is caused due to abnormal curling of leaves.
v) Abscission :- This means the fall of immature leaves, flowers, buds and fruits.
Q.7. Write a note on toxicity of micronutrient.
Ans :- The micronutrients are required in very low amount but if there is a moderate increase in their amount, toxicity occurs. The level of toxicity vary for different plants. Many a times, excess of an element may inhibit the uptake of another element e.g. the prominent symptom of manganese toxicity is the appearance of brown spot surrounded by chlorotic veins. Manganese also inhibit calcium translocation in shoot apex. So, the excess of manganese induces deficiencies of iron, magnesium and calcium.
Q.8. Soil is a reservoir of essential element. Comment.
Ans :- Due to weathering and breakdown of rocks, mineral are available to the roots for the proper growth and development of plants. This process enrich the soil with dissolved ions and inorganic salts. Since they are derived from the rock minerals, their role in plant nutrition is referred as mineral nutrition soil not only supplies minerals but also harbours nitrogen fixing bacteria, other microbes, holds water, supplies air to the roots and acts as a matrix that stabilises the plant. Both macro and micronutrient form component of fertiliser too.
Thus, it is clear that soil is the reservoir of essential element.
Q.9. Explain the process of nitrification.
Ans :- Ammonia formed by the process of ammonification gets converted into nitrate by soil bacteria in the following steps.
2NH₃ + 30₂ → 2NO⁻₂ + 24⁻ + 2H₂O
2NO⁻₂ + O₂ → 2NO⁻₃
Ammonia is first oxidised to nitrite by the bacteria Nitrosamine or Nitrococcus. The nitrite is further oxidised to nitrate with the help of bacterium Enterobacteria. These steps are called nitrification.
Q.10. What is biological nitrogen fixation ?
Ans :- Some prokaryotic species are capable of fixing nitrogen. Reduction of nitrogen to ammonia by living organism is called biological nitrogen fixation. The enzyme nitrogenase is capable of nitrogen reduction. Such microbes are called N 2 fixers.
Biological nitrogen fixation is carried by two types of microorganism – symbiotic and non-symbiotic microbes. In symbiotic fixation, the symbiotic nitrogen fixing bacteria form nodules in the rods leguminous plants like pulse, pea, gram etc.
The bacteria fix atmospheric nitrogen.
Non-symbiotic fixation – some free-living bacteria and cyanobacteria present in soil fix atmospheric nitrogen in their cells. Upon their death the nitrogen is liberated into soil which plant absorb. e.g. Azotobacter, bacillus etc.
Q.11. What are the steps involved in the formation of a root nodule ?
Ans :- The principal stages in nodule formation are :
i) Rhizobium multiply and colonies the surrounding of roots and get attached to the epidermal and root hair cells.
ii) The root hairs curl and bacteria invade the root hair.
iii) An infection thread is produced carrying the bacteria into the cortex of root.
iv) The bacteria are released into the cell which leads to the differentiation of specialised nitrogen fixing cells.
v) The nodule thus formed, establishes a direct vascular connection with the host for exchange of nutrient.
Q.12. What is the role of enzyme nitrogenase in nitrogen fixation ?
Ans :- The module contain enzyme nitrogenase. It is a Mo-fe protein and catalyses the conversion of atmospheric nitrogen to ammonia, the first stable product of nitrogen fixation. N₂ + 8e⁻ + 8H⁺ + 16ATP → 2NH₃ + H₂ + 16ADP + 16P₁ . The enzyme nitrogenase is highly sensitive to molecular oxygen, it requires anaerobic condition. To protect these enzymes, nodules contain an oxygen scavenger called leg-haemoglobin.These microbes live as aerobes under free living condition but during nitrogen fixing events, they become anaerobic.
LONG ANSWER TYPE QUESTIONS
Q.1. Explain the criteria for the essentiality of an element.
Ans :- The criteria for the essentiality of an element are –
(i) The element must be absolutely necessary for supporting normal growth and reproduction. In the absence of the elements the plants do not complete their life cycle.
(ii) The requirement of the element must be specific and not replicable by another element. In other words, deficiency of any one element cannot by met by supplying some other element.
(iii) The element must be directly involved in the metabolism of the plant.
These elements are further divided into two broad categories based on their quantitative requirement.
Micronutrients are required in very small amount where as micronutrients are needed in large amount.
Essential elements can also be grouped into four categories on the basis of their diverse function.
(i) Essential elements as components of biomolecules and hence structural element of cells.
(ii) Essential elements that are component of energy related chemical compounds in plants.
(iii) Essential elements that activate or inhibit enzymes.
(iv) Some essential elements can alter the osmotic potential of a cell.
Q.2. Write the name of five essential elements and describe any three with their forms and functions.
Ans :- The essential elements are nitrogen, potassium, calcium, iron and chlorine.
(i) Nitrogen :- It is the essential nutrient element required in greatest amount. It is absorbed as NO₃ mainly. Nitrogen is required particularly by the meristematic tissue and metabolically active cells. Nitrogen is one of the major constituent of protein, nucleic acid, vitamins and hormones.
(ii) Potassium :- It is absorbed as potassium ion. It is required in more quantities in the meristematic tissues, buds, leaves and root tips. Potassium helps to maintain an anion cation balance in cells and is involved in protein synthesis, opening and closing of stomata and in the maintenance of turgidity of cells.
(iii) Iron :- Plants obtain iron in the form of ferric ion (Fe³⁺). It is an important constituent of protein involved in the transfer of electron like ferredoxin and cytochrome. It is reversibly oxidised from ferrous to ferric ion during electron transfer. It activates catalase oxygen, and is essential for the formation of chlorophyll.
Q.3. Describe any five micronutrients with their functions.
Ans :- The chief five micronutrients are copper, zinc, manganese, boron and chlorine.
Manganese :- It is absorbed in the form of manganous ion (Mn²⁺). It activates many enzymes involved in photosynthesis, respiration and nitrogen metabolism. The main function of manganese is in the splitting of water to liberate oxygen during photosynthesis.
Zinc :- Plants obtain zinc as Zn²⁺ ions. It activates various enzymes, especially carboxylases. It is also needed in the synthesis of auxin.
Copper :- It is absorbed as cupric ions (Cu²⁺). It is essential for the overall metabolism in plants. Like iron, it is associated with certain enzyme involved in redox reaction and is reversibly oxidised from cu+ to Cu²⁺.
Boron :- Boron is absorbed as BO₃³⁻ or B₄O₇²⁻. Boron is required for uptake and utilisation of Ca²⁺, membrane functioning, pollen, germination, cell elongation and cell differentiation.
Chlorine :- It is absorbed in form of chloride onion (cl-). Along with Na+ and k+, it helps in determining the solute concentration and onion-cation balance in the cells. It is essential for water splitting reaction in photosynthesis.
Q.4. Why is that is certain plants deficiency symptom appear first in younger parts of the plant while in others they do so in mature organs ?
Ans :- The deficiency symptoms vary from element to element and they disappear when the deficient mineral nutrient is provided to the plant. The parts of the plant that show the deficiency symptom also depend on the mobility of the element in the plant.
The deficiency symptoms tend to appear first in the young tissues whenever the element are relatively immobile and are not transported out of the mature organs for example elements like sulphur and calcium are a part of structural component of the cell and hence are not easily released.
For elements that are actively mobilised within the plants and are exported to young developing tissue, the deficiency symptoms tend to appear first in the older tissues. For example, the deficiency symptom of nitrogen, potassium and magnesium are visible first in the senescent leaves. In the older leaves, biomolecules containing these elements are broken down, making these elements available for mobilising to the younger leaves.
So, these are the reasons why the deficiency symptoms appear first in younger parts of the plants while in others they do so in the mature organs.
Q.5. Explain the mechanism of absorption of element ?
Ans :- Like water, various solutes necessary for plant life are absorbed form the soil. These solutes remain present in the soil in their dissolved state. The minerals pass inside the root in their dissolved state.
When mineral enter the plant cells without involvement of energy, that is by free diffusion, it is called passive absorption. So in the first phase, on initial rapid uptake of ions into the free space or outer space of cells the apoplast, is passive. In the second phase of uptake, the ions are taken in slowly in the ‘inner space’ – the symplast of the cell.
The passive movement of ions into the apoplast usually occurs through ion channels, the trains-membrane. Protein that function as selective pores. On the other hand, the entry or exit of ions to and from the symplast requires the expenditure of metabolic energy, which is an active process. The movement of ions is usually called flux, the inward movement in to the cells is called influx, the inward movement into the cells is called influx and outward movement is afflux.
Q.6. Diagrammatically explain nitrogen cycle.
Ans :- Nitrogen is a constituent of amino acid, protein, hormone, chlorophyll and many of the vitamins. Plants compete with microbe for the limited nitrogen that is available in soil. Thus, nitrogen is a limiting nutrient for both natural and agricultural ecosystems. The process of conversion of nitrogen to ammonia is termed as nitrogen fixation. In nature, lightning and ultraviolet radiation provide enough energy to convert nitrogen to nitrogen oxide. Decomposition of organic nitrogen of dead plants and animals into ammonia is known as ammonification. Some of the ammonia volatilizes and re-enters the atmosphere but most of it is converted into nitrate by soil bacteria in the following steps :
2NH₃ + 30₂ → 2NO⁻₂ + 2H⁻ + 2H₂O
2NO₂⁻ + O₂ → 2NO₃⁻
Ammonia is first oxidised to nitrite by the bacteria Nitrosamine or Nitrococcus. The nitrite is further oxidised to nitrate by the bacterium Enterobacteria. This process is called nitrification.
The nitrate thus formed is absorbed by plants and is transported to the leaves. Nitrate present in the soil is also reduced to nitrogen by the process of denitrification which carried by bacteria Pseudomonas and Thiobacillus.
Q.7. What are the steps involved in nitrogen fixation through rhizobium bacteria.
Ans :- The bacteria Rhizobium forms nodule and establishes a direct vascular connection with the host for exchange of nutrients. The nodule contains enzyme nitrogenase and leghaemo globin. The enzyme nitrogenase is a Mo-Fe protein and catalyses the conversion of atmospheric nitrogen to ammonia the first stable product of nitrogen fixation. The enzyme nitrogenase is highly sensitive to molecular oxygen, it requires anaerobic conditions. The nodules have adaptation that ensure that the enzyme is protected from oxygen. To protect these enzymes, nodules contain an oxygen scavenger called leg haemoglobin. Ammonia synthesis by a nitrogenase requires a vary high input of energy. This energy is obtained from respiration of host cells.
Ammonia is protonated to form NH₄⁺ ion. This ammonium ion is used to synthesis amino acid in plants. There are two main ways in which this takes place.
i) Reductive animation In this process, ammonia reacts with a-keto glutaric acid and forms glutamic acid.
ii) Transamination :- In involves the transfer of amino group from one amino acid to the keto group of a keto acid. Glutamic acid is the main amino acid from which the transfer of NH 2, the amino group takes place and other amino acid are formed through transamination.
Asparagine and glutamine are formed from two amino acid namely aspartic acid and glutamic acid, by addition of another amino group to each. Since amides contain more nitrogen than amino acid, they are transported to other part of the plant through xylem vessels.
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