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Give an account of heterotrophic nutrition in plants.

Heterotroph organism cannot manufacture their own food. They are usually of three types, 

(i) Saprophytes, 

(ii) Parasites, 

(iii) Insectivorous plants or carnivorous plants.

(i) Saprophytes are non-green organisms which get their food from dead and decaying bodies. E.g. bacteria, fungi and some angiosperms. Monotrapa is known as Indian pipe. It grows in the soil rich in humus. Birds nest orchid or Neottia also grows in forest’s humus rich soil.

(ii) Parasite get their food from the host plant or animal. Parasitic plants are mainly of two types based upon their association with the host plant. They may be complete or partial parasites. The example of these parasites are,

Total stem parasiteCuscuta reflexa (Dodder or Amarbel) on the host Citrus, Duranta etc.

Total root parasiteOrobanche, Rafflesia, Balanophora (Frown rope) and Strigia.

Partial stem parasiteViscum (Mistletoe) and Loranthus and Cassytha.

Partial root parasiteSantalum album (Sandlewood).

(iii) Insectivorous plants feed on insects to obtain nitrogen food requirement. They are called partly autotrophs and partly heterotrophs. E.g. Nepenthes khasiana. (Pitcher plant), Drosera (Sundew), Dionea muscipula (Venus fly trap), Aldrovanda (water flea trap) and Utricularia (Bladder wort). 

Some green plants only prepare their own carbonaceous food as for nitrogenous compounds they capture insects and small animals and feed upon them absorbing only the nitrogenous compounds from their bodies. Such plants are called carnivores or insectivorous plants, E.g. Sundew, Venus fly trap, Pitcher plant. Etc.

In the pitcher plant the leaf becomes modified into a pitcher and the mouth of the young pitcher is covered by a lid. The inner surface of the pitcher contains various digestive glands, which secrete the digestive agent, which helps in the digestion of proteins only. Hair like structures is present below the mouth, which prevents the insects from coming out. Pitcher is partially filled with a fluid, and animals and small insects when enters the pitcher they get drowned and after their death digestion starts. Proteins are converted into peptones and peptones to amines. Only amines are absorbed by the pitcher and rest of the material.

The leaves of the sundew plants are covered with hairs that secrete sticky fluid at the trips. This sticky fluid glisten in light and hence this plants is called as sundew. An insect when visit this plant gets struck and the enzymes secreted by the heirs digest the insect and the product are absorbed by the leaf surface.


Explain briefly the special modes of nutrition in plants.

Special modes of nutrition in plants – There are two modes of nutrition in plants, 

(a) Autotrophic nutrition and

(b) Heterotrophic nutrition.

(a) Autotrophic nutrition – Green plants prepare their own food. They fall into two categories namely chemoautotrophic and photoautotrophic. Nitrosomonas and Nitrosococcus are chemosynthetic bacteria. All green plants are autotrophic.

(b) Heterotrophic nutrition – They may be parasitic, saprotrophic, symbionts and insectivorous plants.

(i) Parasites – They may be obligate parasite and semi parasites. Obligate parasites get their food from their host plants. They may be total root parasites or total stem parasites. Orobanche and Rafflesia are total root parasites while Cuscuta reflexa is a total stem parasite. Partial parasites may be partial stem parasites and partial root parasites. Loranthus and Viscum are partial stem parasites. Sandal wood tree is partial root parasites.

(ii) Saprophytes – E.g. Monotropa, Neottia. They grow in soil rich in humus and organic matter. Monotropa occurs in pine forests and its underground part forms endotropic Mycorrhizae to absorb food.

(iii) Symbiotic plants – E.g. Lichens. They are an association of algae and fungal partners. Algae provide food to the fungal partner. Fungal partner gives minerals and water to the algae.

(iv) Carnivorous plants – These plants trap insects to get nitrogen. Insectivorous plants are Nepenthes, Sundew, Utricularia, Drosera etc.


What are parasites? How are they dependant on other plants for their food?

Parasites drive their food from the host e.g. fungi and bacteria. They are non-chlorophyllus plants. They live at the expense of others. They show parasitism. They are classified into two types: 

(i) Total parasites and

(ii) Partial parasites.

Classification of parasites:
Types of parasites Sub-type Examples
Total parasites Total stem parasites Cuscuta is a pale thin stem parastite on the host plants like Citrus and Zizyphus etc.
Haustaria penetrate into host tissue and absorb water and minerals from host.
  Total root parasites Orobanche grows on the root of potatoes, brinzal, turnip etc. Balanophora grows on forest trees.
Partial parasites Partial stem parasites Viscum parasitizes pear, apple and walnut trees. Its shoot remains attached by Haustoria to the host plant and absorbs water and minerals.
  Partial root parasites Santalum grows on roots of Dalbergia. It has green leaves. It absorbs water and minerals from the host.



What type of condition is created by leghaemoglobin in the root nodules of legumes?

Anaerobic condition is created by leghaemoglobin in the root nodules of legumes.


Define mineral nutrition.

The process, which involves absorption and utilization of mineral elements by the plants for their growth and development, is called mineral nutrition.


In which process nitrogenase enzyme is useful?

Nitrogenase enzyme is useful in biological fixation of nitrogen.


Differentiate between macro-elements and micro-elements.




(i) They are present in plants in relatively large concentrations. (i) They are present in plants in very small amounts.
(ii) Their concentration per gram of plant dry matter is atleast 1mg. (ii) Their concentration is less than 1mg per gram of plant dry matter.
(iii) They build up the plant body and different cell constituents. (iii) They do not have such roles.
(iv) Some of the macronutrients contribute to the development of osmotic potential in the cells. (iv) They have no significant role in the development of osmotic potential in the cells.
(v) They do not become toxic in slight excess. (v) Microelements are toxic in slight excess.



Write the symptoms of mineral deficiency in plants.

The most common type of deficiency symptoms developing in plants are

(i) Chlorosis: Loss or non-development of chlorophyll, resulting in yellowing of leaves.

(ii) Necrosis: Localised death of tissues.

(iii) Mottling: Appearance of patches of green and non-green areas on the leaves.

(iv) Stunted growth: Retardation of growth resulting in rosette appearance of the plant.

(v) Abscission: Premature fall of flowers and fruits.

(vi) Leaf curls: Curling of leaves due to unequal growth.

(vii) Wilting: Loss of turgor resulting in the drooping of leaves and young shoots.

(viii) Heart rot: Softening or rotting of internal tissues.

(xi) Die-back: Death of shoot apex.

(x) White bud: Chlorosis of young leaves and buds.


Define mineral nutrition.

Plants require a number of mineral nutrients for their growth and development which do not occur in the plant body in free of state. The utilization of these elements by the plant for its growth and development is called mineral nutrition.


What do you understand by the term hunger signs?

Specific deficiency symptoms of a particular mineral nutrient are called hunger signs.


What are fertilizers?

Fertilizers are the chemicals or mixture of chemicals, which are added to the soil to overcome the deficiency of minerals.


Name a soil bacteria which is capable of converting ammonia to nitrates.

Nitrosomonas is a soil bacterium, which is capable of converting ammonia to nitrates.


How does nitrate get assimilated in plants?

Nitrate is the most important source of nitrogen for plants. Though it can accumulate in the cell sap of several plants and take part in producing osmotic potential, it cannot be used as such by the plants in the synthesis of organic compounds. It is first reduced to ammonia before being incorporated into organic compounds. The process of nitrate reduction to ammonia is carried out in two steps, each mediated by a specific enzyme.

(i) Reduction of nitrate to nitrite: First the nitrate is reduced to nitrite by an enzyme called nitrate reductase. The enzyme contains FAD as prosthetic group, which receives hydrogen from reduced coenzyme for the reduction of the nitrate. The reduced coenzyme serves as hydrogen donor and molybdenum serves as an electron carrier in the process.

(ii) Reduction of nitrite: The nitrite ions are then reduced to ammonia by an enzyme called nitrite reductase. This enzyme does not require molybdenum but requires copper and iron for its activity. The enzyme nitrate reductase occurs inside the chloroplasts in the leaf cells and leucoplasts of other cells. The reduced coenzyme serves as a hydrogen donor in illuminated cells and NAD + H+ in others for the reduction of nitrites. The process of reduction also requires ferredoxin, which occurs in higher plants mostly in the leaves. Therefore, nitrite ions formed in other parts of the plant are transported to leaves for their reduction to ammonia. Ammonia combines with some organic acids to produce amino acids. Amino acids then form various types of nitrogenous compounds.


What protects nitrogenase ?

Leghaemoglobin protects nitrogenase.


Mention the criteria to determine the essentiality of an element.

The criteria to determine the essentiality of an element are as follows:

(i) The element must be absolutely necessary for supporting normal growth and reproduction.

(ii) The requirement of the element must be specific and not replaceable by another element.

(iii) The element must be directly involved in the nutrition of the plant. For example, magnesium is an essential element because it is the constituent of chlorophyll and is essential for photosynthesis. It cannot be replaced by any other element for the same function. It is also required as a co-factor by many enzymes involved in cellular respiration and other metabolic pathways.


What are the sources of essential elements for plants?

All elements, which enter into plants, are ultimately derived from the atmosphere, water and soil. Carbon enters the plants from the atmosphere as carbon dioxide, while hydrogen is obtained mainly from water. Oxygen is supplied from the air or water and often in the form of inorganic ions. Although, free nitrogen is present in abundance in the atmosphere, it is inert and most plants are unable to use it directly. Due to atmospheric activities, free atmospheric nitrogen combines with oxygen and is brought down by rain to the soil. Certain microorganisms called nitrogen fixers, present in the soil, convert nitrogen gas to ammonic form such as nitrate or ammonium. These are absorbed by the plants through the roots and are assimilated as organic nitrogen. The plants in turn provide organic nitrogen to the heterotrophic organisms. All the other elements needed by the plants, are absorbed from the soil, which are ultimately derived from the parent rocks by disintegration and weathering.


Name the enzyme that can reduce nitrogen to ammonia?

The enzyme that can reduce nitrogen to ammonia is nitrogenase enzyme.


What is hydroponics? Mention their uses.

The system of growing plants on a large scale in soil less cultures is known as hydroponics. Hydroponics is useful in areas having infertile and dry soils. They grow free of soil pathogens and do not require weeding. They often provide consistently good yield of season vegetables and flowers.


Which are the two macronutrients that usually play the most important role in limiting plant growth globally.

Nitrogen and calcium are the two macronutrients that usually play the most important role in limiting plant growth globally.


Write some general functions of mineral elements in plants.

The general function of mineral elements in plants are,

(i) Constituents of plant body: Various mineral elements become permanent constituents of molecules found in the protoplasm and cell wall. Elements like carbon, hydrogen and oxygen are used up in the formation of carbohydrates, which are important constituents of the cell. Nitrogen is an essential component of all amino acids, proteins, nucleic acids, chlorophyll, auxins, cytokinins and vitamins. Magnesium is an essential part of the chlorophyll molecule and also activates certain enzymes. Sulphur is a constituent of some essential amino acids and some proteins. Phosphorus is a constituent of many important organic compounds such as ATP, NAD, NADP, DNA, RNA and phosphorylated sugars and lipids.

(ii) Osmotic potential of cells: The osmotic potential of a cell is maintained by the inorganic salts present in the cell sap. Osmotic potential is required for water absorption and maintenance of the cell’s turgidity.

(iii) Acidity and buffer action: The mineral elements absorbed from the soil, affect the H+ ion concentration and thus influence pH of the cell sap. They also constitute a major buffer system for the plants.

(iv) Permeability of cytoplasmic membranes: The permeability of cytoplasmic membranes is affected by the presence of various cations and anions in the external medium. Monovalent cations commonly increase the membrane permeability, while divalent cations decrease the same.

(v) Toxic effects: Many mineral elements in their ionic form produce a toxic effect on the protoplasm.

(vi) Catalytic effects: Several mineral elements participate in the catalytic systems of plants. For example, calcium, magnesium, manganese, sodium, potassium and chlorine serve as co-factors of enzymes.

(vii) Antagonistic effects: Some of the mineral elements antagonize or balance the harmful effects of certain other elements. For example, manganese in barley plant is toxic in the absence of silicon, but is harmless in the presence of silicon.


Name a free living nitrogen fixing aerobic bacteria.

Clostridium is free-living nitrogen fixing aerobic bacteria.


What are the two steps involved in physical nitrogen fixation?


Physical nitrogen fixation includes two steps. They are,

(i) Natural nitrogen fixation and

(ii) Industrial nitrogen fixation

(i) Natural nitrogen fixation: Atmospheric nitrogen combines with oxygen under the effect of lightning and thunder in the clouds to form nitric oxide. The nitric oxide is then oxidised with oxygen to form nitrogen peroxide. During rains, the nitrogen peroxide combines with water to form nitrous acid and nitric acid. On the ground, the acids react with the alkaline radicals to form water-soluble nitrates and nitrites, which are directly absorbed by the plants.

(ii) Industrial nitrogen fixation: Ammonia is produced industrially by direct combination of nitrogen with hydrogen at high temperature and pressure. Later, it is converted into various types of fertilizers including urea.


Which cyanobacterium has symbiotic association with Azolla.

Anabaena is a cyanobacterium has symbiotic association with Azolla.


What are essential elements?

Plants require a large number of elements, probably more than 40 of which about 16 are most essential for the growth and development of plants. These 16 elements are termed as essential elements.


Name the best known symbiotic nitrogen fixing bacteria.

Rhizobium is the best -known symbiotic nitrogen-fixing bacteria.


What are the framework elements of a plant ?

Carbon, hydrogen and oxygen are called framework elements.


Why is leghaemoglobin so called? What is its function?

It is a pink coloured pigment found in root nodules of legumes. This pigment is closely related to haemoglobin that is why it is called leghaemoglobin. It is an oxygen scavenger like haemoglobin. It combines with oxygen and protects enzyme nitrogenase, which functions under anaerobic conditions.


What is the term given to the elements which are used by the plants in large quantities ?

Macronutrient is the elements, which are used by the plants in large quantities.


Name the three factors essential for conversion of dinitrogen molecule to ammonia.

The three factors essential for conversion of dinitrogen molecule to ammonia are

(i) Strong reducing agent (NADP)

(ii) Energy rich compound (ATP)

(iii) Enzyme nitrogenase.


Give names of four major essential elements other than carbon, hydrogen and oxygen.

Nitrogen, sulphur, phosphorus and potassium are the four major essential elements other than carbon, hydrogen and oxygen.


Explain the process of nitrate assimilation.

The nitrates absorbed by the plants are reduced to nitrites, and nitrites are reduced to ammonia which is used for the synthesis of amino acids. The nitrates are reduced to nitrites by nitrate reductase enzyme. This enzyme is a flavoprotein and contains molybdenum. The nitrite ions are reduced to ammonia by nitrite reductase enzyme. This enzyme required copper and iron. It also requires ferredoxin as an electron donor which is located in the leaves only. Therefore the nitrites formed in other parts of the plant are transported to leaves where they are reduced to ammonia.


What are saprophytes? Give one example.

Saprophytes are non-green and heterotrophic plants which derive their nutrition from dead and decaying organic matter. Example: Neottia


What do you mean by the term chlorosis ?

The term chlorosis means lack of development of chlorophyll in the leaves.


Describe an important functions of each of the elements, phosphorus, boron and sulphur in green plants and also write the deficiency symptoms of any two of them.

Phosphorus – It is the constituent of cell membrane, protein, nucleic acids, nucleotides, NADP and energy rich compounds.

Boron – It helps in uptake and utilization in calcium. It helps in germination of pollen and celldifferentiation.

Sulphur - It is the constituent of protein, vitamins, thymine, biotin, and ferredoxin.

Deficiency symptoms

Phosphorus – Poor plant growth, dull green leaves and chlorosis.

Boron - It causes brown heart disease.

Sulphur – It causes chlorosis.


Why do chlorosis occur in plants ?

Chlorosis occur in plants due to the nitrogen deficiency in plants.


Write the differences between mottling and interveinal chlorisis.

Mottling Interveinal chlorisis
It is the patchy appearance of green and non-green areas of a leaf. The yellowing of leaf between the veins.
It is caused due to the deficiency of zinc and molybdenum. It is due to the deficiency of iron and molybdenum.



Pick out from the following list two minerals which are not needed by the magnity of plants but very much needed by almost are animals. Calcium, sodium, potassium, iron , Iodine.

Iodine and sodium are not needed by every plant but they are needed by animals.


What are macronutrients ?

Elements which are required by the plants in large quantities are known as micronutrients.


"Sundew plant has a rosette of leaves modified to trap insects". Explain.

Drosera is called sundew plant because of the sticky substance drops glister on the leaf margins. This plant possesses a rosette of leaves. The leaves are provided with hairs. The glands on the leaves secrete sticky substance. When an insect sits on the leaf, the hairs entrap this and the insect dies. It is digested and absorbed there. This is how the sundew plants trap the insects for their survival.


Name the important macronutrients ?

Carbon, hydrogen, oxygen, nitrogen, sulphur, phosphorus, potassium, magnesium, calcium and iron are the macronutrients because they are required in large quantities by the plants.


Name any parasitic plant and explain how does it absorb its nutrition?

Cuscuta reflexa is a parasitic plant and it grows on other plants. It is devoid of leaves and possesses a wire stem. Its seeds geminate in the soil. On finding a suitable host, it twines around it and loses connection with the soil. It sends out parasitic roots to penetrate the host tissue. They establish connection with its xylem and phloem and the Cuscuta thrives.


What are mobile elements?

N,P, Mg and K move from old leaves towards the young leaves and are called mobile elements.


Which part of the plant body normally absorbs mineral nutrients?

Root is the part of the plant body normally absorbs mineral nutrients.


What is the function of enzyme nitrate reductase ?

The enzyme nitrate reductase converts nitrate to nitrite.


What is the principle of Mass Flow hypothesis?

Movement of solutes from the source to the sink along the concentration gradient.


What form the carbohydrates synthesized in leaves by photosynthesis are translocated and through which tissue of the plant?

The carbohydrates synthesized in leaves are translocated in the form of sucrose and through phloem tissue.


Define mineral absorption.

The process by which ions and molecules penetrate into living cells or tissue from the surrounding medium, crossing the cell membranes.


Why is leghaemoglobin so called? What is its function?

Leghaemoglobin is a pink coloured pigment found in a root nodules of legumes. This pigment is closely related to haemoglobin that is why it is called leghaemoglobin. It is an oxygen scavenger like haemoglobin. It combines with oxygen and protects enzyme nitrogenase which functions under anaerobic conditions.


Explain the terms plant macro elements and plant microelements. Give one example of each ?

Macronutrients are those nutrients which are required in large amount and are involved in composition of plant body. Without macronutrients plant shows many deficiency symptoms and normal plant metabolism is affected.

Examples – Carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium and calcium.

Micronutrients – Plants require certain nutrients in small amounts or traces for their normal growth and developments. These elements are called micronutrients or trace nutrients. These are not involved in composition of plant body. Examples of micronutrients are manganese, zinc, boron, copper, molybdenum and chlorine.


Which mineral nutrient is a major constituent of the middle lamella between two adjoining plant cell walls ?

Calcium is the mineral nutrient, which is a major constituent of the middle lamella between two adjoining plant cell walls.


Which macronutrient helps in auxin formation ?

Zinc is the macronutrient helps in auxin formation.


Who gave the criteria of essentiality of an element in plants ?

D.I. Arnon and P.R. Stout in 1939, gave the criteria of essentiality of an element in plants.


Name the cyanobacteria which take part in N2 fixation.

Trichodesmium, Aulosira, Nostoc and Anaeba are the cyanobacteria, which take part in N2 fixation.


Which mineral is essential for synthesis of IAA ?

Zinc is the mineral which is essential for synthesis of IAA.


What are mobile elements ?

N, P, Mg and K move from old leaves towards the young leaves and are called mobile elements.


How is essentiality of an element for plant growth determined ?

The essentiality of an element is determined by water culture experiments. Water culture or hydroponics is the cultivation of plants in the nutrient solution by placing their rooted part in the nutrient solution. By water culture experiment essentiality of an element for plant growth can be determined by excluding a particular element in the culture solution and by observing the symptoms caused by its deficiency.


Why do the symptoms of deficiency of certain nutrients appear in the old leaves first? Explain with examples.

Symptoms appear in the old leaves first because of the high mobility of these mineral nutrients. The nutrients like nitrogen, phosphorus, potassium and magnesium are translocated from the old leaves to the young growing leaves.


Give any three functions of potassium in plants.

The functions of potassium in plants are,

(i) It helps in opening and closing of stomata.

(ii) Protein synthesis, and

(iii) It helps to determine anion and cation balance in the plant cells.


Why do plants need potassium and magnesium ?

Potassium is involved in activating enzymes and to maintain the turgidity of cells. It helps in determining anion-cation balance in cells, formation of cell membrane, in opening and closing of stomata and in translocation of organic solutes in the phloem. Magnesium is a constituent of chlorophyll and it activates enzymes in phosphate metabolism, nucleic acid synthesis and in fat synthesis.


What is non-symbiotic N2 fixation ? Give examples of microorganisms.

Some microbes can fix nitrogen. They may be free living bacteria or fungi and blue green algae.

(i) Free living bacteria:

(a) Aerobic bacteria – E.g. Azotobacter

(b) Anaerobic bacteria – E.g. Clostridium

(c) Chemosynthetic bacteria – E.g. Chlorobium.

(d) Photosynthetic bacteria – E.g. Thiobacillus

(ii) Free living fungi:

(a) Pullularia and

(b) Yeast

(iii) Blue green algae- Tolypothrix, Nostoc, Anlosir fertilissima and Cylindrospermum etc.


Mention some examples of symbiotic N2 fixers.

Some example of symbiotic N2 fixers are.

(a) Frankia in root nodules of Alnus, Purshia, Casurina and Discordia.

(b) Nostoc as well as Anabaena in coralloid roots of gymnosperm cycas.

(c) Anabaena found in the leaves of Azolla.

(d) Nostoc is Anthoceros thallus.

(e) Cyanobacteria in thallus of lichen.

(f) Klebsiella found in leaf nodules of Disoscorea and Paretta.

(g) Aerorhizobium found in stem nodules of Sesbania rostrata.


Name the pigment found in the root nodules of legumes.

Leghaemoglobin is the pigment found in the root nodules of legumes.


How does the above pigment function ?

Leghaemoglobin is an oxygen scavenger. It combines with oxygen and protects nitrogenase enzyme, which functions under anaerobic conditions.


Differentiate between the two manners of absorption of minerals in plants from soil through roots.

(a) Active absorption and (b) Passive absorption.
Difference between active and passive absorption of minerals are,
            Active absorption               Passive absorption
Absorption of minerals is against the concentration gradient. Absorption of minerals is along the concentration gradient by simple diffusion.
Energy is utilized for absorption . Energy is not utilized for absorption.
It is fast. It is slow.



Write the deficiency symptoms of different mineral nutrients in plants.

Deficiency symptoms of different mineral nutrients are,
Solution used symptoms Different deficiency
With normal culture solution. Growth of seedlings normal with bright green leaves.
Solution lacking nitrogen salts. Unhealthy seedlings with weak and yellow leaves.
Solution lacking potassium salts. Growth checked. Carbohydrate formation reduced. Leaves become white and the plant dies at last.
Solution lacking phosphorus salts. Seedlings with weak roots. Growth is slow.
Solution lacking magnesium salts. Chlorophyll formed. Carbohydrate formation slow. Growth stunted.
Solution lacking iron salts. Seedlings yellowish show chlorosis.
Solution lacking calcium salts. Root system is not well developed. Leaves spotted, deformed and yellowish. Seedling weak and short.
Solution lacking sulphur salts. Stem slender and weak but the leaves are yellowish.



Explain some symptoms of mineral deficiency in the plants.

The deficiency of minerals cause certain morphological symptoms in plants such as yellowing of leaves, chlorosis, necrosis etc. These are known as hunger signs. Any deviation from normal structure and function is a symptom in the plant. Some of these are given below:

(i) Leaf curl – Due to abnormal growth, the leaf is curled in some plants.

(ii) Molting – Green and non green zones are observed in the leaves of plants.

(iii) Wilting – The leaves drop down.

(iv) Growth retarded – The plant become rosette shaped due to stunted growth.

(v) Heart rot – Rottening of tissues in plant parts.

(vi) Necrosis – Death of tissues in leaves or plant parts.

(vii) Chlorosis – Yellowing of leaves due to loss of chlorophyll.

(viii) Abscission – Premature fall of leaf, fruit and flowers.


Describe briefly the roles of minerals in plants.

Roles of micro and microelements in plants:

(i) Components of plant parts - S, P and N are essential components of proteins and nucleic acids as well as protoplasm. C,H and O make plant body. There are cellular components of fats, carbohydrates etc.

(ii) As catalysts – Fe, Cu, Zn and Mn function as biocatalyst in some reactions occurring within the plants.

(iii) Acidity and buffer – Some minerals affect pH of the cell sap and make buffer system in the plants.

(iv) Osmotic potential of cells – Mineral salts present in cell sap maintain osmotic potential in the cells.

(v) Permeability of cytoplasmic membrane - It is affected by various cations and anions of mineral elements.

(vi) Toxic effects – Some minerals found in higher concentration have toxic effects e.g. arsenic and mercury etc.

(vii) Phloem transport – Boron is involved in the translocation of organic substances by the phloem to different parts of the plants.


What is the role of micronutrients in the plant’s life.

Micronutrients Role in plants life
Boron Pectin formation in cell wall.
  Translocation of sugar.
  Absorption of water.
Molybdenum Reduction of nitrates constituent of nitrate reductase.
  Activation for photophosphorylation.
Manganese Nitrogen metabolism.
  Chlorophyll synthesis.
  Activation of enzymes.
Copper Component of enzymes.
Chlorides Transfer of electron.
Zinc Synthesis of auxins.
  Acts as an activator.



Explain how Nepenthes and sundew (Drosera) trap and digest insects ?

The Nepenthes plant bears pitcher shaped leaves in which small amount of water gets collected. Insects are attracted by the bright colour or nectar secreted at the rim of pitcher. As the insect alight on the pitcher, it slips into the water and is prevented from coming out by incurved hair like structures. The trapped insect dies and is decomposed by microorganisms. The decomposed products are absorbed.

The Sundew (Drosera) plant has rosette shaped leaves bearing hairs that secrete drops of sticky fluid at the tip of the insect alights on leaf, it gets stuck by sticky fluid and other hairs bend on it and prevent from escaping. It is digested by the enzymes secreted by the hairs and products are absorbed by leaf surface.


Show only by schematic diagram for the progressive reduction of one molecule of nitrogen into two molecules of ammonia during nitrogen fixation in plants.



"Mistletoe is a partial stem parasite". Explain in short.

Mistletoe is a scientific name for Viscum. It grows on host stem like oak, apple etc. It possesses green leaves. The Haustoria suck food from the host stem.


What are carnivorous plants ? Give two examples.

Carnivore plants prepare their own carbonaceous food but as for nitrogenous compounds they capture insects and feed upon them, absorbing only the nitrogenous compounds from their bodies. Such plants are called carnivorous or insectivorous plants Sundew (Drosera), Pitcher plant (Nepenthes khasiana), Venus fly trap (Dionaea).


Name any parasitic plant and explain how does it absorb its nutrition.

Cuscuta reflexa (Dodder) is a parasitic plants and it grow on other plants. It is devoid of leaves and possesses a wire stem. Its seeds germinate in the soil. On finding a suitable host, it twines around it and loses connection with the soil. It sends out parasitic roots to penetrate the host tissue. They establish connection with its xylem and phloem and Cuscuta thrives.


Differentiate between epiphyte ad parasite.

Epiphytes Parasites
Epiphytes grow on other plants. Parasites grow on or within other plants.
They do not derive nutrition from the supporting plant. They derive nutrition from the most partially or totally from the supporting plant.
They do not cause diseases. They cause diseases.
They have epiphytic roots to absorb moisture from the air. They may have haustria to derive nutrition from the host.



What are autotrophs ? Name one heterotroph ?

All green plants are able to manufacture their own food in the presence of sunlight and because of this they are termed as autotrophs.
But some plants are not able to prepare their own food and they depend on other plants for their food. This type of nutrition is called heterotrophic nutrition e.g. Cuscuta, grows on green plants and send out root like structures haustoria which penetrate the host’s vascular tissue and absorbs water, mineral and organic compounds.


A farmer has been advised to sow soyabean seeds inoculated with a bacterial culture. Name the bacterium in the culture. How is this bacterium useful to the crop ?

Soyabean belongs to the family Leguminoseae, which are characterized by the presence of root-nodules. This structure occurs by the harbouring of bacteria which fix the atmospheric nitrogen to be utilized by these plants. The bacteria are Rhizobacter, Rhizobium etc. Hence, the bacterium in the culture may be Rhizobium – a common bacteria present in the root – nodules of many leguminous plants. This bacterium supplies nitrogen to the plant by fixing atmospheric nitrogen.


What are saprophytes? Give one example.

Saprophytes are non-green and heterotrophic plants, which derive their nutrition from dead decaying organic, matter e.g. bacteria and fungi. Among the angiosperms Neottia, Monotropa and Corallorhiza are saprophytes.

Neottia is called bird’s nest orchid. It grows in the forests. This plant bears a rhizome having a cluster of roots linked to fungal hyphae.


If you grow a potted plant that initially weighed 200 and eventually weighed 50 kg, would you expect the soil in the pot to change weight ? Explain.

The soil in the pot will change its weight due to accumulation of minerals, fertilizers, capillary and hygroscopic water and the micro organisms. The plants increase its weight due to manufacturing of food during photosynthesis. Plants depend largely on air, water and soil organisms in the soil of pot to fulfil its need. This results in growth of plant by increasing the weight of soil in the pot.


How would you determine whether or not a particular element is essential for plants?

Water culture experiments are carried out to find the essentiality of a particular element by the plants for their normal growth. Firstly, the culturing of some seedlings is done under controlled solution containing all the essential elements. Its effect are studied on seedlings regarding growth and development. These seedlings show the normal growth without any symptoms.

Secondly, the seedling are grown in a test solution, lacking one or the other essential element. Seedlings growth and development are studied with the appearance of specific hunger sign on the seedlings. These specific hunger signs are due to the deficiency of any particular macronutrients or micronutrient. For example, brown patches on leaves and stunted growth. Similarly, deficiency of potassium shows the symptom like chlorosis and stunted growth.


Describe two important functions of each of the element P, Fe and Zn in green plants. Mention deficiency symptoms of any two of these elements.

Phosphorus – It forms the constituent of cell membrane protein, nucleic acids, nucleotides, ATP, NADP and energy rich compounds.

Deficiency symptoms – It causes poor growth, leaves become full green and chlorosis occurs.

Iron – It helps in chlorophyll synthesis, cytochrome synthesis, ferredoxin synthesis, activates enzyme and activates catalase.

Deficiency symptoms – It results in chlorosis.

Zinc – It activates enzymes synthesis. It is constituent of carbonic anhydrase. This is also a constituent of dehydrogenase.

Deficiency systems – Leaves are not properly formed.


Describe two important functions each of K, Mg and Zn in green plants and also write the deficiency symptoms of any two of these elements.

They helps in the various physiological processes like respiration, photosynthesis and chlorophyll development. It helps in maintaining cation and anion balance.

Deficiency symptoms:

(i) Yellow edges in leaves appear. 

(ii) Premature death.


What are the functions of phosphorous?

Phosphorus is a macronutrient. It is absorbed by the roots as H2PO6 and HPO42- ions. It is an important constituent of nucleic acid, nucleo-proteins, phospholipids and sugar phosphates.


Give any three functions of potassium in plants.

Potassium is a macronutrient required by plant root tips, buds, leaves and meristematic tissues. Its three main functions are,

(i) Involved a protein synthesis.

(ii) Involves in the formation of cell membrane and opening and closing of stomata.

(iii) It helps in determining anion and cation balance in cells.


What are symbionts ? Explain symbiosis with suitable examples from plants.

Symbionts – Two different species of plants living together and getting benefits from each other are called symbionts. 

The interaction of this type is called symbiosis.

Examples – Association of leguminous plant and Rhizobium is present on the roots of leguminous plants as nodules. The bacteria supply free nitrogen from the air by converting into nitrates and nitrites to the plant and in turn gets shelter and food from the plant.

(ii) Lichen is another example of symbiosis. In this alga and fungus benefit each other. Fungus takes food from the alga and in turn give shelter and supplies water to the alga.

(iii) Nostoc and Anabaena live in the leaves of Azolla fern plant as symbiosis. Azolla gives food to the alga and alga supplies nitrates to the fern.


What is the terms used for long distance movement of carbohydrates in plants ? How and in what form do the carbohydrates synthesized in the leaves, reach long distance parts in a plant ? Explain the most accepted view.

The food material synthesized in the leaves is translocated to the different regions of the plants through the phloem either by cytoplasmic streaming hypothesis or by mass flow hypothesis.

According to mass fluid hypothesis proposed by Munch (1926) the translocation of food takes place from leaves to the storage organs of the plant. The food in the form of glucose is prepared by leaves by the process of photosynthesis. It increases the osmotic potential. As a result the water from the xylem cells enters into the leaf cells by increasing turgor pressure. At the other end or in fruits and seeds, there is low concentration of sugar, which results in a low turgor and osmotic pressure. This difference in the pressure on the two extreme sides on, on the one side there are leaves and on the other side there are other organs of the plant.


What are the various steps involved in biological nitrogen fixation in plants?

(i) During biological nitrogen fixation reduction of dinitrogen molecule occurs by the addition of pairs of hydrogen atoms.

(ii) As a result of this reaction three bonds between the two nitrogen atoms are cleaved and ammonia is formed, which is used for synthesis of amino acids.

(iii) Enzyme nitrogenase is essential for all these reactions.

(iv) Two things are necessary for biological fixation, (a) a reducing agent, (b) ATP to transfer hydrogen atom to dinitrogen and subsequent immediate products.

(v) Ammonia is toxic to plants but ammonium ions can be taken up safely by higher plants because of their adaptation to nitrate.

(vi) Soil bacteria Nitrosomonas and Nitrosococcus convert ammonia to nitrite and then Nitrobacter oxidized this nitrite to nitrate.

(vii) The process of converting ammonia to nitrate is called nitrification.


Mention in a tabular form the main plant diseases caused due to deficiency of minerals.

Name of mineral (Deficiency) Name of disease caused
Calcium Wither tip in Citrus.
  Blossom and roots.
Sulphur Tea yellows.
Molybdenum Water core of Turnips.
  Whip tail in Crucifers.
  Yellow spots in Citrus.
  Scald of beans.
Zinc White bud of Maize plant.
  Sickle leaf of Cocoa plant.
  Little leaf of Peaches and Apples.
Copper Dieback of Citrus.
  Split bark of Citrus.
  Reclamation disease of Legumes and Cereals.
Boron Heart rot or Sugar beet.
  Water case in Turnips.
  Drought spot of Apples.
  Top sickness of Tobacco.
  Corky core of Apples.
Manganese Marsh spots of Pea plant.
  Grey specks of Oats.
  Speckled yellow of Beet.



Explain the mechanism of mineral uptake in detail.

Mineral uptakes takes place by two methods,

(a) Active absorption of minerals,

(b) Passive absorption of minerals.

Active absorption of minerals – Accumulation of ions was studied by Davis and Hogland in plant cells. Active absorption needs energy. It is transport against concentration gradient. Its rate is low. It occurs by the carriers. In cell membranes these are some carrier molecules for particular ions. The cell membrane is permeable to these. They move across the membrane.

Passive absorption of minerals – It does not need metabolic energy. It occurs by physical forces. It occurs by physical forces. It occurs by diffusion, facilitated diffusion, ion exchange mechanism, Donnan equilibrium as well as mass flow.
In simple diffusion ions move from a region of higher concentration to lower concentration along a concentration gradient. In facilitated diffusion, ions or mineral mover by a carrier. Minerals are absorbed passively in the form of ions or molecules by ion exchange mechanism.


Mention the differences between passive and active salt absorption.

Passive salt absorption Active salt absorption
Does not need energy. Linked to expenditure of energy.
Rate of respiration is not affected by it. Active salt absorption enhances rate of respiration.
Occurs along chemical and electrochemical gradient. Occurs against chemical and electro chemical gradient.
The accumulation of salt is less. The accumulation of salts is more.
Passive salt absorption is a physical process. Active salt absorption is a biochemical process.
Mediated through channels and permeases. Mediated through carrier proteins and vesicles.
It may be bi-directional. It is unidirectional process.
Metabolic inhibitors and activators is affect is not generalized. Metabolic inhibitors and activators have a marked effect in this process.



Write explanatory note on bladderwort plant.

Utricularia is called bladderwort. It is submerged, aquatic carnivorous plant. Its leaves are much reduced, some are modified into bladder. Roots are entirely absent. Small insects are trapped in the bladder but they never come out and digested there. The small bladder possesses a valve. There are glandular hairs on the inner walls of the bladder. Proteolytic enzymes digest the insects inside the bladder. The digested food is then absorbed inside the bladder.


What are epiphytes ? Give examples.

Epiphytes – These plants grow on other plants but do not absorb water and food from them. They have no relation to the soil. They are autotrophic. This velaman tissue absorbs water from the environment. E.g. Vanda, moss, ferns and orchids.


Write note on Aldrovanda plant.

Aldrovanda is an insectivorous plant, which grows in ponds, pools and ditches. It is also found in saline lakes. It is free floating plant. Roots are totally absent in this plant. The leaves are like spoons. Each leaf has 2 parts. Leaf margins are serrated and have hairs and digestive glands. When the insect comes in contact of leaf, it parts are closed and the insect is digested there.


Sundew plant has a rosette of leaves modified to trap insects. Explain with the help of a diagram.

Drosera is called sundew plant because sticky substance drops glister on leaf margins. This plant possesses a rosette of leaves. The leaves are provided with hairs growing vertically. The glands on the leaves secrete sticky substances. When an insect sits on the leaf, the hairs entrap this and the insect dies. It is digested and absorbed there.

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