ESSENTIAL ELEMENT

The elements which are needed by the plants for normal and healthy life are called essential elements. Only 16 elements, are essentigl elements. Mere are two ty pes olessential elements:

1. Macronutrients or major elements: These elements are required tiy the plants in large qiiantiB lhe major elements are C. F. 0. N. S. P. Ca. K and Mg.

/. Micronutrients or trace elements: fhe remaining 7 elements are required in small quantity . Riese are called trace micronutrients. I he micromitrients are Fe. AN, B. Cu. Zni Ma and Cl.

Important functions and deficiency symptoms of mineral elements

Element Function                                  Deficiency syndrome
Nitrogen Constituent of:     ‘Proteins Chlorophyll Nucleic acids

Cell membranes

Stunted growth,Leaf chlorosis

Leaf shedding

Purple vein formation

in tomato

Poor   floweringand

Sulphur Constituent of:Amino acids: Methioninine Cystine. Cy steine

Vitamins: Iliotin. Thiamine

  1. Sulphydrill
    bonds of Proteins
Leaf chlorosis    alongwith Leaf roiling. Leaf

shedding      Younger
leaves affected first

Inhibition  of terminal

buds,  Emergence  of
lateral bud

Phosphorus Constituent of:Proteins, Nucleic acids Cell membranes

ADP, ATP. NADP Takes pail in Energy transactions Oxidation- reduction

Leaf chlorosis Leaf curling andDeath   of    root  and

shoot     tips    Shoot
branching bushy habit

Stunted  growthPoor
nodulation in legumes

Leaf    chlorosis  Leaf
curling Death of root

and  shoot tips Shoot

branching and  bushy

habit   Poor  flowering
and fruiting

Calcium Constituent Middle lamella Necessary Ibr: Structural integrity of chromosomes and membranes Cell division
Potassium Activator of several enzymes Takes part in:Respiration Protein synthesis Carbohydrate metabolism Stomata’ opening and closing Stunted  growth    Dieback of young shoot Poor development of mechanical tissues Chlorotic and necrotic leaf margin Older. leaves affected

first

Magnesium Constituent of chlorophyll Necessary for:Membrane integrity Integrity of ribosomes Protein sy nthesis

Nucleic acid synthesis Activator of decarboxylases

Leaf chlorosis mottling and wilting I .eaf necrosisI .eal sheddino.., Older leaves affected first
Iron Constituent of: Interveinal-chlorosis

 

Ferredoxin, Cytochromes, Catalase peroxidases Leghaemoglobin Necessary ion chlorophyll formationElectron transport chain ‘ ofleaves

Necrotic pots on leaves, and stem Young leaves affected first

Manganese Activator of enzymes: Oxidases, Peroxidases, Dehydrogenases. Decarboxylases, Necessary for: Chlorophyll formationNitrogen metabolism Mottled leaf chlorosis Leaf necrosis Browning and withering of leaves
Boron Take part in:Carbohydrate metabolism, Calcium and phosphorus metabolism. pollen germination and fertilization Stunted growth Death of root and shoot apices Shoot branching Stumpy root, Necrotic leaf shedding Inhibition of flowering and fruitinr
Copper Constituent of enzymes: AA oxidases. Cytochrome ox idase, Ty rosinase, PhenolaseConstituent of electron carrier, Plastocyan in, Plastoqu i none Yellowing of leaf tip Leaf necrosis Wilting of terminal shooting
Zinc Activator of enzymes: Alcohol dehydrogenation Carbonic anhydrase Carboxy peptidase Essential for Tryptophan sy nt hesis and auxin sy nthesis Leaf margin and tip chlorosisLeaf mottlinot7, and necrosis Stunted :growth, Failure of seed setting
Molybdenum Activator of enzy Ines:                            •Dehydrogenase. Nitrate reductase


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Constituent of: Nitrogenase

Mottling and curling of leaves. Failure of nodulation, Failure o! leaf expansion. Elm’ shedding
Chlorine           IActiVator of enzymes
concerned with photolysis
Wilting of leaf Leaf chlorosis Stunted root growth
 

 

 

 

NITROGEN

The chief source of nitrogen is the nitrate ion of the soil. Plants also uses nitrites and ammonia salts. Certain bacteria can utilize atmospheric nitrogen.

Physiological role

I. Nitrogen is an essential component of proteins and nucleic acids.

  1. It is also an important component of chlorophyll.
  2. It promotes cell division and cell enlargement.
  3. It increases respiratory rate. Deficiency Symptoms
  4. Leaves turn yellow and start falling. These effects appear first in the older leaves. In many species, like tomato, leaf veins turn purple or red due to anticyclonic formation.
  5. The starch contents are increased due to its deficiency. But there is a decrease in the protein content. Therefore, plant growth remains stunted
  6. The lateral buds remain dormant.
  7. Flower formation is delayed or suppressed. If flowers are formed, the fruits and seeds remain small and weak.

Excess supply of nitrogen

Excess supply of nitrogen causes abundant vegetative growth and poor flowering. The insects and pathogen attack on plant. The stem becomes weak and tender. The leaves become dark-green and succulent. Excess nitrogen inhibits the development of mechanical tissues like sclerenchy ma.

CALCIUM

Physiological role

Calcium is essential for all plants. It is rich in the older tissues.

I. Calcium ls deposited in the cell wall in the form of calcium pectate. Calcium’ pectate forms middle lamella. Cell wall remains weak  without this compound.

  1. Calcium concentrates around the chromosomes. It plays role in binding of nucleic acid to protein.
  2. Calcium is necessary for cell division.
    1. It stimulates the development of root hairs. It promotes the activity of chloroplasts.
    2. It promotes the movement and utilization of carbohydrates and amino acids in the plant.
    3. Calcium help in neutralizing acids like oxalic acid, both inside and outside theplant.
    4. Sometimes, crystals of calcium sulphate and calcium oxalate are found in plant cells. Deficiency symptoms I. Chlorotic patches appear near the leaf margin in young leaves.
    5. Calcium deficiency causes rapid disintegration of the growing tips of roots and shoots in many plants.
    6. Its deficiency inhibits seed formation.

    POTASSIUM

    Physiological role

    The plants need potassium in large quantities. It plays following physiological roles:

    I. It provides the necessary ionic balance. This ionic balance is necessary for the survival of plant.

    1. It plays an important role in the plant metabolism. It acts as an activator of many plant enzymes.
    2. It promotes the growth of apical meristem, secondary roots and newly developing leaves.
    3. Potassium is essential for the synthesis and translocation of carbohydrates in plants like sugar beets and potatoes. It is essential for the enzymatic hydrolysis of starch.
    4. Potassium control respiration in some way.

    Deficiency. symptoms

    I. Young shoots and leaves start dying due to deficiency of potassium. The foliage leaves are suffered from its deficiency. Their tips take up a scorched appearance. Their margins become dull yellow. The growth of internodes is retarded.

    1. Sometimes, the dominance of apical bud is diminished. So the lateral buds start growing. It gives bushy growth, It affects the NV eight of the grain.
    2. Its deficiency decreases the protein synthesis.
    3. The cells fail to divide and instead become elongated ‘Elms arrow th remains stunted.
    4. Its deficiency reduces resistance to disease. So there is a poordevelopment of mechanical tissue in the stem.

      PHOSPHORUS

      Physiological roll

      I. It is an essential constituent of protein part of the membranes of the cell.

      1. It is also part of nucleoproteins, many coenzymes and organic molecules such as ADP. ATP and NADP. These compounds play an important role in the energy transfer reactions of cell metabolism and in oxidation-reduction reactions.
      2. It is also necessary for the functioning of mitochondria.
      3. Phosphorus is more abundant in the growing and storage organs.
      4. It helps in the trans location of carbohydrates.
      5. It promotes root growth. It promotes fruit ripening.
      6. Phosphorus is necessary for cambial activity. It is essential for reduction of nitrates for protein formation.

      Deficiency symptoms

      I. Growth is retarded and leaf color becomes dark-green.

      2. Sometimes dead patches appear on leaves, petioles and fruits and the leaves fall early.

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