Role Of Macronutrients And Micronutrients - Practice Questions & MCQ

Nitrogen

required by plants in the greatest amount

- absorbed mainly as NO3- though some are also taken up as NO2- or NH4+

- essential for meristematic tissues and metabolically active cells

- one of the major constituents of proteins, nucleic acids, vitamins and hormones

- increases the size of the leaves, promotes rapid growth along with fruit and seed development and hastens the maturity of the crop

plants show reduced growth, chlorosis, purples and red may intensify and reduced lateral breaks

Phosphorus

absorbed by plants in the form of phosphate ions, i.e. HPO2- or H2PO4

- one of the constituents of certain proteins, nucleic acid, cell membranes and nucleotides

- required in phosphorylation reactions and is easily redistributed in several organs of plants

- activates coenzymes for the production of amino acid used in the synthesis of protein, and is important in metabolic processes as well

the plant show stunted growth, reddish-purple tips and margins of leaves, dark green leaves with leathery texture and maturity is delayed

Potassium

- absorbed as (K+) potassium ion and helps in maintaining anion – cation balance in leaves

- required in meristematic tissues, root tips, leaves and buds

- involved in the opening and closing of stomata, protein synthesis, maintenance of turgidity of cells, facilitates cell division and growth and activation of enzymes

the plants remain smaller and show brown margin on its leaves

Calcium

-calcium ions (Ca2+) are also absorbed from soil and are required by differentiating and meristematic tissues

- improves the penetration of water and root via soil and helps in maintaining the stability of soil particles

- calcium is used in the formation of wall of cells in the form of calcium pectate in middle lamella

- involved in normal functioning of cell membranes during the formation of mitotic spindle

- regulates several metabolic activities and activates certain enzymes as well

the growth of the bud is inhibited, followed by cupping of mature leaves and weak growth

Magnesium

- absorbed in the form of divalent Mg2+

- responsible for activating the enzymes of photosynthesis, respiration and is involved in the synthesis of nucleic acid (RNA and DNA)

- important constituent of ring structure of chlorophyll and helps in regulating metabolic activities

- helps in the formation of fruits and nuts and in germination of seeds as well

extensive interveinal chlorosis that initiates with basal leaves and progresses to younger leaves

Sulphur

-obtained by plants in the form of sulphate ion

- present in two amino acids methionine and cysteine and is the main constituent of several coenzymes

general chlorosis of leaves, including vascular bundles

Iron

- obtained in the form of ferric ions (Fe3+)

- plenty of ferric ions are required by plants as compared to other micronutrients

- an important constituent of protein which is involved in the transference of electrons such as cytochromes and ferredoxin

- reversibly oxidized from Fe2+ to Fe3+ during the transfer of an electron, activates catalase enzyme and is important for the formation of chlorophyll

interveinal chlorosis, starting with younger leaves

Manganese

-absorbed in the form of manganese ions Mn2+

- helps in activating enzymes required in respiration, nitrogen metabolism and photosynthesis

- the main role is in the splitting of water to release oxygen during the process of photosynthesis

disorganization of the chloroplast thylakoid membrane

Zinc

- obtained as Zn2+ ions

- activates enzymes like carboxylase

- important in the synthesis of auxin

slowing down of shoot, resulting in the rosette-like  appearance of plants

Copper

 -associated with the enzymes involved in redox reactions as iron and is irreversibly oxidized from Cu+ to Cu2+

- more than half of the copper is present in chloroplast and plays an integral role in photosynthesis

dieback of shoots

Boron

-absorbed as BO33- or B4O72-

- required for uptake and utilization of Ca2+, pollen germination, the functioning of the membrane, cell differentiation, cell elongation and translocation of carbohydrate

- terminal buds are damaged, resulting in rosette effect on leaves.

- fruits, roots and tubers are discoloured, cracked and flecked with brown spots