3) Essential nutrient elements

Out of 105 elements discovered so far, less than 21 are essential and beneficial for normal plant growth and development.

  • Criteria for essentiality of elements
  1. Element must be directly involved in plant metabolism.
  2. Element can’t be replaced by another element with similar properties.
  3. Deficiency symptoms are produced and completion of life cycle are prevented due to deficiency of element.
  • Types of nutrients
  1. Micronutrients (trace elements)
  1. Present in plant tissues in conc. In less then 10m mole per kg.
  2. Zinc, boron, copper, iron, manganese, chlorine, nickel, and molybdenum.
  1. Macronutrients (Major elements)
  1. Present in plant tissues in conc. In conc. of in excess of 10 m mole per kg of dry matter.
  2. Carbon, hydrogen, oxygen, nitrogen, sulphur, phosphors, calcium, calcium and magnesium.

Critical Elements : Elements in which soil is deficient. i.e. phosphors, potassium and Nitrogen.

  • Functions of essential element        
  1. Balancing elements : these elements minimize toxic effect of heavy elements : e.g. ca2+, K+, Mg2+.
  2. Framework elements: they store products of plants C, H,O and produce cell walls.
  3. Turgor movements : these are due to influx and efflux of K+ ions i.g. stomata movement.
  4. Enzymatic effects : elements like Ca, K, Mg etc. are either components of enzymes, thus co-factor or activators.
  5. Protoplasmic elements : produce protoplasmic constituents like proteins, nuclu acids, chlorophyll, cytochromes e.g. P,S,N,C,H,O.

Role of essential elements:-

 

S.no.

Elements

Role and Deficiency symptom

Absorbed form

1

Nitrogen
  • Dormancy of lateral buds.
  • Inhibition of cell division.
  • Chloroses of older leaves.
  • Major constituent of protein, nuclu acid, hormones, vitamins.
  • Wrinkling of ureal grains.

 

No2-,No3- or NH4+

Required in greatest form

2

Potassium
  • Maintenance of turgidity of cells.
  • Shorter internodes and dieback.
  • Loss of apical dominance.
  • Loss of cambial activity.
  • Interveinal chloroses first in older learns.   

K+

3

Phosphorus
  • Delay in seed germination.
  • Poor vascular tissues.
  • Necrosis and chlorosis in older leaver first.
  • All phosphorylation reaction.
  • Premature leaf fall and flower bud.   

H2PO4- OR HPO42- (phosphate ions )

4

Magnesium
  • Abscission of premature leaf.
  • In maintenance of ribosome structure.
  • Intervienal chlorosis with antho ajnanin pigmentation ( in older leaves first).
  • In synthesis of DNA and RNA.

Mg2+

5

Iron
  • For activation of catalare and cytochromes constituent.
  • Interveinal chloreosis  ( in young leaver).

Fe3+

(required more than other micronutrients)

6

Calcium
  • Premature flower fall.
  • Stunted growth.
  • Degeneration of merirtems.
  • Chlorosis and necrosis ( first in young leavers)
  • Meiotic spindle and middle lamella formation.   

Ca2+

(not rasily released )  = C,S

7

Zinc
  • Malformed leaves
  • Interveinal chlorosis
  • Carboxyrases lactate dehychogenose etc. enzyme activation.
  • Stunted growth.
  • Synthesis of auxin. 

Zn2+

8

Nickel
  • Necroses of leaf tip.

Nu2+

9

Sulphur
  • Defoliation in tea.
  • Reduced nodulation in legumes.
  • Anthocyanin accumulation.
  • Constituent of thiamine, methionine, biotin, ferrdoxinete etc.  

SO42

10

Boron
  • Flowers abscission.
  • Loss of apical dominance.
  • Cell elongation and carbohydrate translocation.
  • Reduced nodulation in legumes.
  • Calcium uptake and utilization.
  • Pollen germination.

BO33- and B4O72-

11

Chlorine
  • Bronze colour in leaves.
  • Balance of anion-cation in cells.
  • Leaves wilting.
  • Chloroses and necroses of leaves.

u-

12

Manganese
  • Photolysis of water to liberate O2.
  • Interveinal chloresis with guy spots.

Mn2+

13

Copper
  • Leaf tip necrosis.
  • Potato tubers blackening.
  • Involved in redox reaction.
  • Die back.

Cuprie ion Cu2+

14

Molybdenum
  • Delay flowering.
  • Nitrogen metabdism.
  • Interveinal chlorosis with marginal necrosis and infolding.

Molybdate ions

Mo O2-

 

Toxicity of micronutrients :-

  • Toxic nutrients ore those which reduces dry weight of tissues about 10%.
  • Mn-toxicity causes appearance of brown spots surrounded by chronotic vein (may be due to deficiency of Fe, Mg, Ca).
  • Translocation of Ca and uptake of Mg and Fe are inhibited.
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11    PMT    Biology    Mineral Nutrition    3) Essential nutrient elements