Functions, mode of absorption and deficiency symptoms of micronutrients:
Essential mineral which are required in low concentrations are called micro nutrients.
Micronutrients even though required in trace amounts are essential for the metabolism of plants. They play key roles in many plants.
1. Iron (Fe) :
( i) Iron is required lesser than macronutrient level and larger than micronutrients level hence, it can be placed in any one of the groups.
(ii) Synthesis of chlorophyll and carotenoids, component of cytochrome, ferredoxin Flavoprotein, formation of chlorophyll porphyrin, activation of catalase, peroxidase enzymes.
(iii) Absrobed as ferrous `(Fe^(2+))` and ferric `(Fe^(3+))` ions.
mostly fruit trees are sentitive to Iron.
Deficiency : Interveinal chlorosis, short and slender stalk and inhibition of chlorophyll formation.
2. Manganese (Mn) : Activator of carboxylases, oxidases, dehydrogenases and kinases, involved in splitting of water to liberate oxygen (photolysis). Absorbed as manganous `Mn^(2+)` ions.
3. Copper (Cu) : constituent of plastocyanin, component of phenolases, tyrosinase, enzymes involved in redox reactions synthesis of ascorbic acid, maintains carbohydrate and nitrogen balance part of oxidase and cytochrome oxidase. Absorbed as cupric `(Cu^(2+))` ions.
Deficiency : die back of citrus, reclamation disease of cereals and legumes, cholorosis, Necrosis and exanthema in citrus.
Zinc (Zn) : Essential for the synthesis of indole acetic acid (auxin ) activator of carboxylase, alcohol dehydrogenase, lactic dehydrogenase, glutamic acid dehydrogenase, carboxy peptidases and tryptophan synthetase. absorbed as `Zn ^(2+)`ion.
Deficiency , Little leaf and mottle leaf due to deficiency fo auxin, interveinal chlorosis, stunted growth, Necrosis and khaira disease of rice.
5. Boron (B) : Translocation of carbohydrates uptake and utilisation of `Ca^(++)` pollen germination, nitrogen metabolism fat metabolism cell elongation and differentiation. absorbed as Borate `BO^(3-)` ions.
Deficiency : Death of root and shoot tips premature fall of flowers and fruits, brown heart of beet root, internal cork of apple and fruit cracks.
6. Molybdenum (Mo) : component of nitrogenase nitrate reductase involved in nitrogen metabolism , and nitrogen fixation. absorbed as molybdate `(Mo^(2+))` ions.
Deficiency : chlorosis, growth and whip tail disease of cauliflower.
7. Chlorine (Cl) : it is involved in anion-cation balance, cell division photolysis of water. absorbed as `Cl^-` ions.
Deficiency : Wilting of leaf tips.
8. Nickel (Ni) : cofactor for enzyme urease and hydrogenase.
Deficiency : Necrosis of leaf tips.
