MINERAL NUTRITION IN PLANTS

BY:B.NAVEENKUMARBHAKTHA,PGT BIOLOGY

M.Sc[Botany] B.Ed,PGDGC,Dip in GT,

JAWAHARNAVODAYA VIDYALAYA,PERIYA

KASARAGOD Dist,KERALA

OBJECTIVES

After completing this lesson, you will be able to :

• Define the terms mineral nutrition, macro and micro nutrients;
• Explain the functions of minerals with reference to the techniques
• of hydroponics.
• List the role of macro and micro nutrients;
• Mention the deficiency symptoms of macro and micro nutrients.
• Describe the cycling of Nitrogen in the nature diagrammatically.
• Explain the formation of root nodules in leguminous plants

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HYDROPONICS

• Hydroponics is a method of growing plants using mineral nutrient solutions in a water solvent .

Mineral Nutrients

• The 13 mineral nutrients, which come from the soil, are dissolved in water and absorbed through a plant's roots. There are not always enough of these nutrients in the soil for a plant to grow healthy. This is why many farmers and gardeners use fertilizers to add the nutrients to the soil.  The mineral nutrients are divided into two groups:  �macronutrients and micronutrients.   

MACRO NUTRIENTS

• The macro nutrients are nitrogen (N), phosphorus (P), and potassium (K). These major nutrients usually are lacking from the soil first because plants use large amounts for their growth and survival.  The secondary nutrients are calcium (Ca), magnesium (Mg), and sulphur (S). There are usually enough of these nutrients in the soil so fertilization is not always needed. Also, large amounts of Calcium and Magnesium are added when lime is applied to acidic soils.

Micronutrients 

  Micronutrients are those elements essential for plant growth which are needed in only very small (micro) quantities . These elements are sometimes called minor elements or trace elements. The micronutrients are boronboron (B), copperboron (B), copper (Cu), ironboron (B), copper (Cu), iron (Fe), chlorideboron (B), copper (Cu), iron (Fe), chloride (Cl), manganeseboron (B), copper (Cu), iron (Fe), chloride (Cl), manganese (Mn), molybdenum (Mo) and zinc (Zn). Recycling organic matter such as grass clippings and tree leaves is an excellent way of providing micronutrients (as well as macronutrients) to growing plants.

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CRITERIA OF ESSENTIALITY OF MINERALS

• The element must be absolutely necessary for supporting normal growth and reproduction.
• The requirement of the element must be specific and not replaceable by another element
• The element must be directly involved in the metabolism of plant

MacronutrientsNitrogen (N)�

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• Nitrogen is a part of all living cells and is a necessary part of all proteins, enzymes and metabolic processes involved in the synthesis and transfer of energy. .
• Helps plants with rapid growth, increasing seed and fruit production and improving the quality of leaf and forage crops. 
• Nitrogen often comes from fertilizer application and from the air (legumes get their N from the atmosphere, water or rainfall contributes very little nitrogen)

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• Deficiency symptoms: Plants containing enough nitrogen to attain limited growth exhibit deficiency symptoms consisting of general chlorosis, especially of older leaves. In severe cases these leaves yellow and die. Younger leaves remain green longer, because they receive soluble forms of nitrogen transported from older leaves. In many plants, excess nitrogen often stimulates shoot growth more than root growth and may favor vegetative growth over flowering and seed formation.

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Phosphorous

• Occurs and reacts as orthophosphate, the fully oxidized and stable form.
• Participates in metabolism by forming water-stable phosphate esters and anhydrides. In these forms P has several fundamental roles: linkage (as in nucleic acids), substrate mobilization (particularly of non-polar compounds, energy conservation (phosphorolysis instead of hydrolysis conserves bond energy), source of free energy in bond formation, H+ pumping, etc.

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• Deficiency symptoms: Phosphorous-deficient plants are stunted and , in contrast to those lacking nitrogen, are often dark green. Maturity is often delayed. Phosphate is easily redistributed in most plants from one organ to another and is lost from older leaves, accumulating in younger leaves, developing flowers and seeds. As a result, deficiency symptoms occur first in more mature leaves.

Potassium (K+):

• K+ is quite mobile in the plant, presumably because there are many membrane carrier systems adapted to K+. It is so abundant that it is a major contributor to the osmotic potential of cells and therefore to their turgor pressure. K+ regulation of osmotic potentials forms the basis for turgor movements in plants (eg., stomate opening, leaf movements).

• Deficiency symptoms: As with N and P, K+ is easily redistributed from mature to younger organs, so symptoms first appear in older leaves. Leaves develop necrotic lesions and light chlorosis. The tips often die first. K+ deficient cereals develop weak stems so they are easily lodged.

Calcium (Ca++):

• Important component of cell walls.
• Calcium is also important for maintaining the integrity of membranes, especially the plasma membrane.

• Deficiency symptoms: Meristematic regions die. Margins of younger leaves become chlorotic then necrotic. Young leaves are malformed. Symptoms appear first in young tissues since Ca++ is not very mobile.
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Magnesium (Mg++):

• Involved in most reactions involving ADP and ATP. Activates enzymes for DNA and RNA synthesis. Constituent of chlorophyll. Activates key enzymes involved in CO2 fixation. Magnesium also has structural roles in membranes, especially in organelles.

• Deficiency symptoms: Deficiency causes extensive interveinal chlorosis which starts with basal leaves and progresses to younger leaves (it is mobile).

Iron (Fe++):

• Iron forms a locus for electron transfer in many enzymes (eg., cytochromes, peroxidases, catalyses). It is also required for chlorophyll synthesis.

• Deficiency symptoms: Extensive interveinal chlorosis, starting with younger leaves (iron is relatively immobile). Similar to Mg deficiency except in younger leaves.

Copper (Cu++):

• Copper is an important component of several critical enzymes (eg., plastocyanin for photosynthesis and cytochrome oxidase for respiration).

• Deficiency symptoms: Plants need very little copper so they are rarely deficient in it (usually sufficiently available in soil). Experimentally, copper deficiency leads to misshapen and dark green younger leaves. Copper can be very toxic if in excess.

Sulphur (S)

• Deficiency symptoms: General chlorosis of leaf, including vascular bundles. Sulfur is nSot easily redistributed from mature tissues in some species, so deficiencies are usually noted first in younger leaves.

• Sulphur is the main constituent of several co enzymes., vitamins and ferredoxin.
• It is present in two aminoacids cystein and methionine

Molybdenum (Mo6+):

• Important for it oxidation-reduction properties.
• It is a key component of nitrate reductase where it functions as an e- carrier for nitrate reduction. It is also important in organisms that can carry out nitrogen fixation (from N2).

• Deficiency symptoms: Most plants require less molybdenum than any other element, so deficiencies are rare. Symptoms often consist of interveinal chlorosis, first in older leaves. Young leaves may be severely twisted (whiptail disease).

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Manganese (Mn++):

• A major role for manganese is in the removal of electrons from water during photosynthesis (water oxidation). Manganese also is essential in respiration and nitrogen metabolism. It can function effectively in some metal catalyzed enzymatic reactions which require magnesium.

• Deficiency symptoms: The absence of Manganese causes disorganization of chloroplast thylakoid membranes. Plants become chlorotic. However, deficiencies are rare since low amounts are required and it is usually in plentiful supply in soil.
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Zinc (Zn++):

• Important in enzymes with oxidation-reduction properties

• Deficiency symptoms: Interveinal chlorosis and inhibition of stem growth. Zinc deficiency causes the disorders "little leaf" and "rosette" in apples, peaches, and pecans. Leaf margins are distorted and puckered.
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Boron (B(OH)3):

• boron is found in cell walls complexed with raffinose-containing polymers. It is also found in phloem complexed with sorbitol. In the absence of boron, meristems stop growing. In addition, pollen tubes can't elongate without boron. Some research suggests a role for boron during synthesis of nucleic acids.

• Deficiency symptoms: Several disorders related to disintegration of internal tissues such as "heart rot" of beets and "stem crack" of celery result from inadequate boron supply. Root and shoot tips stop growing.

�CHLORIDE (Cl-)

• Plants frequently contain a good deal of chloride but very little is required as a nutrient. It has important functions in photosynthesis. It may play a general role in maintaining electrical equilibrium.

Name Chemical Relative Function in plant

symbol % in plant

to N

Primary macronutrients

Nitrogen N 100 Proteins, amino acids

Phosphorus P 6 Nucleic acids, ATP

Potassium K 25 Catalyst, ion transport

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Secondary macronutrients

Calcium Ca 12.5 Cell wall component

Magnesium Mg 8 Part of chlorophyll

Sulfur S 3 Amino acids

Iron Fe 0.2 Chlorophyll synthesis

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Micronutrients

Copper Cu 0.01 Component of enzymes

Manganese Mn 0.1 Activates enzymes

Zinc Zn 0.03 Activates enzymes

Boron B 0.2 Cell wall component

Molybdenum Mo 0.0001 Involved in N fixation

Chlorine Cl 0.3 Photosynthesis reactions

NITROGEN FIXATION

AMMONIFICATION

NITRIFICATION

DENITRIFICATION

RHIZOBIUM,

AZOTOBACTER,AZOSPIRILLUM

CYANOBACTERIA,FRANKIA

NITROSOMONAS

2NH3 +02--+2NO2+2H+ +2H2O

NITROBACTER

2NO2 +O2 –2NO3

N2+8e+8H++16ATP—2NH3+H2+16ADP+16Pi

PSEUDOMONAS

THIOBACILLUS

NODULE FORMATION

Recapitulation

1.The major mineral component of chlorophyll is-------------

IRON

MAGNESIUM

2.Calcium pectate is found in----------------

Middle lamella Cell membrane

3.The leghaemoglobin is referred to as ------------.

Natural scavenger Oxygen scavenger

4.Which among the following is a denitrifying bacterium---------------.

Thiobacillus Nitrosomonas

5.Which of the following is a micronutrient----------.

Boron Sulphur