NUTRIENT DEFICIENCY AND TOXICITY

NITROGEN

Deficiency of Nitrogen

• Plants are stunted and yellow in appearance. 
• The loss of protein N from chloroplasts(പ്രകാശ സംശ്ലേഷണത്തിനു സഹായിക്കുന്ന സസ്യഭാഗം). 
• In older leaves produces the yellowing or chlorosis(ധാതുക്കളുടെ കുറവുനിമിത്തം ചെടികളുടെ പച്ചനിറം മങ്ങിപ്പോകുന്ന രോഗം). 
• It appears first on the lower leaves, the upper leaves remain green, while under severe N deficiency lower leaves will turn brown and die. 
• The necrosis(കോശങ്ങള്ക്ക്  ഉണ്ടാവുന്ന നാശം) begins at the leaf tip and progress along the midrib(മുഖ്യസിര, ഈര്ക്കിൽ) until the leaf is dead. 
• In cauliflower - young leaves turn pale yellow and old leaves become orange.
• In coffee – Veins(സിരകള്) becomes yellow and new leaves are very small. 
• Tomato - Stem become purple and hard. Flower buds become yellow and flower dropping rate also increases

Excess of Nitrogen (Toxicity of Nitrogen) 

• Causes excess vegetative growth, dark green leaves, maturity is delayed with increases susceptibility to pest and disease. 
• In cotton, weak fiber are resulted.
• In rice, lodging is common. 
• Lengthening of crop duration and narrow leaf. 
• Slender (മെലിഞ്ഞ, ശോഷിച്ച) shoot (മൊട്ട്, തളിര്), profuse (അത്യധികമായ) vegetation (ചെടിയുടെ വളര്ച്ച), thick peel and skin will be rough and leathery in the case of citrus. 
• Excess N in coffee plant, interferes the K uptake causing imbalance between N and K.

PHOSPHORUS

Deficiency symptoms 

P is mobile in plants and when a deficiency occurs it is translocated(സ്ഥലംമാറല്) from older tissues to the active meristematic (ഒരു ചെടിയില് ആദ്യം പൊട്ടിയുണ്ടാകുന്ന ഇല) regions. 

• It arrests metabolism resulting in reduction of total N of Plants. 
• Reduced sugar content. 
• Premature leaf fall. 
• Develops necrotic(producing death of a usually localized area of living tissue) area on the leaf petiole and in the fruit 
• Leaves will show characteristic bluish green colour.

Toxicity of Phosphorus 

• Profuse root growth i.e. lateral and fibrous root lets. 
• It develops normal growth having green leaf colour. 
• It may cause in some cases trace elements deficiencies i.e. Zinc and Iron.

POTTASSIUM

Functions of Potassium 

• Essential for photosynthesis, development of chlorophyll. 
• It improves vigour of the plants to enable to with stand adverse climatic conditions. 
• Reduces lodging in cereal crops. 
• It regulates stomata opening and closing. 
• It regulates the movement of ions with in the plants and hence it is called traffic policeman of the plant. 
• Activation of enzymes, enzyme synthesis, peptide bonds synthesis. 
• Regulates H2O imbalance within the plant.

 Plant factors affecting K availability 

• CEC (Cataion Exchange Capacity) of Roots :Important for determining the ability of plants to absorb like more slowly available forms of soil K. 
• Root system and crop :Higher root density, higher the removal of exchange K and soil solution K. 
• Fibrous root system absorbs more K than tap root system. 
• Variety or Hybrid :Hybrid absorbs more K than variety. 
• Plant population :Higher plant population and closer spacing increased the K removal. 

Deficiency symptoms 

• Plant becomes stunted in growth with shortening of internodes and busy in appearance.
• K deficiency in plants show reduced rate of photosynthesis. 
• Chlorosis, yellowing of leafs and leaf scarch in case of fruits trees. 
• Rice : The leave tips will dark brown in colour and blades will blueish green, chlorotic and necrotic are seen. 
• Banana : Deficiency is seen in the margin and bottom of leaves. 
• Grapes : Leaves are yellow with brown spots which are necrotic, brittle with uneven ripening.

 Toxicity

• Usually not absorbed excessively by plants. 
• Excess potassium can aggravate the uptake of magnesium, manganese, zinc and iron
• Leaf size will be reduced and overall growth will be stunted
• Leaves yellowing or scorched at edges.

CALCIUM

Calcium is absorbed by plants as Ca2+ and its concentration ranges from 0.2 to 1.0% and it is supplied through mass flow method.

Functions of Calcium 

• It is immobile in plants and hence the deficiency is observed in younger leaves. 
• It is a constituent of cell wall and increases in stiffness of plants. 
• Promotes root development and growth of plants, root elongation and cell division. 
• Helps to translocate the sugar in the plants. 
• It involves chromosome stability and that it is a constituent of chromosome structure. 
• Affects translocation of CHO in plants. 
• Encourages seed production. 
• Activates enzyme phosphate and kinease. 
• Accumulated protein during respiration by mitochondria and it increases their protein content. 
• It binds DNA to protein molecules.

Deficiency of Calcium 

• Young leaves of terminal buds dieback at the tip and margins. 
• Normal growth in affected. 
• Root may become short, stubby and brown. 
• Causes acidity of soil. 
• Cell may become rigid and brittle.
• Young leaves of cereals remain folded.

Toxicity symptoms

• Interveinal chlorosis of new leaves with tips and edges green, followed by veinal chlorosis.
• Leaves at the top of the plant wilt easily followed by chlorotic and necrotic areas in the leaves
• High Ca can cause Mg or Boron (B) deficiencies.

MAGNESIUM

Magnesium is absorbed as Mg2+ and the concentration in crop varies between 0.1 and 0.6%. It was taken by plant by Mass flow and diffusion. 

Functions of Mg in plants 

• Primary constituent of chlorophyll 
• Imports dark green Colour in leaves.
• Serves as a structural components in ribosomes and stabilizing the ribosome configuration for protein synthesis. 
• Involves numbers of physiological and biochemical function. 
• Activates phosphorylating enzymes in CHO metabolism.
• Act as a cofactor for certain enzymes other than Po4 transfer enzyme. 
• Increases in the oil content of oil seed crops. 8. Regulates the uptake of other nutrients. 

Deficiency of Magnesium 

• Interveinal chlorosis of the leaf in which only the leave veins remain green. 
• Stiff brittle, twisted leaves, wrinkled and distortion of leaves. 
• cotton –lower leaves may develop a reddish purple finally nicrotic (Redding of leaves) 
• In brassica, Chlorosis with interveinal mottling uniformly distributed in older leaves while the other vascular tissues remain green. This condition is called “Puckering”.

Toxicity

• Magnesium toxicity are rare and not generally exhibited visibly.
• High levels of magnesium can compete with plant uptake of calcium or potassium and can cause their deficiencies in plant tissue.

SULPHUR

Functions of Sulphur 

• Essential for synthesis of sulphur containing amino acids cystine, cysteine and methionine.
• Essential for synthesis of other metabolites including Co-enzyme A., Biotin, Thiamin of vitamin B and Glutothione. 
• Synthesis of chlorophyll. 
• It is a vital part of ferredoxins i.e Fe – S – protein occurring in the chloroplasts. 
• Responsible for the characteristic smell or odor and taste of mustard, onion and Garlic. (Puncy smell) 
• Enhances the oil formation in crops (Soya bean) 
• Increasing root growth. 
• Stimulate seed formation. 
• Promote nodule formation – Leguminous species.

Deficiency of Sulphur

• Stunted growth pale green to yellow colour. 
• Immobile in plants and plants symptoms start first at younger leaves. 
• Poor seed set in rapeseed. 
• Tea –Tea yellows.

Toxicity: 

• Leaf size will be reduced and overall growth will be stunted.
• Leaves yellowing or scorched at edges.

IRON

Functions of Iron 

• It helps in the synthesis of chlorophyll. 
• Structural component of porphyrin molecules like cytochromes, hematin, hemes, ferrichrome and hemoglobin. These substance are involved in oxidation-reduction reactors in respiration and photosynthesis. 
• Structural component of non hemine compounds like ferredoxins. 
• Constituent of enzyme systems Egl cytochrome oxidase, catalase, nitrogenase reaction in plants. 
• Component of flavoprotein

Deficiency symptoms 

• Deficiency symptoms occurs in younger leaves since Fe is immobile element within plant. 
• It occurs in soils of calcareous or alkaline soils and poorly drained H2O logged soils. 
• Younger leaves develop interveinal chlorosis with progresses rapidly over the entire leaf. Severe cases entire leaf turns yellow colour.

Toxicity :

• Excess accumulation is rare but could cause bronzing or tiny brown spots on leaf surface.

MANGANESE

Functions of Mn 

• Helps in chlorophyll formation 
• Involves in photosynthesis, particularly in evolution of O2. 
• Involves in oxidation - reduction - process in decarboxylation and hydrolysis reactions. 
• Involves in enzyme systems and various enzyme reactions in the citric acid cycle. 
• It is a substitute for Mg2+ in many of the phosphorylating and group transfer reactions.

Deficiency of Mn 

• Immobile in plant and def. starts in the younger leaves. 
• Interveinal chlorosis occur 
• Oats - Gray specks / streaks 
• Peas - Marsh spot 
• Sugarbeet - speckled yellow 
• Sugar cane - Pahala blight - midrib pale green and white. 
• increasess asparatic acid and decreases glutamine 
• Increases respiration 
• Accumulation N compounds mainly as amines.

Toxicity:  

• Like boron toxicity, manganese toxicity causes necrotic spots to appear on the older leaves of the vine.
• Manganese toxicity also frequently causes chlorosis (pale or yellow colour), most severe on the younger leaves, due to an induced iron deficiency.
• yellowish brown spots between leaf veins, extending to the whole interveinal area.
• brown spots on veins of lower leaf blades and leaf sheaths.
• leaf tips dry out eight weeks after planting.
• chlorosis of younger (upper) leaves.
• stunted plants.
• reduced tillering.

ZINC

Functions of Zn 

• Essential to formation of growth harmones 
• Helps in reproduction of certain plants. 
• Stabilise rhibosomal fractions 
• Influence the activity of dehydrogenase enzymes 
• Involves in auxin metabolism like tryptophan synthetase. 

Deficiency of Zn 

• Light yellow or white areas bet the veins of leaves particularly older leaves. 
• Death of tissue, discolored 
• Mal formation of fruits 
• Reduced growth hormone production

Toxicity:  

• Zinc in excess is extremely toxic and will cause rapid death.  
• Excess zinc interferes with iron causing chlorosis from iron deficiency.

COPPER 

Copper is absorbed by plants as cupric ion Cu2+ Normal concentration in plants 5-20 ppm. 

Functions of copper 

• Essential for the synthesis of vitamin A 
• Act as a catalyst in respiration 
• Act as a “electron carrier” in enzyme which bring about oxidation reduction reactions in plants. 
• Constituent of chlorophyll. 

Deficiency of copper 

• Chlorosis, withering and distortion of terminal buds. 
• Dead tissue appears along the tips and edges of leaves. 
• Multiple bud formation in the leaf axil and mal formation of leaves. 
• Guava - cracking of fruits and terminal bud die back 
• Heavy liming, excessive application of N and P - induces Cu deficiency.

Toxicity:  

• Reduced growth followed by symptoms of iron chlorosis, stunting, reduced branching, abnormal darkening and thickening of roots.  
• This element is essential but extremely toxic in excess.

BORON

Deficiency:  

• Stem and root tips often die.  Root tips often become swollen and discolored. 
• Internal tissues may rot and become host to fungal disease.  
• Leaves show various symptoms which include drying, thickening, distorting, wilting, and chlorotic or necrotic spotting.

Toxicity:  

• Yellowing of leaf tip followed by necrosis of the leaves beginning at tips or margins and progressing inward.  
• Some plants are especially sensitive to boron accumulation.

MOLYBDENUM

Deficiency:  

• Often interveinal chlorosis which occurs first on older leaves, then progressing to the entire plant. 
• Developing severely twisted younger leaves which eventually die.

Toxicity: 

• Excess may cause discoloration of leaves depending on plant species.  
• This condition is rare but could occur from accumulation by continuous application. 
• Used by the plant in very small quantities.