Plant Nutrition :: Mineral Nutrition

Rapid tissue test for nutrients

The crop growth and productivity is conditioned by many factors of which, the nutrient status (Content) of plant parts such as leaf, stem, etc play a critical role. Moreover the leaf and stem are considered as the indicator parts of plants for assessing the nutrients content of plant. Each crop plant requires the essential element at a specific concentration at different growth stages and it is known as ‘critical level’. When the nutrients content of plant depletes below the critical level the plants may exhibit some symptoms. The requirement or otherwise the availability of nutrients can be assessed by i) plant diagnosis ii) soil analysis and iii) plant analysis by two methods a) by qualitative test and b) by quantitative estimation. Based on the plant or soil tests, the required nutrients can be applied for crops to sustain the growth and rectify the deficiency disorders. The rapid tissue test would pave way for rectifying the nutritional problems for quick recovery, however the quantitative estimation of both plant and soil for nutrients concentration will be more useful and economic for applying fertilizers either as basal or foliar and would be the long term strategy to cope up with nutritional problems.

On dry weight basis, the normal healthy cultivated crop plant will have the foliar concentration of essential elements. Nevertheless it will vary depends up on the variety, type of soil, growth stage and other environmental and cultural operations.

Nitrogen      : 1.0 to 3.0   % Iron                : 20 to 100   ppm
Phosphorus  : 0.05 to 1.0 % Zinc               : 15 to 50     ppm
Potassium    : 0.8 to 1.2   % Manganese    : 2.0 to 10    ppm
Calcium       : 0.3 to 0.6   % Copper          : 10 to 20     ppm
Magnesium  : 0.2 to 0.4   % Boron             : 5 to 15     ppm
Sulphur          : 0.2 to 0.3   % Molybdenum : 0.5 to 5.0   ppm

For rapid tissue test to assess the nutrient status, different parts of plant should be taken as indicator tissue and some of the representative crops are furnished below:

Crops Nutrients
N P K Ca Mg S
Cereals Stem/Midrib Leaf blade Leaf blade Leaf lamina Leaf lamina Leaf blade
Pulses Petiole Leaf blade Leaf blade Leaf lamina Leaf  lamina Leaf blade
Oil seeds Petiole Leaf blade Leaf blade Leaf lamina Leaf  lamina Leaf blade
Cotton Petiole Petiole Petiole Petiole Petiole Petiole
Banana Leaf lamina Leaf lamina Leaf lamina Leaf lamina Leaf  lamina Leaf lamina
Papaya Petiole Petiole Petiole Petiole Petiole Petiole
Vegetables Petiole,
Leaf  blade
Leaf blade
 Leaf  blade
Leaf blade
 Leaf  blade
Leaf blade

Fruit trees      
            Either leaf blade/mid rib/leaf lamina can be taken.

Ornamentals, Tea, coffee, etc.,
The leaf blade should be taken.

            The leaf lamina/ leaf blade/ mid rib portion of leaf can be taken.

Procedure for tissue test

1. Nitrogen

Reagent: 1-% diphenylamine in conc. sulphuric acid.

Small bits of leaf or petiole are taken in a petridish and a drop of 1% diphenylamine is added. The development of blue colour indicated the presence of nitrate – nitrogen. The degree of colouration indicates the amount of nitrogen present in that leaf.

Dark blue        : Sufficient Nitrogen
Light blue        : Slightly deficient Nitrogen
No colour        : Highly deficient Nitrogen

2. Phosphorous

Reagents: (1) Ammonium molybdate solution, (2) Stannous chloride powder.

Eight gm ammonium molybdate is dissolved in 100 ml of distilled water. To this, add 126 ml of conc. Hydrochloric acid (Hcl) and volume is made up to 300 ml with distilled water. This stock solution is kept in an amber coloured bottle and at the time of use it is taken and diluted in the ratio of 1:4 using distilled water.

A tea spoonful of freshly chapped leaf bits are taken in a test tube and 10 ml of ammonium molybdate reagent is added and kept for few minutes. After shaking, a pinch of stannous chloride is added. Colour development is observed.

Dark blue        : Sufficient Phosphorus                      

Bluish green    : Slightly deficient Phosphorus

No colour        : Highly deficient Phosphorus

3. Potassium

Reagent: (1) Sodium cobalt nitrate reagent, (2) Ethyl alcohol (95%).

Take 5 gm cobalt nitrate and mix with 30 gm of sodium nitrate in 80ml of distilled water. To this, 5ml of glacial acetic acid is added. The volume is made up to 100 ml distilled water. Dilute reagent prepared (5 ml) with 15 mg sodium nitrate to 100 ml using distilled water.

Finally cut leaf bits are taken in a test tube and 10 ml diluted reagent is added and shaken vigorously for few a minutes and kept for 5 minutes. Then add 5 ml of ethyl alcohol reagent, allowed to stand for 3 minutes. The solution is observed for the formation of turbidity.

No turbidity          : Deficiency of Potassium
Slightly turbidity   : Moderate deficiency
High turbidity       : Sufficient Potassium

4. Calcium

Morgan’s Reagent: 30 ml of glacial acetic acid and 100 grams of sodium acetate are dissolved in a little of distilled water

Procedure: 0.5 g of finally cut plant material is taken into a glass vial (both of healthy plant and deficient plant in different vials) and 5 ml of Morgan’s reagent is added in test tube. After allowing it to stand for 15 minutes, 2 ml of glycerin and 5 ml of 10% ammonium oxalate is added and the solution is shaken for 2 minutes. The turbidity resembling after 15 minutes indicate the amounts of calcium in normal plant tissue.

5 .Magnesium

(1) 5% pure sucrose solution
(2) 2% Hydroxylamine hydrochloride
(3) Titan yellow
(4) Sodium hydroxide

150 mg of Titan yellow is dissolved in 75 ml of 95% ethyl alcohol and 25 ml distilled water. This solution is stored in darkness.


To a tea spoonful of finely cut material, following reagents are added in sequence. One ml of 5 % sucrose solution, 1 ml of 2 % Hydroxylamine hydrochloride and   1 ml of Titan Yellow. Finally solution was made alkaline with 2 ml of 10% NaoH. Red colour indicates the presence of magnesium and yellow colour indicates absence or traces of Magnesium.

6 .Iron 

Finely cut leaf materials (0.5g) are taken into a glass vial and 1ml of con. Hcl is added in it. After 15 minutes, 10ml of distilled water and 2-3 drops of con HNO3 are added. 10 ml of this solution is pipetted out into a specimen tube after 2 minutes and 5ml of 20% ammonium thiocynate is added and stirred. Further, 2 ml of amyl alcohol is added, shaked well and allowed to stand for few minutes. The intensity of red colour in amyl alcohol layer indicates the quantity of iron.

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