Aim: To demonstrate the effects of mineral deficiency on plants.
Material required: Nine wide-mouthed glass jars, corks, nine bean seedlings, glass tube, Sach’s or Knop’s complete culture solution (to provide macro-nutrients), black paper or black paint, 1% copper chloride solution, ammonium molybdate, manganese chloride, sodium borate and zinc chloride (to provide the required micronutrients).
The experiment is set up as shown in (fig.6.7).
Take a mouthed glass jar and fill it with complete culture solution, including macro and micro-nutrients. Take another and fill it with distilled water and the remaining seven glass jars, each lacking one element are also prepared. Nine seedlings held by corks are inserted into each of the nine jars. A glass tube each is placed in the other hole for daily aeration. Cover each bottle with black paper or paint it with black colour to prevent the growth of algae. The water culture should be changed weekly. Observe the seedlings daily over a period of two to six weeks.
a) Plant or seedling growing in complete culture solution will show a more luxuriant growth because it contains all nutrients.
b) Seedling growing in distil water will not grow because it lacks all the nutrients.
c) Seedlings growing in the glass jars (the remaining seven) will show some deficiency symptoms as follows:
- Without nitrogen – will show stunted growth and yellow leaves.
- Without potassium – will show weak slender stem, premature loss of leaves and brown colour at margin of leaves.
- Without phosphorus – will show unhealthy growth with reddish colour of leaves or stunted growth.
- Without calcium – will show stunting of root system, weak slender stem and pale yellow colour in leaves.
- Without magnesuim – will show stunted growth and chlorosis along the leaf veins.
- Without sulphur – will show stunted growth with slender stem and yellow leaves.
- Without iron – will show slender stem, stunted growth and yellow leaves.
Plant will grow well and healthy if all the elements are present but lack of one of the elements will affect the normal growth of the plant.
Precautions to be Taken when Performing the Experiment
- The apparatus must be kept clean to prevent infection of seedling or contamination of nutrient solution.
- Vessel or jar should be painted with black or covered with black paper to prevent algal growth or to cut off light from the culture solutions which might damage the roots.
- There should be constant aeration to provide air for the roots.
- The stoppers and cotton wool must be kept dry to avoid the growth of microbes.
- There should be frequent topping-up or replacement of the culture solution every fortnight to ensure adequate supply of nutrients.