Growth of plant in different nutrients solutions

• Pathogens are disease-causing viruses, bacteria, fungi or protists which attack plants as well as animals.
• Plants have physical and chemical defences against pathogens.
• A deficiency disease is a disease that develops because an organism (plant or animal) does not have enough vitamins or mineral ions when they do not have enough minerals.
• Minerals are necessary for both plant and animal health.
• Minerals can be investigated in science experiments by measuring the growth of barley seedlings.
• The method for investigating the growth of barley seedlings involves sowing ten barley seeds onto cotton wool in a Petri dish, adding 10 cm3 of distilled water, sealing using tape to avoid water loss through evaporation and placing on a sunny windowsill to germinate.
• The experiment can be repeated with three other Petri dishes.
• One week after germination, the Petri dishes are opened, the distilled water is poured out and 10 cm3 of the following solutions are added: Petri dish 1 - Distilled water, Petri dish 2 - Culture solution containing magnesium sulfate and potassium nitrate, Petri dish 3 - Culture solution containing magnesium sulfate (deficient in nitrogen), Petri dish 4 - Culture solution containing potassium nitrate (deficient in magnesium).
• The Petri dishes are replaced on the window sill and left for two weeks.
• At the end of the two-week period, the Petri dishes are opened and the seedlings are carefully removed from the cotton wool, dried in an oven and the total dry mass of each set of ten seedlings is recorded.