A: The technique of growing plants in a standard, specific,
nutritional liquid medium or solution without or outside the soil is
called Hydroponics. It was first started by Julius von Sachs. It is
also called soil - less culture or solution culture.
Q: How do you categorize a particular essential element as a macro or
micronutrient?
A: The essential element which is required in large amounts (more than
10 m mole kg-1 of dry matter) and forms a part of the protoplasm is
called macronutrient or Major element. Ex: Mg, Ca
The essential element which is required in less amounts (less than 10
m mole kg-1 of dry matter) is called micro or minor or trace element.
It do not forms a constituent of the protoplasm. Ex: Fd, Zn
Q: Give two examples of essential elements that act as activators for enzymes?
A: Iron - Minor element - Activator for Catalase.
Manganese - Minor element - Activator for IAA Oxidase.
Q: Name the essential mineral elements that play an important role in
photolysis of water?
A: Calcium, Manganese and Chlorine play important role in photolysis
of water. Chlorine is not a mineral element.
Q: Out of the 17 essential elements, which elements are called
non-mineral essential elements?
A: Carbon, Hydrogen, Oxygen are non-mineral, essential macro elements.
They are absorbed in the form of CO2, H2O and O2.
Q: Name 2 amino acids in which sulphur is present?
A: Cysteine, Cystine and Methionine consist Sulphur.
Q: When is an essential element said to be deficient?
A: The concentration of the essential element below which plant growth
is retarded is termed as critical concentration. The element is said
to be deficient when present below the critical concentration.
Q: Name two elements whose deficiency symptoms first appear in young leaves?
A: Deficiency symptoms of Sulphur and Calcium first appear in young
leaves as they are not mobile elements.
Q: Explain the role of pink colour pigment in the root nodules of
legume plants? What is it called?
A: The pink colour pigment protects nitrogenase enzyme from Oxygen. It
is called Leg - haemoglobin. It is an Oxygen scavenger.
Q: Excess Mn in soils leads to deficiency of Ca, Mg and Fe. Justify.
A: Manganese competes with Iron and Magnesium for uptake. Manganese
competes with Magnesium for binding with Enzyme. Manganese inhibits
the translocation of Calcium in the shoot apex. Therefore excess of Mn
in soil leads to the deficiency of Ca, Mg & Fe.
Q: What acts as a reservoir of essential elements for plants? By what
process it is formed?
A: Soil is reservoir of essential elements for plants. They are formed
physical weathering and break down of rocks.
Q: Which element is regarded as the 17th essential element? Name a
disease caused by its deficiency?
A: Nickel is the 17th essential element.
The physiological disease caused by its deficiency is Mouse ear in Barley.
Q: Nitrogen fixation is shown by prokaryotes only. Why not by eukaryotes?
A: The enzyme, Nitrogenase or Dinitrogenase which can reduce
atmospheric molecular nitrogen to ammonia is present in certain
prokaryotes only.
Ex: Nostoc, Anabaena (Blue green algae), Rhizobium (Bacteria). So
prokaryotes alone fix nitrogen. As eukaryotes do not have this
enzyme they can not fix nitrogen.
Q: Give an example for each of the aerobic and anaerobic nitrogen
fixing prokaryotes?
A: Aerobic ... Azotobacter, Beijernickia; Anaerobic - Rhodosphirillum.
Q: Non- legume plants also form root nodules. Justify.
A: Frankia, a microbe produces root nodules in non- legume called Alnus.
Q: Name the essential elements present in nitrogenase enzyme? What
type of essential elements are they?
A: Iron and Molybdenum. These two are micro mineral essential elements.
Q: How many ATPs of energy is required to fix one molecule of
atmospheric nitrogen by biological mode? What is the source of that
energy?
A: 16 ATPs are required to fix one molecule of atmospheric nitrogen by
biological mode. The source of this energy is respiration of host
cells.
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