Chapter 12: Mineral Nutrition

a) If it is observed that deficiency of a particular element showed its symptoms initially in older leaves and then in younger leaves than this indicates that the element is actively mobilized.

b) Highly Mobile elements: Nitrogen and Magnesium.

Relatively Immobile elements: Calcium and Boron

c) agriculturist and horticulturist to understand the deficiency of a particular element, they observed that the deficiency of a particular element is first in older leaves then comes to younger leaves which shows the elements is actively mobilized. Sulphur is an immobile element so it’s deficiency is seen in younger leaves first.

a) Yes, the property of nitrogen fixation in a plant – leguminous or non-leguminous can be artificially induced by genetic engineering.

b) Mycorrhiza and Pine trees show a symbiotic relationship. In this type of relationship both the organisms benefit from each other.

c) Yes, a microbe must be in close association with a plant to provide mineral nutrition.

An example is the rod-shaped Rhizobium has such a relationship with several legumes like sweet pea, lentils, garden pea etc.

There are two types of essential elements they are macro and microelements. Macro elements are present in large amounts like calcium, magnesium etc. Whereas microelements are present in small amounts like iron and zinc.

Criteria of essentiality: The essentiality not only depends on the presence of an element in the plant but also on the following criteria:

1. Without an element, the plant cant grow and reproduce

2. The element cannot be replaced by other elements because it is specific.

3. The element is directly involved in the metabolism process.

i. Essential elements as components of energy-related compounds

Example: Magnesium in chlorophyll and phosphorus in ATP molecule

ii. Components of Structural elements of cells

Example: Hydrogen bonds are seen in the secondary structure of proteins, Carbon and Oxygen in proteins, lipids, carbohydrates and nucleic acids.

iii. Essential elements as Activator and Inhibitor of enzymes:

Example: Magnesium (Mg2+) is an activator of both Ribulose Bisphosphate and Phosphoenolpyruvate enzyme which are involved in photosynthetic carbon fixation.

iv. Essential elements which can alter osmotic pressure:

For example, Potassium plays an important role in the opening and closing of Stomata.

No, excess of nutrients should not be given because if we supply these nutrients in excess reduces the dry weight of the tissue by 10% and leads to toxicity. It also inhibits the uptake other elements. For example, Increased level of Manganese inhibits the uptake of Calcium, Iron etc.

Event 1: Trace the events starting from the coming in contact with Rhizobium to a leguminous root till nodule formation. Add a note on the importance of leghemoglobin.

Event 2: The root hair cells curl and the bacteria enter the root hairs.

Event 3: After entering the root hair an infection thread is formed.Which carries the bacteria to the cortex of the root.

Event 4: Formation takes place in the cortex nodule

Event 5: The differentiation of nitrogen-fixing cells takes place

Event 6: Avascular connection is established with the host for the exchange of nutrients.

Leghaemoglobin is considered as the oxygen molecule scavenger helping enzyme nitrogenase in nitrogen fixation, which only works in the absence of molecular.

The process of nitrogen fixation involves the conversion of free nitrogen in the air into Ammonia or other nitrogenous compounds in the presence of enzyme Nitrogenase.

N2 + 8H+ + 8e- → 2NH3 + H2

The end product of the biochemical events is Ammonia (NH3).

The Ammonia produced through nitrogen fixation is incorporated in the amino acids as an amino group. At physiological pH NH3 group is protonated to NH4+ group is the fate of ammonia.

1. Reductive Amination: In this reaction, alpha Ketoglutaric acid forms glutamate. In this reaction, Ammonia reacts with a-ketoglutaric acid to form glutamate.

2. Transamination: In this reaction amino group (NH2) transfers from one amino acid to other amino acid transaminase enzyme catalyses this reaction

Hydroponics is the technique where the plants are grown in mineral nutrient instead of soil. This requires the addition of mineral regularly and change of water. Examples like tomato, cucumber etc culture like this. Most of the crops are grown still in the land because minerals are already present in the soil there is no need of adding extra into it.

The chapter Mineral Nutrition deals with the nutrients which are required for the well-being of plants. Nutrients such as macro-nutrients and micro-nutrients – in large concentrations – are essential to ensure the healthy life of plants.

The different types of nutrients required by plants are as follows.

1. Carbon
2. Nitrogen
3. Oxygen
4. Hydrogen
5. Potassium
6. Calcium
7. Magnesium
8. Phosphorous
9. Sulphur
10. Chlorine

1. Methods to Study the Mineral Requirements of Plants
2. Essential Mineral Elements
   1. Criteria for Essentiality
   2. Role of Macro- and Micro-nutrients
   3. Deficiency Symptoms of Essential Elements
   4. Toxicity of Micronutrients
3. Mechanism of Absorption of Elements
4. Translocation of Solutes
5. Soil as a Reservoir of Essential Elements
6. Metabolism of Nitrogen
   1. Nitrogen Cycle
   2. Biological Nitrogen Fixation