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Correct Answer is : (d) Pistia

(d) Nitrosomonas

Transfer of amino group (NH₃⁺ ) from glutamic acid glutamate to keto group of keto acid. Glutamic acid is the main amino acid from which other amino acids are synthesised by transamination.

(d) Ammonia is converted into amino acids

The process by which nitrate is reduced to – ammonia is called nitrate assimilation and occurs during nitrogen cycle.

A – (iii), B – (iv), C – (i), D – (ii).

(c) sulphur di oxide

Two ways of non – biological nitrogen fixation: 

1. Nitrogen fixation by chemical process in industry. 

2. Natural electrical discharge during lightening fixes atmospheric nitrogen.

(a) Anabaena and Nostoc

(i) Plants absorb phosphorus from the soil in the form of phosphate ions (either as H₂PO₄ or as H₂PO₂^-4 ).

(ii) Phosphorus is a constituent of cell membrane. 

(iii) It is a constituent of nucleic acids, proteins and the nucleotides. 

(iv) Two phosphorus deficiency symptoms are : 

(a) Delay in seed germination. 

(b) Purple spots on the leaves of the plants.

The plants absorb phosphorus in the form of inorganic monovalent H₂PO₄^- or divalent (H₃PO₄)^-2 ions.

Essential Elements: An essential element is the one which has a specific structural or physiological role and without which plants cannot complete their life cycle.

Amon and Stout proposed criteria for knowing the essentiality of an element. They are :

(a) It is indispensable for the growth of plant.

(b) The element is directly involved in the nutrition
of plants. It becomes a component of either a structural or functional molecule. The element may additionally have a corrective effect of mineral balance and other soil conditions.

(c) A plant is unable to complete its vegetative or reproductive phase in the absence of the element, 

(d) The element cannot be replaced by any other element.

(e) The absence or deficiency of the element produces disorders that are a direct result of the lack or deficiency of the element.

(f) The element alone can correct the disorders produced by its absence or deficiency.
16 elements have been found to be essential. They are C, H, O, N, P, K, S, Mg, Ca, Fe, B, Mn, Cu, Zn, Mo, Cl. Nickel has been made the seventeenth essential element.

Plants which are growing in nitrogen deficient areas develop insectivorous habit to resolve nitrogen deficiency.

The criteria required for essential minerals in plants:

1. Elements necessary for growth and development. 

2. They should have direct role in the metabolism of the plant. 

3. It cannot be replaced by other elements. 

4. Deficiency makes the plants impossible to complete their vegetative and reproductive phase.

Plants uptake essential elements from the soil through their roots and from the air through leaves. Nutrient uptake in the soil is achieved by cation exchange, wherein root hairs pump hydrogen ions into the soil through proton pumps. These hydrogen ions displace cations attached to negatively charged soil particles so that the cations are available for uptake by the root. In the leaves, stomata open to take in carbon dioxide and expel oxygen. The carbon dioxide molecules are used as the carbon source in photosynthesis.

Absorption of minerals takes place in two main phases. In the first phase, passive absorption takes place through apoplast pathway. In the second phase, absorption takes place through symplast pathway. The first phase involves passive transport (facilitated diffusion), while the second phase involves active transport. After that, minerals are transported through xylem.