Optionals IAS Mains Botany: Questions 264 - 272 of 511

Mode of Virus Infection in T- Even Phage

• The T- even phage search and bind to receptors.
• At specific protein structure found on the surface.
• Every phage has different receptor.
• There are some receptor like cell wall protein, flagella, pilli, lipopolysaccharides and teichoic acid to bind.
• Phage tail structure and tail fibres help the it to bind it with t…

Medullary Vascular Bundle

• Medullary vascular bundle is situated in the peripheral part of the pith of the stem and in some cases extended to the leaf trace.
• They are generally small in size.
• Medullary bundles do not supply to the lateral organs.
• They traverse throughout the length of the stem without any branching.
• Large number of medullary bundle is pr…

Range Thallus Structures in Lichens

Crustose Lichen

• This type of encrusting lichens with an inconspicuous, thin and flat thallus, firm in texture.
• The thallus is very closely adhered to the substratum and provides a crust like appearance.
• They are wholly or partially embedded in the substratum.
• In the latter case only fruiting bodies are visible above t…

Male Flower of Euphorbia

• In euphobiace the inflorance is cyanthium type. Cyanthium is surrounded by the four or five connate bracts and between these bracts large and often coloured glands are present.
• In middle the single female flower is present and in axil of each bract a number of male flower are arranged in scorpioid cyme.

Characteristics of Archaea

• Cell wall- Archaea lack peptidoglycan in its cell wall. it is a distinguishable feature between bacteria and archaea.
• Fatty acid-Archaea has ether bonds connecting fatty acids to molecules of glycerol.
• RNA polymerase complexity-Archaea has multiple RNA polymerase that also contains multiple polypeptides (some have 8 polypept…

Cladode

• It is a modification of stem in which a branch of single internode is flatted and becomes leaf like.
• The leaves reduced to scales in the axil of which develops a group of linear, acute, narrow and circular structure.
• They are green and photosynthetic.
• It is a xerophytic adaptation.

  Example of cladode-Asparagus.

Phyllode

• Ph…

Hypanthium

• In this type of in Florence the peduncle modified in a narrow cup likes structure.
• At the base of cup the female flower develops whereas at mouth side the male flower develops.
• All three types of flower are present in this in Florence.

  Example: Peepal and banyan.

Hypanthodium

• In this type of in Florence the receptacle is flask shaped.
• Receptacl…

Plant Disease Caused by a Bacterium

Citrus canker

Causal Organism

Xanthomonas Citri

• It is gram negative, Monotrichous, capsulated bacillus which is strictly aerobic in nature.
• It shows a yellow, copiously mucoid growth on 2 % sucrose peptone agar but on beef agar colonies are circular and straw yellow to amber yellow.

Symptoms

• Affects all above ground par…