Question Discussion & Solution

Concept:

• Plant growth hormones or phytohormones are simple molecules with complex chemical composition, that regulates the growth and physiology of plants.
• Based on their functions on the living plant body they can be classified into two groups:

1. Plant growth promoters - Promotes activities like cell division, cell enlargement, flowering, fruiting, etc. Eg. Auxins, Gibberellins & cytokinins.
2. Plant growth inhibitors - They are involved in various growth-inhibiting activities like dormancy, and abscission. Eg. Abscisic acid.

• Gaseous PGR like ethylene can be put into both groups, however, it is largely an inhibitor of growth activities.

Explanation:

• Ethylene is a simple gaseous PGR.
• It is synthesized in large amounts by tissues undergoing senescence and ripening fruits.
• Influences of ethylene on plants include horizontal growth of seedlings, swelling of the axis, and apical hook formation in dicot seedlings.
• Ethylene promotes senescence and abscission of plant organs, especially of leaves and flowers.
• Ethylene is highly effective in fruit ripening. It enhances the respiration rate during the ripening of the fruits. This rise in the rate of respiration is called respiratory climactic.
• Ethylene breaks seed and bud dormancy, initiates germination in peanut seeds, sprouting of potato tubers.
• Ethylene promotes rapid internode/petiole elongation in deepwater rice plants.
• It helps leaves/ upper parts of the shoot to remain above water.
• Ethylene also promotes root growth and root hair formation, thus helping the plants to increase their absorption surface.

Additional Information

The correct answer is 4°C.

• Freezing of Water:
  • As water freezes, cold water (or ice formed) comes on the surface and warm water goes down.
  • Since the freezing temperature of the water is 0ºC or 273 K.
  • So water at the bottom should be at a higher temperature.
  • Water density at 4ºC is more than the density of water at 0ºC, hence the correct option is 4ºC.

​Key Points

• Reason of low temperature at bottom of the top layer:
  • This is due to the process of convection.
  • When the temperature of the water at the top layer reaches the freezing point, it is converted to ice.
  • But ice is lighter than water, so it will not sink to the bottom.
  • So there will be ice on the top surface and water would remain at the bottom of the lake. 

CONCEPT:

• Force: The interaction which after applying on a body changes or try to change the state of motion or state of rest is called force.
• Force is denoted by F and the SI unit is Newton (N).

• Force (F) = Mass (m) × acceleration (a)

EXPLANATION:

• Both Dyne and Newton are units of force in the CGS and S.I system.
• Newton and dyne can also be written as (1 N = kg-m/s2) and (1 dyne = gm-cm/s2).
• The relation between the Newton and  Dyne is given as 

⇒ 1 N = 105 dyne

• Therefore, the ratio of SI unit and CGS unit of force is

\(\Rightarrow \frac{N}{Dyne} = 10^5\)

Battery and Engine are part of car but battery and engine are two different entity.

Therefore, above diagram best express relationship between Battery, Engine and Car.

Here the pattern is,

Hence, B9 is the correct answer.