Question

ABA acts antagonistic to which hormone with regards to seed and bud dormancy?
1. Cytokinin
2. IAA
3. Ethylene
4. Gibberellins

Answer 1

Correct Answer - Option 4 : Gibberellins

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 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:

• Gibberellins are plant growth-promoting hormones, they break the seeds, buds, and tubers dormancy. ABA acts antagonistic to this and induces dormancy.
• Other physiological applications of Gibberellins are:
• Increase the axis length in plants such as grape stalks.
• Delay senescence (i.e. aging) in fruits. As a result, their market period is extended.
• Help fruits like apples to elongate and improve their shape

•  IAA (Indole acetic acid) is a type of auxin that prevents premature abscission of plant organs.
• Cytokinin - Help in the formation of new leaves and chloroplasts. Promote lateral shoot growth and adventitious shoot formation. Help overcome apical dominance. Promote nutrient mobilization which in turn helps delay leaf senescence.
• Ethylene - Stimulation of senescence & abscission of leaves. Post-harvest ripening of fruits like CItrus, oranges, banana, apple, tomato.