Question

Which of the following is not an effect of ethylene?
A)Promotes senescence and abscission of plant organs
B)Breaks seed and bud dormancy
C)Brings about horizontal growth of seedlings
D)Hastens fruit ripening
E)Helps to overcome apical dominance

Answer 1

Hint: Ethylene is an important plant hormone which is gaseous in nature. It is produced from all the parts of the higher plants like leaves, stems, flowers, fruits, tubers, seeds, roots etc. The ethylene production is regulated by environmental and developmental factors.

Complete answer:
Ethylene is an important plant hormone which is produced by the plants naturally and can be synthesised chemically and used. The major function of ethylene in plants are:

1)It helps in ripening of the fruits. The fruits produce ethylene gas which starts the ripening process. The rapid rise in ethylene leads to quick softening of the fruit and senesce after storing. Slower the ethylene rising rate, slower is the ripening process.

2)Senescence and abscission of plant organs- Senescence means aging and abscission is the natural detachment from the plants. The ethylene promotes the senescence and ripening in plants. The fruits and flower leaves fall off from the plants due to abscission.

3)Breaks seed Dormancy- Breaking seed dormancy means changes in the seed coat or embryo which facilitates proper germination. The gibberellins are an important hormone for breaking seed dormancy. Ethylene also helps in inducing the same.

4)Horizontal growth of seedling- Ethylene inhibits the stem elongation and thus brings about horizontal growth of the seeding.

Apical dominance is the process in which the main stem is dominant over the other apical stem. This dominance is overcome by the hormone called cytokinin.

Hence, the correct answer is option (E)

Note: Cytokinin is another important plant hormone which helps in overcoming apical dominance. It also promotes cell division in roots and shoots. It is majorly associated with growth and differentiation, leaf senescence and bud growth.