Question

Give functional significance of Ethylene and ABA​

Answer 1

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The role of ethylene and abscisic acid is both positive and negative. Ethylene is a simple gaseous plant growth regulator. As a negative effect, it is synthesized in large amount by tissues undergoing senescence and ripening. It also promotes senescence and abscission of plant organs especially of leaves and flowers.

As a positive effect, ethylene breaks seed and bud dormancy, initiates germination in peanut seeds, sprouting of potato tubers. It promotes internode/petiole elongation in deep water rice plants. It helps leaves/ inner parts of the shoot to remain above water.

Answer 2

Functional significance of Abscisic Acid (ABA)

• ABA is an active substance inducing abscission of different plant parts.
• It induces dormancy of seeds and buds
• ABA inhibits flowering in long day plants but stimulates flowering in short day plants.
• ABA causes partial closure of stomata under drought and thus acts as anti-transpirant. Hence it is also known as stress hormone.
• Leaves produces large amount of ABA during drought and this ABA functions as a messenger that enables plants to conserve water.
• Senescence of leaf is promoted by ABA.
• ABA also counteracts many effects of GA.

Functional significance of Ethylene

• Ethylene is mainly concerned with maturation and fruit ripening.
• Ethylene promotes seed germination and hence overcomes dormancy.
• It induces feminisation i.e., increases the number of female flowers.
• Ethylene promotes abscission and senescence of leaves flowers, etc.