Biology · Plant Growth and Development · NEET
NCERT says ethylene can fit either group, but it is largely an inhibitor of growth activities. It promotes senescence (ageing), abscission (organ drop) and dormancy - these are inhibitory. So for NEET, remember: ethylene is grouped with inhibitors even though it does a few promoting jobs like fruit ripening and root hair growth.
Ethylene. It is highly effective in fruit ripening and raises the respiration rate during ripening. This sudden rise in respiration is called the respiratory climacteric. This is why one ripe fruit gives off ethylene gas and speeds up ripening of nearby fruits.
Ethylene. It promotes female flowers in cucumbers, which increases the yield (more female flowers means more fruits). This exact point was asked in NEET 2022 and again in the NEET 2023 match-the-column question, so it is high-value for NEET.
Ethephon is the most widely used source of ethylene. In water it is absorbed and moved inside the plant and slowly releases ethylene. It hastens fruit ripening in tomatoes and apples, accelerates abscission (thinning) in cotton, cherry and walnut, and promotes female flowers in cucumber.
Ethylene promotes rapid internode and petiole elongation in deep-water rice plants. This helps the leaves and upper shoot stay above rising water so the plant does not drown. NEET 2023 asked this directly - the answer is ethylene, not GA3.
Yes. Ethylene promotes root growth and root hair formation, which increases the absorption surface of the plant. This is one of its few growth-promoting roles, so students often forget it - keep it in mind for NEET matching questions.
Production of Cucumber has increased manifold in recent years. Application of which of the following phytohormones has resulted in this increased yield as the hormone is known to produce female flowers in the plants?
Which hormone promotes internode/petiole elongation in deep water rice?
It takes very long time for pineapple plants to produce flowers. Which combination of hormones can be applied to artificially induce flowering in pineapple plants throughout the year to increase yield?
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Yes. Among the five main plant growth regulators, ethylene is the only one that is a gas (C2H4). This makes it easy to spread from fruit to fruit through the air.
During fruit ripening, ethylene raises the respiration rate. This sharp rise in respiration during ripening is called the respiratory climacteric.
Yes. Ethylene breaks seed and bud dormancy, starts germination in peanut seeds, and causes sprouting of potato tubers.
In dicot seedlings coming out of soil, ethylene causes horizontal growth, swelling of the axis, and a bent apical hook that protects the tender shoot tip as it pushes up through the soil.
Because it controls many processes - ripening, abscission, flowering, female flower formation - it is heavily used, usually through its source compound ethephon.
