Control and coordination — AQA GCSE Biology
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Control and coordination explained
Ethene (C₂H₄) is a gaseous plant hormone that coordinates fruit ripening and influences cell division.
Read the full explanation
It is produced by ripening fruit and by damaged or ageing plant tissue. Ethene stimulates enzymes that soften cell walls, convert starches to sugars and produce the characteristic colours and aromas of ripe fruit. It also promotes cell division in some tissues, such as the abscission zone where leaves or fruits separate from the plant. Because ethene is a gas, it diffuses between fruits and can synchronise ripening in a crop. Commercial growers use ethene to ripen fruit such as bananas after transport. Students should not confuse ethene with ethane, a different alkane, nor with respiration, although ripening involves increased respiration.
Your focus
- State that ethene is a plant hormone controlling cell division and fruit ripening.
- Describe the changes that occur in a fruit as it ripens.
- Explain how the gaseous nature of ethene allows it to affect nearby fruit.
Control and coordination exam tips
Marking Points
- Ethene is a gaseous plant hormone involved in fruit ripening.
- It promotes cell division in specific plant tissues, such as the abscission zone.
- It stimulates enzymes that soften fruit cell walls and convert stored starch to sugars.
- It produces changes in colour, texture, aroma and taste associated with ripe fruit.
- Ethene diffuses through the air, so one ripening fruit can trigger ripening in nearby fruit.
- Commercial growers may use ethene to ripen fruit such as bananas after transport.
Examiner Tips
- 💡Link each ripening change to an observable effect, such as softening, colour change or sweetness.
- 💡Use the fact that ethene is a gas to explain how ripening spreads through a fruit bowl or crop.
- 💡When comparing plant hormones, contrast ethene with auxin and gibberellin in one clear sentence each.
Common Mistakes
- Confusing ethene with ethane: ethene is the plant hormone C₂H₄, while ethane is a different alkane.
- Stating that ethene is a respiratory gas: it is a hormone; ripening involves increased respiration but ethene is not the respiratory substrate.
- Saying ethene only softens fruit: it also affects cell division, colour, aroma and the separation of fruit from the plant.