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Gibberellins initiate seed germination by activating enzymes that break down the stored starch into glucose. Free notes and 12 questions answered.
Gibberellins and Ethene in Plant Development is part of Plant hormones (biology only) in GCSE AQA Higher Biology.
4 min
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22
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GCSE AQA Higher
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Gibberellins initiate seed germination by activating enzymes that break down the stored starch into glucose. Free notes and 12 questions answered.
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Use this lesson to stay inside Plant hormones (biology only) while connecting the detail back to the wider Homeostasis and response topic.
Read the core explanations from Gibberellins and Ethene in Plant Development before testing yourself from memory.
Plants can't move like animals, but they still need to respond to their environment. How does a seed know when to germinate? How does a fruit know when to ripen? The answer lies in chemical messengers called plant hormones.
Unlike animal hormones that travel in blood, plant hormones move through the plant's transport system. Today we'll focus on two crucial ones: gibberellins and ethene. These control some of the most important moments in a plant's life cycle.
Picture a seed sitting in soil. It contains everything needed to grow - stored starch, proteins, and a tiny embryo plant. But something needs to tell it 'now is the time to grow'. That's where gibberellins come in.
When conditions are right (correct temperature, moisture), gibberellins are produced. They activate enzymes that break down the stored starch into glucose. This glucose provides energy for the embryo to start growing and push through the seed coat.
Trap: Many students think seeds just need water to germinate. Actually, they need gibberellins to activate the process - water alone isn't enough.
You've probably noticed that bananas ripen faster when kept together, or that one rotten apple spoils the bunch. This happens because of ethene gas. As fruits mature, they release ethene, which triggers ripening in nearby fruits.
Ethene has two main jobs. First, it controls cell division during fruit development. Second, it triggers the ripening process - breaking down chlorophyll (green colour disappears), converting starch to sugars (fruit becomes sweet), and softening cell walls (fruit becomes tender).
This makes evolutionary sense. Ripe fruits are more likely to be eaten by animals, which then disperse the seeds. Ethene ensures fruits ripen at the right time and all together for maximum impact.
Understanding plant hormones isn't just academic - it's big business. Fruit growers use this knowledge to control when their crops ripen and reach the shops.
Bananas are picked green and hard (unripe) because they'd be too soft to transport if picked ripe. When they reach their destination, suppliers expose them to ethene gas in ripening rooms. This triggers uniform ripening just before they go to shops.
Conversely, apples are often stored in low-oxygen environments to prevent ethene production, keeping them fresh for months. Some packaging even contains ethene absorbers to slow ripening.
Both hormones control crucial life processes, but they work at different stages and in different ways. Here's how they compare:
Gibberellins: Work at the start of plant life (germination), activate breakdown of stored food, promote growth and elongation. They're about 'getting started'.
Ethene: Work at the end of fruit development (ripening), trigger changes that attract animals, can affect neighbouring plants. They're about 'finishing the job'.
Plant hormone questions often test your understanding of processes rather than just facts. Here's how to tackle them successfully.
Worked example: Worked Example: Applying Gibberellins and Ethene in Plant Development
Use this method to answer an exam-style question about plant hormones - the chemical controllers.
Answer: A complete response links mechanism, evidence, and conclusion for gibberellins and ethene in plant development.
Exam depth extension: In gibberellins and ethene in plant development, connect plant hormones - the chemical controllers to gibberellins - the germination trigger using clear cause-and-effect statements. When you explain biological processes, include what changes, why it changes, and the consequence for cells, organisms, or populations. If calculations appear, show each step, include units, and end with a sentence that interprets the result in biological context.
Common mistake: Students often say 'hormones make plants grow' without being specific. Always state which hormone does what - gibberellins initiate germination, ethene controls ripening.
Published by Revise Right. Use the official specification reference to check the requirements for your course. Content updated: 2026-03-20.
Move to the related lessons or back to the topic page when you need the wider sequence before exam-style practice.
Gibberellins initiate seed germination by activating enzymes that break down the stored starch into glucose. This glucose provides energy for the embryo to start growing and push through the seed coat; seeds need gibberellins as well as water to germinate.
Fruits ripen because ethene triggers changes that make them soft, sweet and attractive to animals: chlorophyll breaks down, starch converts to sugars and cell walls soften. Ripe fruits are more likely to be eaten by animals, which then disperse the seeds.
Bananas ripen faster when kept together because maturing fruits release ethene gas, which triggers ripening in nearby fruits. This is also why one rotten apple spoils the bunch.
Gibberellins work at the start of plant life, initiating germination by activating the breakdown of stored food and promoting stem elongation. Ethene works at the end of fruit development, controlling cell division and triggering ripening, and as a gas it can affect neighbouring plants.
Apples are often stored in low-oxygen environments to prevent ethene production, keeping them fresh for months. Some packaging also contains ethene absorbers to slow ripening.
Seeds do not just need water to germinate; they also need gibberellins to activate the process. When conditions such as temperature and moisture are right, gibberellins are produced and activate enzymes that break down stored starch into glucose for the embryo.
Gibberellins break seed dormancy by activating enzymes that break down the seed's stored food reserves, such as starch into glucose. The glucose provides energy for the embryo plant to start growing and push through the seed coat.
One rotten apple spoils the bunch because ripening fruits release ethene gas, which triggers ripening in nearby fruits. This is also why bananas ripen faster when kept together.
Ethene controls cell division during fruit development and triggers ripening: it breaks down chlorophyll so the green colour disappears, converts starch to sugars so the fruit becomes sweet, and softens cell walls so the fruit becomes tender.
Fruits ripen at the same time because ethene released by maturing fruits triggers ripening in nearby fruits. This makes evolutionary sense, because ripe fruits are more likely to be eaten by animals, which then disperse the seeds.
Plant hormones move through the plant's transport system, unlike animal hormones, which travel in the blood. Ethene is a gas, so it can also affect neighbouring plants and fruits.
As well as initiating seed germination, gibberellins promote stem elongation and growth. They work at the start of plant life, 'getting started', whereas ethene works at the end of fruit development.