Plant hormones are chemical messengers that control how plants grow... Show more
SociologySign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
278
•
9 Dec 2025
•
Plant Hormones and Their Functions
Seren White
@serenwhite_muwd
1 / 3
How Auxins Control Plant Movement
Ever wondered why plants always seem to grow towards windows? Auxins are the clever chemicals behind this behaviour. These hormones are produced in plant tips and control growth by making cells elongate rather than multiply.
When light hits a plant evenly from all sides, auxins spread equally throughout the stem, causing straight upward growth. But here's where it gets interesting - when light comes from just one direction, auxins move to the shaded side of the plant.
This uneven distribution makes only the shaded cells elongate, causing the plant to bend towards the light source. It's basically the plant's way of maximising photosynthesis by chasing the best light available.
Quick Tip: Remember that roots show positive gravitropism (grow towards gravity) whilst shoots show negative gravitropism (grow away from gravity).
Gravitropism and Root Growth
Roots are brilliant at finding their way down, even in complete darkness. Gravitropism explains how auxins help roots navigate towards water and nutrients underground.
When gravity affects a root, auxins accumulate on the bottom side where gravitational pull is strongest. Unlike in shoots, auxins actually inhibit growth in roots. This means the bottom cells stop growing whilst the top cells continue, forcing the root to curve downward.
Without gravity (like in space), roots would grow horizontally because auxins can't tell which way is down. Phototropism experiments show that removing the tip of a plant stops this bending response entirely, proving that's where the auxins are made.
Remember: Auxins promote growth in shoots but inhibit growth in roots - they work opposite ways in different parts of the plant!
Commercial Uses of Plant Hormones
Plant hormones aren't just fascinating science - they're big business in agriculture and horticulture. Gibberellins are particularly useful because they control seed germination, shoot elongation, and flowering timing.
Ethene gas is the reason bananas ripen faster when you put them in a bag together. This hydrocarbon hormone speeds up fruit ripening, which is why citrus fruits that stay green when ripe can be treated to turn the familiar orange colour we expect.
Gardeners and farmers use synthetic auxins in rooting powder to help plant cuttings develop strong root systems quickly. The natural version, Indoleacetic acid (IAA), can be cheaply manufactured to break seed dormancy and force buds to flower on command.
Commercial Advantage: Understanding these hormones means farmers can control when crops germinate, flower, and ripen - making food production more predictable and profitable.
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
Where can I download the Knowunity app?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
Most popular content: Auxins
Most popular content in Biology
Most popular content
Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.9/5
App Store
4.8/5
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
Plant Hormones and Their Functions
Seren White
@serenwhite_muwd
Plant hormones are chemical messengers that control how plants grow and respond to their environment. Understanding how auxins, gibberellins, and ethene work helps explain why plants bend towards light, grow roots downward, and how farmers can manipulate these processes for... Show more
How Auxins Control Plant Movement
Ever wondered why plants always seem to grow towards windows? Auxins are the clever chemicals behind this behaviour. These hormones are produced in plant tips and control growth by making cells elongate rather than multiply.
When light hits a plant evenly from all sides, auxins spread equally throughout the stem, causing straight upward growth. But here's where it gets interesting - when light comes from just one direction, auxins move to the shaded side of the plant.
This uneven distribution makes only the shaded cells elongate, causing the plant to bend towards the light source. It's basically the plant's way of maximising photosynthesis by chasing the best light available.
Quick Tip: Remember that roots show positive gravitropism (grow towards gravity) whilst shoots show negative gravitropism (grow away from gravity).
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Gravitropism and Root Growth
Roots are brilliant at finding their way down, even in complete darkness. Gravitropism explains how auxins help roots navigate towards water and nutrients underground.
When gravity affects a root, auxins accumulate on the bottom side where gravitational pull is strongest. Unlike in shoots, auxins actually inhibit growth in roots. This means the bottom cells stop growing whilst the top cells continue, forcing the root to curve downward.
Without gravity (like in space), roots would grow horizontally because auxins can't tell which way is down. Phototropism experiments show that removing the tip of a plant stops this bending response entirely, proving that's where the auxins are made.
Remember: Auxins promote growth in shoots but inhibit growth in roots - they work opposite ways in different parts of the plant!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Commercial Uses of Plant Hormones
Plant hormones aren't just fascinating science - they're big business in agriculture and horticulture. Gibberellins are particularly useful because they control seed germination, shoot elongation, and flowering timing.
Ethene gas is the reason bananas ripen faster when you put them in a bag together. This hydrocarbon hormone speeds up fruit ripening, which is why citrus fruits that stay green when ripe can be treated to turn the familiar orange colour we expect.
Gardeners and farmers use synthetic auxins in rooting powder to help plant cuttings develop strong root systems quickly. The natural version, Indoleacetic acid (IAA), can be cheaply manufactured to break seed dormancy and force buds to flower on command.
Commercial Advantage: Understanding these hormones means farmers can control when crops germinate, flower, and ripen - making food production more predictable and profitable.
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
Where can I download the Knowunity app?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
4
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Mock Exam
Quiz
Flashcards
Essay
Similar content
SB6 GCSE Biology - Plant Structures and their Functions - Notes from Specification
Grade 9 Edexcel GCSE Biology notes for Topic 6
Biology11
Understanding Plant Hormones
Explore the role of plant hormones in growth and responses to environmental stimuli. This summary covers key concepts such as tropism, hormonal coordination, and the five major plant hormones essential for OCR A A-Level Biology. Ideal for students seeking to grasp the intricacies of plant physiology and hormonal control.
Biology12
Homeostasis and Body Systems
Explore the intricate mechanisms of homeostasis, including the nervous and endocrine systems, reflex actions, and the role of hormones. This study note covers essential topics such as diabetes management, kidney failure treatments, puberty, the menstrual cycle, contraception methods, and plant hormones. Ideal for students preparing for exams or seeking a comprehensive understanding of physiological responses and regulatory systems.
Biology11
Most popular content: Auxins
Most popular content in Biology
Most popular content
Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.9/5
App Store
4.8/5
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user