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Lucy Robinson
10/3/2025
Biology
Mass Transport in plants
770
•
Oct 3, 2025
•
Mass Transport in Plants A Level Biology: Xylem, Phloem, and Transpiration
Lucy Robinson
@lucyhoperobinson
Mass Transport in Plants: Xylem and Phloem
The mass transport mechanisms in xylem and phloem are essential for plant survival and growth. This page provides an overview of these transport systems and their functions in plants.
Xylem Structure and Function
Xylem is responsible for transporting water and mineral ions from the roots to the leaves. Its structure is adapted for efficient water transport:
Highlight: Xylem vessels are long with no end walls, allowing water to move freely upwards through the plant.
The movement of water through the xylem is driven by transpiration, which creates tension in the water column:
Definition: Transpiration is the evaporation of water from plant surfaces, primarily through the leaves.
Water evaporates from the leaf surfaces, creating a suction effect that pulls more water up through the xylem due to the cohesive properties of water molecules.
Phloem Structure and Function
Phloem transports dissolved substances, primarily sucrose, throughout the plant. Its structure includes:
- Sieve tube elements
- Companion cells
Vocabulary: Companion cells are specialized cells that support the function of sieve tube elements in the phloem.
Companion cells provide energy for active transport of solutes into the sieve tubes.
Mass Flow Hypothesis
The mass flow hypothesis explains the mechanism of translocation in phloem:
- Solutes are actively loaded into the phloem at source tissues (e.g., leaves).
- This creates a concentration gradient and lowers water potential in the phloem.
- Water enters the phloem from the xylem via osmosis, increasing pressure.
- The pressure gradient pushes solutes along the phloem towards sink tissues.
- At sink tissues, solutes are removed and used or stored.
Example: The higher the concentration of sucrose in the phloem, the faster the rate of translocation.
Factors Affecting Transpiration
Several environmental factors influence the rate of transpiration:
- Light intensity: Higher light intensity increases transpiration as stomata open wider for CO₂ uptake.
- Wind: Increased wind speed accelerates transpiration by removing water vapor from leaf surfaces.
- Temperature: Higher temperatures increase evaporation rates, leading to faster transpiration.
- Humidity: Low humidity increases the water potential gradient, promoting faster transpiration.
Highlight: These factors affect the water potential gradient between the leaf and the surrounding air, which drives transpiration.
Understanding these mass transport mechanisms in plants is crucial for A Level Biology students studying topics such as water movement, nutrient transport, and plant physiology.
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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 😍😁😲🤑💗✨🎀😮
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This app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
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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
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
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
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
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 app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user
Mass Transport in Plants A Level Biology: Xylem, Phloem, and Transpiration
Lucy Robinson
@lucyhoperobinson
Mass transport mechanisms in xylem and phloemplay a crucial role in plant biology, facilitating the movement of water, minerals, and organic compounds throughout the plant. This summary explores the key aspects of these transport systems, including the structure and... Show more
Mass Transport in Plants: Xylem and Phloem
The mass transport mechanisms in xylem and phloem are essential for plant survival and growth. This page provides an overview of these transport systems and their functions in plants.
Xylem Structure and Function
Xylem is responsible for transporting water and mineral ions from the roots to the leaves. Its structure is adapted for efficient water transport:
Highlight: Xylem vessels are long with no end walls, allowing water to move freely upwards through the plant.
The movement of water through the xylem is driven by transpiration, which creates tension in the water column:
Definition: Transpiration is the evaporation of water from plant surfaces, primarily through the leaves.
Water evaporates from the leaf surfaces, creating a suction effect that pulls more water up through the xylem due to the cohesive properties of water molecules.
Phloem Structure and Function
Phloem transports dissolved substances, primarily sucrose, throughout the plant. Its structure includes:
- Sieve tube elements
- Companion cells
Vocabulary: Companion cells are specialized cells that support the function of sieve tube elements in the phloem.
Companion cells provide energy for active transport of solutes into the sieve tubes.
Mass Flow Hypothesis
The mass flow hypothesis explains the mechanism of translocation in phloem:
- Solutes are actively loaded into the phloem at source tissues (e.g., leaves).
- This creates a concentration gradient and lowers water potential in the phloem.
- Water enters the phloem from the xylem via osmosis, increasing pressure.
- The pressure gradient pushes solutes along the phloem towards sink tissues.
- At sink tissues, solutes are removed and used or stored.
Example: The higher the concentration of sucrose in the phloem, the faster the rate of translocation.
Factors Affecting Transpiration
Several environmental factors influence the rate of transpiration:
- Light intensity: Higher light intensity increases transpiration as stomata open wider for CO₂ uptake.
- Wind: Increased wind speed accelerates transpiration by removing water vapor from leaf surfaces.
- Temperature: Higher temperatures increase evaporation rates, leading to faster transpiration.
- Humidity: Low humidity increases the water potential gradient, promoting faster transpiration.
Highlight: These factors affect the water potential gradient between the leaf and the surrounding air, which drives transpiration.
Understanding these mass transport mechanisms in plants is crucial for A Level Biology students studying topics such as water movement, nutrient transport, and plant physiology.
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI companion is specifically built for the needs of students. Based on the millions of content pieces we have on the platform we can provide truly meaningful and relevant answers to students. But its not only about answers, the companion is even more about guiding students through their daily learning challenges, with personalised study plans, quizzes or content pieces in the chat and 100% personalisation based on the students skills and developments.
Where can I download the Knowunity app?
You can download the app in the Google Play Store and in the 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.
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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
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
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
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
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 app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
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
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
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
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
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 app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user