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Explain the Roles of Xylem and Phloem in Plants

In this worksheet, students will explain the structures and roles of xylem, phloem and specialised transport cells.

'Explain the Roles of Xylem and Phloem in Plants' worksheet

Key stage:  KS 4

Curriculum topic:  

Curriculum subtopic:  

Difficulty level:  

Worksheet Overview

QUESTION 1 of 10

Like humans have arteries and veins to carry blood, plants need their own ways of transporting substances so they can survive.

 

Plants have two main transport systems: XYLEM and PHLOEM

 

And between them there are 4 types of specialised cells we need to know: VESSELS of the xylem, SIEVE TUBES and COMPANION CELLS of the phloem, and ROOT HAIR CELLS in the roots.

 

 

Let’s begin with Xylem:

 

 Water and minerals are transported by xylem

 

They are hollow tubes with continuous walls that are made from specialised dead cells called vessels.

 

Looking at the brown columns in the picture below, these cells are now empty and have no end walls (no ceilings or floors) so they can be joined together smoothly, helping the water flow easily.

 

This secure structure allows the transport of water and minerals UPWARDS from the roots and through the stem, so think root to leaves!

 

Surprisingly, this antigravity direction is what we call a physical process, meaning the xylem doesn’t need energy to push it’s water contents around.

 

 

Next, the Phloem:

 

Phloem manoeuvres sugars and amino acids around the plant in a dissolved form, and they are transported UPWARDS and DOWNWARDS to where the plant needs them.

 

Phloem has its own term for this transport called TRANSLOCATION!

 

But the phloem is actually a combination of two cell types, both of which are alivedepend on each other and are well adapted for their roles (see the diagram above):

 

Sieve tube cells have no nuclei and are stacked on top of each other, making the tunnels of the phloem. The cytoplasm of the neighbouring cells interacts through the gaps in the ends of each cell.

 

But translocation needs energy, which companion cells provideso every sieve tube gets at least one companion cell so it can function!

 

 

But if you look through a microscope, a section of stem looks very different to a root because of the different arrangements of xylem and phloem.

 

In the roots, xylem is in the middle with phloem around the outside, but in the stem they are arranged in pairs.

 

 

 

Finally, we need to mention the Root Hair Cells:

 

These allow a plant to absorb water from the soil using osmosis

 

They are specially adapted to be long and thin so they can get through pieces of soil and they have a larger surface area for water absorption.

 

(Reminder: Osmosis is the movement of water from a high water concentration to a lower water concentration, with the difference in water levels creating a natural gradient that makes water diffuse across)

 

The gradient here is dependent on there being less water in the root hair cytoplasm than the soil, and so as water comes in, the cell also actively transports mineral salts from its low concentration in the soil to an already high concentration in the cytoplasm, maintaining the influx of water. 

 

And as active transport ALWAYS needs energythese cells respire a lot to get the energy the cell needs to function.

Identify which substance is transported by which transport system: 

Column A

Column B

Phloem
Sugar and Amino Acids
Xylem
Water and Minerals
Root Hair Cells
Water (Absorbed)

Regarding the xylem's structure:

Column A

Column B

Phloem
Sugar and Amino Acids
Xylem
Water and Minerals
Root Hair Cells
Water (Absorbed)

In the xylem, the transport of water and minerals occurs in which direction?

Only Upwards

Upwards and Downwards

Only Downwards

For the specialised cells below, indicate which transport system they each belong to:

Only Upwards

Upwards and Downwards

Only Downwards

Discuss the arrangement of xylem and phloem in plants.

Only Upwards

Upwards and Downwards

Only Downwards

Sieve tubes make up the phloem, but they don't work alone.

 

[Select all the option below that are CORRECT about the phloem's structure]

Companion cells provide energy

Every sieve tube needs at least one companion cell

Phloem transport is a physical process

Every companion cell has at least one sieve tube

Phloem uses translocation

How does being long and thin help the Root Hair Cells perform their function?

 

[Select ALL the correct options below]

They can reach water in between soil particles

They don't disrupt other root hair cells

This increases their surface area

More cells can be packed together

The process root hair cells depends on several factors.

They can reach water in between soil particles

They don't disrupt other root hair cells

This increases their surface area

More cells can be packed together

The root hair cells use osmosis and active transport to absorb water from the soil into the roots. 

 

Indicate the normal distribution of substances in the following areas:

In which transport system would you find these arrangements?

Column A

Column B

Dead cells make up the hollow columns
Xylem
Alive cells make up the hollow columns
Xylem
There are gaps in the end walls
Phloem
There are no end walls
Phloem
  • Question 1

Identify which substance is transported by which transport system: 

CORRECT ANSWER

Column A

Column B

Phloem
Sugar and Amino Acids
Xylem
Water and Minerals
Root Hair Cells
Water (Absorbed)
EDDIE SAYS
Did you feel confident answering this first question? Plants organise their transport systems based on what they're moving: -xylem transports water and minerals through the stem - phloem is in charge of moving sugars and amino acids that have been dissolved in water - root hair cells are responsible for water absorption
  • Question 2

Regarding the xylem's structure:

CORRECT ANSWER
EDDIE SAYS
How did you do? Xylem has some special adaptions to its structure that helps it fulfill its function. It's a hollow tube made from dead cells who are now empty, and the bottoms of the cells have also been removed so all their cytoplasm melds together into one steady stream. The continuous shape means with no end walls means their is less turbulence in the water flow, making transport easier.
  • Question 3

In the xylem, the transport of water and minerals occurs in which direction?

CORRECT ANSWER
Only Upwards
EDDIE SAYS
Was this question easy or hard to you? Well, it's important to remember these points: The xylem only moves water and minerals UP BUT the phloem transports substances up AND down!
  • Question 4

For the specialised cells below, indicate which transport system they each belong to:

CORRECT ANSWER
EDDIE SAYS
The questions are getting harder now but you need to be familiar with these terms. The xylem\'s specialised cells are known as VESSELS. The phloem has two types of cells that work together to carry out the phloem\'s function, as the living sieve tubes have no nuclei and have gaps in their end walls to help substances flow, but this all requires energy, wihch is what the companion cells supply. (Tip: think of companion cell as a buddy cell that the sieve tubes rely om!)
  • Question 5

Discuss the arrangement of xylem and phloem in plants.

CORRECT ANSWER
EDDIE SAYS
How did you feel answering this question? In the root, xylem is the central structure that gives the main support, while the phloem wraps around it. But when you move up the stem, if you broke it in half and put it under a microscope, you see that the xylem and phloem are actually arranged in pairs in a circle formation, which we call vascular bundles.
  • Question 6

Sieve tubes make up the phloem, but they don't work alone.

 

[Select all the option below that are CORRECT about the phloem's structure]

CORRECT ANSWER
Companion cells provide energy
Every sieve tube needs at least one companion cell
Phloem uses translocation
EDDIE SAYS
So this was a mean question but it sums up a lot of the topic all at once so it's great for testing your understanding of how xylem and phloem work! Let's be clear: The phloem works using translocation, while the xylem's method of transport is referred to as a physical process! Like we said, the xylem undergoes physical process, which means it DOESN'T use energy to do its function, meaning it's passive. However, the phloem's translocations need energy to work, which is when we think about the purpose of the companion cells! Companion cells provide the energy needed for sieve tubes to function, but at sieve tubes are the main player and makes up the transport system, we say that each sieve tube gets at least one companion cell (not the other way around!)
  • Question 7

How does being long and thin help the Root Hair Cells perform their function?

 

[Select ALL the correct options below]

CORRECT ANSWER
They can reach water in between soil particles
This increases their surface area
EDDIE SAYS
Being adapted to be long and thin to help them reach the water in between soil particles, but this also increases their surface area for water absorption
  • Question 8

The process root hair cells depends on several factors.

CORRECT ANSWER
EDDIE SAYS
The root hair cells are interesting because the processes involved in water absorption vary in whether they use energy or not! The osmosis drawing the water into the cell from the soil is by simple diffusion, so this part doesn't use energy. BUT osmosis can only be maintained as long as the water concentration in the cytoplasm stays lower than that in the soil, and to do this the cell has to use active transport to force in minerals, which is very energy-dependent.
  • Question 9

The root hair cells use osmosis and active transport to absorb water from the soil into the roots. 

 

Indicate the normal distribution of substances in the following areas:

CORRECT ANSWER
EDDIE SAYS
So this final question is really testing your grasp of what osmosis and active transport mean and how they apply in the context of root hair cells. For osmosis to bring water into the cytoplasm, there has to be more water in the soil than the cell for the gradient to favour moving water into the cell. For the active transport used to maintain the osmosis, we have to follow the defintion and if the point is to move mineral salts into the cell, then the cell must already have a high concentratino and we\'re trying to pack more in by taking salts from an area of already low concentration, which here would be the soil. Well done on getting through this activity, and remember to make note of any explanations that helped you understand this topic better and that you think might help your revision!
  • Question 10

In which transport system would you find these arrangements?

CORRECT ANSWER

Column A

Column B

Dead cells make up the hollow col...
Xylem
Alive cells make up the hollow co...
Phloem
There are gaps in the end walls
Phloem
There are no end walls
Xylem
EDDIE SAYS
How have you been finding questions that ask you to compare xylem and phloem? Let's make their differences clear: Xylem is made up of DEAD cells with no contents that now make up the walls of the hollow columns water and minerals pass through. The tube is also continuous as the cells have no floor or ceiling which we call END WALLS. Phloem, however, has ALIVE cells making up its structure, although they have no nuclei. BUT they're not fully empty as they all still have cytoplasm which actually mixes together through GAPS in the end walls, and this is how phloem transports dissolved sugars and amino acids.
---- OR ----

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