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Plant transport system

In primary 4, you learnt the two functions of the stem:

  • Provide support for the plant
  • Transport food, water and mineral salts to all parts of the plant


But before you read on, you might want to download this entire revision notes in PDF format to print it out for your child, or to read it later.

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In P5 and P6, you need to learn the different parts of the stem.

In your primary syllabus, there are two types of carrying tubes found in the stem.

You need to know these:

1) Where are the carrying tubes found?

2) What do they carry?



Cross-section of the stem of the balsam plant


Hold on a sec

What is cross-section?

We use a sharp object (Can be a knife) and cut open the object. An example is orange. We use a knife to cut the orange into 2 parts. We can see the insides of the orange. When we see what’s inside the orange, we are looking at the cross-section of the orange.

An orange


Cross-section an orange

Cross-section can refer to any objects. It can be the smartphone. Using a sharp cutter to slice the phone, we can see and analyse the cross-section of the phone. See the image below. 😊

Where are the carrying tubes found?

To help you see the difference, we have coloured the different carrying tubes.

The water-carrying tubes are found near the centre (inner part of the stem). Food-carrying tubes are found near the outer part of the stem.

To help you remember the science knowledge, remember this acronym (words where each letter represents a keyword).



What does it mean?


Now, look back at the cross-section of the stem, do you see the water-carrying tubes are positioned closer to the centre of the stem?

What are the functions of the carrying tubes?


Water-carrying tubes – To transport water and mineral salts from the roots to all parts of the plant

Food-carrying tubes – To transport glucose / sugars from the leaves / fruits to all parts of the plant.


Take note:

You can write “carry” or “transport” substances.

Don’t write “bring water”.


Let’s see the diagram to show how water and mineral salts are transported in the plant

*blue coloured arrows represent the movement of water and mineral salts in the plant.



Water is absorbed by the roots of the plant.

Take note: We don’t recommend “take in water”. “Take in” is similar to a hand reaching out to take an item. Roots don’t do that. A better word to use is “absorb”.

Water-carrying tubes transport water and mineral salts to the leaves of the plant.

Let’s see the diagram to show how glucose or sugars are transported from leaf X.

*Yellow coloured arrows represent the movement of glucose or sugars in the plant.


Glucose is produced by the leaves during photosynthesis.


What is photosynthesis?

For P3 and P4 students, you learnt this is a life-process carried out by the leaves to make food.

For P5 and P6 students, you need to be clearer in your answer. This is the proper explanation:

Leaves absorb light energy using its chlorophyll, take in water and carbon dioxide to photosynthesise and produce oxygen and glucose.


The proper explanation is as follows:

Glucose produced by the leaves is transported using the food-carrying tubes from leaf X to the rest of the plant.

What do you see from the two diagrams above?

You noticed the diagram shows a few science concepts.

Let’s look at the wrong and correct concepts.


Wrong concept:

Direction of food substances is always downwards.


Teachers’ comments: We always learnt food is needed by the roots. Hence the direction of glucose is transported downwards to the roots. However, there are other parts of the plant that needs food.

Some examples include flowers or fruits. Both of them need glucose.

Flowers can be found above the leaves which brings you to the correct concept.



Correct concept: Depending on where the leaves located, the glucose or sugars can be transported from leaf X to the flower (which is situated above leaf X).

Direction of the food substances can be upwards or downwards.


Always remember the function of food-carrying tubes:

To transport glucose / sugars from the leaves / fruits to all parts of the plant.

The keywords are “all parts”.

Need help with the scientific keywords?

You might want to download this Free Ebook.

This ebook contains a list of 81 Must-know Keywords for the primary science exams.

Similar to English vocabulary words, there are science vocabulary words that your child needs to master.

What’s the difference between seed leaves and true leaves? What’s the difference between photosynthesis and respiration?

The keywords are revealed in this ebook.

Easy to Read, Revise and Review.

Let’s explore the other concept.

Wrong concept:

Starch is transported in the food carrying tubes.


Teachers’ comments: Glucose and starch are different types of food.

How to differentiate them?

In the Primary level,

Glucose is simplified food substances. Glucose is similar to digested food. Digested food means it can be absorbed into our body.

Starch is complex food substances. Starch is similar to undigested food. Starch is stored food. It is not transported.


Correct concept: Glucose or sugars is transported from the leaves to the rest of the plant.

What can we take away from this revision notes?

We learnt the position of the water and food-carrying tubes in the stem.

Proper explanations of the carrying tubes are required. This explanation is similar to the functions of the carrying tubes.

There are important keywords I need to muster. Words such as “absorb”, “transport/carry” are used in my open-ended answers.

You can download this revision notes so your child can revise them anytime.

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Talk again soon!

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Andy Ling

Guiding your child to be the master of science concepts

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