Name: Structure Of The Leaf | Plant | Biology | The FuseSchool
Uploaded: 2025-05-21T08:10:23.000Z
Duration: 3 min 43 s
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So we know that plants make their own food through photosynthesis.

But how does a plant get together the ingredients it needs for this?

Sunlight, carbon dioxide and water, and then combine those to create glucose and oxygen?

A leaf is like a plant's food factory, and its parts work together to get the reactants into one place so that photosynthesis can happen.

The top of it is exposed to the most light, so the cells specialized for trapping light are on top.

These cells are called palisade mesophyll, and they're packed full of chlorophyll, the green chemical that plants use to absorb light.

That's why the top side of the leaf is darker than the bottom side.

You should also note that most leaves have a large surface area, so they can trap as much sunlight as possible.

That's where the bottom of the leaf comes in, it's got these little pores called stomata, which open up so carbon dioxide can diffuse into the leaf.

They're controlled by sausage shaped guard cells, which open up to let carbon dioxide in, but they can also close the stomata to prevent other things like water from escaping.

So the carbon dioxide comes in through the stomata, makes its way through the gaps in an airy layer of cells called the spongy mesophyll at the bottom part of the leaf, and then heads up to the palisade layer for photosynthesis.

Leaves are thin so that the carbon dioxide won't have too far to travel.

So we've got sunlight and carbon dioxide now, what's left?

Water comes up through the roots and stem, and enters the leaf through a vascular bundle, which contains a hollow tube for water transport called the xylem.

Look at how the vascular bundle spreads out in the leaf to form veins so that it can spread water throughout.

So now the leaf's palisade cells have water, carbon dioxide and sunlight, all they need to photosynthesize and make glucose, their food, and oxygen.

But how does the leaf prevent unwanted intruders like bacteria from getting in and stop important reactants from escaping?

Above the palisade mesophyll and below the spongy mesophyll are epidermis cells, which produce a waxy coating called the cuticle.

So that the only way in and out is through the stomata, which are regulated by those guard cells.

Now let's go back through the parts of a leaf.

We've got the thin waxy cuticle, then the epidermis cells.

Then comes the chlorophyll rich palisade mesophyll, where the bulk of photosynthesis occurs.

Below that's the spongy mesophyll, which have plenty of space in between them for reactants to move through.

Through that space stretches the vascular bundle with xylem to transport water and phloem, which transports sugars after photosynthesis.

And below that, we've got another layer of epidermis and cuticle.

Space around the lower epidermis and the cuticle.

Are the stomata with guard cells on either side, leaves come in all different shapes and sizes, look at a cabbage leaf and an oak tree leaf, but most of them have these same parts in common, which allow them to get their reactants in and perform photosynthesis.

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Structure Of The Leaf | Plant | Biology | The FuseSchool

basically

plenty

common

bacteria