GCSEScienceAQACombined Science: TrilogyBiologyRevision NotesOrganisationPlant Tissues, Organs & SystemsPlant Tissues

Plant Tissues (AQA GCSE Combined Science: Trilogy: Biology): Revision Note

Exam code: 8464

Updated on 3 September 2026

Plant tissue: Structures & functions

The structures of plant tissues are related to their functions
Some important plant tissues include:
- epidermal tissues
- palisade mesophyll
- spongy mesophyll
- xylem and phloem
- meristem tissue found at the growing tips of shoots and roots

Leaf structures and functions

Structure	Description
Waxy cuticle	Protective layer on top of the leaf, prevents water from evaporating
Upper epidermis	Thin and transparent to allow light to enter palisade mesophyll layer underneath it
Palisade mesophyll	Column shaped cells tightly packed with chloroplasts to absorb more light, maximising photosynthesis
Spongy mesophyll	Contains internal air spaces that increase the surface area to volume ratio for the diffusion of gases (mainly carbon dioxide)
Lower epidermis	Contains guard cells and stomata
Guard cells	Absorb and lose water to open and close the stomata to allow carbon dioxide to diffuse in, oxygen to diffuse out
Stomata	Where gas exchange takes place Opens during the day, closes during the night, evaporation of water also takes place from here In most plants, found in much greater concentration on the underside of the leaf to reduce water loss
Vascular bundle	Contains xylem and phloem to transport substances to and from the leaf
Xylem	Transports water into the leaf for mesophyll cells to use in photosynthesis and for transpiration from stomata
Phloem	Transports sucrose and amino acids around the plant

The leaf

The leaf is a plant organ adapted specifically for photosynthesis

Leaf cross-section diagram

Diagram of a leaf cross-section showing upper and lower epidermis, palisade and spongy mesophyll, air spaces, vascular bundle, guard cells and chloroplasts — **A leaf contains many different cell types that contribute to its function**

Use this image

Adaptations of the leaf

Large surface area: increases surface area for the diffusion of carbon dioxide and absorption of light for photosynthesis
Thin leaf shape: allows carbon dioxide to diffuse to palisade mesophyll cells quickly
Chlorophyll: absorb light energy so that photosynthesis can take place
Vascular bundles: thick cell walls of vascular cells support the stem and leaf and allows the transport of water and carbohydrates
Stomata: allow carbon dioxide to diffuse into the leaf and oxygen to diffuse out
Epidermis is thin and transparent: allows more light to reach the palisade cells
Thin waxy cuticle: to protect the leaf without blocking sunlight
Palisade layer at the upper side of the leaf: maximises the absorption of light as it will hit chloroplasts in the cells directly
Air spaces in the spongy layer: allow carbon dioxide to diffuse through the leaf

Diagram of a leaf cross-section showing CO₂ diffusing through a stoma into spongy mesophyll air spaces, then into mesophyll cells and chloroplasts during photosynthesis

Pathway of CO₂ molecule when leaf is photosynthesising

1. Higher concentration of CO₂ in atmosphere compared to inside of leaf
2. CO₂ diffuses into leaf through open stoma into air space in spongy mesophyll
3. CO₂ diffuses through cell wall + cell membrane of mesophyll cell, dissolves in cytoplasm + diffuses into chloroplast — **The structure of a leaf maximises the diffusion of carbon dioxide into the mesophyll cells for photosynthesis**

Use this image

Examiner Tips and Tricks

You should be able to observe and draw a transverse section of a leaf

Unlock more, it's free!

Join the 100,000+ Students that ❤️ Save My Exams

the (exam) results speak for themselves:

I would just like to say a massive thank you for putting together such a brilliant, easy to use website.I really think using this site helped me secure my top gradesin science and maths. You really did save my exams! Thank you.

Beth
IGCSE Student

This website is soooo useful and I can’t ever thank you enough for organising questions by topic like this. Furthermore, the name of the website could not have been more appropriate as it literally did SAVE MY EXAMS!

Fathima
A Level Student

Incredible! SO worth my money, the revision notes have everything I need to know and are so easy to understand. I actually enjoy revising! It makes me feel a lot more confident for my GCSEs in a few months.

Kate
GCSE Student

Absolutely brilliant, both my girls used it for A levels and GCSE. It's saves on paper copies, also beneficial exam questions ranked from easy to hard. It's removed a lot of stress from the exams.

Sameera
Parent

Just to say that your resources are the best I have seen and I have been teaching chemistry at different levels for about 40 years

Mark
Chemistry Teacher

Excellent