Plant StructureEdexcel GCSE Biology: Revision notes
Section 1
Root Hair Cells
Long extension increases surface area; large vacuole aids osmosis; many mitochondria enable active transport of mineral ions.
Key termsroot hair cellosmosisactive transport
Common mistake
Water enters by osmosis; ions enter by active transport — don't mix up.
Section 2
Xylem
Dead, lignified cells forming hollow tubes; transport water/minerals one-way (up).
Key termsxylemlignintranspiration
Exam tip
Xylem=dead, one-way; phloem=living, two-way.
Section 3
Phloem
Living sieve tube elements with sieve plates; companion cells provide energy for translocation of sucrose (both directions).
Key termsphloemtranslocationcompanion cell
Section 4
Leaf Structure
| Feature | Adaptation |
|---|---|
| Palisade mesophyll | Chloroplast-rich, near top, max light absorption |
| Spongy mesophyll | Air spaces for gas diffusion |
| Stomata | Gas exchange pores, mostly on lower surface |
| Guard cells | Control stomata opening/closing |
Key termspalisade mesophyllstomataguard cells
Section 5
Extreme Environment Adaptations
Small/needle leaves, thick waxy cuticle, fewer/sunken stomata, stomata closing in the day — all reduce water loss.
Key termscuticlexerophyte
Think of it like this
A thick cuticle acts like a raincoat sealing in water.
Must Know
- Root hair: surface area, vacuole (osmosis), mitochondria (active transport).
- Xylem: dead, lignified, one-way. Phloem: living, companion cells, two-way.
- Leaf: palisade (photosynthesis), spongy (gas exchange), stomata/guard cells.
- Xerophytes: small leaves, thick cuticle, fewer/sunken stomata.
That's the notes covered.
Carry on to the next subtopic.