The tissues of a leaf, xylem and phloem, transpiration and the factors that change it, potometer calculations and stomatal density.
What you will learn
- Name leaf tissues and say what each does
- Compare xylem and phloem, transpiration and translocation
- Explain how temperature, humidity, wind and light change the rate of transpiration
- Calculate water uptake with a potometer and the number of stomata per mm²
A leaf is an organ
- Epidermis with a waxy cuticle covers the leaf and cuts water loss.
- Palisade mesophyll: packed with chloroplasts, most photosynthesis.
- Spongy mesophyll: air spaces for gases to diffuse.
- Stomata, opened and closed by guard cells, let carbon dioxide in and water vapour out.
- Xylem: hollow tubes of dead cells strengthened with lignin; water and mineral ions go up from the roots.
- Phloem: columns of living cells with pores in the end walls; dissolved sugars go up or down (translocation).
- Meristem at shoot and root tips makes new cells.
The rest of this lesson and its 12 practice questions are locked.
In this lesson
- A leaf is an organ
- Transpiration
- Counting stomata
- Try it: A potometer rate
12 practice questions, marked as you go; about 25 minutes in all.
Key terms
Epidermis, Stomata, Translocation, Meristem, Transpiration stream, Down, Potometer
In this unit: Organisation: tissues, organs, digestion and circulation
Levels of organisation, digestion and enzymes with the amylase and food test practicals, the heart, blood and lungs, heart disease and cancer, and transport in plants.
- Organisation, digestion and enzymes
- Enzyme activity and the food tests
- The heart, blood vessels and blood
- The lungs and gas exchange
- Heart disease, risk factors and cancer
- Plant tissues and transport
- Health, lifestyle and body measurements
- Cancer: tumours, risk factors and data
All of Organisation: tissues, organs, digestion and circulation