What is photosynthesis?
Process by which plants make food (glucose) using sunlight and chlorophyll. Happens in leaves of all green plants. CO2 + Water —> Glucose + Oxygen
What are palisade cells?
At the top of a leaf, adapted for photosynthesis because packed with chloroplasts, big surface area, near to light.
How are leaves adapted to photosynthesis?
1 Large surface area
2 Chloroplasts near top of leaf (most light)
3 Upper epidermis is transparent to let more light thorough it
4 Waxy cuticle reduces water loss
What are guard cells?
Control the opening and closing of the stomata. If the plant has lots of water they go turgid and the stomata open. If little water they go flaccid and stomata close (no water can escape)
What is transpiration?
The loss of water from a plant (mainly through leaves)
What are four factors that affect rate of transpiration?
Wind speed, light intensity, temperature, humidity.
What are xylem tubes?
They carry water and mineral salts from the plant roots to the leaves
What are phloem tubes?
Carry food (sugars and amino acids) from leaves to other parts of the plants
What do the root hairs do?
Create large surface area for absorbing water and minerals from the soil. Water drawn in by osmosis (because higher concentration of water in soil).
What three factors affect the rate of photosynthesis?
Amount of light; amount of CO2; temperature.
What is a limiting factor?
Something which stops photosynthesis from happening any faster. In winter will be limited by temperature, at night will be limited by light.
How do you test a leaf for starch?
- Dunk in boiling water 2. Heat with ethanol to remove chlorophyll 3. Test with iodine (starch will turn it blue-black)
How can you show that chlorophyll is needed for photosynthesis?
Do starch test on variegated leaf (some green parts, some white). Starch only produced in green parts because they contain chlorophyll.
How can you show that CO2 is needed for photosynthesis?
Leave plant in sealed jar with soda lime (to absorb CO2) . Test to show that no starch has been produced (because no photosynthesis)
How can you show that light is needed for photosynthesis?
Grow plant in cupboard without light (but with CO2 and warmth). Test to show that no starch has been produced (because no photosynthesis)
How do you show rate of photosynthesis using pondweed?
Pondweed left to photosynthesise in test tube; oxygen produced is collected in capillary tube. Length of gas bubble is proportional to volume of oxygen produced
