Plant organisation Flashcards
Waxy cuticle
Reduces evaporation from the surface of the leaf
Helps prevent the leaf from drying out
Upper and lower epidermis
Protects surface of the leaf
Upper is transparent that allows light to pass through for photosynthesis
Lower epidermis has stomata - controls water vapour levels
Palisade cells
Packed full of chloroplasts, where photosynthesis occurs
As chlorophyll absorbs sunlight
Spongy mesophyll
Air spaces to allow carbon dioxide to diffuse from the stomata through the spongy mesophyll so it can reach palisade cells for photosynthesis
Allows oxygen to diffuse through the spongy mesophyll to the stomata
Stomata
Allows carbon dioxide to enter and oxygen to leave the leaf
Also controls amount of water vapour to pass out of the leaf by osmosis
As there’s a high concentration of water inside than outside leaf
Guard cells
Opens and closes stomata to control water vapour loss
Xylem
Made up of dead cells with lignin
Transports water and minerals from the roots to stem and leaf
Dissolved mineral ions (Mg+ ions) to make chlorophyll
Water for photosynthesis
Phloem
Transports products of photosynthesis to where it is needed ie sucrose and amino acids. This is translocation
Can be used for respiration
Store east starch
Adaptation: Large surface area
Absorbs more light
Adaptation: Network of veins
To support the leaf and transport water, mineral ions and sucrose
Adaptation: Thin
Shorter diffusion distance
Epidermal tissue
Made of epidermal cells at the top and bottom
Cover the leaf to protect the surface
Translocation
Movement of sugars through the phloem tissue
Meristem tissue
At growing tips such as shoots/roots
Contain stem cells that can differentiate into any different type of cell
Transpiration
When water vapour evaporated from surface of the leaves because the plant takes in too much water at a given time for photosynthesis to remove excess
Stages of transpiration stream
Water vapour in the palisade evaporate inside to be vapour Then diffuses through air spaces in spongy mesophyll
Out the leaf
Water in the xylem passes into the leaf to replace lost water
More water from soil into root hair cell up the xylem to the leaf
Why do we need transpiration?
Brings water to the leaf for photosynthesis
Transports dissolved magnesium ions in water to the leaf for minerals
Cools plant down in warm weather
How does temp affect transpiration?
Higher temp = higher rate of transpiration
Higher temp means evaporation is faster
How does humidity affect transpiration?
Dryer conditions = higher rate of transpiration
Evaporation quicker under dry conditions
As there is a higher concentration of water molecules in cell than in air = higher concentration gradient
How does the wind effect transpiration?
More wind = higher rate of transpiration
More wind removes water vapour
More water to evaporate
How does light intensity affect rate of transpiration?
More light = higher rate of transpiration
More light means more photosynthesis
Which causes the stomata to open and let CO2 in, meaning water vapour can pass out more
How does a stomata/guard cells work in high light conditions?
Guard cells swell and change shape to open stomata
CO2 can diffuse in for photosynthesis
How does a stomata/guard cell work in dryer/ hot conditions?
Guard cells change shape to close stomata
To reduce water loss through transpiration once enough cooling has happened
Saves water since it’s dry
However plant can’t photosynthesis
Use of glucose (c)?
Forms cellulose which strengthens plant cell wall
Use of glucose (s)?
Forms starch which is the storage form of glucose
Glucose is soluble in water and so will disrupt transport of water
Therefore converted into insoluble starch
Use of glucose (a)?
Join with nitrate ions to form amino acids
To synthesise proteins
