Studied by 10 peopleThe leaf is…
A plant organ
What does the waxy cuticle do?
Protective layer on the top of the leaf that prevents water from evaporating
What does the upper epidermis do?
Thin and transparent to allow light to enter the palisade mesophyll layer easily
What does the spongy mesophyll do?
Contains air spaces that increases the surface area to volume ratio for the diffusion of gases
What does the lower epidermis contain?
Guard cells and stomata
What do the guard cells do?
Absorbs and loses water to open and close the stomata to allow carbon dioxide to diffuse in and oxygen to diffuse out.
What does the stomata do?
It is where gas exchange takes place. Opens during the day and closes during the night. Evaporation occurs here as well. In most plant, higher concentration of stomata is found on the bottom side to reduce water loss.
What does the vascular bundle do?
Contains the xylem and phloem to transportsubstances to and from the leaf
What does the xylem do?
Transport water into the leaf for the mesophyll cells to use in photosynthesis and for transpiration in the stomata
What does the phloem do?
Transportssucrose and amino acids around the plant
What is the adaptation of large surface area in leaves?
Increases surface area for the diffusion of carbon dioxide and absorption of light for photosynthesis
What is the adaptation of being thin in leaves?
Allows carbon dioxide to diffuse into the palisade mesophyll cells more quickly
What is the adaptation of chlorophyll in leaves?
Absorbs light energy so that photosynthesis can take place
What is the adaptation of network of veins in leaves?
Allows transport of water from cells of the leaf and carbohydrates from the leaf for photosynthesis
What is the adaptation of stomata in leaves?
Allows carbon dioxide to diffuse into the cell and oxygen to diffuse out
What is the adaptation of epidermis being thin and transparent in leaves?
Allows more light to reach the palisade cells
What is the adaptation of a thin article made of wax in leaves?
To protect the leaf without blocking sunlight
What is the adaptation of a spongy layer in leaves?
Air spaces allow carbon dioxide to diffuse through the leaf, increasing the surface area
What is the adaptation of a palisade cell layer at the top of the leaf in leaves?
Maximises the absorption of light as it will hit the chloroplasts in the cells directly
What is the adaptation of vascular bundles in leaves?
Thick cell walls of tissue in the bundles to help support the stem and leaves
What process happens in the xylem?
What is the xylem’s direction of flow?
Transpiration stream
One way from roots to leaves (unidirectional)
What process happens in the phloem?
What is the phloem’s direction of flow?
Translocation
All directions (bidirectional)
What cells are in the xylem and how does it’s adaptation help?
Dead cells to help in efficient transport of water absorbed by roots to other parts of the plant. Resistance to water flow is low
What cells are in the phloem and how does it’s adaptation help?
Living cells are in the phloem and they transport substances in the phloem (which require energy)
What features do xylem cells have?
Lignin- strengthen cell wall and waterproof elongated cells
No end walls- successive cells make a long tube for easy transport
Dead- means the tube is hollow, so resistance to water flow is low
What do root hair cells do?
Absorb water from the soil via osmosis. Mineral ions are taken up via active transport.
What features do root hair cells have?
Long projections- they stick out from the cells and into the soil to increase surface area over which water and mineral ions can be absorbed
Mitochondria- ensure there is enough energy for active transport of minerals up the stem
What happens if there is abundant water in the stomata?
When there is abundant water, the plant can afford to lose some, so it opens the stomata to allow gases for photosynthesis to move freely in and out of the leaf.
What happens when there is scarce water in the stomata?
The stomata closes in order to prevent further water loss, which is achieved by guard cells returning to a limp state.
What happens to the stomata during the time of day?
At night, the stomata closes because in the absence of sunlight, carbon dioxide is not required for photosynthesis. The only objective is to prevent water loss.
What factors increase the rate of transpiration?
Increase temperature, decreased humidity, increased light intensity, increased air flow
Why doesn’t increased humidity increase the rate of transpiration?
Increased humidity increases the amount of water in the air, making it harder for water to evaporate.
What do the holes in the end wall of the phloem allow?
Allow cell sap (which stores sugars, salts and amino acids) to pass through the cells
Photosynthesis is a ____ reaction.
Endothermic
What is the role of leaves?
Help plants to photosynthesise and absorb light
How are leaves adapted for photosynthesis?
Broad- large surface area for light absorption
Thin- short diffusion distances for gases
Vascular bundles- to transport reactants and products
Word equation for photosynthesis
Carbon dioxide + water —> glucose + oxygen
Symbol equation for photosynthesis
6CO2 + 6H2O → C6H12O6 + 6O2
What are the uses of glucose in photosynthesis?
Used in the process of respiration
Converted into insoluble starch for storage
Used to produce fat or oil for storage
Used to produce cellulose to strength the cell walls
Used to produce amino acids for protein synthesis
What are the factors affecting the rate of photosynthesis?
Temperature, light intensity, carbon dioxide concentration, amount of chlorophyll
Photosynthesis is controlled by ______.
Enzymes
The higher the light intensity, ________. (factors affecting rate of photosynthesis)
The more light can be absorbed by the chlorophyll in the chloroplasts.
Chlorophyll absorbs light to transfer ___________. (factors affecting the rate of photosynthesis)
The energy required for photosynthesis.
The more chlorophyll that is present, _____________. (factors affecting the rate of photosynthesis)
The more light is absorbed
Dependant variable
The variable that is measured for each change
Independent variable
The variable that is changed
Control variable
The variable that stays the same
What is the transpiration stream?
The movement of water from the roots to the leaves
What are the three stage of transpiration?
Diffusion out of the spongy mesophyll cells
Evaporation of water from the surface of these cells into the air spaces
Diffusion out of the stomata into the atmosphere
What are the factors affecting the rate of transpiration?
Light intensity, temperature, wind speed, humidity
Note
Flashcard