Transport, Storage And Gas Exchange In Flowering Plants Flashcards
Autotroph
Organism that makes its own food
Metabolism
Sum of all chemical reactions in an organism
Transpiration
Loss of water vapour from aerial parts of plant by evaporation
Diffusion
The movement of molecules from a region of high concentration to a region of low concentration
Osmosis
The moment of water across a semi permeable membrane from an area of high water concentration to low concentration
Passive transport
Does not require energy
eg osmosis
Active transport
Does require energy
Why Plants need a transport system
To provide the materials needed for various plant metabolic processes:
Photosynthesis: CO2 taken in from atmosphere, water from roots
Respiration: 02 used from photosynthesis
Reproduction and growth
Materials transported by plants
Water
Minerals ( nitrates & phosphates by diffusion and active transport)
Carbon dioxide
Carbohydrates ( glucose from photosynthesis, transported through phloem, stored as starch in the leaf or used in respiration)@
Leaf adaptations for photosynthesis
Flat (large surface area)
Large number of chloroplasts present ( mostly on the palisade layer)
Contains stomata
Leaf structure
Stomata Epidermis Vascular bundle Ground tissue Guard cells
Stomata
What : small pores on underside of leaves
Location: undersides of leaves
Function: gas exchange- co2 in, o2 and water vapour out
Adaptations/features: large numbers= large surface area for gas exchange
Epidermis
Composition/derived from: dermal tissue
Function: protection
Vascular bundle
Composition: xylem + phloem
Function: transport of water, minerals and food
Ground tissue
Function: food storage, photosynthesis
Palisade layer: contains more chloroplasts so more photosynthesis occurs here as it is closer to sunlight
Guard cells
Function: control opening and closing of stomata
How: swell/ become turgid due to high concentration of water/guard cells open/ become flaccid/ shrink when water lost/ guard cells close
Sources of carbon dioxide
From the atmosphere, diffuse into stomata
Product of respiration
How intake of co2 is controlled
Stomata opening and closing
Day: OPEN (water vapour out and co2 in when photosynthesis is occurring)
Night: CLOSED ( stomata closed, reducing water loss and co2 intake, photosynthesis not occurring)
High levels of co2
Stomata close- no more needed for photosynthesis
Low levels of co2
Stomata open- more needed for photosynthesis
Why do the stomata close sometimes during the day?
If the plant has lost too much water by evaporation
If temperatures are too high
By closing stomata….
Plant reduces water loss
How water enters root hairs to vascular tissue
Water enters the root hair cells by osmosis - through a selectively permeable membrane
Cytoplasm of root hair cells has a higher solute concentration than the water in soil
Water moves from cell to cell by osmosis
Adaptations of root hairs
Walls only one cell thick
Large numbers=> large surface area for absorption
Methods of transport through roots
Osmosis -> from soil to root hair cells
Diffusion -> from root hair cells to root cells (across tissues)
How water reaches great heights
Root pressure
Transpiration
Root pressure
Build up of water in the root cells creates pressure pushing water upwards
Transpiration outline
Water evaporates from stomata and diffuses into atmosphere
As water diffuses from the leaf it pulls more water out of the leaf
Osmotic gradient created: lower water concentration in leaves
Water moves from xylem to leaf cells
Why control transpiration
Prevents wilting (high transpiration rate will cause plant to wilt)
How to control transpiration
Leaves have a waxy cuticle - water cannot pass through
Stomata location- lower surface area of the leaf where less evaporation occurs
Guard cells - control shape of stomata open and close
Movement of water through the xylem
How: cohension-tension model
What: explains movement of water against the force of gravity
Who: Henry Dixon and John Joly
Cohesion tension model
Cohesion- water molecules stick to each other due to hydrogen
Adhesion- water adheres to the walls of xylem
Cohesive forces stronger than adhesive forces
As each water molecule evaporates(or by transpiration) more water is pulled up through xylem(strong cohesion between water molecules and adhesion between water and walls)
Water in xylem vessels now under tension which ensures water movement - xylem stretches and becomes narrow
A continuous stream of water is now moving
This tension is great enough to pull water to great heights
Daylight
Stomata open: transpiration occurs
Nighttime
Transpiration stops : tension is released, xylem vessels return to normal width
Adaptation of xylem for transpiration
Lignified
Continuous and narrow lumen with no cell contents
Modified storage organs
Plant organs that are modified and used to store food as starch/sucrose/cellulose
Examples of modified storage organs
Modified root: tap root eg carrot
Modified stem: potato tuber
Modified leaf: tulip, onion (produce bulbs)
