Transport in Plants, 3.3 Flashcards
How does a plant get water and minerals?
Through the roots
How does a plant get sugars?
Photosynthesis
What are vascular bundles?
Groups of vascular tissues
What is the role of the xylem?
Transports water and dissolve minerals. Move upwards.
What is the role of the phloem?
Transports products of photosynthesis all over the plant.
What are the structures found in the roots? Draw a diagram.
Endodermis. Epidermis. Phloem. Xylem. Root hair.
What are the structures found in the stem? Draw a diagram.
Epidermis. Phloem. Xylem. Layer of cambium between xylem and phloem.
What are the structures in the leaf? Draw a diagram..
Cuticle. Upper epidermis. Spongy mesophyll layer. Phloem. Xylem. Guard Cell. Stomata.
How does lignin affect the xylem?
Lignin impregnates the walls - waterproof and strong. Lignification kills the cells.
How are bordered pits formed?
In some places lignification is not complete leaves gaps. Allow water to leave.
How does the killing of the cells help the structure of the xylem?
Decay leaves long columns with no content - continuous
Why are xylem vessels able to carry water?
- Cell walls overlap - continuous
- Tubes are narrow - water column doesn’t break
- Bordered pits allow water to ‘leak’ through
What are the two components of the phloem?
Sieve tube elements and companion cells..
Describe the structure of sieve tube elements.
Elongated. Line up forming sieve tubes. No nucleus. Ends are perforated (sieve plates) allow movement.
Describe the structure of companion cells.
Between sieve tube elements. Large nucleus. Dense cytoplasm. Numerous mitochondria.
What is the function of a companion cell?
Carries out metabolic processes - needs lots of ATP
What is a gap in the cell wall where the cytoplasm joined called?
Plasmodesmata
How permeable is cellulose?
Fully permeable
Describe the Apoplast pathway
Water passes through space in or between cells. Doesn’t pass through the membrane. Stops at endodermis - casparian strip
Describe the process of the symplast pathway.
Water enters the cell through the plasma membrane. Passes through plasmodesmata.
Describe the Vacuolar Pathway
Not confined to cytoplasm - move through vacuole
Why is the water potential in plant cells always negative?
Has dissolved solutes in it
How does water move into the roots from the soil?
Roots take in ions by active transport - lowers water potential. Water moves by osmosis into cells - until its turgid..
How does water leave?
Evaporates through the leaves
What is transpiration?
The loss of water vapour through stomata
What are the stages of water moving through a plant?
- Water enters the leaf from the xylem
- Water evaporates
- Water vapour moves by diffusion through stomata
How does light intensity affect transpiration?
Light causes. Stomata to open. Let’s water vapour diffuse out. Increases rate.
How does temperature affect transpiration?
High temperature increases kinetic energy. Decrease in vapour water potential near stomata. Rate increases.
How does humidity affect transpiration?
More water vapour in the air around the stomata. Smaller gradient. Decreases rate.
How does wind affect the rate transpiration?
Moves humid air away from the plant so a bigger water vapour potential. Increases rate.
How does water water availability affect transpiration?
Insufficient water causes stomata to close. Cells not turgid..
How do we use a potometer to measure transpiration?
Water drawn through a straw wads to a leafy shoot. Distance an air bubble tracks in the capillary tube over a set time. Place apparatus in different conditions.
What is the role of root hair cells?
Absorb mineral ions and water from the soil.
What is the role of the Casparian strip?
Block the apoplast pathway. Forces water through the symplast pathway.
How does root pressure cause transpiration?
Pressure in root medulla builds up. Forces water up the xylem.
How does the transpiration pull help move water up the xylem?
Loss of water drags water up the xylem. Whole column gets pulled up. Cohesion and adhesion.
What is cohesion?
Water molecules attract to each other
What is adhesion?
Water molecules attracted to the walls of the xylem.
What is the source?
Part of the plant that loads materials eg leaves (sucrose)
What is the sink?
Part of the plant that removes materials eg meristem or roots (sucrose)
Describe the stages of active loading?
- Companion cell actively pumps H+ out - produces conc. gradient
- H+ ions diffuse back if they’re carrying sucrose
- Creates a high sucrose conc. in the cells
- Sucrose then diffuses into sieve tube
How do assimilates move through the phloem?
Through sap. Caused by hydrostatic pressure.
What happens when sucrose concentration is high?
Water enters via osmosis increasingly hydrostatic pressure
What is an xerophyte?
Plants adapted to liv in arid conditions (cacti and marram grass)
Name some adaptations of a xerophyte
Hairy leaves. ‘Sunken’ stomata. Rolled up leaves. Widespread roots. Succulent plants. Waxy cuticle. Spikes.
What is an hydrophyte?
Plants that live in water/wet conditions (water lilies)
What are some adaptations of a hydrophyte?
Large air spaces so it floats. Stomata on the upper side.
