Transport In Plants Flashcards
Name the main tissues dicotyledonous plants (8)
Epidermis
Cortex; collenchyma and parenchyma
Vascular bundle; sclerenchyma fibres, phloem, cambium, xylem
Parenchyma (pith)
Parenchyma (3)
Parenchyma cells, forms pith
Storage of glucose molecules
Secretion of carbohydrates
Epidermis (4)
Outer layer of cell
Guard cells; form stomata that regulate water intake
Waxy cuticle; reduces water loss
Could contain trichomes; increases surface area
Xylem (4)
Transports water and minerals(and amino acids) UP the stem from roots
Dead and hollow cells
Lignified cell walls for support
Bordered pits that allow water to pass in adjacent vessels
Tracheids (3)
Feature of Xylem tissue; cells tapered at the end
- thicker and narrower than vessel elements
- contains pits
Vessel elements (3)
- feature of xylem tissue
- wider and thinner walls than trachieds
- perforated ends arranged in chains allow continuous flow of water
Phloem (4)
Tissue located in vascular bundle
- Alive and functioning cells; companion cells, sieve tube elements and drive plates
- perforated cross walls
- plasmodesmata between companion cells and drive tube elements
Companion cells (3)
- part of phloem tissue
- contains organelles sieve tubes elements do not have
- contains plasmodesmata that comes to contact with the cytoplasm
Sieve tubes
- chain of sieve tube elements
- sieve plates with perforated walls that allow continuous water flow
- sieve tube elements have no nucleus, ribosome and Golgi apparatus
Symplast pathway
- water does not enter vacuole
- goes through plasmodesmata and cytoplasm
Endodermis (3)
In root cells; located in the middle
- surrounds vascular bundle
- contains casparian strip that blocks apoplast route
Translocation
- transport of organic products from source to sink
- via mass flow
Describe 1st step of translocation (3)
- Phloem loaded at the source (eg leaves and stem)
- WP in driver tube cells decreases as solute concentration increases
- therefore water is drawn form other cells via osmosis
Describe second step of translocation
- As sieve tube cells draw water, the HP increases and pushes sap to the sink
3rd step of translocation (4)
- Organic material unloaded at the sink; decreases SC and increases WP
- water is lost and moves out through osmosis into xylem and up transpiration stream
- Water in transpiration stream is recycled again for the first step of translocation
Describe the transportation of water from root to leaves (5)
1- Water moves into roots via osmosis= high HP at the bottom on xylem
2- water pulled up stem due to cohesive and adhesive forces. As well as capillary action
- Water travels through symplast or apoplast but joins at endodermis when the casparian strip arises
- ) transpiration occurs at the leaves cause sling low HP at top of xylem
Therefore this is bulk flow as water moves from high HP at bottom of xylem to low HP at the top of xylem
Casparian strip
Waterproof band in radial and transverse walls of endorser is
Prevents apoplast pathway
Blocks passive move my of materials into Steele
Xerophytes
Plants added to dry habitats
Trichome adaption in xerophytes
Abundant:
Increases surface area for osmosis
Reduces air movement which builds up more humid air, leaving a less steep water vapour gradient to prevent transpiration.
Stomata adaptation on Xerophytes
Reduced number of stomata: Reduces loss of water via transpiration
Sunken stomata: Reduces are movement. This creates a microclimate that increases water vapour. A less steep water vapour gradient is made, which reduces the rate of transpiration.
Leave adaption of xerophytes
Sometimes leaves are curled: Reduces surface area so less water is lost. Also allows more humid air to form.
Thick waxy cuticle; prevents evaporation of water.
Reduced number of leaves: Less surface area for leaves so less water is lost in transpiration.
Hydrophytes
Plants adapted to cope with high water availability
Contains Sclerid; filled with lignin, prevents rolling of leaves
Contains aerenchyma; allow buoyancy
Trichomes adaptation of hydrophytes
- very scarce; increases air movement to increase rate of transpiration
Succulents
Present in some xerophytes:
Specialised parenchyma capable of storing large amounts of water.
Leave adaptation of hydrophytes (2)
- Large SA increases rate of gaseous exchange and water loss
- waxy cuticle; thin to prevent water evaporation
Root adaptation on some hydrophytes
- aerated (pneumatophores)
- increases gaseous exchange
Apoplast
Water pathway across root tissue between and through adjoining cell walls
How is transpiration measured?
- Potometer
- Measures the water uptake of a plant
Factors that affect Transpiration? (8)
- Temperature:
Increases kinetic energy of water molecules which increases the rate of transpiration.
Decreases humidity which also increases the rate. - Humidity:
Increased humidity decreases the rate as there is a less steeper concentration gradient between water inside and outside cell. - Air movement:
Increased air movement increases the rate as it dries accumulation of water vapour around the stomata. - Light Intensity:
Increases as the light increases because more photosynthesis will occur which opens the stomata (when CO2 enters) and causes water vapour to be released.
Describe the coupled transport of sucrose. (3)
- H+ ions are pumped out companion cells using ATP
- The ions always move down a concentration gradient
- When the H+ ions diffuse back into the cell, it is coupled transport with sucrose using a protein
Evidence to support couple transport?
- Companion cells have a much higher pH that the surrounding cells which shows how a gradient of H+ ions is maintained.
- Companion cells have a high amount of mitochondria due ATP being need.
- Companion cells also have a folded membrane for greater surface area to increase sucrose transported
Features of xylem that allow continuous water flow (4)
- conjoined from end to end
- lignified walls
- pits in the walls
- hollow vessels
Transpiration (2)
- evaporation of water vapour
- via the stomata
Transpiration stream (2)
- movement of water using adhesive and cohesive properties in the xylem vessels
- from the roots to the leaves
Root adaptations in xerophytes.
Very long tap roots:
Allows greater surface area to seek out more water in the soil.
