Chapter 3.3 Transport In Plants Flashcards
Why do plants need a transport system ?
2
1- to move water and Mineral ions from roots to leaves
2-sugar from leaves to rest of plant
3-support
4-they respire
Why does oxygen not need to be transported ?
3
- it can enter by diffusion
- plants aren’t active
- demand is low
What’s diffusion ?
3
- result of random motion of particles
- down concentration gradient
- may move in different directions
What’s mass flow ?
2
- particles move together
- down pressure or temperature gradient
What is the distribution of Xylem in -root -stem -leaf (3)
- root = centre of root
- stem = inner vascular bundle
- leaf= upper part of vascular bundle
What’s the distribution of phloem in -root -stem -leaf (3)
- root : near centre around Xylem
- stem : middle of vascular bundle
- leaf : lower part of vascular bundle
What are the main features of Xylem ?
4
1-thick lignified walls (dead)( withstand water pressure / water proof )
2-empty lumen allows easy flow
3-long straight column ( no end cell wall )
4-bordered pits to allow water to pass between vessels
What are the main feature of phloem?
4
1- living cells
2-connected via sieve tubes
3-sieve tube elements = no nucleus and thin layer of cytoplasm ( no metabolic functions )
4- companion cells - carry out all function for tube and itself ( lots of mitochondria )
What’s the apoplast pathway ?
1
Apoplast pathway - water moves through spaces in cell walls
What’s the Symplast pathway ?
1
- water movement through cytoplasm
What’s the vacuolar pathway ?
1
Water moves Through cytoplasm and vacuoles
What’s water potential.
1
Tendency of water molecules to move from one place to anther
What’s the route water takes up the plant ?
3
- Xylem via osmosis
- apoplast pathway (between cell walls)
- evaporates out of leaf via open stomata.
What is the importance of water transport.
4
- transports mineral ions up plant
- maintains Turgidity
- supplies water for growth
- supplies water that can keep plant cool when it evaporates
What environmental effects effect transpiration.
5
- light intensity
- Temp
- relative humidity
- air movement ( wind )
- water Availability
What does high light intensity do to transpiration rate ?
1
INCREASE
Stomata opennn
High temp - transpiration rate?
1
Increases
Stomata opennnn
HIGH humidity ? Transpiration rate?
2
- reduces transpiration rate Because water potential gradient is less steep
Windy ? Transpiration rate ?
2
- more wind ( takes away water vapour so gradient is steeeep)
how’s Transpiration rate calculated ?
- VOLUME / TIME
What’s adhesion
1
Attraction of water molecules to walls of Xylem
What’s cohesion
2
-attraction between water molecules caused by H bonding !
How does water enter plant ?
-3
- root hair cells
- osmosis
- apoplast pathway
What does the casparian strip do ?
2
- block apoplast pathway
- water , dissolved mineral ions have to pass through cytoplasm
What are the 3 processes that help water move up the stem ?
3
- transpiration pull
- root pressure
- capillary action
What’s root pressure?
3
- active transport moves minerals into medulla and Xylem( low water potential)
-pressure rises in medulla (packing tissue)
Water moves from high —> low pressure
-water is forced into Xylem = pushes water a few meters
What’s the transpiration pull ?
4
- cohesion keep water molecules in one long chain
- molecules lost at top
- whirl column moves up
- PULL IS CREATED BY TENSION ( Xylem is strengthened by lignin o support this )
What’s capillary action ?
2
- ADHESION attracts water molecules to side of Xylem vessel and pull water up
How does water leave he leaf ?
- air spaces
- stomata
- evaporates
What’s a xerophyte ?
1
Plant adapted to living in DRY conditions
What’s a hydrophyte ?
1
Plant adapted to living in water or wet conditions !
Name some adaptations of Xerophytes …
6
- reduce water loss :
1-hairs on epidermis trap moist air
2-roll leaves - trap air
3-thick waxy cuticle layer ( water can’t move through it )
4-cacti = spines SA REDUCED FOR WATER LOSS
5-Closure if stomata
Name some adaptations of hydrophytes
5
1-Air spaces ( store O2 & float ) 2-stomata only present on top surface 3-flexible leaves and stems 4- supported by water so no rigid stem 5- HYDRATHODES -produce water droplets which may evaporate from leaf for transpiration
What’s a source ?
1
Part of plant that loads material into transport system
What’s a sink ?
1
Materials are removed from transport system
What’s translocation ?
- transport of assimilates through plant
What’s the mass flow hypothesis of phloem transport at SOURCE ?
(3)
1- AT SOURCE
solutes diffuse into phloem tube ( lower water potential)
2-water then follows via Osmosis ( to phloem tube )
3-at the SOURCE there is Highe pressure in phloem and Low water potential !
What happens at the SINK in mass flow hypothesis ?
4
1- solutes move to sink via active transport or diffusion depending on concentration
2-water potential in phloem rises
3-water leaves phloem to XYLEM
= HIGH WATER POTENTIAL AND LOW PRESSURE
What does the mass flow in phloem create ?
2
- PRESSURE GRADIENT !
High to low ( from source to sink ) - pressure flow
What’s happens in active loading in companion cells ?
7
1- H+ ions move out via active transport
2-high concentration H+ ion in photosynthesising cell
3-H+ move back to Companion cell via facilitated diffusion ! ( H+ brings sucrose )
4-in the companion cell sucrose levels rise !
5-then sucrose diffuse into phloem ( high to low conc)
6-the water potential in lowered
7-water moves into phloem via OSMOSIS
Explain why large multicellular plants need a transport system ?
(2)
- too small sa:v so diffusion is too small
- transport system needed to transport waste / nutrients
What organelles yield the pigments present in the leaf ?
1
- chloroplast
