3.3 Transport in plants Flashcards
What travels in the xylem?
water and soluble minerals
What travels in the phloem?
assimilates, e.g sugars
What are dicotyledonous plants?
Often flowering, have two seed leaves
Where are the xylem and phloem stored in dicotyledonous plants?
In vascular bundles, often with other types of tissues such as collenchyma and sclerenchyma
What is the sheath around the vascular bundle called?
Endodermis
What cells do the endodermis contain?
A layer of meristem cells
What is the layer of meristem cells in the root endodermis called?
The pericycle
State the layers of the vascular bundle in the stem cross section
Xylem in the middle, phloem on the outside
What is the role of lignin in the xylem?
strengthens the walls and keeps them open
What 3 patterns are there of lignification in the xylem?
spiral, annular (rings) or reticular (network of broken rings)
What are the gaps in xylem called?
bordered pits
What are the adaptations of the xylem?
- one long column
- narrow so water column doesn’t break and capillary action can be effective
- bordered pits allow water movement out
- lignin patterns allow flexibility
What is the barrier between the sieve elements called?
sieve plates
What organelle do companion cells contain a lot of?
mitochondria to produce ATP
What are gaps in the cell walls called?
plasmodesmata
What is the pathway that only goes through the cell walls?
Apoplast
What is the pathway that goes through the cytoplasm but not the vacuole?
Symplast
What is the pathway that goes through the cytoplasm and vacuole?
Vacuolar
a whole page on movement
more ions = lower water potential
flows from high to low
Where is water lost during transpiration?
stomata and waxy cuticle
What is the typical transpiration pathway?
xylem to spongy mesophyll to diffuse out of stomata
Why is transpiration important?
helps to keep the flow of water which maintains plant health by transporting water and minerals around the plant
What 4 factors affect transpiration rate?
- light intensity (more = more bc stomata open for photosynthesis)
- temperature (more = more because more kinetic energy)
- humidity (more = less)
- wind (more = more)
- water availability (less = less)
What measures are taken to ensure the potometer is set up correctly?
- set up underwater to prevent air bubbles
- ensure shoot is healthy
- cut stem underwater to prevent air in the xylem
- cut stem at an angle for a large SA:V
- dry the leaves for maximum diffusion
What is the equation for rate of transpiration?
pi x r^2 x Length
What blocks the water in the apoplast pathway?
the casparian strip
What happens when the water from the apoplast pathway is pushed into the cell?
transporter proteins attach to dissolved minerals to be transported into the medulla and xylem
what happens when ions move into the medulla and xylem?
lower water potential in the xylem forces water in via osmosis
What are the 3 ways water moves up the stem?
- root pressure (water pressure in the root forces it up the xylem)
- transpiration pull (cohesion in the water column called cohesion-tension theory)
- capillary action (water attracted to sides of xylem called adhesion)
What is a xerophyte (plus examples)?
plant adapted to arid conditions (e.g cacti and marram grass)
what is a hydrophyte (plus examples)?
adapted to live in water (e.g water lillies)
What is translocation?
the transport of assimilates around the plant
What is the process at the source?
hydrogen ions (H+) go from companion cell to leaf cell to actively transport sucrose in cotransport into sieve tube element
What happens when the hydrogen ions with sucrose enter the phloem?
water goes down the water potential into the phloem, pressure builds up so moves to a low hydrostatic pressure .
sucrose moves into sink followed by water
