vascular plant transport Flashcards
___ encourage water to move
forces
forces can include
- Differences in solute concentration (tonicity)
- Differences in physical pressure
- Gravity
water potential
energy for moving water
bigger differences in water potential value =
more energy available to move water
water potential can have difference sources of energy differences such as
Tonicity, pressure, or gravity
water potential can have difference sources of different locations of energy differences such as
- Soil, roots, stem, leaf, atmosphere
water moves from
higher energy to lower energy
water is required in… for…
leaves for photosynthesis
water is available in …
roots (absorbed form soil)
transpiration
water evaporation from leaves
transpiration involves water moving through plant from
soil to atmosphere
water energy:
soil > root > stem > leaf > atmosphere
water flow
soil –> root –> stem –> leaf –> atmosphere
Always moves DOWN gradient
water flows through
xylem: tubes that conduct water
roots have higher… than…
solute concentration than soil
there is lower water energy in roots than soil, so…
water wants to go into the roots (water flows down energy gradient into roots)
root pressure
water entering pushes previous water upward
atmosphere has low water content and energy… which does what?
atmosphere provides energy for transpiration where water exits leaves via evaporation
stem cohesion
water molecules attract each other
stem adhesion
water molecules are attracted to surfaces
water lost via… pulls…
water lost via transportation pulls water UP stem via cohesion
adhesion to…. helps…
adhesion to xylem walls helps hold water against gravity making an unbroken chain of water from leaf to root
when a stem is injured…
the chain of water may be broken
embolism
air bubbles that form in xylem due to broken chain of water
plants wilt because
because water is lost from the leaves but cannot be replaced with water from the roots
why is it a problem if ice forms in plants?
- Ice in xylem forms embolisms
- Ice outside cells pulls water out of the cells
- Ice crystals can form in the cell and puncture the cell membrane
___ drives most water flow
transpiration
roots contribute a little flow with
root pressure
___ in roots provide energy
solutes
leaf mesophyll cells use energy to ..
absorb water for photosynthesis
most water must transpire to provide…
energy to pull more water up
managing transcription: transpiration rate
level of transpiration isn’t constant
managing transcription atmospheric conditions change
Warmer atmosphere conditions provides more energy
Drier atmosphere provides more energy
leaves control transpiration rate via
stomata
stomata is usually located on bottom of leaf
- Avoid energy added by sunlight
- Reduces transpiration rate
guard cells can open or close stomata:
- Cells fill with water to open
- More k+ ions in cells pulls water in
why does stomata open during day:
- Water is needed for photosynthesis
- CO2 needs to flow in through stomata
why does stomata close at night?
- No photosynthesis
- Conserves water in the soil
stomata opens if ___ is low in leaf
CO2 (needed for photosynthesis)
stomata close if _____ is present
abscisic acid
abscisic acid is released by…
roots and leaves that don’t have enough water
shuts down transpiration to conserve water
epiphytes
waxy leaves that reduce transpiration
floating water plants continually transpire :
- stomata on top of leaves
- stomata cannot be closed (they are permanently open)
translocation
movement of sugar rich sap
sugary sap flows through
phloem
sugar flows from
sugar sources to sugar sinks
sugar source
creates sugar via photosynthesis
* releases stored sugar via starch breakdown
sugar sink
consumes sugar for energy or growth
* stores sugar
sieve tube elects make up
phloem tubes
sieve tube elements carry
phloem sap (up to 30% sugar)
companion cells
- assist sieve tube cells
- actively transport sugar into sap
phloem sap flow is driven by
PHYSICAL pressure
sugar is loaded into phloem at
source
water follows sugar via
osmosis
water flow increases
physical pressure
__ removes sugar
sink