Plant Tranport Flashcards
1
Q
lTranslocation
A
- H+ pumped out of CC using ATP by AT
- H+ gradient buildup in leaf enter CW/apoplast via FD
- Sucrose enter companion cell by co transport VIA cotransporter w protons down conc gradient
- BY facilitated diffusion
- Sucrose ENTERS against conc gradient
- Sucrose diffuses into STE via plasmodesmata + loaded
- Sucrose lowers Ψ
- Water enters xylem into sieve tube VIA osmosis
- INCREASED HYDROSTATIC PRESSURE
- Root/sink sucrose UNLOADED by hydrolysis —> glucose + fructose
- Ψ Increases
Water by osmosis –> xylem - DECREASED hydrostatic pressure
- MF = HHP to LHP
2
Q
Transpiration
A
- Water moves from high Ψ to low Ψ
- apoplast pathway water moves from CW:CW Via mass flow
- symplast pathway water moves from cytoplasm + plasmodesmata VIA osmosis
- Water saturates mesophyll CW
- EVPA from MEsophyll CW into air spaces = water vapor
- WV diffuses out VIA stomata to atmosphere
3
Q
Water from soil to xylem
A
- VIA RHC - increases SA via osmosis through cortex
- apoplast pathway via CW + Mass flow
- Symplast pathway via Cytoplasm + plasmodesmata
- AT ENDODERMIS/casparian strip apoplast BLOCKED by waterproof suberin
- All water goes from A to S at ENDODERMIS
- water goes through passage cells INTO xylem w/ lower Ψ VIA OSMOSIS down Ψ gradient through ppm
- XYLEM low Ψ = small area + accumulation of nitrate ions
4
Q
Xerophytic adaptation
A
- sunken stomata
- trichomes
- rolled
- high humidity + retains moisture to reduce diffusion
- small leaves –> reduced SA for transpiration
- thick leaves + reduces SA:V
- Thick waxy cuticle = decreases permeability
- Reflective layer/few stomata = reduced diffuion of water
5
Q
role of endodermis in water uptake at xylem
A
- AT of nitrates using ATP
- Lowers Ψ at bottom of xylem
- water in symplast enters passage cells
- water enters AP + osmosis
- high ROOT pressure at bottom of xylem
- high HP at bottom end
- low HP at top due to transpiration
- tension + cohesion/adhesion
- MASS FLOW
6
Q
explain why water loss in unavoidab;e
A
- stomata open for gasesous exchange
- for photostnthesis to gain energy
- some water lost through cuticle
7
Q
Describe features of xylem enabling steam to pass from heated end of stem to cut end
A
- continous/hollow
- no cytoplasm
- lignified
- pits in wall
8
Q
SIEVE TUBE ADAPTAIONS
A
- end walls form sieve plates = support to prevent phloem ST collapsing ++ phloem seal up rapidly by clotting if damaged
- sieve plates = hold walls of STE + prevent bursting
- sieve pores = allow easy flow of water
- no nucleus/few organelles = little reisstnac to flow of water
- plasmodesmata = easy flow to/from CC
- LIving cells need ATP
- TRanslocation
9
Q
XYLEM VESSEL ELEMEMT
A
- lignified cell walls= waterproof polar subst to withstand high HP to prevent collapse, imperable to water, adhesion for transpiration stream
- no end plates= MF of water, no resistance to flow of water
- no cytoplasm, organelles= reduced resistance to flow of water + continius column of water
- pits in wall = lateral movement of water, allows continual flow in case of airbubbles in vessel
- small diamater= prevents water column bursting + capillary action assited
10
Q
phloem tube viewed longtidunally
A
- sieve plates
- sieve pores
- less cytoplasm
- no nucles
- thin wall
11
Q
suggets why tomataos arent sweet
A
- sucrose used in respiration + stored as STARCH
- used to make cellulose
- converted into lipid/protein
12
Q
explain the term transpiration
A
- loss of water vapor from leaves
13
Q
companion cell under EM
A
- many large mitochondria
- plasmodesmata
- many ribosomes
- many plasma proteins in CSM
14
Q
Function of companion cells in transport in phloem
A
- movement of sucrose from cells to roots
- move sucrose into/out sieve tube
- pump H+ into cell wall
- provides ATP for sieve tubes
15
Q
explain how H+ bonding occurs between 2 water mol
A
- cohesion between water mol = column of water
- H+ adhesion of polar water mol to hydrophilic cellulose cell wall/polar = adhesion
- adhesion supports column. of water pulled upwards by transpiration/pull
