AP Bio Plant Transport(KFogler)

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Transport in Plants

AP Biology

2006-2007

Transport in plants H2O & minerals

transport in xylem transpiration evaporation, adhesion & cohesion negative pressure

Sugars

transport in phloem bulk flow Calvin cycle in leaves loads sucrose into phloem positive pressure

Gas exchange

Why does over-watering kill a plant?

photosynthesis CO2 in; O2 out stomates

respiration

O2 in; CO2 out AP Biology roots exchange gases within air spaces in soil

Ascent of xylem fluidTranspiration pull generated by leaf

AP Biology

Water & mineral absorption Water absorption from soilosmosis aquaporins

Mineral absorptionactive transport proton pumps

active transport of

H+

aquaporin root hair

AP Biology proton pumps

H2O

Mineral absorption Proton pumps

active transport of H+ ions out of cell chemiosmosis H+ gradient

creates membrane potential difference in charge drives cation uptake

creates gradient cotransport of other solutes against their gradient

AP Biology

Water flow through root

Porous cell wallwater can flow through cell wall route & not enter cells plant needs to force water into cells

Casparian strip

AP Biology

Controlling the route of water in root

Endodermis

cell layer surrounding vascular cylinder of root lined with impermeable Casparian strip forces fluid through selective cell membrane filtered & forced into xylem cells

Aaaah StructureFunction yet again!

AP Biology

Root anatomy

dicot

monocot

AP Biology

Mycorrhizae increase absorption Symbiotic relationship between fungi & plant

symbiotic fungi greatly increases surface area for absorption of water & minerals increases volume of soil reached by plant increases transport to host plant

AP Biology

Mycorrhizae

AP Biology

Transport of sugars in phloem Loading of sucrose into phloemflow through cells via plasmodesmata proton pumps

cotransport of sucrose into cells down proton gradient

AP Biology

Pressure flow in phloem Mass flow hypothesis

source to sink flow direction of transport in phloem is dependent on plants needscan flow 1m/hr

phloem loading active transport of sucrose into phloem increased sucrose concentration decreases H2O potential

water flows in from xylem cells increase in pressure due to increase in H2O causes flowOn a plant Whats a sourceWhats a sink?

AP Biology

Experimentation Testing pressure flowhypothesis

using aphids to measure sap flow & sugar concentration along plant stem

AP Biology

Maple sugaring

AP Biology

Control of StomatesGuard cell

Epidermal cell Nucleus K+ H2O K+ H2O

Chloroplasts

Uptake of K+ ionsby guard cells

proton pumps water enters by osmosis guard cells become turgid

H2O K+

H2O K+

H2O K+

H2O K+

K+ H2O

K+ H2O

Loss of

ions by guard cellswater leaves by osmosis H2O K+ guard cells become flaccid

K+

Thickened inner cell wall (rigid)

H2O K+ Stoma open water moves into guard cells

H2O K+ Stoma closed water moves out of guard cells

H2O K+

AP Biology

Control of transpiration Balancing stomate function

always a compromise between photosynthesis & transpiration leaf may transpire more than its weight in water in a daythis loss must be balanced with plants need for CO2 for photosynthesis

AP Biology

Dont get mad Get answers!! Ask Questions!

AP Biology

2006-2007