Download Ch 32 uptake

Chapter 32 Plant nutrition and
transport
Review/Overview
• http://highered.mcgrawhill.com/sites/9834092339/student_view0/ch
apter38/animation_-_water_uptake.html
• http://www.sciencemag.org/site/feature/misc
/webfeat/vis2005/show/transpiration.swf
Transport Summary
1- uptake and loss of water
and solutes by individual
cells (root cells)
2- short-distance transport
from cell to cell (sugar
loading from leaves to
phloem)
3- long-distance transport of
sap within xylem and
phloem in whole plant
Whole Plant Transport
1- Roots absorb water and dissolved
minerals from soil
2- Water and minerals are transported
upward from roots to shoots as
xylem sap
3- Transpiration, the loss of water from
leaves, creates a force that pulls
xylem sap upwards
4- Leaves exchange CO2 and O2
through stomata
5- Sugar is produced by
photosynthesis in leaves
6- Sugar is transported as phloem sap
to roots and other parts of plant
7- Roots exchange gases with air
spaces of soil (supports cellular
respiration in roots)
Cellular Transport
Water transport
 Osmosis
 Water moves from high to
low water potential
 Plasmolysis (cell loses
water plasma membrane
pulls away)
 Turgor pressure (influx of
water due to osmosis)
Transport within tissues/organs
 Pathway is from soil thru
epidermis, cortex, and
then into xylem.
 Blue arrows represent
intracellular pathway thru
plasmodesmata.
 Red arrow represents
extracellular route.
Transport stopped by
Casparian strip, where
water and ions must pass
thru endodermal cells.
Transport of Xylem Sap
 Transpiration: loss of
water vapor from leaves
pulls water from roots
(transpirational pull);
cohesion and adhesion of
water – transpirationcohesion-tension
mechanism.
 Root pressure: at night
(low transpiration), roots
cells continue to pump
minerals into xylem; this
generates pressure,
pushing water upwards.
Guard cells control transpiration
 Guard cells open when they gain potassium.
 Guard cells close when they lose potassium.
Phloem Transport
 Translocation:
food/phloem
transport
 Sugar source:
sugar production
organ (mature
leaves)
 Sugar sink:
sugar storage
organ (growing
roots, tips,
stems, fruit)
Pressure flow mechanism
1. Sugar is loaded into phloem.
2. Water enters by osmosis.
3. Sugar departs phloem.
4. Water depart the phloem.
Allows for flow of sugars from source to sink.
Pressure flow animations
• http://bcs.whfreeman.com/thelifewire/conten
t/chp36/36020.html
• http://academic.kellogg.edu/herbrandsonc/bi
o111/animations/0032.swf
Plant nutrients
 Macronutrients – C, H, N, O, P, S, and K,
Ca, and Mg.
 Micronutrients – Fe, Ca
 The advent of man made fertilizers made it
possible to sustain large populations on
Earth.
Plant nutrition and symbiosis
Nitrogen fixation
 Bacteria in the soil convert nitrogen into
ammonia = nitrogen fixation.
 Nitrifying bacteria convert ammonia into
nitrate (NO3-) a form of nitrogen that plants
take up.
Plant nutrition and symbiosis
Mycorrhiza and bacteria
 Symbiotic relationship between fungi and
plants.
 Mycorrhiza is more efficient at absorbing
nutrients (phosphate) and water than
plant roots.
 Nodules are symbiotic relationship
between members of the pea family and
a nitrogen fixing bacteria Rhizobium.
Nutritional adaptations of plants
 Epiphytes-parasitic plants that absorb
nutrients from host – orchids, dodder,
mistletoe.
 Carnivorous-plants that obtain nutrients
(especially N) from insects – sundew,
Venus’flytrap.