Download Fig. 30-18a, p.523

PowerLecture:
Chapter 30
Plant Nutrition And Transport
Carnivorous Plants
Fig. 30-18a, p.523
Carnivorous
Plants
Fig. 30-18b, p.523
base of epidermal hairlike trigger
epidermal gland
Fig. 30-18c, p.523
Carnivorous
Plants
Fig. 30-18d, p.523
Soil
-
Minerals and Humus
 Optimal Soil - Loam

equal proportions of sand, silt, and clay
10 to 20 percent humus
Humus
organic material
- charged organic acids help humus
attract + charged minerals
Absorbs water - swells;
releases water - shrinks
Helps to aerate soil
Soil Horizons
 See
next slide
O HORIZON
Fallen leaves and other organic
material littering the surface of
mineral soil
A HORIZON
Topsoil, with decomposed organic
material; variably deep (only a few
centimeters in deserts, elsewhere
extending as far as thirty centimeters
below the soil surface)
B HORIZON
Compared with A horizon, larger soil
particles, not much organic material,
more minerals; extends thirty to sixty
centimeters below soil surface
C HORIZON
No organic material, but partially
weathered fragments and grains of
rock from which soil forms; extends
to underlying bedrock
BEDROCK
Fig. 30-2, p.513
Soil
Horizons
O

Horizon - top organic layer
leaf litter and humus
 A Horizon
- Topsoil;
 humus mixed with mineral
particles.
E
Horizon - eluviation
(leaching) layer light in color

mostly sand and silt

lost most minerals and clay
to eluviation.
Soil
Horizons







B Horizon - subsoil clay and mineral deposits
received from layers above
C Horizon - regolith:
broken bedrock
Plant roots do not penetrate
very little organic material
R Horizon - bedrock layer
Macronutrients
Mineral elements required above 0.5
percent of plant’s dry weight
Carbon
Hydrogen
Oxygen
Nitrogen
Potassium
Calcium
Magnesium
Phosphorus
Sulfur
Micronutrients
Plant requires trace amounts
Chlorine
Iron
Boron
Manganese
Zinc
Copper
Molybdenum
Leaching
 Removal
 Most
of nutrients from soil by water
pronounced in sandy soils
 Clays
hold nutrients better
Leaching
Fig. 30-3a, p.513
Fig. 30-3b, p.513
Casparian
Strip


Forces water and
solutes to flow through
cells
Transport proteins
control flow
exodermis
root hair
epidermis
forming
vascular
cylinder
cortex
Casparian
strip
Figure 30.6.a
Page 515
vascular cylinder
endodermal cells with
Casparian strip
In root cortex, water
molecules move around
cell walls and through
them (arrows)
Casparian strip
Fig. 30-6c, p.515
wall of one
endodermal
cell facing
root cortex
the only way that water (arrow)
moves into vascular cylinder
Waxy, water-impervious Casparian strip (gold) in abutting
walls of endodermal cells that control water and nutrient uptake
Fig. 30-6d, p.515
Root Nodules

Swelling on some plant
roots containing
nitrogen-fixing bacteria

Example - legumes
infection
thread
root hair
ROOT
NODULES
infected plant cells
w bacteria is
becoming a root
nodule.
b Fully formed
root nodule of a
soybean plant
Fig. 30-4a, b, p.514
Fig. 30-4c, p.514
Root
Hairs
Fig. 30-5a, p.514
root hair
root epidermal cells
Fig. 30-5b, p.514
Water Use
 Evaporation
from plant is transpiration
(aka Evapotranspiration)
Cohesion-Tension
Theory of Water Transport
 Transpiration
creates negative tensions
in xylem (leaves to roots)
 Hydrogen-bonded
upward
water column pulled
Transpiration
Drives Water Transport
Water evaporates
from leaves
through stomata
This creates a
tension in water
column in xylem
Figure 30.8.a,b
Page 517
Replacement Water Drawn in
through Roots
Figure 30.8.c
Page 517
Fig. 30-8a1, p.517
mesophyll (photosynthetic cells)
vein
upper epidermis
Transpiration
is the evaporation of
water molecules from
aboveground plant
parts, especially at
stomata. The process
puts the water in
xylem in a state of
tension that extends
from roots to leaves.
stoma
The driving force of evaporation in air
Fig. 30-8a2, p.517
xylem
vascular
cambium
phloem
The collective
strength of hydrogen
bonds among water
molecules, which
are confined within
the narrow waterconducting tubes
in xylem, imparts
cohesion to water.
Hence the narrow
columns of water
in xylem can resist
rupturing under the
continuous tension.
Cohesion in root, stem, leaf xylem
Plus water uptake in growth regions
Fig. 30-8b, p.517
vascular cylinder
water
molecule
endodermis cortex
root hair
cell
For as long as
water molecules
continue to escape
by transpiration,
that tension will
drive the uptake of
replacements from
soil water.
Ongoing water uptake at roots
Fig. 30-8c, p.517
Cuticle
 Wax,
pectin, cellulose embedded in cutin
 Secreted
by epidermal cells
cuticle (gold) on upper epidermis stoma
cuticle on lower epidermis
stoma
Fig. 30-10, p.518
Stomata
 Openings
 Turgor
across cuticle and epidermis
pressure in guard cells opens
and closes stomata
guard cell
guard cell
stoma
Fig. 30-11a, p.519
chloroplast
(guard cells
are the only
epidermal
cells that
have these
organelles)
20 µm
Fig. 30-11b, p.519
Closing Stomata
 ABA binds
to receptors on guard cell
membranes
 Calcium
ions flow into cells
 Chloride,
malate, and Potassium ions flow
out
 Water
moves out
ABA
signal
K+
K+
Ca++
Ca++
malate
a Stoma is open;
water has moved in.
malate
b Stoma is closed;
water has moved out.
Fig. 30-12, p.519
Transportable
Organic Compounds
 Cells
break starches, proteins, and fats
down to smaller molecules for transport

Sucrose is main carbohydrate transported
Transport
through
Phloem

Driven by pressure
gradients

Companion cells
supply energy to
start process
sieve plate
companion
cell
sieve-tube
member
Translocation
 Fluid
pressure greatest at a source
 Solute-rich fluid flows
from high-pressure
region toward lower
pressure regions
section from
a stem