Transcript Nutrition and Transport

NUTRITION AND
TRANSPORT
Chapter 39
AP
Plant Nutrition

9 Macronutrients

7 Micronutrients
 Carbon
 Chlorine
 Oxygen
 Iron
 Hydrogen
 Manganese
 Nitrogen
 Zinc
 Potassium
 Boron
 Calcium
 Copper
 Magnesium
 Molybdenum
 Phosphorus
 Sulfur
Soil


Mixture of sand, rocks, clay, silt,
humus
Most roots found in topsoil
mixture of minerals, living organisms,
and humus (partly decayed organic
material)
 About half is water spaces or air
spaces


Cultivated crops change the soil
composition
Must be supplied with necessary
nutrients
 Farmers employ different practices to
maintain fields

Nutritional Adaptations

Carnivorous plants
 Obtain
nitrogen directly from other organisms
 Venus flytrap, sundews, pitcher plants, bladderworts

Nitrogen-fixing bacteria
 Cannot
use N2, need NH3
 Some bacteria live in close association or
within cells in plant roots that convert N2 to
NH3
 Nodules

Mycorrhizae
 Fungi
and plant roots (about 90% of plants
have this type of relationship
 Increase surface area of roots (phosphorus)
Water Movement

How does water get up a 300 ft tree?
 Pushing
from pressure of water coming into roots
 Cohesion of water molecules pulling up and out through
leaves (transpiration)
 Negative pressure generated by transpiration responsible
for most movement through xylem
 Forces
acting on water in plant is called potential
 Turgor pressure, also pressure potential, is “+”
 Potential can be caused by uneven distribution of solute divided
by membranes (water will move to higher concentration of
solutes)
 osmosis can be stopped if solute potential of solute is reached


Smallest amount of pressure needed to stop osmosis
Generally negative number
 Water
potential is combination of pressure potential and solute
potential


Total potential energy within a plant
Water moves to cells with more negative water potential
Water potential in roots
may be close to zero
 Farther up the tree you go
the more negative water
potential becomes



Negative water potential
achieved when water exits
leaves through transpiration
Osmotic absorption in
roots and negative water
potential by transpiration
= most upward movement
of water in xylem
Water & Mineral Absorption


Many ions move into root hairs using energy
(ATP)
Ions move through or around cells until they
reach the Casparian strip


At night, transpiration may not occur, but
active transport of ions continues


Water & ions must pass through cell membranes
(selective)
Increases solute potential causing more water to
enter roots = root pressure
Because of this water may ooze out of
special cells in leaves = guttation
Movement Through Xylem


Air moving across leaf surface = loss of water
Water is pulled from roots because of cohesion
 Strength
 Smaller

of cohesion inversely related to diameter of tube
tube = greater strength
Water columns fail if air bubbles get in
 Water
can be redirected in order to maintain continuity of
water flow
Transpiration

More than 90% of water taken in is lost through
leaves
 Photosynthesis
requires CO2 to enter from stomata
 But this allows water to be lost in the form of vapor
 Plants have developed ability to close stomata, have
thick cuticle, or are C4 and CAM plants to conserve
water

Opening & closing stomata
 Guard
cells are thick on inside and
thinner on outside
 This
produces a bulging effect when turgid
(full)
 When
guard cells take in K+ water
moves into the cell by osmosis
 K+ passively leaves, so does water and
stomata close

Factors that regulate transpiration
 CO2
 If
concentration
CO2 is high in leaf, stomata close
 Light
 Some
plants close stomata during day and open at night (CAM)
 Temperature
 If
temps are high, transpiration effects would outweigh
photosynthesis effects, thus stomata close
Responses to Flooding

Plants can drown
 Standing
water has less oxygen than moving water
 Flooding depletes oxygen in soil and reduces mineral
uptake
 Hormonal levels can change
 Physical changes to waterlogged roots can halt water
movement through plant
 Stomata
close in order to keep cells turgid

Adaptations for life in water

Aerenchyma—parenchyma cells with large air spaces

Oxygen can be transported from tissues above water to tissues below
water
Larger lenticels
 Adventitious roots


Life in salt water

Need supply of oxygen and control of salt balance



Pneumatophores with large lenticels for oxygen
Succulent leaves to dilute salt intake
At root level


Secrete large amounts of salt
Block salt uptake
Phloem Transport

Translocation—distribution of sugars made in leaves
to the rest of the plant
 Through
phloem tissue
 Also hormones

Mass-flow hypothesis
 Source
 From
to sink
photosynthetic tissues to wherever needed
 Storage areas of plants can become sources

Phloem loading
 Carbs
enter sieve tubes through veinlets at source
 Energy
required
 Provided by companion cells
 Water flows into sieve tubes by osmosis
 Turgor pressure increases
 At sink carbs are removed
 Water moves out of sieve tubes dropping turgor
 = mass flow from more positive pressure at source to more
negative pressure at sink