Transcript Root

Chapter 37: Plant Nutrition
1. What are the nutritional requirements of plants?
Figure 37.2 The uptake of nutrients by a plant: a review
CO2, the source
of carbon for
Photosynthesis,
diffuses into
leaves from the
air through
stomata.
H2O
CO2
O2
Through
stomata, leaves
expel H2O and
O2.
O2
Minerals
Roots absorb
H2O and
minerals from
the soil.
CO2
H2O
Roots take in
O2 and expel
CO2. The plant
uses O2 for cellular
respiration but is
a net O2 producer.
Chapter 37: Plant Nutrition
1. What are the nutritional requirements of plants?
2. Why do plants need K+? Mg++ P S
N
- Macronutrients – needed in large amounts (9)
- Micronutrients – needed in small amounts (8)
Table 37.1 Essential Elements in Plants
Chapter 37: Plant Nutrition
1. What are the nutritional requirements of plants?
2. Why do plants need K+? Mg++ P S
N
3. What makes up soil?
- Weathered rock
- Topsoil – mixture of weathered rock, living organisms, & humus
- Humus – remains of partially decayed organic matter
- Loams – most fertile soils made of equal amounts of clay, silt & sand
Figure 37.5 Soil horizons
The A horizon is the topsoil, a mixture of
broken-down rock of various textures, living
organisms, and decaying organic matter.
A
B
The B horizon contains much less organic
matter than the A horizon and is less
weathered.
C
The C horizon, composed mainly of partially
broken-down rock, serves as the “parent”
material for the upper layers of soil.
Chapter 37: Plant Nutrition
1.
2.
3.
4.
What are the nutritional requirements of plants?
Why do plants need K+? Mg++ P S
N
What makes up soil?
How do minerals become available to plant roots?
- Cation exchange
Figure 37.6 The availability of soil water and minerals
Soil particle surrounded by
film of water
Root hair
K+
–
Water
available to
plant
Soil particle
–
Cu2+
–
–
–
K+
–
–
Mg2+
–
+
– K
Ca2+
H+
H2O + CO2
H2CO3
HCO3– + H+
Root hair
Air space
(a) Soil water. A plant cannot extract all the water in the
soil because some of it is tightly held by hydrophilic soil
particles. Water bound less tightly to soil particles can
be absorbed by the root.
(b) Cation exchange in soil. Hydrogen ions (H+) help
make nutrients available by displacing positively
charged minerals (cations such as Ca2+) that were
bound tightly to the surface of negatively charged soil
particles. Plants contribute H+ by secreting it from root
hairs and also by cellular respiration, which releases
CO2 into the soil solution, where it reacts with H2O to
form carbonic acid (H2CO3). Dissociation of this acid
adds H+ to the soil solution.
Chapter 37: Plant Nutrition
1.
2.
3.
4.
5.
What are the nutritional requirements of plants?
Why do plants need K+? Mg++ P S
N
What makes up soil?
How do minerals become available to plant roots?
How is soil conservation achieved?
- Fertilizers
- N-P-K
- Organic
- Irrigation - problems
- Erosion prevention
Chapter 37: Plant Nutrition
1.
2.
3.
4.
5.
6.
What are the nutritional requirements of plants?
Why do plants need K+? Mg++ P S
N
What makes up soil?
How do minerals become available to plant roots?
How is soil conservation achieved?
How do plants obtain nitrogen?
- nitrogen-fixing bacteria
Figure 37.9 The role of soil bacteria in the nitrogen nutrition of plants
Atmosphere
N2
Atmosphere
Soil
N2
Nitrogen-fixing
bacteria
H+
(from soil)
Soil
NH3
(ammonia)
NH4 +
(ammonium)
Ammonifying
bacteria
Organic
material (humus)
Figure 37.9 The role of soil bacteria in the nitrogen nutrition of plants
Atmosphere
N2
N2
Atmosphere
Soil
N2
Nitrogen-fixing
bacteria
Denitrifying
bacteria
H+
(from soil)
Soil
NH3
(ammonia)
NH4 +
(ammonium)
Ammonifying
bacteria
Organic
material (humus)
Nitrifying
bacteria
NO3 –
(nitrate)
Figure 37.9 The role of soil bacteria in the nitrogen nutrition of plants
Atmosphere
N2
N2
Atmosphere
Soil
N2
Nitrogen-fixing
bacteria
Denitrifying
bacteria
H+
(from soil)
Soil
Nitrate and
nitrogenous
organic
compounds
exported in
xylem to
shoot system
NH4 +
NH3
(ammonia)
NH4 +
(ammonium)
Nitrifying
bacteria
NO3 –
(nitrate)
Ammonifying
bacteria
Organic
material (humus)
Assimilation
Legumes have root nodules with symbiotic bacteria
Rhizobium
Root
Figure 37.10 Root nodules on legumes
5 m
Bacteroids
within
vesicle
Nodules
Roots
(a) Pea plant root. The
bumps on this pea plant
root are nodules
containing Rhizobium
bacteria. The bacteria fix
nitrogen and obtain
photosynthetic products
supplied by the plant.
(b) Bacteroids in a soybean
root nodule. In this TEM,
a cell from a root nodule
of soybean is filled with
bacteroids in vesicles.
The cells on the left are
uninfected.
Chapter 37: Plant Nutrition
1.
2.
3.
4.
5.
6.
7.
What are the nutritional requirements of plants?
Why do plants need K+? Mg++ P S
N
What makes up soil?
How do minerals become available to plant roots?
How is soil conservation achieved?
How do plants obtain nitrogen?
What are some nutritional adaptations that aid plants?
Figure 37.13 Unusual Nutritional Adaptations in Plants
EPIPHYTES
Staghorn fern, an epiphyte
PARASITIC PLANTS
Host’s phloem
Dodder
Haustoria
Mistletoe, a photosynthetic parasite Dodder, a nonphotosynthetic
parasite
Indian pipe, a nonphotosynthetic parasite
CARNIVOROUS PLANTS
Venus’ flytrap
Pitcher plants
Sundews
37.13 Sun Dew Trap Prey
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