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Chapter 37
Plant Nutrition
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Overview: A Nutritional Network
• Every organism continually exchanges energy and
materials with its environment
• For a typical plant, water and minerals come from
the soil, while carbon dioxide comes from the air
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Concept 37.1: Plants require certain chemical
elements to complete their life cycle
H2O
CO2
• Plants derive most
of their organic
mass from the CO2
of air, but they also
depend on soil
nutrients such as
water and minerals
O2
O2
Minerals
CO2
H2O
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Macronutrients and Micronutrients
• A chemical element is considered essential if it is
required for a plant to complete its life cycle
• Researchers use hydroponic culture to determine
which chemicals elements are essential
Control: Solution
containing all minerals
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Experimental: Solution
without potassium
• Nine of the essential elements are called
macronutrients because plants require them in
relatively large amounts
• The remaining are called micronutrients because
plants need them in very small amounts
Symptoms of Mineral Deficiency
• Symptoms of mineral deficiency depend on the
nutrient’s function and mobility within the plant
• The most common deficiencies are those of
nitrogen, potassium, and phosphorus
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Healthy
Phosphate-deficient
Potassium-deficient
Nitrogen-deficient
Texture and Composition of Soils
• Topsoil is a mixture of particles of rock, living
organisms, and humus (the remains of partially
decayed organic material)
A
B
C
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Animation: How Plants Obtain Minerals from Soil
• After a heavy rainfall, water drains from the larger
spaces of soil, but smaller spaces retain water
because of its attraction to clay and other particles
Soil particle surrounded by
film of water
Soil particle
Root hair
Water
available
to plant
Root hair
Air space
Soil water
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Cation exchange in soil
Concept 37.4: Plant nutritional adaptations often
involve relationships with other organisms
• Two types of relationships plants have with other
organisms are mutualistic:
– Symbiotic nitrogen fixation, involving roots
and bacteria
– Mycorrhizae, involving roots and fungi
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The Role of Bacteria in Symbiotic Nitrogen Fixation
• Symbiotic relationships with nitrogen-fixing
bacteria provide some plant species with a built-in
source of fixed nitrogen
• For agriculture, the key symbioses between plants
and nitrogen-fixing bacteria occur in the legume
family (peas, beans, and other similar plants)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Along a legume’s roots are swellings called
nodules, composed of plant cells “infected” by
nitrogen-fixing Rhizobium bacteria
5 µm
Bacteroids
within
vesicle
Nodules
Roots
Pea plant root.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Bacteroids in a soybean
LE 37-11
Infection
thread
Rhizobium
bacteria
Dividing cells
in root cortex
Bacteroid
Infected
root hair
Dividing cells in
pericycle
Developing
root nodule
Bacteroid
Bacteroid
Nodule
vascular
tissue
Symbiotic Nitrogen Fixation and Agriculture
• Crop rotation takes advantage of the agricultural
benefits of symbiotic nitrogen fixation
• A non-legume such as maize is planted one year,
and the next year a legume is planted to restore
the concentration of nitrogen in the soil
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Mycorrhizae and Plant Nutrition
• Mycorrhizae are mutualistic associations of fungi
and roots
• The fungus benefits from a steady supply of sugar
from the host plant
• The host plant benefits because the fungus
increases the surface area for water uptake and
mineral absorption
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The Two Main Types of Mycorrhizae
• In ectomycorrhizae, the mycelium of the fungus
forms a dense sheath over the surface of the root
Epidermis
Cortex
Mantle
(fungal
sheath)
100 µm
Endodermis
Fungal
hyphae
between
cortical
cells
Mantle
(fungal sheath)
Ectomycorrhizae.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
(colorized SEM)
• In endomycorrhizae, microscopic fungal hyphae
extend into the root
10 µm
Cortex
Epidermis
Cortical cells
Endodermis
Fungal
hyphae
Vesicle
Casparian
strip
Root
hair
Arbuscules
(LM, stained specimen)
Endomycorrhizae.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Epiphytes, Parasitic Plants, and Carnivorous
Plants
• Some plants have nutritional adaptations that use
other organisms in nonmutualistic ways
Video: Sun Dew Trapping Prey
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 37-13a
Staghorn fern, and epiphyte. This tropical
fern (genus Platycerium) grows on large
rocks, cliffs, and trees. It has two types of
fronds: branched fronds resembling antlers
and circular fronds that form a collar
around the base of the fern.
LE 37-13b
Host’s phloem
Dodder
Haustoria
Mistletoe, a photosynthetic
parasite.
Dodder, a nonphotosynthetic
parasite.
Indian pipe, a
nonphotosynthetic parasite.
LE 37-13c
Venus’ flytrap.
Pitcher plants.
Sundews.