Plant Nutrition
Biology Chapter 17
(Science Content Standards for California Public Schools, Grades 9-12,
Biology/Life Sciences: 1a-b, 1d-j)
One of the largest differences
between plants and animals is that
plants . . .
MAKE THEIR OWN FOOD!
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•Early 1600s.
•Flemish
physician Jan
van Helmont.
•Concluded that
new plant
material came
directly from
water.
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•1770s.
•Joseph Priestley
found that plants
could grow in
“damaged” air.
•By early 1800s
scientists knew
plants need CO2,
water and light.
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Photosynthesis
 Process
of capturing and
transforming the energy of sunlight
into chemical energy.
 Requires
light energy. Visible light is
part of the electromagnetic spectrum.
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Light
 Travels
as waves, but acts as
particles. Particles called photons.
 Photons
can excite electrons of an
atom. When e- return to ground state,
heat and light emitted.
 This is what happens to the pigment
chlorophyll in plants.
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In photosynthesis, this energy is captured to make
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sugars (reduced carbon).
Sunlight
+
Water
+
Sugars
+
carbohydrates
+
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Inputs and outputs from
Photosynthesis:
Inputs

Sunlight (430, 670 nm)
 Carbon dioxide
 Water
Outputs

Sugars
 Carbohydrates
 Oxygen
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The big picture
6CO2 + 6H2O
C6H12O6 + 6O2
+ energy from sunlight
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Photosynthesis
 There
are 2 parts:
and
Light-independent reactions
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Light-dependent reactions
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4.2
ATP mill
 Driven
by chemiosmosis
Cellular respiration
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Energy
from
sunlight
Used with permission from: http://student.ccbc.cc.md.us/biotutorials/photosyn/atpasep.html
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Look
Familiar?
Used with permission from: http://student.ccbc.cc.md.us/biotutorials/photosyn/atpasep.html
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Adapted from: http://138.192.68.68/bio/Courses/biochem2/Photosynthesis/Photosystem1.html
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Light-independent
reactions (dark reactions)
Calvin cycle
ATP and NADPH from light reactions
are used to “fix” or reduce carbon
(CO2) into sugars.
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Most
abundant
protein on
earth!
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17-3: Special cases
 C4


Photosynthesis
CO2 incorporated into 4-carbon
compound* prior to the Calvin cycle.
Examples: sugar cane, corn
• *PEP Carboxylase vs. RUBISCO
 CAM

Photosynthesis
CO2 incorporated into 4-carbon
compound at night when water loss is
minimized.
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Q: How do
these
alternate PS
pathways
allow these
types of
plants to
save water?
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It is estimated that photosynthesis makes
about 160 billion metric tons of
carbohydrate per year (a metric ton is
1,000 kg, about 1.1 tons). That’s organic
matter equivalent to a stack of about 60
trillion copies of this textbook--17 stacks of
books reaching from Earth to the sun! No
other chemical process on the planet can
match the output of photosynthesis. And
no process is more important than
photosynthesis to the welfare of life on
Earth.
Respiration vs. Photosynthesis
Same
1.
2.
3.
4.
5.
Different