Chapter 15 Optimizing food production
? Golden rice,two European scientists created a
new strain of rice enriched in β-carotene,which
the body uses to make vitamin A,This is a kind
of transgenic plant (转基因植物 ).
15.1 Humans eat at all trophic levels
? Only about 1 percent
of the solar energy
reaching the Earth’s
surface is used in
photosynthesis,
producing 170 billion
tons of organic
material per year.
? Trophic structure (food
chains)
? No more than 10 percent of the energy contained in the
organic material of one trophic level is incorporated into
the next higher level,
? The higher the trophic level,the smaller the possible
population of organisms.
? Eating meat is a luxury,The amount of biochemical
energy people will obtain from eating the chickens is
minuscule compared with the amount of biochemical
energy in raising the chickens,In the US,more than 70
percent of grain production is fed to livestock.
? If people in US ate 10 percents less meat,the savings in
resources could feed 100 million people.
15.2 Plants require nutrients
Element From available to plants Relative number of ions in
dry plant material
Macronutrients
Nitrogen,N NO3-,NH4+ 1,000,000
Potassium,K K+ 250,000
Calcium,Ca Ca2+ 125,000
Magnesium,Mg Mg2+ 80,000
Phosphorus,P H2PO4-,HPO42- 60,000
Sulfur,S SO42- 30,000
Micronutrients
Chlorine,Cl Cl- 3000
Iron,Fe Fe3+,Fe2+ 2000
Boron,B H2BO3- 2000
Manganese,Mn Mn2+ 1000
Zinc,Zn Zn2+ 300
Copper,Cu Cu+,Cu2+ 100
Molybdenum,Mo MoO42- 1
table15.1 essential elements for most plants
Measured relative to molybdenum=1
Source,Salisbury and ross,plant physiology,Belmont,CA,Wadsworth,1985
? Plants utilize nitrogen,phosphorus,and potassium
? Plants need nitrogen to build proteins and a variety of
other biomolecules,such as chlorophyll (叶绿素 ).
? Nitrogen fixation
Soil
bacteria N2+8H++6e- 2NH4+
nitrogenase
lightening
N2+3O2+2e- 2NO3-
fig 15.4 two pathways
for nitrogen fixation,a
source of nitrogen for
plants,(a) both free-
living bacteria in the
soil and
microorganisms in
root nodules produce
ammonium ions,(b)
lightning provides the
energy needed to form
nitrate ions from
atmospheric nitrogen.
Root
nodule
? Plants need phosphorus to build nucleic acids,phospholiqids,and
ATP.
? Potassium ions activate many of the enzymes essential for
photosynthesis and respiration.
? Plants also utilize calcium,magnesium,and sulfur
? Calcium ions are essential for building cell walls.
? Magnesium ions are essential for the formation of chlorophyll.
15.3 Soil fertility is determined by soil structure and
nutrient retention
? Topsoil usually
contains sand,silt,
and clay.
? Fertile topsoil is a
mixture of at least
four components,
mineral particles,
water,air,organic
matter.
Soil readily retains positively charged ions
humus
Positively charged
nutrient ions
Plant
root
mineral
Mineral particle
phenolate
Fig 15.10 the negatively charged surfaces of soil mineral particles and
humus help retain positively charged nutrients
? The pH value of soil is largely a function of carbon dioxide
present,A healthy soil may have enough carbon dioxide
as a product released from to give a pH value of 4-7.
? Hydronium ions are able to displace nutrient ions held to
mineral particles and humus.
Fig15.11 by releasing carbon dioxide,a plant guarantees a
steady flow of nutrients from the soil to its roots
① Root releases CO2
② CO2 Reacts
with H2O,
forming H2CO3
③ H2CO3 reacts with H2O,
forming HCO3- and H3O+
④ H3O+ displaces nutrient
ion (K+ shown),which is
then available to root
Soil
particle
root
15.4 Natural and synthetic fertilizers help restore
soil fertility
? Natural occurring fertilizers are compost (堆肥 ) and minerals.
? The natural occurring minerals are limited.
? In 1913,a German scientist,Fritz Haber,developed a
process for producing ammonia from hydrogen and nitrogen.
N-P-K system
Fig 15.13 between 1956
and 1972 world crop yields
grew in tandem with
increases in the use of
nitrogen fertilizers
Year
15.5 Pesticides kill insects,weeds,and fungi
? Insecticides kill insects
? The most widely used
insecticides are chlorinated
hydrocarbons,
organophosphorus compounds
and carbamates.
? The chlorinated hydrocarbons
have a remarkable persistence,
killing insects for months and
years on treated surface since
they are not degradable and
water soluble.
? DDT,The early increased crop
yields resulting from DDT use
were not sustainable.
Fig 15.15
the chemical name for DDT is
dichlorodiphenytrichloroethane
Silent Spring and bioaccumulation
Fig15.17 the DDT
concentration in a
food chain can be
magnified from
0.000003 parts per
million (ppm) as a
pollutant in the
water to 25 ppm in
a bird at the top of
the chain
Alternatives to DDT
C
H
C C lC l
C l
O OH
3
C C H
3 E n z y m e
H
2
O
H
3
C O H C
H
C C lC l
C l
-
O O C H
3 +
+ H
+
e t h e r
g r o u p
methoxychlor
Polar products
(water-soluble)Fig 15.18 methoxychlor is one of many
alternatives to DDT,enzymes in the liver
can clean the ether groups to produce
polar products,Look back to Fig15.15,and
you will see that DDT lacks ether groups
Phosphorous compounds and carbamates
C H 3 O P
O C H 3
S
S
C H C
C H 2
C
O C H 2 C H 3O
O
O C H 2 C H 3
p h o s p h o r u s
O
C
N
H
C H 3
O
c a r b a m a t e
g r o u p
Malathion
(an organophosphorus compound)
Carbaryl
A carbamate
Fig 15.20 the widely used pesticides malathion and carbaryl
Herbicides kill weeds
O C H 2 C O HC l
C l
O
2,4-D
C l
C l
C l
O C H 2 C O H
O
2,4,5 -T
O
OC l C l
C lC l
TCDD
C H 2H O C C H 2 N H
O
P
O
O H
O H
glyphosate
+ N N + C H
3H 3 C
C l -C l -
paraquat
N N
N C l
N H C H 2 C H 3
C H 3 C H N H
C H 3
Atrazine
Fig 15.21 the herbicides 2,4-D
and 2,4,5-Tand the dioxin
contaminant TCDD
Fig 15.22 the herbicides atrazine,
paraquat,and glyphosate
Fungicides kill fungi
CN ( H 3 C ) 2 S
S
S C
S
N ( C H 3 ) 2
Fig 15.23
the fungicide thiram
thriam
15.6 There is much to learn from past agricultural
practice
? Pesticides are toxic.
? Fertilizers damage the ecosystem,(Blue-baby
syndrome caused by excessive amount of
nitrate in water).
? Over-use of fertilizers also hardens the top-soil,
which would be much easily to be removed.
15.7 High agricultural yields can be sustained with
proper practice
? Organic farming is environmentally friendly
(concern for environment and a commitment to
using only chemicals that occur in nature)
? Crop rotation
? Compost
? Organic farming is energy effective.
? Integrated crop management is a strategy for
sustainable agriculture
? Multi-cropping
? Integrated pest management
? Pheromones (信息素 )
Fig 15.34 female gypsy moths
emit the pheromone disparlure
(top) to entice male gypsy moths
(bottom left) into mating,The
males are so sensitive to one
molicule in 1017 molecules of air,
This astounding sensitivity
enables them to respond to a
female who may be more than 1
kilometer away,However,they can
also be tricked into responding to
insecticide traps laced with
synthetic disparlure (bottom right)
? 15.8 A crop can be improved by inserting
a gene from another species
? Transgenic organisms
? Bovine growth hormone (牛生长激素 )
? 15.9 World hunger is not inevitable
? Golden rice,two European scientists created a
new strain of rice enriched in β-carotene,which
the body uses to make vitamin A,This is a kind
of transgenic plant (转基因植物 ).
15.1 Humans eat at all trophic levels
? Only about 1 percent
of the solar energy
reaching the Earth’s
surface is used in
photosynthesis,
producing 170 billion
tons of organic
material per year.
? Trophic structure (food
chains)
? No more than 10 percent of the energy contained in the
organic material of one trophic level is incorporated into
the next higher level,
? The higher the trophic level,the smaller the possible
population of organisms.
? Eating meat is a luxury,The amount of biochemical
energy people will obtain from eating the chickens is
minuscule compared with the amount of biochemical
energy in raising the chickens,In the US,more than 70
percent of grain production is fed to livestock.
? If people in US ate 10 percents less meat,the savings in
resources could feed 100 million people.
15.2 Plants require nutrients
Element From available to plants Relative number of ions in
dry plant material
Macronutrients
Nitrogen,N NO3-,NH4+ 1,000,000
Potassium,K K+ 250,000
Calcium,Ca Ca2+ 125,000
Magnesium,Mg Mg2+ 80,000
Phosphorus,P H2PO4-,HPO42- 60,000
Sulfur,S SO42- 30,000
Micronutrients
Chlorine,Cl Cl- 3000
Iron,Fe Fe3+,Fe2+ 2000
Boron,B H2BO3- 2000
Manganese,Mn Mn2+ 1000
Zinc,Zn Zn2+ 300
Copper,Cu Cu+,Cu2+ 100
Molybdenum,Mo MoO42- 1
table15.1 essential elements for most plants
Measured relative to molybdenum=1
Source,Salisbury and ross,plant physiology,Belmont,CA,Wadsworth,1985
? Plants utilize nitrogen,phosphorus,and potassium
? Plants need nitrogen to build proteins and a variety of
other biomolecules,such as chlorophyll (叶绿素 ).
? Nitrogen fixation
Soil
bacteria N2+8H++6e- 2NH4+
nitrogenase
lightening
N2+3O2+2e- 2NO3-
fig 15.4 two pathways
for nitrogen fixation,a
source of nitrogen for
plants,(a) both free-
living bacteria in the
soil and
microorganisms in
root nodules produce
ammonium ions,(b)
lightning provides the
energy needed to form
nitrate ions from
atmospheric nitrogen.
Root
nodule
? Plants need phosphorus to build nucleic acids,phospholiqids,and
ATP.
? Potassium ions activate many of the enzymes essential for
photosynthesis and respiration.
? Plants also utilize calcium,magnesium,and sulfur
? Calcium ions are essential for building cell walls.
? Magnesium ions are essential for the formation of chlorophyll.
15.3 Soil fertility is determined by soil structure and
nutrient retention
? Topsoil usually
contains sand,silt,
and clay.
? Fertile topsoil is a
mixture of at least
four components,
mineral particles,
water,air,organic
matter.
Soil readily retains positively charged ions
humus
Positively charged
nutrient ions
Plant
root
mineral
Mineral particle
phenolate
Fig 15.10 the negatively charged surfaces of soil mineral particles and
humus help retain positively charged nutrients
? The pH value of soil is largely a function of carbon dioxide
present,A healthy soil may have enough carbon dioxide
as a product released from to give a pH value of 4-7.
? Hydronium ions are able to displace nutrient ions held to
mineral particles and humus.
Fig15.11 by releasing carbon dioxide,a plant guarantees a
steady flow of nutrients from the soil to its roots
① Root releases CO2
② CO2 Reacts
with H2O,
forming H2CO3
③ H2CO3 reacts with H2O,
forming HCO3- and H3O+
④ H3O+ displaces nutrient
ion (K+ shown),which is
then available to root
Soil
particle
root
15.4 Natural and synthetic fertilizers help restore
soil fertility
? Natural occurring fertilizers are compost (堆肥 ) and minerals.
? The natural occurring minerals are limited.
? In 1913,a German scientist,Fritz Haber,developed a
process for producing ammonia from hydrogen and nitrogen.
N-P-K system
Fig 15.13 between 1956
and 1972 world crop yields
grew in tandem with
increases in the use of
nitrogen fertilizers
Year
15.5 Pesticides kill insects,weeds,and fungi
? Insecticides kill insects
? The most widely used
insecticides are chlorinated
hydrocarbons,
organophosphorus compounds
and carbamates.
? The chlorinated hydrocarbons
have a remarkable persistence,
killing insects for months and
years on treated surface since
they are not degradable and
water soluble.
? DDT,The early increased crop
yields resulting from DDT use
were not sustainable.
Fig 15.15
the chemical name for DDT is
dichlorodiphenytrichloroethane
Silent Spring and bioaccumulation
Fig15.17 the DDT
concentration in a
food chain can be
magnified from
0.000003 parts per
million (ppm) as a
pollutant in the
water to 25 ppm in
a bird at the top of
the chain
Alternatives to DDT
C
H
C C lC l
C l
O OH
3
C C H
3 E n z y m e
H
2
O
H
3
C O H C
H
C C lC l
C l
-
O O C H
3 +
+ H
+
e t h e r
g r o u p
methoxychlor
Polar products
(water-soluble)Fig 15.18 methoxychlor is one of many
alternatives to DDT,enzymes in the liver
can clean the ether groups to produce
polar products,Look back to Fig15.15,and
you will see that DDT lacks ether groups
Phosphorous compounds and carbamates
C H 3 O P
O C H 3
S
S
C H C
C H 2
C
O C H 2 C H 3O
O
O C H 2 C H 3
p h o s p h o r u s
O
C
N
H
C H 3
O
c a r b a m a t e
g r o u p
Malathion
(an organophosphorus compound)
Carbaryl
A carbamate
Fig 15.20 the widely used pesticides malathion and carbaryl
Herbicides kill weeds
O C H 2 C O HC l
C l
O
2,4-D
C l
C l
C l
O C H 2 C O H
O
2,4,5 -T
O
OC l C l
C lC l
TCDD
C H 2H O C C H 2 N H
O
P
O
O H
O H
glyphosate
+ N N + C H
3H 3 C
C l -C l -
paraquat
N N
N C l
N H C H 2 C H 3
C H 3 C H N H
C H 3
Atrazine
Fig 15.21 the herbicides 2,4-D
and 2,4,5-Tand the dioxin
contaminant TCDD
Fig 15.22 the herbicides atrazine,
paraquat,and glyphosate
Fungicides kill fungi
CN ( H 3 C ) 2 S
S
S C
S
N ( C H 3 ) 2
Fig 15.23
the fungicide thiram
thriam
15.6 There is much to learn from past agricultural
practice
? Pesticides are toxic.
? Fertilizers damage the ecosystem,(Blue-baby
syndrome caused by excessive amount of
nitrate in water).
? Over-use of fertilizers also hardens the top-soil,
which would be much easily to be removed.
15.7 High agricultural yields can be sustained with
proper practice
? Organic farming is environmentally friendly
(concern for environment and a commitment to
using only chemicals that occur in nature)
? Crop rotation
? Compost
? Organic farming is energy effective.
? Integrated crop management is a strategy for
sustainable agriculture
? Multi-cropping
? Integrated pest management
? Pheromones (信息素 )
Fig 15.34 female gypsy moths
emit the pheromone disparlure
(top) to entice male gypsy moths
(bottom left) into mating,The
males are so sensitive to one
molicule in 1017 molecules of air,
This astounding sensitivity
enables them to respond to a
female who may be more than 1
kilometer away,However,they can
also be tricked into responding to
insecticide traps laced with
synthetic disparlure (bottom right)
? 15.8 A crop can be improved by inserting
a gene from another species
? Transgenic organisms
? Bovine growth hormone (牛生长激素 )
? 15.9 World hunger is not inevitable
