Thursday Lecture – Legumes
Reading: Textbook, Chapter 6
Optional Assignment - Due Tuesday March 1
Where do “baby carrots” come from? - How are they produced?
[is there such a thing as a pregnant mama-carrot?!]
Quiz
Quiz
1. What is a legume?
2. List two crop plants that are members of the legume family
Fabaceae
Fabaceae = Leguminosae
Legume family (also called bean family or pea family)
Fabaceae = Leguminosae
Legume family (also called bean family or pea family)
“legere” – Latin for “too gather”
Fabaceae = Leguminosae
Legume family (also called bean family or pea family)
“legere” – Latin for “too gather”
19,000+ species – 3d largest
Fabaceae = Leguminosae
Legume family (also called bean family or pea family)
“legere” – Latin for “too gather”
19,000+ species – 3d largest
41 crop species – most of any family
Fabaceae = Leguminosae
Legume family (also called bean family or pea family)
“legere” – Latin for “too gather”
19,000+ species – 3d largest
41 crop species – most of any family
Cereal + Legume  complete protein
Legume – Papilionoid flower
See Fig. 6.1, 6.2, page 138
Legume – Papilionoid flower
See Fig. 6.1, 6.2, page 138
Banner petal
Legume – Papilionoid flower
See Fig. 6.1, 6.2, page 138
Banner petal
wing
Legume – Papilionoid flower
See Fig. 6.1, 6.2, page 138
Banner petal
wing
keel
Legume – Papilionoid flower
See Fig. 6.1, 6.2, page 138
Banner petal
wing
keel
Stamens: 9 + 1
Papilionoid legumes
Papilionoid legumes
Other Legumes
Acacia - Mimosoideae
See Fig. 6.1, page 137
Other Legumes
Acacia - Mimosoideae
See Fig. 6.1, page 137
Senna - Caesalpinoideae
Nitrogen Fixation
Paradox – atmosphere is 80% nitrogen (N) yet N is a limiting
factor for plant growth in almost all ecosystems
Nitrogen Fixation
Paradox – atmosphere is 80% nitrogen (N) yet N is a limiting
factor for plant growth in almost all ecosystems
Resolution – atmospheric nitrogen is in a form (N2) that is not
available for chemical reactions in biological organisms
Nitrogen Fixation
Paradox – atmosphere is 80% nitrogen (N) yet N is a limiting
factor for plant growth in almost all ecosystems
Resolution – atmospheric nitrogen is in a form (N2) that is not
available for chemical reactions in biological organisms
How does nitrogen become available to living organisms?
Nitrogen Fixation
Paradox – atmosphere is 80% nitrogen (N) yet N is a limiting
factor for plant growth in almost all ecosystems
Resolution – atmospheric nitrogen is in a form (N2) that is not
available for chemical reactions in biological organisms
How does nitrogen become available to living organisms?
- reaction is called “fixation”
Nitrogen Fixation
Paradox – atmosphere is 80% nitrogen (N) yet N is a limiting
factor for plant growth in almost all ecosystems
Resolution – atmospheric nitrogen is in a form (N2) that is not
available for chemical reactions in biological organisms
How does nitrogen become available to living organisms?
- reaction is called “fixation”
- can occur with input of energy (lightning strike)
Nitrogen Fixation
Paradox – atmosphere is 80% nitrogen (N) yet N is a limiting
factor for plant growth in almost all ecosystems
Resolution – atmospheric nitrogen is in a form (N2) that is not
available for chemical reactions in biological organisms
How does nitrogen become available to living organisms?
- reaction is called “fixation”
- can occur with input of energy (lightning strike)
- some microorganisms can carry out this reaction
Nitrogen Fixation
Paradox – atmosphere is 80% nitrogen (N) yet N is a limiting
factor for plant growth in almost all ecosystems
Resolution – atmospheric nitrogen is in a form (N2) that is not
available for chemical reactions in biological organisms
How does nitrogen become available to living organisms?
- reaction is called “fixation”
- can occur with input of energy (lightning strike)
- some microorganisms can carry out this reaction
- mutualism between bacteria (Rhizobium etc.) and members of
Fabaceae
Nitrogen-fixing
Root Nodules
Nitrogen-fixing
Root Nodules
Bacteria
in cells
Can we transfer N-fixation to
other crops?
See Box 6.1, page 141
Can we transfer N-fixation to
other crops?
See Box 6.1, page 141
1. Morphological changes – development of nodule
Can we transfer N-fixation to
other crops?
See Box 6.1, page 141
1. Morphological changes – development of nodule
- critically important because need to exclude O2
Can we transfer N-fixation to
other crops?
See Box 6.1, page 141
1. Morphological changes – development of nodule
- critically important because need to exclude O2
2. Host/symbiont recognition
Can we transfer N-fixation to
other crops?
See Box 6.1, page 141
1. Morphological changes – development of nodule
- critically important because need to exclude O2
2. Host/symbiont recognition
3. Chemical reactions to carry out N2 fixation
Can we transfer N-fixation to
other crops?
See Box 6.1, page 141
1. Morphological changes – development of nodule
- critically important because need to exclude O2
2. Host/symbiont recognition
3. Chemical reactions to carry out N2 fixation
 Multiple genes, multiple chromosome locations, not trivial
Nitrogen Cycle
1. nitrogen fixation
2. ammonification
3. nitrification
4. denitrification
See Fig. 6.4, page 140
atmospheric
fixation
ammonification
nitrification
denitrifying bacteria
nitrogen fixing
bacteria
Nutritional Aspects of Legumes
See Box 6.2, page 142
1. Legumes produce many N-containing compounds
- nutritious foods (proteins, vitamins)
Nutritional Aspects of Legumes
See Box 6.2, page 142
1. Legumes produce many N-containing compounds
- nutritious foods (proteins, vitamins)
- poisons (alkaloids, cyanogens)
Nutritional Aspects of Legumes
See Box 6.2, page 142
1. Legumes produce many N-containing compounds
- nutritious foods (proteins, vitamins)
- poisons (alkaloids, cyanogens)
2. Amino acid content of proteins – complements grains
Nutritional Aspects of Legumes
See Box 6.2, page 142
1. Legumes produce many N-containing compounds
- nutritious foods (proteins, vitamins)
- poisons (alkaloids, cyanogens)
2. Amino acid content of proteins – complements grains
3. High fiber levels
Nutritional Aspects of Legumes
See Box 6.2, page 142
1. Legumes produce many N-containing compounds
- nutritious foods (proteins, vitamins)
- poisons (alkaloids, cyanogens)
2. Amino acid content of proteins – complements grains
3. High fiber levels
4. Isoflavones – appear to lower cholesterol levels
Nutritional Aspects of Legumes
See Box 6.2, page 142
1. Legumes produce many N-containing compounds
- nutritious foods (proteins, vitamins)
- poisons (alkaloids, cyanogens)
2. Amino acid content of proteins – complements grains
3. High fiber levels
4. Isoflavones – appear to lower cholesterol levels
5. Phytoestrogens  may help relieve menopause symptoms
Nutritional Aspects of Legumes
See Box 6.2, page 142
1. Legumes produce many N-containing compounds
- nutritious foods (proteins, vitamins)
- poisons (alkaloids, cyanogens)
2. Amino acid content of proteins – complements grains
3. High fiber levels
4. Isoflavones – appear to lower cholesterol levels
5. Phytoestrogens  may help relieve menopause symptoms
6. Oligosaccharides (beans, beans, the musical fruit … - see
Box 6.3, page 150)
A Poisonous Legume
Abrus precatorius – Precatory Bean
Abrin – toxin, one of most toxic
substances known
1 crushed seed can be fatal if ingested
Legumes – Changes Under
Domestication
1. Annual habit, selfing breeding system
Legumes – Changes Under
Domestication
1. Annual habit, selfing breeding system
2. Less seed scattering
Legumes – Changes Under
Domestication
1. Annual habit, selfing breeding system
2. Less seed scattering
3. Greater seed size
Legumes – Changes Under
Domestication
1. Annual habit, selfing breeding system
2. Less seed scattering
3. Greater seed size
4. Synchronous fruiting
Legumes – Changes Under
Domestication
1. Annual habit, selfing breeding system
2. Less seed scattering
3. Greater seed size
4. Synchronous fruiting
5. Loss of dormancy
Legumes – Changes Under
Domestication
1. Annual habit, selfing breeding system
2. Less seed scattering
3. Greater seed size
4. Synchronous fruiting
5. Loss of dormancy
- question: which came first, domestication or loss of dormancy?
Legumes – Changes Under
Domestication
1. Annual habit, selfing breeding system
2. Less seed scattering
3. Greater seed size
4. Synchronous fruiting
5. Loss of dormancy
- question: which came first, domestication or loss of dormancy?
Recent studies – no common set of “domesticated genes”
Major Legume Food Crops Pulses
Pulses: dried legume seeds used for food
Major Legume Food Crops Pulses
Pulses: dried legume seeds used for food
Near East: lentils, peas, chick-peas, broad beans
Far East: soybean, pigeon pea
Africa: cowpeas
Mexico: common bean, lima bean
South America: common bean, lima bean, peanut
Major Legume Food Crops Pulses
Pulses: dried legume seeds used for food
Near East: lentils, peas, chick-peas, broad beans
Far East: soybean, pigeon pea
Africa: cowpeas
Mexico: common bean, lima bean
South America: common bean, lima bean, peanut
Commonality: Legumes – food of the poor
Near Eastern Pulses – 1. Lentils
Lens culinaris – genus name refers to
shape of seeds
Near Eastern Pulses – 1. Lentils
Lens culinaris – genus name refers to
shape of seeds
Near Eastern Pulses – 2. Peas
Pisum sativum – used as food since
ancient times (8-9,000 yrs ago) and
domesticated by about 5,800 yrs ago.
Peas – porridge or green
Pease porridge hot
Pease porridge cold
Pease porridge in the pot
Nine days old
1600s – first use as fresh green vegetable (Holland)
Specialized peas: snow peas, sugar snap peas – bred so that pods
are edible in entirely, have high sugar levels
Near Eastern Pulses – 3. Broad
Beans
Vicia faba – from Mediterranean region,
cultivated 8800 yrs ago.
Favism – type of anemia, aggravated in
susceptible individual by Vicia alkaloids
Near Eastern Pulses – 4. ChickPeas
“cow-without-bones” - soybean
Glycine max – domesticated in China
>3000 yrs ago.
The “Cinderella Crop”
U.S. –
introduced as
crop in 1765
The “Cinderella Crop”
U.S. –
introduced as
crop in 1765
1920s – used for
fruit rather than
just forage
The “Cinderella Crop”
U.S. –
introduced as
crop in 1765
1920s – used for
fruit rather than
just forage
Soybeans
contain a trypsin
inhibitor,
destroyed by
heating
Soybean Products
Oriental Foodstuffs: Miso, Tofu, Tempeh, Soy Milk, Soy Sauce
Soybean Oil – widely used
Soy proteins – used in many products
Soy lecithin – widely used in chocolate products
Non-food uses: inks, plastics, cleaners
Other Old World Pulses
Pigeon peas, Cajanus cajan – from India
Black-eyed peas (Cowpeas), Vigna unguiculata – from Africa, in
U.S. considered to be southern regional specialty
Soybean Products
Oriental Foodstuffs: Miso, Tofu, Tempeh, Soy Milk, Soy Sauce
Soybean Oil – widely used
Soy proteins – used in many products
Soy lecithin – widely used in chocolate products
Non-food uses: inks, plastics, cleaners
Roundup - Glyphosate
Herbicide – chemical structure:
Roundup - Glyphosate
Herbicide – chemical structure:
Mode of action: blocks synthesis of certain amino acids
(aromatic amino acids produced by the shikimic acid pathway)
Roundup - Glyphosate
Herbicide – chemical structure:
Mode of action: blocks synthesis of certain amino acids
(aromatic amino acids produced by the shikimic acid pathway)
 Toxic to most plants, but not to animals
Roundup - Glyphosate
Herbicide – chemical structure:
Mode of action: blocks synthesis of certain amino acids
(aromatic amino acids produced by the shikimic acid pathway)
 Toxic to most plants, but not to animals
Note: can still be toxic to animals, not just the active chemical
but other components of the formulation
Roundup - Glyphosate
Herbicide – chemical structure:
Mode of action: blocks synthesis of certain amino acids
(aromatic amino acids produced by the shikimic acid pathway)
 Toxic to most plants, but not to animals
Note: can still be toxic to animals, not just the active chemical
but other components of the formulation
Monsanto Chemical Company – major moneymaker – while
under patent protection
Monsanto - post-Roundup
Next stage  produce genetically modified crops that are
resistant to glyphosate
Monsanto - post-Roundup
Next stage  produce genetically modified crops that are resistant
to glyphosate
Source of resistance:
(1) microorganisms, have enzyme that is resistant to glyphosate
Monsanto - post-Roundup
Next stage  produce genetically modified crops that are resistant
to glyphosate
Source of resistance:
(1) microorganisms, have enzyme that is resistant to glyphosate
(2) Microorganisms or plants, find enzymes that alter glyphosate
structure to make it harmless
Monsanto - post-Roundup
Next stage  produce genetically modified crops that are resistant
to glyphosate
Source of resistance:
(1) microorganisms, have enzyme that is resistant to glyphosate
(2) Microorganisms or plants, find enzymes that alter glyphosate
structure to make it harmless
Using (1) – Monsanto has created crops that are resistant to
glyphosate “Roundup Ready”
Monsanto - post-Roundup
Next stage  produce genetically modified crops that are resistant
to glyphosate
Source of resistance:
(1) microorganisms, have enzyme that is resistant to glyphosate
(2) Microorganisms or plants, find enzymes that alter glyphosate
structure to make it harmless
Using (1) – Monsanto has created crops that are resistant to
glyphosate “Roundup Ready”
First Major Target: Soybeans, very successful
Monsanto - post-Roundup
Next stage  produce genetically modified crops that are resistant
to glyphosate
Source of resistance:
(1) microorganisms, have enzyme that is resistant to glyphosate
(2) Microorganisms or plants, find enzymes that alter glyphosate
structure to make it harmless
Using (1) – Monsanto has created crops that are resistant to
glyphosate “Roundup Ready”
First Major Target: Soybeans, very successful
Can spray crop after germination, kill weeds but crop little affected
Roundup Ready Wheat
The Latest Battlefield in the “Biotech Wars”:
Roundup Ready Crops: corn, soybeans, cotton
None of these have major use in human consumption
Roundup Ready Wheat: produced and marketed by Monsanto
- major use of wheat = human food
- major export crop ( Japan, Europe)
Worry: if any farmers grown GM Wheat, some importers
(Japan) will ban all wheat from U.S.  all farmers will lose this
market
New World Beans – 1. Lima
Beans
Phaeolus lunata – Mexico to Peru, independently domesticated
in the two areas. Mostly used dry. Wild plants and some
cultivars contain cyanogenic glycosides – release toxic cyanide
(cooking destroys compounds)
New World Beans – 2. Common
Beans
Phaseolus vulgaris – source of many types
Another independent domesticate in Mexico
and South America
Beans, Beans, Beans
Selection for the variations in the seed in color and size have
produced a bewildering number of variants, several of which have
widespread use in our country.
Kidney bean
Black bean
Pinto bean
Another New World Legume Peanut
Arachis hypogaea – peanut, ground
nut, goober central South America
The Underground Crop
Forage Legumes – Sitting in the
Clover
Alfalfa – Medicago sativa - king of forage crops – associated with
horse husbandry
Clovers – Trifolium
Lespedeza
Sweet Clovers - Melilotus
Thursday Lecture – Leaf, Stem
and Root Crops
Reading: Textbook, Chapter 7