Thursday Lecture – Legumes Reading: Textbook, Chapter 6

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)



“legere” – Latin for “too gather”




19,000+ species – 3d largest





41 crop species – most of any family





41 crop species – most of any family

Cereal + Legume complete protein

Legume – Papilionoid flowerSee Fig. 6.1, 6.2, page 138

Legume – Papilionoid flower

Banner petal

See Fig. 6.1, 6.2, page 138


Banner petal

wing

See Fig. 6.1, 6.2, page 138


Banner petal

keel

wing

See Fig. 6.1, 6.2, page 138


Banner petal

keel

wing

See Fig. 6.1, 6.2, page 138

Stamens: 9 + 1

Papilionoid legumes

Papilionoid legumes

Other LegumesAcacia - Mimosoideae

See Fig. 6.1, page 137

Other LegumesAcacia - Mimosoideae Senna - Caesalpinoideae


Nitrogen FixationParadox – 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






- some microorganisms can carry out this reaction

- mutualism between bacteria (Rhizobium etc.) and members of Fabaceae

Nitrogen-fixing Root Nodules


N2 Fixing Nodules



Bacteriain cells

Bacteriain cells

N2 Fixing Nodules

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






3. Chemical reactions to carry out N2 fixation

Multiple genes, multiple chromosome locations, not trivial

Nitrogen CycleNitrogen Cycle

1. nitrogen fixation

nitrificationdenitrifying bacteria

nitrogen fixing bacteria

3. nitrification atmospheric

fixation4. denitrification

2. ammonification

ammonification


Nutritional Aspects of LegumesSee 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








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



2. Less seed scattering




3. Greater seed size





4. Synchronous fruiting






5. Loss of dormancy






5. Loss of dormancy

- question: which came first, domestication or loss of dormancy?






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



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



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. Chick-Peas

“cow-without-bones” - soybean

Glycine max – domesticated in China >3000 yrs ago.

The “Cinderella Crop”

U.S. – introduced as crop in 1765



1920s – used for fruit rather than just forage



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:



Mode of action: blocks synthesis of certain amino acids (aromatic amino acids produced by the shikimic acid pathway)



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




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



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







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

Documents

Thursday Lecture – Legumes Reading: Textbook, Chapter 6