PMT: Class 8 Outline:
The Legumes (Nodulation)
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Last time: Agriculture and the Grains, Wheat, Maize and Rice.
Feb 19, Monday – in one week is Exam I
Carrot family – Apiaceae, Also know as the parsley family Umbelliferae.
300 genera & ~ 3000 Species: ¼ of genera native to U.S.
Contains important food plants: Carrots, parsnips, celery Coriander seeds, cilantro, Caraway, parsley & dill – also poison hemlock.
Poisonous Hemlock Conium maculatum L.
Description: A tall, usually much – branched, imposing plant with purple-spotted stems, compound leaves, and small compound umbels of white Flowers.
Height: Two to ten feet.
Leaves: Pinnate compound.
Flowering: 2mm long, five petals, compound umbel.
Habitat: Waste places, weedy areas, and woodland borders.
Range: Throughout East, except Newfoundland & Arctic, also in much of Western U.S.
All parts of this plant are poisonous, containing the toxic alkaloid called coniine.
Toxin is a volatile oily compound.
Coniine was the first alkaloid synthesized in the laboratory.
Piperidine structure: nitrogen in a six-member ring.
Coniine killed Socrates!
Socrates drank a potent solution of poisonous hemlock 399 BC
Coniine causes paralysis of the diaphragm and subsequent respiratory failure
No plant extract should be consumed by unqualified practitioners! Poisonous hemlock is a narcotic herb that sedates and relieves pain.
The young leaves and fresh seeds contain the highest alkaloid content.
Used by Greek and Arab physicians for a variety of problems including arthritis. It was not always effective …caused death… as the difference btw. a therapeutic and a toxic amount or measure can be very slight..
Poisonous Hemlock: Overdoses can produce paralysis and loss of speech being followed by depression of the respiratory function then death!
No plant extract should be consumed by unqualified humans (practitioners)!
A current issue with poisonous hemlock is: prevent livestock from consuming poisonous hemlock while grazing (in large open rangelands)!
Paper: Hemlock alkaloids and Socrates to poison Aloes (Aloe ruspoliana): on mycourses
• 399 BC poisoning of Socrates by poisonous hemlock.
• Active constituents are of the piperidine alkaloids family
• ~all related to coniine alkaloids all of very simple chemical structures.
The Legumes: Legume family (Leguminosae)
Synonymous with pod, the fruit produced
Seeds are inside the pod or legume
Examples include: Peas, Soybean, Beans, Clover, Alfalfa & Peanuts
With N-fixing root nodules
Importance of Legumes: Major plant source of protein & oil
Major nitrogen fixers with symbiotic bacteria in root modifications called root nodules – fixes nitrogen from air and makes it available to plant
Vegetative Characteristics: Legumes plants are mostly herbs with compound leaves and most are annuals
Flowers are irregular, bilaterally symmetric
Pollination is by bees (hive decline, pesticide- pathogen interactions)
Fruit is a pod or legume, a long fruit with two rows of seeds, easily splits on two seams, two rows of seeds; example, peas in a pod.
Seeds of legumes Seeds are large with two cotyledons that make up most of the seed, no endosperm at maturity
Nitrogen fixation was discovered in legumes, due to symbiotic association of Rhizobium species of bacteria that inhabit nodules on roots
Bacteria give plant nitrogen and plant gives bacteria carbon
Nitrogen Fixation: Conversion of atmospheric N2 to ammonia NH3,
which reacts with water to form NH4+
Performed biologically by:
Nitrogen-fixing bacteria and cyanobacteria
Bacteria may be free-living in soil or in symbiosis with plant
Legumes are the only agricultural families that have symbiotic N-fixing bacteria (woody)
Rhizobium and related bacteria that form symbioses with legumes: Bacterial Species Host Plants Sinorhizobium meliloti Alfalfa, Sweetclover
S. fredii Glycine (Soybean), Cowpea
S. sp. NGR234 Broad host range: many genera of legumes
Rhizobium leguminosarum biovar trifolii
Mesorhizobium loti Lotus (trefoil), Lupinus (lupine)
Bradyrhizobium japonicum Glycine max
Events to the formation of legume-Rhizobium symbiosis:
two way chemical-mediated communication
Release of bacteria from plant produced infection thread into target plant cells and formation of bacterial derived: bacteroids
Some bacterial genes used in the symbiotic formation with legume plants
Stage or symbiosis
Known or proposed function
Host plant signal nodD, nolR Activate or repress transcription of nod box promoters
Nodule formation, Host recognition
exo, lps, ndv Enzymatic synthesis of Nod factors
Differentiation Bacteroid metabol.
bacC dct genes
Signal import / export Import of dicarboxylic acids
Regulation of N- fixing genes , N- fixing
fixL, fixJ, nifA, fixK; nifHDK
Response to O2; control nif promoters; Nitrogenase & cofactors
Plant genes encoding specific proteins involved in N- fixation in nodule = Nodulins, leghemoglobins (Lb)
First: Plant signals associated with Rhizobium nod gene expression: signaling Rhizobium that are host legume is near!
Regulatory circuit of rhizobium NodD and plant inducer molecules
Bacterium-produced Nod Factor induction leads to Plant- produced infection thread and nodule development
Summary of Nodule Development (overtime, clockwise)
Nitrogen fixation as observed by chlorophyll content
Soybean not Nodulated
Food Legumes: Beans
Bean: Phaseolus vulgare: Green bean and others – native to Mexico and the Andes (S.A.)
Rich in protein and also some carbohydrates Intestinal gas – alleviate gas production in us by
long cooking time, treatment of cooked beans with enzyme, and plant breeding to eliminate complex carbohydrates
Red kidney, black, kidney, mung, adzuki, black-eye pea, fava, broad
Food Legumes: Peas Peas: Pisum sativum – garden pea plus other genera and species – native to near East
Rich in protein and carbohydrates
Immature pod also eaten, as snow peas or sugar snap peas
Peas grown in U.S. as field pea for livestock, a garden pea and as an edible-podded pea
Food Legumes: Peanuts Peanut: Arachis hypogea – native to South America; introduced into Europe then from there to Africa then from Africa to U.S.
Rich in oil and protein Unusual growth characteristics: after fertilization, the flower stalk dips downward and grows into the ground where the pod matures to produce peanuts – also called ground nuts
Uses: Half of U.S. crop for peanut butter, rest for snack food, candy, peanut oil
Food Legumes: Soybeans Soybeans: Glycine max – Native to China and introduced into Georgia in 1765. Now the most valuable crop in the U.S. – grown in Midwest and South
Oil used for cooking oil, salad dressing, margarine, shortening, mayonnaise
Oilcake is rich in protein, used for animal feed, used as meat substitute for humans
Food Legumes: Soybeans Soybeans: Glycine max
Traditional uses in the Orient:
Soy sauce – fermented soybeans and grain Tofu – soy milk curds Miso – fermented soybean & rice past in Japan Tempeh – fermented soy cake in Indonesia Soybeans also eaten as sprouts Widely used in health food
Food Legumes: Soybeans Soybeans: Glycine max
Industrial uses: Oil can be used as diesel fuel, or made into plastic, paint, ink, soap
A major crop in the U.S. with production increasing rapidly with greater yields
Forage Legumes: Alfalfa Forage Legumes: Grasses with nutritional balance
Medicago sativa – Alfalfa – some 20 million acres planted in U.S.
Trifolium spp. – True clovers – many species. Red & white clovers
Vicia spp. Vetches planted for hay and erosion control
Next: Last class before test 1
•Ginger the root spice
Exam I – Next Monday (Feb 19)
PMT: Class 9