Transcript Fruits and Vegetables

Fruits and Vegetables
Outline
• This stuff is scattered in the book.
– Pp. 92-101
– pp. 44-47
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Tomato
Apple
Citrus
Brassica
Banana
Carrot
Onion
Squash and Melon
Tropical Fruits
Fruits: Botanical and Popular
• Botanically, a fruit is the ripened ovary wall. The ovary is part of the
carpel, the innermost whorl of a flower, the female reproductive
structure. The ovary contains the ovules, the haploid equivalent to
mammalian eggs.
– Some fruits also contain parts of the flower base.
• Botanical fruits can be classified as fleshy, dry dehiscent, and dry
indehiscent. Most of what are popularly called fruits are fleshy fruits.
• The generally understood common definition of a fruit is sweet and
aromatic fleshy plant products that are mainly eaten as dessert or a first
course in a meal, and not as the main meal.
• Thus, many fleshy fruits (in a botanical sense), such as tomato and
cucumber, are considered vegetables in popular culture.
• In botany, a vegetable is simply any plant or plant part.
• In the common definition, vegetables are plant products eaten with the
main course. In taste, they are salty or sour or savory, but not sweet.
Some vegetables are botanical fruits: tomatoes and cucumbers for
example. Others are plant stems, leaves, and roots.
Legal Fruits
• Botanically, a fruit is an ovary that has ripened after fertilization.
• However, in 1883 a 10% duty was placed on all vegetables being imported
into the US.
• John Nix, an imported from New Jersey, argued that he shouldn’t have to
pay the duty on tomatoes, because botanists consider them fruits.
• The case went all the way to the Supreme Court (which means at least 3
separate courts examined the question). In 1893, the Court ruled that for
legal purposes, tomatoes were a vegetable, not a fruit.
• Based on popular usage: vegetables (including tomatoes) are eaten at dinner,
while fruits are sweet and are eaten at dessert.
• Tomatoes are the state vegetable of New Jersey. Ohio considers tomatoes to
be the state fruit. In Arkansas, tomatoes are both the state vegetable and the
state fruit (indecisive).
• "Knowledge is knowing a tomato is a fruit; Wisdom is not putting it in a fruit
salad."
Tomato Fight!
• In Spain, they
have an annual
tomato fight
Tomatoes
• The tomato is a New World crop, native to the
west coast of South America and first domesticated
in Mexico. It is in the Solanaceae (nightshade)
family, as are potato, chile pepper, tobacco, and
petunia.
– Species: Solanum lycopersicum, but until recently
Lycopersicon esculentum.
• Brought back to Europe and to Asia (initially to
the Phillipines) by the Spanish. It grew well in the
Mediterranean climate and quickly caught on there.
• Many varieties. A big distinction: determinate vs.
indeterminate.
– Determinate tomatoes flower and set fruit all at once, and
have a sfixedsize. Bush tomatoes, favored by commercial
growers.
– Indeterminate varieties are vine types, which contnue to
flower and set fruit until killed by a frost. Favored by
home growers.
Tomato Stories
• Lycopersicon means “wolf peach”, because it is related to
deadly nightshade. Some thought it could be used to generate
werewolves: this was an old German legend about nightshade,
which Linnaeus borrowed when he named the species.
• It was thought to be poisonous in Britain and America, despite
being eaten in large quantities elsewhere.
– In 1820, Colonel Robert Gibbon Johnson stood on the steps of the Salem
Massachusetts courthouse, in front of 2000 people, and ate an entire
bushel of tomatoes to prove that they weren’t poisonous. He survived.
The local band played a mournful dirge as he ate, because they were sure
he would soon die.
– This story may not actually be true: the first account appeared in print in
1906. It was dramatized in an early television series called “You Are
There”, in 1949.
• First varieties to reach Europe were yellow, not red. In Italy
they were called pomo d’oro (golden apple). This may have
been mistranslated into French as pommes d’amour (love
apple).
– Some thought they were aphrodisiacs (one of the eternal quests of
humankind).
Tomato Pollination
• The wild plants are self-incompatible: they
must be outcrossed to produce seeds and fruit.
– To facilitate this, the female parts extend well
beyond the flower, and the stamens stay enclosed
within the petals.
• The native pollinator, a small bee, didn’t
move with the plants to the Old World.
• Selection for self-fertility was very useful.
However, the anthers shed pollen very slowly,
and is aided by the wind or the wing motion
of bumblebees. In the greenhouse, a vibrator
is used (the “electric bee”). This is called buzz
pollination. The bumble bees want to eat the
pollen: tomato flowers produce very little
nectar.
Growing Tomatoes
• Tomatoes are often picked green (unripe), because
they are firm and survive mechanical harvesting and
shipping better.
– Much plant breeding work went into producing fruit that
could be harvested mechanically. One result was the
“square tomato”.
• They can be ripened with ethylene gas.
– Ethylene is a plant hormone that stimulates flower
opening, fruit ripening, and leaf shedding in many
plants. It has been used since ancient Egyptian times
to stimulate fruit ripening, by burning incense or by
gashing figs in a closed room. A modern use it to put
unripe fruit in a closed paper bag with a banana,
which concentrates the ethylene the banana produces
and speeds ripening. It is produced by almost all
plants, both as part of the natural fruiting cycle and in
response to wounding or other stresses.
– Conversely, florists use ethylene inhibitors to extend
the shelf life of cut flowers.
Flavr-Savr Tomatoes
• The Flavr-Savr tomato was the first
genetically engineered food product allowed
on the US market, starting in 1994.
– It was more resistant to spoiling and rotting, it had a
longer shelf life, than normal tomatoes.
– This was accomplished by blocking the enzyme
polygalacturonidase, which degrades the cell walls
and makes fruit more susceptible to fungal infection
(which is what rotting is).
• Didn’t catch on. A big problem was that the
starting tomatoes were not from a high quality
strain, so yield was less than half of what
good commercial varieties produce, and many
of the fruits were small. Also, the fruits were
more delicate than regular tomatoes.
• Production ceased in 1997.
Catsup
• Or “ketchup” , with lots of variant spellings
• Ketchup is a sauce made from tomatoes, vinegar,
sugar, and various spices.
• It is commonly used on grilled meat and potato
products. It is probably the most heavily used
condiment in the US.
• Probable origin: a fermented fish-based sauce from
the 1690’s called something like “koe-chiap”. It
spread to Malaysia, where British explorers picked
up on it.
• The tomato-based version comes from the late
1700’s/early 1800’s in the US. Ketchup was
popular long before eating fresh tomatoes (which
were thought to be poisonous).
Apples
• Apple trees (Malus pumila) are native to central Asia. The
capital city of Kazakhstan, Alma-Ata, means “father of the
apple”. (The city is now named Almaty).
• Alexander the Great brought them back to Europe in 300 BC.
• Apples are members of the Rosaceae, the rose family. Many
other fruits also come from three subdivisions of this family:
– The apple subfamily also includes pears and quinces. The
fruits are called pomes.
– The plum subfamily includes plums, cherries, apricots, and
peaches: “stone fruit”, also called drupes.
– The rose subfamily includes strawberry, raspberry, and
blackberry. These are aggregate fruits: several ovaries fused
together.
• Apples account for 60% of the temperate region’s fruit
production. It is the world’s second largest fruit crop, after
oranges.
Growing Apples
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Apples can be grown from seeds, that is, by sexual
reproduction. However, apples are genetically diverse, and
the process of meiosis ensures that every seed will be
different from all others. This diversity is good for survival
in nature, but it is bad for agriculture: there is no easy way to
maintain specific varieties if the plants are grown from seed.
Genetic uniformity is achieved by growing them
vegetatively, by grafting cuttings onto the base of other trees.
The base tree, called the rootstock, is from a strain that is
disease-resistant and grows well in the region, but doesn’t
produce high quality fruits. The scion (the grafted plant),
produces good fruits of a specific variety.
When new varieties are desired, the trees are grown from
seed. Most new varieties appear spontaneously among the
offspring of genetic crosses between different strains.
Sometimes “bud sports” appear: mutations that occurred in a
bid, producing a branch on a tree that it noticeably different
from the rest of the tree.
Apple Flower and Fruit
• To produce fruits, apple flowers must be
pollinated, usually by honeybees.
• The apple fruit consists of an ovary with 5
carpels fused together, surrounded by
“accessory tissue”. The accessory tissue
develops from the receptacle, the place where
the flower is inserted into the plant stem.
– The swollen ovary containing the seeds is the
core, and it is separated from the accessory
tissue by a thin brown line.
• Most apples are picked by hand, either directly
by the consumers or by low paid migrant
workers.
• Mechanical harvesters are often used for cider
apples: still not well developed.
A Few Apple Legends
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Adam and Eve, the first man and woman in the Bible. The Devil
tempted Eve to eat the fruit of the Tree of Knowledge of Good and
Evil, which God had forbidden. She then convinced Adam to eat it
also. For this action, God tossed them out of the Garden of Eden and
forced them and all their descendants to work for a living. But, this
fruit may have actually been an apricot: it is not clear that apples grew
anywhere near the Middle East when the Bible was written.
William Tell, the Swiss hero and crossbow expert, refused to bow to
the hat of the Austrian overlord (Gessler), which had been set on a pole
in the town square. For this crime, he was forced to shoot an apple off
his son’s head. When Gessler asked why he had taken out two
crossbow bolts, Tell replied that if he had missed with the first one, the
second arrow was meant for Gessler himself. This sparked a rebellion
that led to Switzerland becoming free of the Austrian Empire in 1315.
Isaac Newton supposedly “discovered” gravity, or at least had the
insight that gravity attracted the Moon towards the Earth in the same
way that it attracted the apple toward the Earth, when an apple fell on
his head.
And: New York City is “the Big Apple”, the Beatles’ record company
Apple Corps, and the Apple computer company.
Johnny Appleseed
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Johnny Appleseed. = John Chapman (1774-1845). He spread
apples to western Pennsylvania, Indiana and Ohio.
– He wore old ragged clothes, a pot on his head, and went barefoot
most of the time. He was a vegetarian who was uncomfortable with
romance, and he never settled down. Well-liked by all, a strong
believer in the Swedenborg version of Christianity.
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At that time, this area was part of the Old Northwest Territory,
land west of the Appalachian Mountains, only lightly settled by
Europeans.
– It had been French territory, but was ceded to Britain in 1763.
– The British forbade European settlement west of the Appalachians.
– After the American Revolution, settlement began, despite armed
resistance from the Native Americans. Resistance east of the
Mississippi River ended in 1832, with the Blackhawk War in this
part of Illinois. Abraham Lincoln participated.
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Johnny Appleseed had a business: he planted apple nurseries
from seeds, then left a local resident in charge. After the trees
grew, they were sold to the settlers.
– Apples were not well adapted to life in America, so using seeds
instead of grafts aided in finding workable varieties.
Cider
• The apples planted by Johnny Appleseed were mostly used to
make cider. We call this stuff hard cider today.
• Cider is made by grinding ripe apples, then pressing out the
juice. The juice is allowed to ferment for up to 3 months.
– During this time period, cider was a common beverage, since
water was generally contaminated.
– Fermentation stops when the alcohol content reaches about
10%: this kills the yeast.
• The alcohol in cider can be concentrated to make applejack.
The pioneer method is freeze-distillation. The cider was
simply left out in winter weather. Some of the water would
freeze, as pure water ice, leaving the alcohol still liquid. The
colder the weather, the stronger the cider.
• During Prohibition (1930’s), alcohol as illegal, and “cider”
got re-defined as unfermented , unclarified apple juice .
Sometimes called soft cider.
Citrus
• The Citrus genus contains many edible
fruits. The 4 main types:
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orange
grapefruit (and pomello)
tangerine (and mandarin and clementine)
lemons and limes
• Also lots of others grown in limited areas,
or as rootstock, or in the wild.
• Not really clear how many species there
are: lots of hybrids, both ancient and
modern. And, some "species" are clonally
propagated and not sexually reproducing.
• Native to tropical parts of eastern Asia:
India, China, Malay peninsula, Australia
– Mentioned in Chinese literature in 2200 BC.
– Known in ancient Rome and Greece
• Most varieties are very sensitive to frost and
can only be grown where it never freezes.
Growing Citrus
• Grows as a tree, and it takes 5-10 years after planting
to produce fruit.
• Grown as upper parts grafted onto a rootstock.
– The rootstock is selected for disease resistance and
hardiness
– The above-ground part (scion) is selected for fruit
quality.
– Rootstock and scion can be different species
• Ripens on the tree, with no further ripening after
picking (unlike tomatoes, which are picked green
and ripen after picking).
– Mostly picked by hand.
• Citrus flowers each have several carpels (female
reproductive structures) fused together. Each
segment in a citrus fruit is derived from a single
carpel and has its own seeds.
Citrus Hybrids
• New citrus varieties come from 2
sources: hybrids between 2 species,
and “budsports”.
• Most of the standard citrus species
started out as hybrids. For instance,
the grapefruit is a hybrid that
occurred in the Caribbean region
sometime between 1493 (when
Columbus brought citrus to the New
World) and 1809 (when it was
introduced in Florida).
• Commercial citrus trees are
genetically identical, but new
mutations arise spontaneously, on
individual branches. These mutants
are called budsports. Citrus
breeders collect and examine them
for useful qualities.
Citrus Reproduction
• Most citrus is propagated through seeds that are
clones of the mother.
– To review: seeds are usually the product of sexual
reproduction, with each seed containing a different
combination of the father’s and mother’s genes.
– Clonal propagation is useful because it maintains the
uniform high quality of the mother plant.
• Citrus uses an unusual system of asexual
reproduction called nucellar embryony.
– The nucellus is the tissue surrounding the ovule, and
when the ovule gets fertilized (by pollen), some of the
cells in the nucellus develop into embryos. The
nucellar embryos are strictly maternal tissue: they are
clones of the mother.
– The seed contains multiple embryos. When it is
planted, usually one of the nucellar embryos
germinates, and the new plant is identical to the
mother.
Scurvy
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Scurvy is a disease caused by a vitamin C deficiency. Vitamin
C is needed to help synthesize collagen, the main protein in our
skin and connective tissue.
A person with scurvy becomes weak and listless, spots form on
the skin, and the mucus membranes bleed. In bad cases, old
wounds open up and the teeth fall out. If not treated, it is lethal.
Scurvy used to be very common on long sea voyages. Vitamin
C is found in fruits, vegetables, and fresh meat, but all of these
were lacking. Sailors ate salted meat and hard biscuits.
Most animals, but not primates (or guinea pigs) can synthesize
their own vitamin C.
James Lind, a surgeon in the British navy, described how citrus
fruits could prevent and cure scurvy in 1753. His ideas weren't
consistently followed until the early 1900's.
– British sailors are called "limey" because they were forced to eat
limes to prevent scurvy.
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Work with guinea pigs starting in 1907 led to the understanding
that a specific nutrient was lacking, and eventually to the
isolation of vitamin C and an understanding of how it works.
Orange Juice
• Most Florida oranges are converted into juice.
• Most fruit is hand picked. But mechanical harvesters are
improving. One method is to shake the tree hard enough to
knock all the fruit off.
• The ripe oranges are squeezed to extract the juice. Then,
pulp and seeds are filtered out: most of this ends up as
animal feed. The juice is then concentrated by evaporation,
then frozen. It is now "frozen concentrated orange juice". It
gets shipped to packaging plants around the country, often
dairies, since the packaging process is the same as for milk.
It gets reconstituted by adding water, then sold to the
consumer.
• Some pulp is added back to produce the pulpy varieties
favored by some consumers.
• Frozen concentrated orange juice is a commodity whose
futures (bets on future costs) are traded publicly.
Brassica
• The Brassica genus is part of the mustard family. A wide
variety of vegetable crops come from Brassica: they are called
cole crops. The condiment mustard also comes from members
of this genus.
• Members of Brassica oleracea include: cabbage, collard greens,
kale, Brussels sprouts, kohlrabi, broccoli, and cauliflower. The
different strains have been bred for different traits.
• Also, B. chinensis is bok-choi, B. campestris is turnip, and
rutabaga is B. rapa.
• Also, B. napus is rapeseed or canola, B. nigra is black mustard,
B. alba is white mustard, and B. juncea is brown mustard.
– The yellow color of prepared mustard (called American mustard in
other countries) is due to tumeric added to the ground mustard
seed.
– The hot taste of mustard is due to an enzyme reaction, which
produces a volatile oil when the ground seeds are mixed with
water.
Brassica Plants
• Brassica oleracea is native to the Atlantic coast of
Europe, and was domesticated in ancient Greece. It is a
cool weather crop.
• Mustard flowers are yellow or white, and they have 4
petals.
• The plants grow as a rosette of leaves that stays low to the
ground. When it is mature, the plant "bolts". It shoots up
a tall stem with the flowers on it.
– Most of the Brassica vegetable crops are harvested before
bolting. The expression "gone to seed", meaning decreased
in quality because of age and neglect, comes from this
phenomenon.
• Although most Brassica vegetables are eaten fresh,
cabbage can be converted to sauerkraut by shredding it
and allowing it to ferment in salt water. Sauerkraut can be
stored for a long time, and it retains vitamin C.
Brassica Breeding
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The different varieties come from breeding for different traits.
Cabbage has lateral branches and meristems suppressed, so all
growth goes into leaves produced by the terminal meristem.
Brussels sprouts are similar to cabbage, except each lateral
meristem develops into a little head.
Kohlrabi is swollen stem bases.
Broccoli heads are immature flower buds
Cauliflower is a mass of stem tips, harvested before the flowers
develop. The white color is due to a mutation that inhibits
chlorophyll.
Triangle of U
• Brassica species easily hybridize, and there
is a set of tetraploid species derived from
hybridization of diploids followed by
doubling the chromosomes.
– Chromosome numbers reflect the ancestral
species.
• First noticed by Woo Jang-choon, a Korean
working in Japan, in 1934. By the time his
name had gone from Korean to Japanese to
English, it came out Nagaharu U.
Jack-o'-Lantern
• Carving faces in turnips is (allegedly) an old tradition
in the British Isles. Pumpkin carving is more recent
(pumpkins are a New World crop).
• An Irish legend, with many variants explains the
origin: Jack was a farmer who met up with the Devil
one day. Jack managed to trap Satan in his wallet by
putting a cross in there (the Devil lost his powers when
faced with a cross). He let Old Scratch out only when
he promised to never take Jack's soul. One day Jack
died, and Heaven refused him: he hadn't been a very
good person. And, due to his bargain, Hell also
refused him. Jack was forced to wander for eternity in
the darkness. But, the Devil, having a sense of humor,
tossed him an ember from Hell, which never goes out.
Jack hollowed out a turnip, his favorite vegetable, and
put the ember in there to use as a lantern. He then
wandered the Earth endlessly, and he became know as
Jack of the Lantern, or Jack-o'-lantern.
Banana
• Genus Musa, several species. All edible bananas are
lumped together as Musa x paradisiaca, which reflects
their hybrid origin.
• Two forms are popular: the sweet banana we eat as a
fruit, and the starchy plantain, which is cooked and eaten
as a vegetable in many tropical countries.
– In Asia, they are also used for beer making, and in general are
used about like we use potatoes. Also, fiber for cloth and paper
can be extracted.
• Native to Southeast Asia and northern Australia. The
wild banana was very important in pre-agricultural days.
Probably first domesticated in New Guinea
• Spread to India by 600 BC, and throughout the Pacific
Ocean region by the Polynesians. Arab traders brought
it to Africa about 2000 years ago. It flourished and
spread throughout the Old World tropics.
• Brought to the New World by the Portuguese in the
1500’s. Did well here too.
Bananas as Plants
• The banana is a monocot, and the trunk of the banana tree
is really tightly packed leaf bases arising from an
underground corm.
• The plant takes about a year to mature, starting from a
cutting. It then flowers and sets fruit. The plant then dies,
but the corm send out new stems (called suckers).
• Fruits are picked green (unripe). Ripening is induced are
they have been shipped to market, by treating them with
ethylene gas.
• Most varieties are sterile triploids, which are propagated
vegetatively. They are seedless for this reason.
– Also leaves them vulnerable to pathogens: bananas are genetically
identical, so a pathogen that kills one will probably be able to kill all
of them. The banana industry is periodically devastated by such
diseases, and much breeding work goes into developing resistant
varieties.
Seedless Fruit
• Banana fruits develop without fertilization. This is
called parthenocarpy, and it is a common way of getting
seedless fruit. It is due to a spontaneous genetic
mutation, and it is found naturally in many plants.
• When a plant is moved from its ancestral home to
another part of the world, the pollinating insect (or bird,
etc.) often doesn’t came along or can’t survive.
• A variation on parthenocarpy: some fruits need
fertilization to develop, even though the embryos abort.
Thus the seeds are tiny or non-existent.
• In some species, spraying with plant hormones like
auxin can induce parthenocarpy. This is commonly
done with garden tomatoes.
– This can also be done with genetic engineering.
• Triploids are naturally sterile and seedless. Triploids
can be propagated vegetatively, or triploid seeds can be
produced by crossing a diploid with a tetraploid.
Banana Republics
• Bananas rot quickly after harvest. Before steam ships,
they were almost unknown in temperate climates.
• Around 1900, refrigerated steam ships were able to
bring them to market in America and Europe. This
led to a vast increase in their popularity. At one point,
bananas were cheaper than local-grown apples!
• The United Fruit Company owned much of the land
and infrastructure in several Central American
countries, including Nicaragua, Honduras, Guatemala,
Panama, and El Salvador.
– The people who had formerly farmed the land were then hired
at extremely low wages to work the plantations.
• Several violent coups were engineered by United Fruit
to remove popular governments that wanted to
interfere. Vastly unequal distribution of wealth and
political problems remain as a legacy in Central
America to the present time.
Carrots
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Daucus carota. Domesticated form of Queen Anne's Lace, a
common roadside flower in late summer.
– Umbel-shaped flower.
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Contains carotene, the orange pigment which the body converts
to vitamin A (retinol), the visual pigment.
– The idea that eating a lot of carrots will improve your night vision
started in England in World War 2, when British gunners were
able to accurately shoot down German airplanes in the dark of
night. This was actually because the British had invented radar,
but they didn't want the Germans to know that, so the British
government propaganda ministry started the rumor about carrots.
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biennial: grow as a low rosette of leaves one year, store food in
underground taproot (which we eat), then send up a flower stalk
the next year using that food.
– We harvest it after the first growing season.
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Diploid, grown from seed. Commercial seed is inbred enough
to give uniform growth, but not so inbred as to produce
inbreeding depression.
Carrots
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Native to Afghanistan (it's the center of
diversity). And other temperate parts of
western Asia and eastern Europe.
In the wild, carrot roots are branched and
woody: we have selected for a single
unbranched taproot.
When first domesticated, carrots were
purple.
– Caused by a pigment called anthocyanin,
which is used in many flowers for red,
pink, and purple shades. It's water
soluble, producing purple-brown stews
– Spontaneous mutants removed this
pigment: same taste, but no ugly color in
the stew.
Other Carrot Family Crops
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Carrots are members of the Apiaceae (also called
Umbelliferaceae) family.
– Aromatic plants with hollow stems, feathery leaves, and flowers
like umbrellas.
– The flowers attract parasitic wasps, which kill garden insects.
This makes carrots good companions for other garden plants.
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We also eat parsnips, which look a lot like white carrots.
And celery is also a member of this family.
Many aromatic herbs: parsley, dill, coriander, cilantro,
cumin, fennel, caraway (seeds in rye bread), anise (licorice
flavor).
– Coriander is the seeds and cilantro the leaves of the same plant.
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Some are quite poisonous. For example, hemlock, which
Socrates was forced to drink for his execution for corrupting
the morals of the young. Hemlock grows wild here in
Illinois
Silphium, a giant member of this family, was used for birth
control in ancient Roman Empire. It is now extinct. Grew
only in a small region of the Mediterranean coast in Libya,
and it was over-used.
Onions
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Allium cepa.
Onions are in the Lily family, which is a monocot.
Onion is really a biennial or perennial: the bulb grows in one
year, then it sends up a flower stalk in the next year. We harvest
them after the first season.
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We eat the bulb: underground stem base surrounded by fleshy
leaves
In former times it was used as medicine for a large number of
ailments.
Smell due to release of smelly sulfur compound
Tears when cutting come from release of sulfuric acid and related
compounds.
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Can be grown from seed or from seed sets, which are small
onions grown from seed: using a seed set gives them a head start
so they get bigger during the growing season.
Onions
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Wild onions are edible: it was probably harvested from the
wild long before it was cultivated.
Cultivated from early times in both Egypt and China by 3000
BC. It stores well.
Wild relatives in Central Asia, so that's probably where it
was first domesticated, but no direct proof of this.
We tend to use onion as a food flavoring, but it can also be
eaten as a vegetable
– unattributed odd "fact": the people who built in Pyramids in
Egypt may have lived on radishes and onions. Wikipedia links
to a food/garden site that just says it out of the blue.
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Onion (as Allium) is a garden flower: blue puffball heads.
It's a perennial.
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Other relatives: garlic, leek, shallot, chives.
– Garlic usage has greatly increased in the US in recent years:
people like spicier food.
Squashes and Melons
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Both are members of the Curcurbitaceae, the
cucumber family. Squashes domesticated in New
World, melons in Old World: Africa and South East
Asia independently. Very early domestication.
All are creeping vines with separate male and female
flowers on the same plant. We eat the fruits, which
have multiple seeds surrounded by a fleshy fruit that
has a hard rind.
Originally grown for the seeds: wild relatives can be
eaten but the flesh is bitter. Seeds high in sulfurcontaining amino acids. Pumpkin seeds are still
widely eaten.
Hard rind makes them easy to store, and soft flesh
works well as a water source in the desert.
Squash
• Squash: four cultivated species in the genus
Curcurbita, with lots of variation in form
within each species, and overlapping
between species. E.g., "winter squash" and
"pumpkin" can be any one of the four.
• Types: pumpkins, zucchini, butternut,
turban, acorn, summer, plus others.
• Squash was grown along with maize and
beans in ancient Mexico. The vine provides
a ground cover that suppresses weeds, the
beans fertilize the soil by fixing nitrogen,
and the maize provides a living pole for the
beans to grow on. This is called the “three
sisters” method.
• Giant pumpkins are Curcurbita maxima.
Current record (2012): 2009 pounds. It’s
been going up by 50 pounds a year or so.
Melons
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Watermelon are from west Africa. Eaten in ancient
Egypt by 2000 BC. King Tutankhamen's tomb contained
many watermelon seeds. Grown in China by 1000 AD.
Cantaloupe and honeydew melons are from central Asia.
Also cucumbers: same species.
Cucumbers can be turned into pickles by soaking them in
salt water (brine) at low pH (acid). Sometimes vinegar is
added, along with spices such as dill and garlic. A
bacterial fermentation process turns them sour.
Originally used for food preservation, now mostly for
flavor. Other vegetables can be pickled.
– Playwright Neil Simon once said, “Words with a k in it are
funny. Alka-Seltzer is funny. Chicken is funny. Pickle is
funny....”
•
Loofah is a species of curcurbit whose fruit is allowed to
partially rot, leaving a network of fibrous tissue. This is
used for scrubbing your body: the loofah sponge. The
fruit can also be eaten as a vegetable before it matures.
Calabash
• The calabash, or bottle gourd, is another curcurbit of
note. It was one of the first domesticated plants.
• It is grown for use as a container, not for food. When
dried out, the woody rind in strong and waterproof.
– Also used as a body for musical instruments,: stringed,
rattles and drums
– and often highly decorated.
– It also has been used for smoking pipe bowls: Sherlock
Holmes (a fictional character) smoked a calabash pipe.
Calabash Origins
• The calabash originated in the dry warm areas of southern Africa, where
there a wild relatives.
– The wild species have thin rinds: the cultivated varieties have clearly been
selected for thick waterproof rinds.
• However, the calabash reached Asia very early: it has been found at
archeological sites that are 8000 years old.
– Today Asian and African varieties are relatively distinct.
• The calabash was also grown in the New World 8000 years ago, long before
Columbus. This leads to. another ancient contact story: how did it get to the
Americas?
• The main theory for the past 150 years: it rafted across the Atlantic Ocean
from Africa in a mass of vegetation without human assistance. The rind is
quite waterproof and the seeds are capable of germinating after a long
dormancy period.
– Alternative: a boatload of African fishermen blown off course and landing in
South America.
– Much less likely: by boat across the Pacific Ocean. Polynesia was settled much
later: between 3000 and 1000 years ago.
More Calabash Origins
• Recent genetic and archeological study shows
that the pre-Columbian calabash in America
came from Asia. (D.L. Erickson et al., 2005, Proc.
Nat. Acad. Sci USA 102:18315-18320)
•
– This suggests it came over the Bering Land
Bridge around 12,000 years ago with the
original inhabitants of the New World, the
Paleoindians. Sea level was much lower at that
time, due to the Ice Age glaciers locking up
much water.
– They were hunter-gatherers: settled agriculture
hadn’t been invented yet. They also brought the
dog to the New World.
Dates from carbon-14 decay. It gets into plants
from carbon dioxide in the atmosphere. When the
plant dies, no new C-14 is added, and it slowly
decays into nitrogen. So, the amount of C-14 left is
proportional to how long ago the plant died.
– Calibrated by counting tree rings. In some places, tree
ring chronologies go back 10,000 years.
Genetic Evidence
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The scientists involved here wanted to compare DNA from New World
archeological specimens to plants grown today in Africa and Asia.
– They collected calabashes from traditional farmers in both Africa and Asia, to avoid
getting seeds form modern cultivars.
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Also needed very careful treatment of archeological material to avoid
contaminating ancient DNA with modern DNA.
Looking for differences in the DNA that would reliably distinguish between Asian
and African varieties. There are a few regions in the genome that are easy to
analyze and known to be quite variable. Mostly, the Asian and African varieties
proved to be very similar in their DNA.
– Found three good differences in the chloroplast DNA. All modern Asian varieties had
one allele and all modern African varieties had the other allele.
•
Results: of the 12 archeological samples, only 10 produced any data. Of these, the
nine that had pre-Columbian dates all had the Asian DNA markers.
– The one with a post-Columbian date had the African markers: Columbus brought the
African variety to the New World, and it has mostly replaced the Asian variety.
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So, there is strong evidence that the pre-Columbian calabash came from Asia.
How it got there is not proven: the Bering Land Bridge theory fits well with other
knowledge of how the New World was settled.
Calabash Data
Tropical Fruits
• Pineapple, date, figs, coconut, avocado,
pomegranate, mango, papaya.
• Plus lots of others that are very tasty but
don't ship well, so are only eaten locally.
• Not to mention nuts, which we haven't even
touched on.
• The mind boggles…