TOMATO
Family: Solanaceae
Genus: Solanum
Species: lycopersicum
The scientific species epithet lycopersicum means "wolf peach", and comes from German werewolf myths. These myths said that deadly nightshade was used to summon werewolves, so the tomato, a close relative, but with much larger fruit was named the "wolf peach" when it arrived in Europe.
Tomato may refer
to both the plant (Solanum lycopersicum) and the fruit which it bears. It Originated in South America. The tomato
fruit is consumed in many ways, including raw, as an ingredient in many dishes
and sauces, and in drinks. While it is botanically a fruit, it is considered a vegetable for culinary purposes. The fruit is rich in lycopene, which may have beneficial health effects. The plants
typically grow to 3–10 feet in height and have a weak stem that often sprawls over
the ground and vines over other plants. (Staking
is essential.)
Tomatoes are one of the most common garden fruits in the
United States and, along with zucchini, have a reputation for outproducing the needs of the
grower. It invariably tops the lists of
America’s favorite home garden crops.
The Aztecs
called the fruit xitomatl (pronounced [ʃiːˈtomatɬ]), meaning plump thing with a navel. Other Mesoamerican
peoples, including the Nahuas, took the name as tomatl, from which some European
languages derived the name "tomato".
The definition of an heirloom tomato is vague, but unlike
commercial hybrids, all are self-pollinators who have bred true
for 40 years or more.
Varieties
There are around 7500 tomato varieties grown for various
purposes. Heirloom tomatoes
are becoming increasingly popular, particularly among home gardeners and
organic producers, since they tend to produce more interesting and flavorful
crops at the cost of disease resistance and productivity. Hybrid plants remain common, since they tend
to be heavier producers, and sometimes combine unusual characteristics of
heirloom tomatoes with the ruggedness of conventional commercial tomatoes.
Tomato varieties are roughly divided into several
categories, based mostly on shape and size.
- "Slicing"
or "globe" tomatoes are the usual tomatoes of commerce, used for
a wide variety of processing and fresh eating.
- Beefsteak
tomatoes are large tomatoes often used for sandwiches and similar
applications. Their kidney-bean shape, thinner skin, and shorter shelf
life makes commercial use impractical.
- Oxheart
tomatoes can range in size up to beefsteaks, and are shaped like large
strawberries.
- Plum tomatoes, or
paste tomatoes (including pear tomatoes), are bred with a higher solids
content for use in tomato sauce and paste, and are usually oblong.
- Pear
tomatoes are obviously pear-shaped, and are based upon the San Marzano
types for a richer gourmet paste.
- Cherry tomatoes are
small and round, often sweet tomatoes generally eaten whole in salads.
- Grape tomatoes, a
more recent introduction, are smaller and oblong, a variation on plum
tomatoes, and used in salads.
- Campari tomatoes are
also sweet and noted for their juiciness, low acidity, and lack of
mealiness. They are bigger than cherry tomatoes, but are smaller than plum
tomatoes.
Early tomatoes and cool-summer tomatoes bear fruit even
where nights are cool, which would otherwise discourage fruit set. There are
also varieties high in beta carotenes and vitamin A, hollow tomatoes and
tomatoes which keep for months in storage.
Tomatoes are also commonly classified as determinate
or indeterminate.
Determinate, or bush, types bear a full
crop all at once and top off at a specific height; they are often good choices
for container growing. Indeterminate
varieties develop into vines that never top off and continue producing until
killed by frost. As an intermediate
form, there are plants sometimes known as vigorous determinate or
semideterminate; these top off like determinates, but produce a second crop
after the initial crop. The majority of heirloom tomatoes are indeterminate,
although some determinate heirlooms exist. Tomatoes grow well with seven hours
of sunlight a day. A fertilizer with an NPK
(Nitrogen, Phosporous, Potassium) ratio
of 5-10-10 is often sold as tomato fertilizer or vegetable fertilizer, although
manure and compost are also used.
Diseases and pests
Tomato cultivars vary widely in their resistance to disease.
Modern hybrids
focus on improving disease resistance over the heirloom
plants. One common tomato disease is tobacco mosaic virus, so smoking or use of tobacco products are discouraged around tomatoes, although there is
some scientific debate over whether the virus could possibly survive being
burned and converted into smoke. Various
forms of mildew and blight
are also common tomato afflictions, which is why tomato cultivars are often
marked with a combination of letters which refer to specific disease
resistance. The most common letters are: V – verticillium wilt,
F – fusarium
wilt strain I, FF – fusarium wilt strain I and II,
N – nematodes,
T – tobacco mosaic virus, and A – alternaria.
Another particularly dreaded disease is curly
top, carried by the beet
leafhopper, which interrupts the lifecycle,
ruining a nightshade plant as a crop. As the name implies, it has the symptom
of making the top leaves of the plant wrinkle up and grow abnormally.
Some common tomato pests are stink
bugs, cutworms, tomato
hornworms and tobacco
hornworms, aphids, cabbage
loopers, whiteflies, tomato
fruitworms, flea
beetles, red
spider mite, slugs, and Colorado potato beetles.
When insects attack tomato plants, they produce the plant peptide hormone, systemin,
which activates defensive mechanisms, such as the production of protease inhibitors to slow the growth of insects. The hormone was first identified in tomatoes, but similar proteins have been identified in other species since.
Companion plants
Tomatoes serve, or are served by, a large variety of companion
plants. In fact, one of the most famous pairings is the tomato plant
and carrots, studies supporting this relationship having produced a popular
book about companion planting, Carrots Love Tomatoes.
Additionally, the devastating tomato hornworm has a major
predator in various parasitic wasps,
whose larvae devour the hornworm, but whose adult form drinks nectar from
tiny-flowered plants like umbellifers. Several species of umbellifer are therefore often grown
with tomato plants, including parsley, and dill. These also attract predatory
flies that attack various tomato pests.
On the other hand, borage is thought to actually repel the tomato
hornworm moth.
Other plants with strong scents, like alliums (onions,
chives, garlic)
and mints (basil,
oregano, spearmint
are simply thought to mask the scent of the tomato plant, making it harder for
pests to locate it, or to provide an alternative landing point, reducing the
odds of the pests from attacking the correct plant. These plants may also subtly impact the flavor of tomato
fruit.
Ground cover plants, including mints, also stabilize
moisture loss around tomato plants and other solaneae, which come from very humid climates, and therefore may
prevent moisture-related problems like blossom end rot.
Finally, tap-root plants like dandelions break up dense soil and bring nutrients from down below a
tomato plant's reach, possibly benefiting their companion.
Tomato plants, on the other hand, protect asparagus from asparagus
beetles, because they contain solanum that
kills this pest, while asparagus plants (as well as marigolds) contain a chemical that repels root nematodes known to
attack tomato plants.
Pollination
In the wild, original state, tomatoes required cross-pollination; they were much more self-incompatible than domestic cultivars. As a floral device to reduce
selfing, the pistil of wild tomatoes extends farther out of the flower than
today's cultivars. The stamens
were, and remain, entirely within the closed corolla.
This is not the same as self-pollination, despite the common claim that tomatoes do so. That
tomatoes pollinate themselves poorly without outside aid is clearly shown in greenhouse situations, where pollination must be aided by artificial
wind, vibration of the plants (one brand of vibrator is a wand called an
"electric bee" that is used manually), or more often today, by
cultured bumblebees.[citation needed] The anther of a tomato flower is shaped like a hollow tube, with the pollen produced within the structure, rather than on the surface,
as in most species. The pollen moves through pores in the anther, but very
little pollen is shed without some kind of outside motion. The best source of
outside motion is a sonicating bee, such as a bumblebee, or the original wild halictid
pollinator. In an outside setting, wind or animals provide sufficient motion to
produce commercially viable crops.
Hydroponic and greenhouse
cultivation
Tomatoes are often grown in greenhouses in cooler climates, and there are cultivars such as the
British 'Moneymaker' and a number of cultivars grown in Siberia that are specifically bred for indoor growing. In more temperate
climates, it is not uncommon to start seeds
in greenhouses during the late winter for future transplant.
Hydroponic tomatoes are also available, and the technique is often
used in hostile growing environments, as well as high-density plantings.
Picking and ripening
Unripe tomatoes
Tomatoes are often picked unripe (and thus colored green)
and ripened in storage with ethylene. Unripe tomatoes are firm. As they ripen they soften until
reaching the ripe state where they are red or orange in color and slightly soft
to the touch. Ethylene is a
hydrocarbon gas produced by many fruits that acts as the molecular cue to begin
the ripening process. Tomatoes ripened in this way tend to keep longer, but
have poorer flavor and a mealier, starchier texture than tomatoes ripened on
the plant. They may
be recognized by their color, which is more pink or orange than the other ripe
tomatoes' deep red, depending on variety.
Recently, stores have begun selling "tomatoes on the
vine", which are determinate varieties that are ripened or harvested with
the fruits still connected to a piece of vine. These tend to have more flavor
than artificially ripened tomatoes (at a price
premium).
At home, fully ripe tomatoes can be stored in the refrigerator, but are best kept at room
temperature. Tomatoes stored cold will still be
edible, but tend to lose flavor;
thus, "Never Refrigerate" stickers are sometimes placed on tomatoes
in supermarkets.
Nutrition
Tomatoes are now eaten freely throughout the world, and
their consumption is believed to benefit the heart, among other organs. They
contain the carotene lycopene,
one of the most powerful natural antioxidants. In some studies, lycopene, especially in cooked tomatoes,
has been found to help prevent prostate
cancer, but
other research contradicts this claim. Lycopene has also been shown to improve the skin's ability
to protect against harmful UV rays. Natural genetic variation in tomatoes and their wild
relatives has given a genetic plethora of genes that produce lycopene,
carotene, anthocyanin, and other antioxidants. Tomato varieties are available
with double the normal vitamin C
(Doublerich), 40 times normal vitamin
A (97L97), high levels of anthocyanin (resulting in blue
tomatoes), and two to four times the normal
amount of lycopene (numerous available cultivars with the high crimson gene).
Medicinal properties
Lycopene has also been shown to protect against oxidative
damage in many epidemiological and experimental studies. In addition to its
antioxidant activity, other metabolic effects of lycopene have also been
demonstrated. The richest source of lycopene in the diet is tomato and tomato
derived products. Tomato consumption has been associated with decreased risk
of breast cancer,
head and neck cancers and might be strongly protective against neurodegenerative
diseases. Tomatoes and tomato sauces and puree are said to help lower urinary tract symptoms (BPH)
and may have anticancer properties.
Storage
Tomatoes that are not yet ripe are optimally stored at room temperature uncovered, out of direct sunlight, until ripe. In this environment, they have a shelf life of three to four days. When ripe, they should be used in one to two days. Tomatoes should only be refrigerated when well ripened, but this will affect flavor.
Safety
Plant toxicity
Like many other nightshades, tomato leaves and stems contain atropine and other tropane
alkaloids that are toxic if ingested. Ripened
fruit does not contain these compounds. Leaves, stems,
and green unripe fruit of the tomato plant contain small amounts of the
poisonous alkaloid tomatine. Use of tomato leaves in tea (tisane) has been responsible for at least one death. However, levels of tomatine are generally too small to be
dangerous.
Tomato plants can be toxic to dogs if they eat large amounts
of the fruit, or chew plant material.
Tomato plants are vines, initially decumbent, typically growing six feet or more above the ground if
supported, although erect bush varieties have been bred, generally three feet tall
or shorter. Indeterminate types are "tender" perennials, dying
annually in temperate climates (they are originally native to tropical
highlands), although they can live up to three years in a greenhouse in some
cases. Determinate types are annual in all climates.
Tomato fruit is classified as a berry. As a true fruit, it develops from the ovary of the plant
after fertilization, its flesh comprising the pericarp walls. The fruit
contains hollow spaces full of seeds and moisture, called locular cavities.
These vary, among cultivated species, according to type. Some smaller varieties
have two cavities, globe-shaped varieties typically have three to five,
beefsteak tomatoes have a great number of smaller cavities, while paste
tomatoes have very few, very small cavities.
For propagation, the seeds need to come from a mature fruit,
and be dried or fermented before germination.
Pronunciation
The pronunciation of tomato differs in different English-speaking
countries; the two most common variants are /təˈmɑːtoʊ/ and /təˈmeɪtoʊ/. Speakers from the British Isles, most of the Commonwealth,
and speakers of Southern American English typically say /təˈmɑːtoʊ/, while most North American
speakers usually say /təˈmeɪtoʊ/.
The word's dual
pronunciations were immortalized in Ira and George
Gershwin's 1937 song Let's Call the Whole
Thing Off ("You like /pəˈteɪtoʊ/ and I
like /pəˈtɑːtoʊ/ / You like /təˈmeɪtoʊ/ and I like /təˈmɑːtoʊ/") and have
become a symbol for nitpicking
pronunciation disputes. In this capacity, it has even become an American and
British slang term: saying /təˈmeɪtoʊ, təˈmɑːtoʊ/ when presented with two
choices can mean "What's the difference?" or "It's all the same
to me."
