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http://www.GeoChemBio.com:
Solanum lycopersicum, tomato
● Taxonomy
● Brief facts
● Tomato flower anatomy
● Developmental stages (Life cycle)
● Tomato fruit anatomy
● References
● Appendix: Tomato reproductive developmental landmarks (Xiao H. et al. (2008))
cellular organisms - Eukaryota - Viridiplantae - Streptophyta - Streptophytina - Embryophyta - Bryophyta - Moss Superclass V - Bryopsida - Funariidae - Funariales - Funariaceae - Physcomitrella - Physcomitrella
patens
Brief facts
● Together with eggplants, potatoes, and peppers it belongs to the Solanaceae (nightshade) family. Tomato is short-lived perennial usually grown as annual plant.
● The tomato is native to Central, South, and southern North America. The Incas and Aztecs began cultivating tomato plants as early as 700 A.D. In the mid-1500s, Spanish conquistadors carried tomato seeds back to Europe, where they gained popularity as a food item in Italy, Spain and Portugal. Thomas Jefferson was one of the first Americans to grow tomatoes at his Virginia home. By 1812, tomatoes were embraced by Louisiana and Maine cooks.
● The tomato is one of the most commonly grown fresh market vegetables. Tomato farm can harvest as much as 19,000-25,000 pound (10-13 tons) per acre. Harvesting tomatoes is very labor intensive. Cultivation, handling, and marketing costs combined can run as high as $4,500 per acre. However, because of high market demands, farming of tomatoes can be quite profitable.
● There are two types of tomatoes: determinate and indeterminate. Determinate tomatoes grow to a certain height, then flower and set their fruit within a short time. "Celebrity" is popular cultivar of determinate tomato. Indeterminate tomatoes continue to grow and produce flowers and fruits until killed by first frost or senesce naturally. The harvest from indeterminate varieties often extends over 2 or 3 months (this is why they are very good for home gardening). Yields are generally heavier than from determinate types. The plants need to be supported by stakes, cages, or trellises. One of popular cultivars of indeterminate varieties is "Better boy".
● Tomatoes' varieties (more than 4,000) are commonly divided into these categories:
❍ Cherry: sweet small round tomatoes, usually eaten whole in salads ("Small Fry", "Super Sweet 100" cultivars)
❍ Plum: pear-shaped, meaty, multi-purpose tomatoes, eaten fresh or processed ("Roma" cultivars)
❍ Slicing: round or globe-shaped, multi-purpose tomatoes ("Celebrity", "Better Boy" cultivars)
❍ Beefsteak: round, juicy, ideal for sandwiches ("Big Beef" cultivar)
❍ Heirloom: old varieties of tomatoes whose seeds were passed from generation to generation; they are not hybrids like many modern tomatoes cultivars; they are popular because many gardeners believe that they have better flavor; they come in all shapes (often quite irregular), colors and sizes
❍ Yellow/Orange: sweet tomatoes rich in vitamin C and potassium but lacking lycopene ("Jubilee", "Lemon boy", respectively)
● The FDA found no credible evidence to support an association between lycopene intake or consumption of tomato and a reduced risk of lung, colorectal, breast, ovarian, or endometrial cancer. The FDA found very limited evidence to support association between tomato consumption and reduced risk of prostate, ovarian, gastric, and pancreatic cancers.
● One cup of chopped tomato contains about 32 calories (3 calories from fat). Tomatoes are valued for their vitamin and antioxidant content.
Tomato flower
Developmental stages (life cycle)
Life Cycle Stages
Tomato is a short-lived perennial, grown as an annual (5-6 months).
● seed stage MeSH
❍ dormant seed
❍ germination MeSH
under optimal conditions seed
germination (emergence of radicle) takes
from 5 to 10 days
● vegetative vegetative stage (from emergence until
the first flower) takes about 10-12 weeks
❍ seedling MeSH
the seedling can be transplanted to the
field 3 to 6 weeks after sowing
● reproductive
❍ flowering a period between floral initiation and
production of mature flower; this process
takes about 2 weeks; during this period
number of carpels and shape of the fruit
are determined;
● fruit development
❍ fruit set at fruit set, flower petals and anthers
senesce and fall away and a pea-sized
green fruit appears; from this point it
takes typically 40-50 days for fruits to be
harvestable
❍ developing fruit the fruit is of light green color and very
firm; an intensive cell division takes place
but overall fruit's growth is relatively
slow; takes about 2-3 weeks
❍ green fruit the fruit is still green; its growth
accelerated by cell expansion rather than
the cell division; cells enlarge up to 20-
fold; this period takes about 3-5 weeks;
fruit almost reached its final size and is
changing colors
❍ breaker stage rapid chemical and structural changes
that determine fruit aroma, color,
texture, etc. begin; fruit just started to
change coloration; tannish-yellow, pink,
or red occupies no more than 10 percent
of the surface of the fruit
❍ turning stage from 10 to 30 percent of surface of the
fruit is tannish-yellow, pink, or red
❍ pink stage from 30 to 60 percent of the surface of
the fruit, in aggregate, shows pink or red
color
❍ light red stage
from 60 to 90 percent of the surface, in
the aggregate, shows pinkish-red or red
color
❍ ripe more than 90 percent of the fruit reached
its final coloration; typically it is uniform
bright red or orange color; unusually for
plants, the ripe tomato fruit accumulates
large amount of carotenoid lycopene, as
the pattern of gene expression occurring
in green fruit during the fruit ripening
Tomato fruit
● Botanically, the tomato is a berry (a simple fruit produced from a single ovary). However, in 1893, the U.S. Supreme Court declared it as a vegetable.
● Ovary is superior (is above the attachment of the petals, sepals and stamens, and is free from the receptacle) and with 2-9 compartments. Mostly self- but partly cross-pollinated. Bees and bumblebees are most important pollinators.
● The tomato fruit is ripening by climacteric mechanism (as opposed to non-climacteric). Climacteric ripening is accompanied by a peak in respiration
and a concomitant burst of ethylene (important phytohormone). Exposure to exogenous ethylene accelerates ripening of green tomatoes. Other examples of climacteric fruits are apple, grape, banana, strawberries. Fruit ripening culminates in dramatic changes in color, texture, flavor, and aroma of the fruit flesh. Chloroplasts are transformed into chromoplasts, chlorophyll is degraded and carotenoids accumulate.
● The characteristic pigmentation of red tomato fruit is due to the deposition of lycopene, the predominant carotenoid found in tomato fruit, and beta-carotene, which are associated with the change from green to red as chloroplasts are transformed to chromoplasts.
● The characteristic flavor of tomato fruits results from the volatile compounds produced within the fruit during the ripening. Over 400 volatile compounds are found in tomato fruit. Among them seven are the most important contributors to the aroma: hexanal, hexenal, hexenol, 3-methylbutanal, 3-methylbutanol, methylnitrobutane, and isobutylthiazole.
● Although fruit-bearing crop species are taxonomically diverse, they share a common feature: fruit from domesticated species often are considerably larger than their wild progenitors. For example, the putative wild ancestor of the cultivated tomato bears fruit that contains only two locules and weighs just a few grams. By contrast, a single fruit of a modern cultivated tomato may contain many locules and weigh up to 1 kg, a nearly 1000-fold increase in weight.
References
PubMed articles
● Tanksley SD. The genetic, developmental, and molecular bases of fruit size and shape variation in tomato. Plant Cell. 2004;16 Suppl:S181-9. Epub 2004 May 6. PMID: 15131251
● Bramley PM. Regulation of carotenoid formation during tomato fruit ripening and development. J Exp Bot. 2002 Oct;53(377):2107-13. PMID: 12324534
● Kavanaugh CJ, Trumbo PR, Ellwood KC. The U.S. Food and Drug Administration's evidence-based review for qualified health claims: tomatoes, lycopene, and cancer. J
Natl Cancer Inst. 2007 Jul 18 PMID: 17623802
● Alexander L, Grierson D. Ethylene biosynthesis and action in tomato: a model for climacteric fruit ripening. J Exp Bot. 2002 Oct;53(377):2039-55. PMID: 12324528
Websites
● Wikipedia: Tomato
● Organic tomato production by Diver S., Kuepper G., and Born H. (ATTRA). 1999 (.pdf)
● Agrodok 17: Cultivation of tomato: production, processing and marketing by Naika S et al., 2005 (.pdf)
Back to top
Appendix
Xiao H, Radovich C, Welty N, Hsu J, Li D, Meulia T, van der Knaap E. Integration of tomato reproductive developmental landmarks and expression profiles, and the effect of SUN on fruit shape. BMC Plant Biol. 2009 May 7;9:49. PMID: 19422692
Flower Development Landmarks
(The timing of the landmarks described by Buzgo et al (2004) in S. pimpinellifolium accession LA1589)
Flower
Development
Landmarks
Days after
flower
initiation in
tomato
Perianth organs Ovary and ovule Stamen and pollen
(1) Inflorescence
formation and
flower initiation
1
Flattened
inflorescence apex
becomes dome-
shaped.
(2) Initiation of
outermost perianth
organs
2
Emergence of
sepal primordia in
a helical pattern.
(3) Initiation of
inner perianth
organs.
4
Simultaneous
emergence of
petal primordia in
alternating
positions to the
sepals. Sepals
overlay the floral
meristem
(4) Stamen initiation 5 Sepals and petals
elongate.
Simultaneous initiation
of stamen primordia.
(5) Carpel initiation 6 Petals start curling
over the stamens. Carpel primordia arise.
7
Central column that will
form the locular cavities
arise.
Central column that will
form the locular cavities
arise.
6) Microsporangia
initiation 8
Central column continues
to elongate. Carpels fuse
at the apex of the ovary.
Style initiation. Initiation
of placental development.
Primary pariety cells
develop into
endothecium, middle
layers and tapetum.
Sporogenous layers
visible.
(7) Ovule initiation 9
Ovule primordia begin to
emerge from the
placenta.
The two lobes of the
anther and the locule are
distinguishable,
microsporocyte and
tapetal cells are
distinguishable.
Binucleate tapetal cells.
(8) Male meiosis 10
Microsporogenesis.
Microsporocytes or
microspore mother cells
undergo meiosis I and II
and forming tetrads.
(9) Female meiosis 11
Megasporogenesis.
Megaspore mother cell
(meiocyte or
megasporocyte) is
visible. Meiosis I. The
nucellus is small resulting
in a tenui-nucellate ovule.
12 Petals grow to the
top of sepals.
The single integument
begins to grow over the
nucellus resulting in
unitegmic ovules.
Callose wall surrounding
the tetrads degrades
releasing the
microspores. Tapetum
starts degenerating.
13 Petals emerge
from the sepals.
Petals emerge from the
sepals.
Free microspores are
being incased in a thick
polysaccharide wall;
tapetum degenerated.
14 Onset of sepal
opening.
Megagametogenesis and
development of the
embryo sac.
Microspores come
vacuolated, and begins
asymmetric mitosis.
15 Bi-cellular pollen grain.
16 Bi-cellular pollen grain.
The vegetative cell and
generative cell are well
distinguishable.
(10) Anthesis 19 Petal opening.
Fruit developmental landmarks
(Timing of the fruit landmarks in S. pimpinellifolium LA1589)
Fruit Development
Landmarks Days post anthesis
Fruit growth (Gillaspy et
al 1993) Embryo/seed development
(1) Anthesis 0 Mature ovary, phase I.
Mature gametes. Pollen is
shed, which will land on the
stigma and germinate. Pollen
tubes growth through the
style.
(2) Fertilization 1 - 2 End of phase I, beginning
of phase II.
Fusion of sperm and egg
nuclei.
(3) 4–16 Cell Stage Embryo 3 - 6
Phase II and III, cell
division and elongation
stage.
First embryo divisions.
(4) Globular Stage Embryo 6 - 10 Phase III, cell expansion
stage. Globular embryo.
(5) Heart Stage Embryo 10 - 12 Phase III, cell expansion
stage.
Heart Stage embryo lasts
approximately one day and
occurs 10–12 dpa.
(6) Torpedo Stage Embryo 13 - 16 Phase III, continued fruit
enlargement.
Torpedo Stage embryo lasts
approximately one day and
occurs 13–16 dpa.
(7) Coiled Stage Embryo 20 Phase III, continued fruit
enlargement.
Cotyledon expansion and
curl as they elongate.
Embryo appears physically
mature, but the seed is not
yet viable.
20 - 28 Seed maturation period.
(8) Seed germination 29 - 31
The fruit has reached the
mature green stage. Fruit
becomes sensitive to
ethylene.
Seeds are becoming viable
for germination.
(9) Fruit ripening 33 - 40
Ripening starts at the onset
of the breaker stage.
Changes in pigmentation
are visible.
After ripening of seed.
(10) Ripe Fruit 40 Red ripe stage of tomato.
Last updated 09/12/09 [email protected]
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