The botanical name of tomato is Solanum lycopersicum.
The tomato is native to western South America and Central America. Native versions were small, like cherry tomatoes, and most likely yellow rather than red. People have long used tomatoes in their cooking and the exact date of domestication is unknown. By 500 BCE, it was already being cultivated in southern Mexico and other areas. The Spanish explorers transferred the small yellow tomato to Europe around 1500 CE and later to Southeast Asia.
Although tomatoes originated in the Americas, they have become extensively used in Mediterranean cuisine.
The tomato is now grown worldwide for its edible fruits. Cultivated tomatoes vary in size, shape, taste and appearance, The most widely grown commercial tomatoes tend to be 5–6 cm in diameter. Most tomatoes are reddish orange but some can be yellow, orange, pink, purple, green, black, or white.
About 161.8 million tonnes of tomatoes were produced in the world in 2012. China, the largest producer producing 50 million tonnes in 2012.
Botanically, a tomato is a fruit: the ovary, together with its seeds. However, the tomato has a much lower sugar content than other edible fruits, and is therefore not as sweet. Typically served as part of a salad or main course of a meal, rather than at dessert, it may be considered as a vegetable.
A flower is a reproductive structure of a plant. Many flowers have both male and female reproductive organs, though some are of a single sex. The floral parts are borne in whorls. The outer whorl is called the calyx, the next, the corolla. Within the corolla is the androecium and finally the gynaecium.
The calyx consists of sepals, which is usually green and small. They enclose and protect the rest of the flower while it is in the flower bud.
The corolla consists of petals, which are often coloured and scented. They attract insects which visit the flowers and collect nectar and pollen, pollinating the flowers as they do so.
The androecium is the male part of the flower and consists of stamens. The stalk of the stamen is the filament. At the end of the filament is the anther which produces the pollen grains. The pollen grains contain the male reproductive cells or gametes.
The gynaecium is the female part of the flower. It consists of carpels, which may be single, many and separate from each other, or joined together. In the carpels there are ovules. The ovules contain the female cells or gametes (ie the eggs). Ovules are enclosed in a case, the ovary. Extending from the ovary is the style, expanded or divided at one end into a stigma, where pollen from another flower or the same flower will be received. The ovules when fertilized will become seeds, while the whole ovary will be the fruit. The wall of the ovary develops into the pericarp (fruit wall) of the fruit.
A drawing of a half-flower is a convenient method of representing a flower structure. The flower is cut in halves with a razor blade, the outline of the cut surface drawn, and the structures visible behind these filled in.
In this domestic variety of tomato, the anther is shaped like a hollow tube, with the pollen produced within the structure, rather than on the surface. The pistil lies within the anther, which facilitates self-pollination. In the wild type, the pistil protrudes out of the syngenesious stamen promoting cross-pollination.
Pollination is the transfer of the pollen grains from the anthers to the stigma of the same flower or a different flower of the same species.
After pollination, fertilization takes place. Fertilization is the fusion of the male cell and the female cell to form a zygote. Then the zygote divides many many times by mitosis to form a baby plant. The process has been oversimplified here.
The ovules become seeds and the ovary becomes a fruit .
Using the formula V = ⁴⁄₃πr³ (V = volume, r = radius)
The volume of an ovary is about 0.5 mm3, the volume of a ripe fruit is about 130 000 mm3,
The ovary has enlarged about 250 000 times.
Tomatoes have the chlorophyll pigment when they are raw and hence they are green in colour. As they start ripening, the pigment lycopene becomes dominant and this is why tomatoes turn red.
Lycopene is a carotenoid and belongs to the same family as beta-carotene. It is a powerful antioxidant that neutralizes free radicals.
I would like to thank the late Mr Donald C Y Siao and Fr A Bogadek, my Biology teachers in Hong Kong for teaching me the fascinating structures of the flowers. I would also like to thank Joe for the tomato specimens.
Mackean, D.G (1962) Introduction to Biology John Murray
Mackean, D.G (1978) Introduction to Biology (Colour Edition) John Murray (0 7195 3676 6)