All about tomatoes

Information about our favourite vegetable... errr... fruit?

Botanically speaking, the tomato you eat is a fruit. So are watermelon, green pepper, eggplant, cucumber, and squash. A "fruit" is any fleshy material covering a seed or seeds.

Horticulturally speaking, the tomato is a vegetable plant. Most fruits, from a horticulture perspective, are grown on a woody plant (apples, cherries, raspberries, oranges); the exception is strawberries.

In 1893, the United States Supreme Court ruled that the tomato was a "vegetable" and therefore subject to import taxes. The suit was brought by a consortium of growers who wanted it declared a vegetable to protect U.S. crop development and prices.

Nomenclature and "genealogy"

The botanical name for the tomato has changed several times. Its earliest name was Lycopersicon or literally, wolf peach. Once the tomato was placed in the Solanum (Solanaceae) family, the botanical name changed to Solanum lycopersicon. Today the tomato is known as Lycopersicon esculentum, literally "edible wolf peach".

Tomatoes belong to the same family (Solanaceae) as potatoes, peppers and eggplants. Lycopersicon esculentum (tomato) is a perennial plant in the tropics but in northern climates it is grown as an annual. Flowers are generally borne in clusters of 4 to 8 but small fruited types may have 30 to 50 flowers per cluster. The flowers are mainly self pollinated by the wind. The fruit has 2 to 18 locules (chambers or sections).

The tomato is a native of the Peru, Bolivia, and Ecuador area of the Andes Mountains. Its antiquity is uncertain in regard to cultivation but it was being cultivated prior to the arrival of the Europeans. It was not until the early 19th century that the tomato was considered suitable as a food crop in the northeastern United States.

Tomatoes and temperature

Tomatoes respond well to warm temperatures. The minimum temperature for seed germination is 10°C with a maximum temperature of 35°C and an optimum range of 17°C to 20°C.

Transparency master

Most field transplants should not be set out until the danger of frost is past.

An optimum growth rate is obtained at 22°C with reductions occurring above 30°C and below 12°C. Fruit setting is inhibited above 30°C and below 16°C. Rough fruit (cat faced) results from growing temperatures below 16°C.

Root growth does not occur below 16°C.

Soil and water

Tomatoes require adequate, even moisture, particularly at flowering and during fruit set.

Tomatoes grow best in well drained soils that are well supplied with organic matter. Sandy soils are suited for the speedy production of fruit. Loam and clay loam soils promote slower development.

Shelter from wind is important.

A pomato plant?

The tomato, pepper, eggplant and potato are closely related. The tomato plant is occasionally grafted to the potato, resulting in a freak plant which may produce tubers below ground (potatoes) and tomatoes above. This odd plant is sometimes called the "potomato" or "pomato".

Student Activities

The following student activities can be used as extensions of the Tomatosphere experiment. Teachers should choose activities to compliment the curriculum and needs of the students or groups of students. The activities may be adapted to individual, small group or whole class settings.

Safety note: Be aware of any student allergies. Remind students to wash their hands well after handling plants.

The tomato plant

Brainstorm the different ways we use tomatoes. Ask students to check the labels of products at home for items containing tomatoes. Prepare a master class list.

Tomatoes are 80-85% water

Drying is the oldest preservation method, traditionally requiring only the sun's energy over several days. It is a very simple process. All you are doing is removing the water from the fruit, leaving all the vitamins, minerals and flavour.

For centuries Italians dried tomatoes in the sunlight on the clay tiles of the roofs of their homes. In order to sun dry tomatoes in the traditional way, you need ideal weather conditions - long, hot, sunny summer days with a gentle breeze and low humidity. For those with less than ideal weather conditions, tomatoes may be dried in an oven or a dehydrator.

Dried tomatoes can be sealed in airtight bags and stored without refrigeration in a cool (15° to 20°C), dry, dark place for up to six months. They can be used chopped or sliced in pastas, sandwiches, salads, and sauces. They can also be rehydrated before use by covering with warm water or wine, and soaking about 10 minutes, until they soften and plump slightly.

By mass, sun-dried tomatoes contain more than 20 times the calcium, 15 times the potassium and four-and-a-half times the folate of fresh tomatoes.*

Dry tomatoes and calculate the percentage of tomato mass that is lost during dehydration .

*Source: Health Canada, Nutrient Value of Some Common Foods

Procedure

Divide the class into groups of 2 or 3 students. Supply each group with a tomato. Ensure that groups in rotation have access to a paring knife, triple beam balance, oven-proof rack and an oven.