Fruits and Vegetables - Plant Products and Human Affairs - Lecture Slides, Slides of Biology

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Fruits and Vegetables

Outline

• This stuff is scattered in the book.

• Pp. 92-
• pp. 44-
• Tomato
• Apple
• Citrus
• Brassica
• Banana
• Carrot
• Onion
• Squash and Melon
• Tropical Fruits

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).

Tomato Fight!

• In Spain, they

have an annual

tomato fight

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). Docsity.com

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.

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.

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.

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

• 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.

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 family (Rutaceae) contains many edible fruits: orange, grapefruit, tangerine, lemon, lime, and several other less well known species. - 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.
• The family is native to tropical southeast Asia. Most varieties are very sensitive to frost and can only be grown where it never freezes.
• Citrus flowers each have several carpels, and the fruits have a thick rind that surrounds a set of segments, each derived from a single carpel. The segments are filled with pulp.

Citrus Fruit

• Orange trees take 3 years to mature, and then bear fruit for about 20 years.
• Citrus fruits have a thick rind that contains oil glands. The glands secrete a fragrant essential oil, which attracts animals.
• The fruits have several fused carpels: each orange slice is derived from a single carpel.
• The fruits only ripen while on the tree, so they have to be picked when ripe, but not over-ripe.
• Oranges on the tree are a mottled yellow and green color. The orange color is due to carotene, which is masked by chlorophyll in the fruit. Ethylene gas can be used to speed up the degradation of the chlorophyll, leading to the orange color.
• Citrus fruits are high in vitamin C, which prevents scurvy.

Scurvy

• 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.
• 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.