Plants & Human Affairs - Fruits & Veggies
Cherries.wmf (7140 bytes) Plants & Human Affairs (BIOL106)  -  Stephen G. Saupe, Ph.D.; Biology Department, College of St. Benedict/St. John's University, Collegeville, MN 56321; ssaupe@csbsju.edu; http://www.employees.csbsju.edu/ssaupe

Vegetables, Fruits & Seeds

 I. Major plant organs
    Recall that the major organs of a plant are: roots, leaves, stems, and flowers (fruits). This might be a good time to review the earlier lab we did on plant structure. In this part of the course we will identify some of the foods/products derived from these structures.

II. Roots as foods

  1. Function of roots – support, anchoring plant, absorption of water and nutrients

  2. Some select root crops (cassava or manihot, parsnip, carrot, rutabaga, turnip)

  3. The importance of biennials – spend first year accumulating nutrients in roots to prepare for flowering the following season

  4. Roots or stems? – A few crops, such as radish and beet, grow underground and appear to be a taproot. These crops actually develop from the hypocotyl, part of the embryonic stem. Thus, even though they look and act like taproots, they are probably best considered stems.

III. Stems as food
    Botanically, a stem is the structure to which the leaves and roots are attached. The stem supports the plant and is characterized by having buds and leaves. We typically think of stems as growing above the ground, but as we discussed earlier, some specialized types of stems (i.e., tubers, rhizome, corm, bulb) grow underground.

  1. Aerial stems - asparagus, bamboo, kohlrabi

  2. Tubers – white potato, yams

  3. Rhizomes – Jerusalem artichoke (sunflower), arrowroot (starch), ginger

  4. Corm – water chestnuts, taro

  5. bulbs – onion, garlic, leek

IV. Leaves as food
    Recall that leaves are the photosynthetic part of the plant and are typically comprised of a blade and stalk (petiole). Crops can be derived from the leaf blade ("greens") or petiole

  1. Greens (leaf blade) - spinach, lettuce, parsley, endive, kale, beet greens, swiss chard, dandelion, amaranth, etc.

  2. Leaf Stalk (petiole) - celery, rhubarb

  3. Onion group - onion, garlic, leek. The tubular leaves of chives and other onions are often eaten. Also, a bulb, which we classified as a stem, is actually made up of the fleshy bases of the onion leaves attached to a small stem. Thus, even though onions are described as modified stems, the leaf base is the major part that is eaten.

V. Meristems as food – cabbage, Brussels sprouts, head lettuce

VI. The Mustard Family (Cruciferae or Brassicaceae) - an important family of veggies (not on exam)

  1. Family characteristics – 4 petals in shape of a cross, 6 stamens, mustard oils (glucosinolates), drought/cold tolerant.
  2. Survey of important crucifers (cabbage, broccoli, cauliflower, Brussels sprouts, kohlrabi, turnip/rutabaga, radish, kale)

VII. Fruits as food.

A. What is a fruit?

  1. Definition.
        Recall that a fruit is a ripened, mature ovary and its contents (seeds). A seed is a ripened ovule. Following pollination and fertilization, ovules develop into seeds and the ovary develops into a mature fruit. Thus, a fruit is really just an enlarged pistil (since the ovary was once part of the pistil). Fruits are frequently associated with accessory structures (such as receptacle tissue).

  2. The pericarp. 
        The covering, or pericarp, of the fruit develops from the outer layers of the ovary. The pericarp has three major layers – endocarp (inner layer), mesocarp (middle), and exocarp (outer). In some fruits these layers are easy to locate, while in others they are impossible to distinguish with the naked eye.

  3. Flowers and Ovaries.
        Fruits can be derived from one or many ovaries. A fruit that forms from a single ovary in a single flower is called a simple fruit. In contrast, some flowers have multiple, separate pistils each with a separate ovary. A fruit that develops from this type of flower is called an aggregate fruit. A strawberry is good example. The separate "seeds" on the surface of the strawberry are actually tiny individual fruits that were formed from separate pistils that were all present within a single flower. Strawberries are also good examples of a fruit with accessory tissues – the red fleshy part that we eat is actually the enlarged receptacle of the flower. A multiple fruit formed from many flowers, each with a separate ovary. Pineapples are good examples.

  4. Fleshy vs. dry. 
        Fruits can be fleshy or dry. As a generalization, fruits that we eat are fleshy, while plants with dry fruits are grown to provide us with seeds.

  5. Dehiscent vs. indehiscent. 
        Fruits can open at maturity (dehiscent) to release their seeds or remain closed (indehiscent). As a generalization, edible fruits are usually indehiscent while those that supply seeds are dehiscent.

B. Fruit History.
    From the dawn of humanity, fruits have been used to supplement our diet. They were particularly important in hunter-gatherer societies, even after the switch to an agrarian lifestyle. Fruit remnants are found in most archaeological digs. Fruits even spurred colonization (think Columbus – among other things he was searching for black pepper, a spice from the fruit of the plant ).


VIII. Fruits vs. veggies.
    Botanically, fruits come from the ovary or "reproductive" parts of the plant and a vegetable comes from "vegetative" parts, such as leaves, roots and stems. Simple, right? So, is a zucchini a fruit or vegetable? How about cauliflower? or tomato? or squash? Many foods that we consider vegetables are actually fruits, and vice versa. The problem arises because "fruit" is commonly used to describe a food that is usually sweet and eaten as dessert or perhaps salad, whereas vegetable is used to describe a food, usually green, that is eaten during the main course of a meal.

IX. Seeds vs. Fruits.
    These terms are often incorrectly applied (from a strict botanical sense) by the non-botanist. Remember that fruits come from the ovary and seeds come from the ovule. Thus, the seeds are inside the fruits. However, there are a few fruits and seeds that cause some confusion. For example, sunflower seeds and corn grains are actually fruits. When you shell a sunflower seed you remove the pericarp and eat the seed. Thus, sunflower "seeds" are examples of an achene – a type of single-seeded fruit that is dry and indehiscent. Similarly, corn grains are a special type of single-seeded fruit in which the seed is completely fused to the pericarp so that you can't tell where one ends and the other begins.

    Conversely, seeds like coconut, are often considered to be a fruit. The coconut is produced inside a hard, fibrous husk which is the fruit.

Take-home-lesson: fruits have seeds, vegetables do not...the seeds are inside the fruit.


Questions
:

  1. What’s the difference between a fruit, seed, and vegetable?
  2. Can you identify the plants and parts used for the species listed in Table 1 – Supermarket Botany? (just the ones with an asterisk)
  3. What do you conclude from Tables 2 & 3?
Table 1. Supermarket Botany
Crop Native region Part eaten/used
Artichoke* Mediterranean Leaves associated with the flowers, receptacle
Asparagus* Mediterranean Young shoot
Avocado* Mexico Fruit
Bamboo* Asia Shoots
Banana* SE Asia Fruit
Beet Mediterranean Root (red pigment, betalain, not readily digested)
Blueberry* North America Fruit
Bok-Choi Asia Leaves; this plant is a variety of Fast Plant
Brazil Nut* South America Seed – the actual fruit is a large hard pod
Broad Bean (Fava Bean) Near East Seeds
Broccoli* Europe Immature flower buds and stems
Brussels Sprouts* Europe Lateral buds (meristems)
Carambola (Star-Fruit) Asia Fruit
Carob Mediterranean Fruit, used as a chocolate substitute
Carrot* Mediterranean Root
Cashew South America Seed from a relative of poison ivy
Cauliflower* Europe Immature flower buds and stems
Chick-Pea (Garbanzo) Near east Seeds of legume
Coconut* pan-tropical Seed of a palm
Cranberry* North America Fruit
Cucumber* Asia Fruit
Eggplant* Asia Fruit
Fig* Mediterranean Fruit – pollinated by wasp, multiple fruit with flowers lining a hollow chamber
Garlic* Mediterranean Bulb; vegetable
Grapefruit* West Indies (hybrid) Fruit
Grapes (Wine)* Mediterranean Fruit, many native species, but our wine grapes are from Europe
Guava South America Fruit, beautiful pink flesh
Kohlrabi* Mediterranean Veggie, hypocotyl swells to form edible structure, like an above ground radish
Leek* Near East Veggie, bulb
Lemon* Asia Fruit
Lentil Near east Seeds of a legume
Lettuce* Eurasia Veggie, head lettuce is essentially a meristem
Macadamia Nut Australia Seed
Maize (Corn) Central America Fruit
Mango Asia Fruit (relative of poison ivy)
Manioc (Cassava)* South America Veggie, root, loaded with HCN, must be detoxified before eating
Melon (Cantaloupe, Honeydew)* Africa Fruits – grain
Millet Africa Fruits – grain
Oats Europe Fruits – grain
Okra Asia Fruit, very mucilaginous
Olives* Mediterranean Fruit
Orange* Asia Fruit; naval oranges are "mutants" – propagated asexually from cuttings
Papaya Central America Fruit
Parsnip Mediterranean Veggie, root, like a white radish
Pea* Near East Seeds of legume fruit
Peanut* South America Seeds of legume fruit
Pecans Mexico, SW America Seeds
Pepper* South America Fruit
Pineapple* South America Fruit, multiple fruit
Pomegranate* Mediterranean Red fleshy covering surrounding seeds
Potato – White* South America Veggie, stem (tuber)
Radish* W. Asia Veggie, root or stem (hypocotyl)
Rhubarb* Europe Veggie, leaf stalk (petiole)
Rutabaga Europe Veggie, root
Sorghum Africa Fruit - grain
Soybean China Seeds of a legume
Spinach* Asia Veggie, leaf
Squash* South America Fruit
Strawberry* South America Aggregate fruit
Sunflower* North America Fruit
Tomatillo South America Fruit
Tomato* South America Fruit
Turnip Eurasia Veggie, root
Walnuts (English)* Eurasia Seed, native walnuts have good flavor but hard to shell
Watermelon* Africa Fruit
Wheat Near East Fruit – grain
Zucchini* Mexico Fruit

 

Table 2. Comparison of nutrient content of various vegetables (data from Simpson & Ogorzaly, 1995)
Average Leafy crops (cabbage, cauliflower, chard, celery, endive, kale, kohlrabi, lettuce, spinach Stem crops (artichokes, asparagus) Bulbs (leeks, onion) Biennial Roots crops (beets, carrot, parsnip, radish, turnip, rutabaga) Starchy tubers & rhizomes (manioc, white potato, sweet potato, yam)
Water content (%)

90.7

89

86.5

87.8

62.2

Calories

27.6

23

48.5

30.6

148.2

Carbohydrates (%)

5.3

8

11

10

35.2

Vitamin A (units)

3148

530

20

1940

1764

Vitamin C (mg/100g)

56.2

22.5

21

23.1

10.8

 

Table 3. Comparison of fruits and nuts (per 100 grams)
Characteristic

Fruit

Nut

Water content

84.3

5.2

Calories

59.6

559.6

Protein

0.82

12.0

Fat

1.25

52.2


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Last updated:  02/23/2005 / Copyright  by SG Saupe / URL:http://www.employees.csbsju.edu/ssaupe/index.html