I .­

Fruits, Spices, Survival Plants, and Poisonous Plants

Materials

1. As complete as possible representation of both dry and fleshy fruit types

2. Demonstration of as many spices as is feasible

3. Display of survival plants (either herbarium specimens

or live material) indicating how each plant is used 4. Display of poisonous plants (either herbarium

specimens or live material) with notes on toxicity

Some Suggested Learning Goals

1. Know how the various fruit types are distinguished from one another.

2. Know at least one or two representatives of each fruit type.

3. Learn which plant parts are used for specific purposes.

4. Know several representative survival plants, how they are used, and how the toxic plants poison humans.

Introduction

In this exercise you will be asked to classify a number of fruits and to know examples of each fruit type. You will also be asked to take notes on what plant parts are used to prepare the various spices on display, know how the sur­vival plants are used, and be able to give examples of com­mon poisonous plants.

A. Fruits

Fruits may be defined as mature ovaries, usually containing seeds. At maturity, the ovaries swell and become fleshy

("juicy"), or the ovary wall shrivels and becomes dry. The separation between dry and fleshy fruits is occasionally in­distinct, but most fruits are relatively easy to categorize in this regard. Dry fruits either release their seeds when the fruit splits at maturity, or the fruit wall layers adhere to the seeds within and remain until the seed germinates. In some instances, these fruit wall layers form wings that aid in dis­persal; such wings should not be confused with the wings of conifer seeds, which are merely extensions of the seed coat.

A mature fruit, such as a peach, has three identifiable regions in addition to the seed(s). The outermost region ("skin") is referred to as the exocarp. The innermost region (the pit in a peach) is called the endocarp; it usually sur­rounds the seed(s). The flesh between the exocarp and the endocarp is the mesocarp. In dry fruits, in particular, two or all three of the layers may be fused together and, collec­tively, are referred to as the pericarp. Some fruits, such as apples and strawberries, consist of other flower parts in ad­dition to the ovary or ovaries. For example, the calyx itself may become fleshy and comprise more extensive fruit tis­sue than the ovary that it surrounds. A fruit that consists of more than just the ovary is said to have accessory tissue or is called an accessory fruit.

The fruit key that follows gives you many of the pri­mary distinctions among the various kinds of fruits, but it is not completely practical unless you have more information about the flowers from which the fruits are derived. Your instructor will help you with whatever additional informa­tion is needed to arrive at the correct botanical classifica­tion for the displayed fruits.

Key to Common Fruits

I a. Fruits fleshy.

2a. Fruits simple (i.e., derived from a flower with a single pistil).

3a. Fruits with a single seed enclosed in a hard pit ..................................................................................................................... DRUPES 3b. Fruits with more than one seed, the seeds not enclosed in a hard pit (only one seed develops in an avocado, and no seeds develop in the common banana).

4a. Fruits with thin or leathery skin or the outer part of the fruit forming a rind; endocarp not

leathery or papery ................................................................................................................................................... BERRIES (Berries with a thin skin are referred to as TRUE BERRIES; berries with a leathery skin containing oils are referred to as HESPERIDIUMS; berries with a rind are referred to as PEPOS).

4b. Fruits with leathery or papery endocarps ............................................................................................................. PONIES

2b. Fruits derived from more than one pistil.

5a. Fruits derived from a single flower having several to many pistils AGGREGATE FRUITS 5b. Fruits derived from several to many separate flowers in an inflorescence, the fruits

coalescing to varying degrees to form a single "fruit" at maturity ..................................... MULTIPLE FRUITS

I b. Fruits dry at maturity.

6a. Fruits not splitting at maturity.

7a. Fruits with a wing........................................................................................................................................................ SAMARAS 7b. Fruits without a wing.

8a. Fruits with a hard shell surrounding the seed........................................................................................................... NUTS 8b. Fruits without a hard shell.

9a. Fruit wall fused to the seed coat.............................................................................................. GRAINS (CARYOPSES)

9b. Fruit wall with seed loosely attached...................... ACHENES 6b. Fruits splitting in various ways at maturity.

I Oa. Fruits splitting along or between carpel lines or forming a cap that comes off or a row of pores

near the top .............................................................................................................................................................. CAPSULES lOb. Fruits splitting lengthwise along the edges.

I la. Fruits leaving a central partition to which the seeds are attached .............................. SILIQUES or SILICLES I I b. Fruits not leaving a central partition.

12a. Fruits splitting along one edge only ............................................................................................................ FOLLICLES

12b. Fruits splitting along both edges .................................................................................................................... LEGUMES

B. Spices

Spices are derived from a wide variety of plants and plant parts, although some plant families seem to produce more of them than others. Make a list of the spices and flavoring materials on display, and indicate which part of the plant (e.g., leaves, flowers) is used as a spice.

C. Survival Plants

The number of plants grown for food, medicine, and other purposes relating to survival is very large, and past cultures made even more extensive use of plants than we do today. It is possible here to examine only a tiny fraction of the local representatives. In addition to making a list of the plants on display, make notes as to what parts of the plants have been or can be used by humans, and indicate the specific uses.

1. What distinguishes a hesperidium from a pepo?

2. Which of the fruit types is derived from more than one pistil?_______________________________________

3. How doe you tell a grain (caryopsis) from an achene?

4. If you were to cut an apple in half, you would notice that the endocarp around the seeds is somewhat papery. How would you classify it as to fruit type?

5. Drupes and nuts both have a single seed. What distinguishes them from one another?_______________________

6. Black raspberries and mulberries look quite a bit alike, but raspberries are aggregate fruits while mulberries are multiple fruits. What is the difference?

7. Choose one of the poisonous plants and tell which part or parts is(are) poisonous.

8. When you use oregano as a spice, what part of the plant is involved?

9. Name two spices that are derived from flowers or flower buds.

10. Choose one of the survival plants and tell how it is used.

1. Which fleshy fruits have a single seed enclosed in a hard pit?

2. Strawberry flowers have numerous pistils on a common receptacle. What fruit type does that make them?

3. How many seeds does a typical berry have?

4. What distinguishes a hesperidium from a true berry?

5. Do both aggregate and multiple fruits come from more than one pistil? Explain.

6. Give a common example of a fruit in which the seeds do not develop.

7. Which dry, splitting fruit has a central partition to which the seeds may be attached?______________________

8. What type of dry, nonsplitting fruit has a wing at maturity?________________________________________

9. What type of dry, splitting fruit splits only along one edge?________________________________________

10. How do you tell a grain (caryopsis) from an achene?______________________________________________

Fruit Types and Classification of Fruits

Introduction

Although most of us have a good idea what fruits and vegetables are when we eat them, it would be difficult provide a definition for someone of just what makes one food a vegetable and another a fruit. For a botanist, the definitions are easier; a fruit is a reproductive structure of an angiosperm which develops from the ovary and accessory tissue, which surrounds and protects the seed. Fruits are important in seed dispersal. A vegetable is a part of one of the vegetative organs of the plant: roots, stems or leaves, or shoot systems. There are a few "vegetables which are difficult; broccoli and cauliflower are inflorescence buds, and artichokes are the entire inflorescence. Since flowers, the reproductive organ of the plant produce fruits and seeds, perhaps those vegetables which are inflorescences are more similar to fruits than they are vegetables. No matter what we call our nutritious dietary components, in botany what constitutes a fruit is straightforward, and this lab looks at the structure and classification of fruits. The process of fertilization initiates both seed and fruit development. While seeds develop from the ovules, the ovary tissue undergoes a series of complex changes which result in the development of the fruit. Many fruits are "fleshy" and contain sugars which attract animals who then disperse the enclosed seeds to new locations. Other, non-fleshy, fruits use other mechanisms for seed dispersal. In some plants, fruits can develop without fertilization. This is called parthenocarpy, and such fruits are seedless. As the ovary develops into a fruit, its wall often thickens and becomes differentiated into three, more or less distinct, layers. The three layers together form the pericarp, which surrounds the developing seed or seeds.

The three fruit layers are:

• Exocarp, the outermost layer often consisting of only the epidermis

• Mesocarp, or middle layer, which varies in thickness

• Endocarp, which shows considerable variation from one species to another

Materials Required per pair of students and for Demonstration

• Fresh snap beans or garden peas. Other available legumes may be substituted.

• Dry and soaked corn grains

• Tomatoes, cranberries or grapes

• Peaches, plums, or cherries

• Apples, pears, or quinces

• In addition, an assortment of various kinds of fruits that are available should be available for demonstration. Dry and fleshy fruits of different types should be provided, as should aggregate and multiple fruits.

Exercise 1 Classifying Fruits

All fruits may be classified into three major groups on the basis of the number of ovaries and the number of flowers involved in their formation. The following outline includes most of the common types of fruits. A simple key to classifying fruits is provided here. Use these descriptions and the "Key to Fruit Types" provided to identify the

A. Simple Fruits.

Simple fruits develop from a single matured ovary in a single flower. Accessory fruits have some other flower part united with the ovary.

1. Fleshy Fruits, pericarp fleshy at maturity

a. Berry, consisting of one or more carpels with one or more seeds, the ovary wall fleshy

(1) Pepo (an accessory fruit), a berry with a hard rind, the receptacle partially or completely enclosing the ovary

(2) Hesperidium, a specialized berry with a leathery rind

b. Drupe, a stone fruit, derived from a single carpel and containing (usually) one seed. Exocarp a thin skin

c. Pome (an accessory fruit), derived from several carpels, receptacle and outer portion. of pericarp fleshy, inner portion of pericarp papery or cartilaginous, forming a core

d. Hip (an accessory fruit), several separate carpels enclosed within the fleshy or semi-fleshy receptacle

2. Dry Fruits, pericarp dry at maturity

a. Dehiscent fruits, those which dehisce or split open when fully mature

(1) Follicle, composed of one carpel and splitting along a single suture

(2) Legume, composed of a single carpel and splitting along two sutures

(3) Capsule, composed of several carpels and opening at maturity in one of four ways:

(a) Along the line of carpel union (septicidal dehiscence)

(b) Along the middle of each carpel (loculicidal dehiscence)

(c) By pores at the top of each carpel (poricidal dehiscence)

(d) Along a circular, horizontal line (circumscissle dehiscence)

(4) Silique, composed of two carpels which separate at maturity, leaving a persistent partition between them

b. Indehiscent fruits, those which do not split open at maturity

(1 ) Achene or akene, a one-seeded fruit with the seed attached to the fruit at one point only

(2) Caryopsis or grain, a one-seeded fruit in which the seed is firmly attached to the fruit at all possible points

(3) Samara, a one- or two-seeded fruit with the pericarp bearing a wing like outgrowth. A modified achene

(4) Schizocarp, consisting of two carpels which at maturity separate along the midline into two one-seeded halves, each of which is indehiscent

(5) Loment, having several seeds, breaking into one-seeded segments at maturity

(6) Nut, a hard, one-seeded fruit, generally formed from a compound ovary, with the pericarp hard throughout

B. Aggregate Fruits.

Aggregate fruits consist of a number of matured ovaries formed in a single flower and arranged over the surface of a single receptacle. Individual ovaries are called fruitlets.

C. Multiple Fruits.

Multiple fruits consist of the matured ovaries of several to many flowers more or less united into a mass. Multiple fruits are almost invariably accessory fruits.

Exercise II The Structure of Some Common Fruits

This exercise is designed to help you become familiar with the structure of several common fruit types, such as the legume, the caryopsis, the berry, the drupe, and the pome.

A. Legume: Bean or Pea

Examine the bean or pea pod on your table. Answer the following questions as you observe its structure.

What part of the carpel does it represent?

What happened to the other parts of the carpel?

.

At which end of the pod were the stamens, the petals, and the sepals attached?

. Is there any evidence of any of these parts?

.

Split the pod lengthwise, along both edges. Do all the seeds adhere to one side, or do they alternate from one side to the other? .

The part of the ovary to which the seeds are attached is called the placenta. How many chambers or locules does the pod contain?

How many carpels are in the legume fruit? .

Identify and label the drawing of the legume.

B. Caryopsis (or Grain): Corn

Examine dry and soaked grains of corn. What part of the carpel do these represent?

Look for a tiny bump on the upper end of the corn grain marking the location where the silk was attached. What is the silk of corn? .

Try to remove the pericarp from a dry grain. Do the same with a grain that has been thoroughly soaked in water. When this skin like structure has been removed, what structures are left? .

Examine a demonstration microscope showing the longitudinal section of a corn grain, and note the fused testa or seed coat and pericarp. How many seeds can you see in this structure? .

Identify and label the drawings of the caryopsis.

C. Berry: Tomato or Grape

Examine fresh or preserved tomato fruits, noting the stalk or pedicel and the green sepals at the basal end. Where do you find the remains the style?

.

Does the berry develop from a superior or an inferior ovary? .

Where were the petals attached? . The stamens? .

Is any other floral part united with the ovary in the formation of this fruit? .

Is the tomato a true fruit or an accessory fruit? .

Examine a cross-section of a tomato. How many locules are visible? .

Of how many carpels is the fruit composed? .

How does the berry differ from the legume? .

Identify and label the drawings of the berry.

D The Drupe: Peach (Cherries, plums, or even soaked prunes)

Examine a fresh or preserved peach. Does this fruit come from a superior or an inferior ovary? . What evidence do you have to support your answer? .

Examine a peach that has been cut lengthwise and one that has been cut crosswise.

How many carpels are involved in the formation of the peach? .

What part of the ovary wall is the rough, fuzzy skin? .

What part of the fruit forms the edible portion of the fruit? .

What part forms the stone or pit? .

How many seeds does this a drupe contain? .

Identify and label the drawing of a drupe.

E. The Pome: Apple (Crab apple, pear, or quince)

Examine the fruit of the apple. Find the fruit stalk or pedicel, and see whether you find near its upper end any scars that might mark the former location of the other flower parts. Examine the other end of the fruit. What are the small, pointed structures which you find there?

. How many of these structures are there? . Do you find any evidence of stamens? .

Does the pome develop from an epigynous or hypgynous flower? .

Examine the cross-section of an apple, noting the star-shaped core. What are the papery or cartilaginous structures found in this region? . How many of them are there? .

Is the pome a true fruit or an accessory fruit? .

Identify and label the drawings of the pome.

III. Identification of Miscellaneous Fruits

There is a key for the identification of fruits at the end of this exercise. Study the various fruits available in the laboratory, having your instructor name them for you if necessary, and record your information on each one on the Table provided. Label the drawings of all of the fruits you have identified.

Characteristics of Some Common Fruits

IV. Types of Fruits: Label the fruit type of each of the drawings below and

on the next two pages.

Key to the Classification of Fruits

1. Simple fruits, formed from a single ovary or carpel .......................................................................2

1. Compound fruits, formed from several carpels or ovaries ............................................................17

2. Dry fruits.................................................................................................................................3

2. Fleshy fruits ...........................................................................................................................12

3. Fruit dehiscent .................................................................................................................................4

3. Fruit indehiscent ...............................................................................................................................7

4. Fruit derived from one carpel only ..........................................................................................5

4. Fruit derived from one to several carpels................................................................................6

5. Fruit splitting at maturity along one suture ........................................................................Follicle

5. Fruit splitting at maturity along two sutures .......................................................................Legume

6. Fruit formed of 2 carpels, separating at maturity, leaving a persistent partition

upright between them ....................................................................................................Silique

6. Fruit formed of several carpels .......................................................................Capsule

7. Fruit several to many-seeded, breaking at maturity into several one-seeded

segments.................................................................................................................................Loment

7. Fruit not as above, generally one-seeded ............................................................................................8

8. Seed coat firmly united with pericarp at all points ................................................Caryopsis

8. Seed coat not attached to pericarp at all points.........................................................................9

9. Pericarp thin, with one or two wings.....................................................................................Samara

9. Pericarp lacking wings....................................................................................................................10

10. Fruit coat very hard .............................................................................................................Nut

10. Fruit coat not particularly hard.............................................................................................11

11. Fruit composed of 2 carpels, separating at maturity into two 1-seeded halves or

mericarps which are indehiscent...................................................................................Schizocarp

11. Fruit coat thin, not separating; fruit small, 1-seeded.......................................................... Achene

12. Fleshy part of fruit derived from ovary only.........................................................................13

12. Fleshy part of fruit derived, at least in part, from the receptacle........................................15

13. Entire ovary becoming fleshy at maturity.......................................................................................14

13. Outer part of ovary fleshy,. inner part stony...........................................................................Drupe

14. Fruit fleshy or juicy, composed of several (usually 10) carpels, each with

2 seeds; rind leathery..........................................................................................Hesperidium

14. Fruit fleshy, of several carpels, each with one to several seeds; leathery rind

lacking.............................................................................................................................Berry

15. Pistils several, separate, non-fleshy, enclosed by the fleshy or semi-fleshy receptacle. .........Hip

15. Ovary compound, carpels united ....................................................................................................16

16. Ovary wall fleshy, berry-like, with hard rind ...............................................................Pepo

16. Inner part of ovary wall papery or cartilaginous, outer part fleshy, surrounded

by and united with a fleshy receptacle ..............................................................................Pome

17. Many simple fruits, usually achenes or drupes, derived from separate carpels of one

flower, located on a single receptacle ....................................................................Aggregate Fruit

17. Many simple fruits derived from the carpels of separate flowers ...............................................18

18. Flowers borne within an enlarged hollow, fleshy receptacle ................................Synconium

18. Flowers borne upon the surface of a more or less fleshy receptacle .............Multiple Fruit