PLANTS AND PEOPLE - FRUIT LAB
  Note that this lab is in THREE PARTS (next two linked at bottom)--you will need all of them.  If you need to print the fruit chart, for best results, DON'T print from this page and the ones linked from the bottom.  Instead, click this link for a PDF that will print everything properly. There may be a few fruits to add in lab--we never know what the local stores are going to have. 
You can download the powerpoint for this lab  HERE.
  INTRODUCTION:

In the flower lab, we observed that the ovary, style, and stigma make up the pistil, and that the ovary is a protective vessel in which ovules are nourished to their mature form--seeds.  Recall that the closed carpel evolved via infolding of the leaf to form an enclosed vessel.   Each of these vessel units is a carpel with its own line of placentation or zone of ovule/seed attachment.  Ovaries and fruits can be composed of one to many free or fused carpels.  The number of ovules associated with each carpel, and thus the number associated with the ovary, can vary from one to many.  Also, ovaries can be separated into several distinct chambers or consist of only one chamber.  These chambers are called locules.  The number of locules is often (but not always) equal to the number of carpels.  Remember to check the number of placentae, number of styles or stigmas, number of ovary lobes, etc.

Dispersal of seeds in nature is accomplished in many ways.  Seeds can be dispersed by animals, wind, water, etc.  Animal dispersers range from insects to birds to mammals to fish.  Modifications in the shape, structure, and often color of the ovary directly correspond to the ways in which seeds are dispersed.  Bright red, fleshy berries are commonly dispersed by fruit-eating birds.  Winged fruits, such as those found on maple trees, have obviously come about through modifications which facilitate wind dispersal.  How might nuts, such as acorns, be dispersed?  What characters would a water-dispersed fruit have?  What characters have humans selected for or against in the fruits that they eat?
Objectives for this lab are to:
□ recognize and interpret the different fruit types and placentation types
□ be able to identify/count locules, carpels, placentae, and ovules/seeds in a given fruit
□ make an educated guess as to the dispersal agent of a fruit
□ recognize fruits by their common and scientific names, family, and class
□ identify what fruit type is represented by the fruits on display
□ demonstrate a basic knowledge of the geographic origins of the fruits

Safety concerns:
□ Do not eat anything until instructed to do so and until you know it has been washed, if needed.
□ Do not eat anything labeled “Demo” or “Do Not Eat.”
□ Do not eat anything raw if it is edible only cooked.
□ Do not eat anything to which you know or suspect you may be allergic.  If you are sensitive to poison ivy, be especially careful with mango, cashew, and pistachio.
□ Handle knives carefully

FRUIT TYPES

Fruits can be classified as either dry or fleshy and either dehiscent (splitting open at maturity) or indehiscent. Some consist of a specific number of carpels or have other diagnostic features.  Learn to recognize the different fruit types.  Keep in mind that some of the fruits we eat are consumed in an immature state.


I. Fruits essential for human survival:  

1. LEGUME: Single carpel, multi-seeded, dehiscent along two sutures (wild types), seed consists mostly of young embryo sporophyte (high protein) Found in families of the Fabales (Leguminosae):

    o Peanut - geocarpic     
    o Green bean - single line of ovules (nearly mature)
    o Bean, chickpea, lentil - major food crops; mature seeds are consumed
    o Snow pea, sugar pea - ovules and fruit, less mature

2. CARYOPSIS or GRAIN: More than one carpel BUT only a single seed. Seed, mostly endosperm (high in starch)  The seedcoat is fused to the pericarp.  Found in members of the grass family–Poaceae

    o Corn (maize) - FRUIT is a CARYOPSIS but the EAR is a MULTIPLE fruit [fruits from separate flowers of a single INFLORESCENCE combined in a single structure. Note inflorescence stalk [RACHIS] or corncob.
    o Other true grains--rice, wheat, oats, rye, barley, sorghum.

II. Other fruits and fruit-like structures:

3. ACHENE: More than one carpel, one seed, pericarp a single layer of tissue and SEPARATED from the seed. The CARYOPSIS [fruit of the grass family - POACEAE] is similar in structure BUT pericarp and seed are united.  
    o Sunflower - Fruit [for the birds] and seed [for people]
    o Strawberry - FRUIT is a tiny achene ( positioned in pits that occur in the expanded, red, sweet RECEPTACLE of the AGGREGATE FRUIT [a 'false' fruit]

4. NUT : a dry, indehiscent, 1-seeded fruit with a hard exocarp.  The ovaries that produce nuts have more than one carpel, but through abortion, only one seed matures.

    o Pecan - edible portion is embryo and cotyledons
    o Walnut, filbert, chestnut, macadamia nut.  
    o NOT: almond, Brazil nut, peanut.  Why?

5. CAPSULE : a dry, dehiscent fruit made up of several carpels.  The ripe pericarp splits open (dehisces) into the carpels or between the carpels or both, or sometimes irregularly or via pores or slits.  

           o Okra - capsule eaten while immature

6. DRUPE: Single carpel, single-seeded, pericarp tissue differentiated into THREE layers: EXOCARP, MESOCARP, ENDOCARP; indehiscent:

    o Peach - exocarp with fuzz
    o Nectarine, plum, and cherry - exocarp without fuzz
    o Almond - exocarp/mesocarp removed, just PYRENE [=endocarp and seed]
    o Avocado - endocarp VERY thin
    o Coconut - mesocarp fibrous ,[dispersal], testa thin, endosperm both solid [meat] and liquid [milk]
    o Raspberry and blackberry - an AGGREGATE (separate ovaries of one flower joined together) of small drupes [druplets]
    o Mango, black pepper, nutmeg, etc.

7. BERRY: More than one carpel, fleshy [usually animal dispersed] and many-seeded; indehiscent

    o Tomato (Roma and 'cherry') - two carpels/locules - primitive
    o Tomato (normal) - extra septa and locules
    o Peppers - midway between a CAPSULE [dry, dehiscent] and a berry
    o Eggplant - selected for extra tissue - no locules
    o Kiwi fruit - leathery, fuzzy pericarp with many carpels, seeds attached on a central mass of white tissue
    o Banana - epigynous - 'peel' is a combination of pericarp and HYPANTHIUM - a sterile polyploid, ovules are aborted
    o Blueberry, grape, papaya, cactus fruit, etc.

8. PEPO: a 'special' BERRY from an epigynous flower of the Cucurbitaceae - leathery or hard 'rind' (Pericarp + hypanthium), 1 locule, and 3 carpels, placentation parietal, with 3 placentae.  

    o Cucurbita - summer squash (eaten immature), winter squash, pumpkin
    o Cucumber - entire fruit is consumed
    o Watermelon - 90% water
    o Honeydew, cantaloupe, musk melons - all one species

9. HESPERIDIUM: a special type of  berry with numerous carpels (separable as 'sections'); locules filled by plump cells (which are modified hairs!); pericarp with oil glands. Produced by the genus Citrus.  

    o Orange, lemon, lime, grapefruit - distinctive essential oils

10. POME: a 'false fruit' that is formed by fusion of the HYPANTHIUM (of an epigynous flower) to the ovary, with the hypanthium forming the edible portion.

    o Apple/Pear - note sepals on the opposite side from the  pedicel (the flower is epigynous) and internal demarcation between ovary wall and hypanthium.

11. AGGREGATE FRUIT:  a multiparted fruit that develops from separate, simple pistils from ONE flower.

    o Blackberry/Raspberry--these are aggregations of tiny drupelets.

12.  MULTIPLE FRUIT: Structure with fruits from separate flowers combined into a single unit (essentially a fruit-like infructescence).
    o The maize ear is a unit formed from a pistillate inflorescence.
    o Pineapple - each perfect flower forms a berry, berries are compressed together to form the pineapple. Note that the central RACHIS of both pineapple and maize ear (cob) is a hard, fibrous, vascularized shoot (as opposed to pericarp) tissue.
    o Fig - inflorescence enclosed within receptacle tissue--this special fruit type is called a syconium
    o Cherimoya, jackfruit, breadfruit


13. ACCESSORY FRUIT: a fruit in which the edible part is derived from something other than the ovary.

    o Strawberry--the real fruits are the little achenes (which most people call seeds) and the juicy red part we eat is an enlarged receptacle
    o Apple/pear--Apples and pears may be placed in this category, since the edible part is the hypanthium, not the ovary.

Go on to the Activity Section, Fruit Review Questions, Return to BOTN 328 homepage or prior lab session (flowers)

last updated  6-16-2010 (revised text)