Biological Foundations 112, Lecture 16


Fruits

Chapter 27, pages 565
Basic Botany-5 20:45-25:51


I.   Development of Fruit (using the garden pea as an example)

     A.   Structure of the carpel before fertilization

            1.   Pistil - composed of one carpel

             2.  Carpel structure

                  a.   Dorsal suture - corresponds to the midrib of the leaf

                  b.   Ventral suture - corresponds to the fusion of the two leaf margins

                  c.   Carpellary bundles

                        (1)  One on each side of the ventral suture

                        (2)  One at the dorsal suture (leaf midrib)

                  d.   Placenta is along the ventral suture and ovules are attached to the placenta

                  e.   Ovary wall is composed of three layers

                        (1)  Outer epidermis

                        (2)  Middle zone several cells thick

                        (3)  Inner epidermis

     B.   Structure of carpel after fertilization

            1.   Ovary wall now called pericarp

            2.   There are three parts to the pericarp:

                  a.   Exocarp - outer epidermal region

                  b.   Mesocarp - middle zone

                  c.   Endocarp - inner layer

            3.   The floral structures wither and may or may not persist

            4.   The seeds develop and mature at the same time the ovary wall does

            5.   Abortive seeds occur - probably unfertilized ovules

II.  Kinds of Fruits

     A.  Simple Fruits - single ovary with either one or many united carpels

           1.   Dry Pericarp - pericarp is dry when the fruit is mature

                 a.   Dehiscent - pericarp splits open and releases the seed when mature

                       (1)  Pod or Legume

                       (2)  Follicle

                       (3)  Capsule

                       (4)  Silique

                 b.   Indehiscent - pericarp remains attached to seed when mature, seed not released

                       (1)  Achene

                       (2)  Grain or Caryopsis

                       (3)  Samara

                       (4)  Schizocarp

                       (5)  Nut

           2.   Fleshy Pericarp - pericarp wet and juicy when mature

                 a.  Drupe

                 b.  Berry

                      (1)  True Berry

                      (2)  Hesperidium

                      (3)  Pepo

                 c.   Pome

     B.   Aggregate Fruits - composed of many simple ovaries on one receptacle within one
                                           flower growing into a single fruit

     C.   Multiple Fruits - composed of many simple ovaries on many receptacles within many  
                                        flowers that grow together in one large single fruit

III. Description of Each Kind of Simple Fruit

      1.   Legume or Pod

            a.   Dehiscent

            b.   Fruit from one ovary and one carpel in the ovary

            c.   Dehisces along two sutures

            d.   Example:  Pea Family (Fabaceae)

      2.   Follicle

            a.   Dehiscent

            b.   Fruit from one ovary and one carpel in the ovary

            c.   Dehisces along one suture

            d.   Examples:  Magnolia and milkweed

      3.   Capsule

            a.   Dehiscent

            b.   Fruit from one ovary that is composed of many carpels

            c.   Dehisces in one of three ways depending upon species

                 (1)   Lengthwise along sutures between carpels  (Example:  cotton and Amaryllis)

                 (2)   Pores around the top like a salt shaker  (Example:  poppy)

                 (3)   Transverse lid like a lid on a pot (Example:  purslane, pigweed, plantain)

      4.   Silique

            a.   Dehiscent

            b.   Fruit from one ovary that is composed of two united carpels

            c.   Dehisces into three portions

                 (1)  Two outer valves

                 (2)  One inner partition containing the seeds

            d.   Example:  Mustard Family (Brassicaceae)

      5.   Achene

            a.  Indehiscent

            b.  Fruit from one ovary that is composed of one carpels

            c.  Pericarp easily separated from the seed coat

            d.  Example:  strawberry seeds, sunflower seeds

      6.   Grain or Caryopsis

            a.   Indehiscent

            b.   Fruit from one ovary that is composed of one carpel

            c.   Pericarp is firmly united to the seed coat

            d.   Examples:  Wheat, Corn, Oats, Grass Family (Poaceae)

      7.   Samara

            a.   Indehiscent

            b.   Fruit from one ovary that is composed of one carpel

            c.   Has a wing-like outgrowth on the ovary wall

            d.   May be one or two seeded

                  (1)  One-seeded Example:  elm or ash

                  (2)  Two-seeded Example:  boxelder or maple

      8.   Schizocarp

            a.   Indehiscent

            b.   Fruit from one ovary that is composed of two united carpels

                  (1)  The two carpeled ovary splits apart at maturity into two separate carpels

                  (2)  Each half contains a seed with the pericarp still firmly attached to the seed

            c.   Example: Carrot Family (Apiaceae)

      9.   Nut

            a.   Indehiscent

            b.   Fruit from one ovary that is composed of one carpel

            c.   Pericarp is hard or stony - the shell of the nut

            d.   Husk or cupule on some nuts - a modified calyx or involucre

            e.   Examples:  Chestnut, Walnut, Hickory Nut, Acorn, Hazelnut, Beechnut

            f.   Fruits that are not nuts:  Almond is a Drupe, Brazil Nut and Pinyon Nuts are seeds,
                                                     and Peanuts are the seeds of a legume or pod

    10.   Drupe

            a.   Fleshy Pericarp

            b.   Fruit from one ovary that is composed of one carpel

            c.   Single seed in the center - thus called a stone fruit

            d.   Structure of the fruit

                  (1)  Endocarp - the hard smooth shell

                  (2)  Mesocarp - edible central juicy portion

                  (3)  Exocarp - skin

            e.   Examples:  Peaches, Apricots, Olives, Cherries, Almonds

    11.   True Berry

            a.   Fleshy Pericarp

            b.   Fruit from one ovary that is composed of many carpels

            c.   Has a very thin skin of exocarp only

            d.   The seeds are embedded in the fleshy mesocarp and endocarp

            e.   The mesocarp and endocarp are the edible portions of the fruit

            f.   Examples:  tomatoes and grapes

    12.   Hesperidium

            a.   Fleshy Pericarp

            b.   Fruit from one ovary that is composed of many carpels

            c.   A modified True Berry

                  (1)  Has a thick oily skin of exocarp and mesocarp

                  (2)  Pulp section is the endocarp where the seeds are embedded

                         (a)  The "wedges" are the carpels

                         (b)  Ten carpels with two seeds each

            d.   Example:  Citrus Fruits such as oranges, grapefruits, lemons, limes

    13.   Pepo

            a.   Fleshy Pericarp

            b.   Fruit from one ovary that is composed of many carpels

            c.   A modified True Berry

            d.   Rind or outer shell of rind is a fusion of the receptacle and the exocarp

            e.   Fleshy part  is the mesocarp and endocarp where the seeds are embedded

            f.   Examples:  Watermelon, Squash, Cucumber, Pumpkin

    14.   Pome

            a.   Fleshy Pericarp

            b.   Fruit from one ovary that is composed of five carpels

            c.   Hypanthium is adnate to the pericarp

            d.   The fleshy edible portion of this fruit comes from the hypanthium

            e.   Structure of this fruit

                  (1)  Endocarp - parchment-like material adjacent to the seeds

                  (2)  Mesocarp between the parchment-like material and the coreline

                  (3)  Exocarp - produces the coreline at the outer limit of the carpels

    15.   Aggregate

            a.   Fleshy fruit composed of many single carpels

            b.   Numerous carpels on one receptacle within one set of floral leaves (or, numerous
                  pistils or ovaries within a single flower)

            c.   Examples:

                  (1)  Aggregate of achenes

                         (a)  Strawberry

                         (b)  The seeds are the achenes

                         (c)  Fleshy receptacle is what is eaten

                  (2)  Aggregate of druplets

                         (a)  Blackberry, Raspberry

                         (b)  The seeds are in each of the little druplets

                         (c)  The fleshy receptacle and the druplets are eaten in the Blackberry

                         (d)  The druplets only are eaten in the Raspberry

    16.   Multiple

            a.   Typically a fleshy fruit

            b.   The enlarged ovaries from several flowers grow together into one single fruit.

            c.   Formed from the individual ovaries of several flowers all developing together into one
                  fruit

            d.   The individual ovaries of this fruit type develop into simple fruits as described above
                  but when mature combine to form one large fruit.

            e.   Examples:

                  (1)  Mulberry

                         (a)  Each ovary develops into a nutlet enclosed by persistent juicy calyx lobes

                         (b)  Individual ovaries all crowd together and collectively the entire fruit is called
                                a mulberry

                  (2)  Fig

                         (a)  Enlarged fleshy receptacle

                         (b)  Flowers small and attached to the inner wall of the receptacle

                         (c)  Staminate and pistillate flowers attached to the inside of the urn-shaped  
                               receptacle

                         (d)  The ovary is one-celled and one-seeded, developing into a nutlet

                         (e)  The entire receptacle with all its little nutlets is the fruit

    17.   Accessory

            a.   Accessory tissue is any part of the fruit that develops fruit-like characteristics that is
                  not part of the ovary or pericarp

            b.   Examples:

                  (1)  Receptacle of the strawberry and blackberry

                  (2)  Rind of the watermelon

                  (3)  The edible hypanthium of the apple and pear


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