Plants and People
Fruits
The Carpel
The carpel is the basic unit of the gynoecium. Each carpel consists of an ovary
connected to a stigma by the style.
Within within each carpel are one or more ovules, which will become the seed(s).
The area of attachment is called the placenta (pl. = placentae) and the empty space
in the chamber is called the locule (pl. = locules). The dividing walls are called the
septa.
single carpel
ovule
transverse
section
locule
longitudinal
section
fused carpels
The Single Carpel
A gynoecium with only one carpel is termed unicarpellate. A gynoecium of
many separate carpels is termed apocarpous.
TS
LS
unicarpellate
apocarpous
Fused Carpels
A gynoecium with many fused carpels is termed syncarpous and the flower is
said to have a compound pistil.
Evolution of the fused carpel
syncarpous
Placentation
basal placentation: attachment of
ovules to the bottom of the ovary. One
locule, no septa. Can be found in an
apocarpous or syncarpous gynoecium.
apical placentation: The attachment of
the ovules is at the apex (top) of the
ovary. One locule, no septa. Can be
found in an apocarpous or syncarpous
gynoecium
Placentation
parietal placentation: ovules are
attached to the side walls of the ovary
(or extrusions of the wall) such that
an ovary usually has one locule and
therefore no septa. Can only be found
in a syncarpous gynoecium;
axile placentation: ovules are
attached to an axis derived from the
connate margins of the component
carpels, such that an ovary is divided
into two or more locules by septa. The
ovules are borne along the central
axis. Can only found in a syncarpous
gynoecium.
Placentation
free or central placentation:
attachment of ovules to a freestanding central column in a
syncarpous, unilocular ovary (one
locule, no septa)
marginal placentation: ovules are
attached to the folded margins of the
carpel, giving the appearance that
there is only one elongated placenta
on one side of the ovary. Can only be
found in a simple pistil. This is
conspicuous in legumes.
How Many Carpels? Locules?
A
B
C
E
F
G
D
Simple Fruits
A simple fruit is one that is derived
from a single ovary, this ovary can be
part of an apocarpous, syncarpous or
unicarpellate gynoecium.
The ovary wall develops into the
pericarp, or fruit wall. This may
have three layers: the exocarp,
mesocarp, and endocarp.
The pericarp can develop in various
ways, leading to the assortment of
simple fruit types.
Dry Fruits
Dry fruits have the pericarp dry at maturity. Fruits which split
open to release the seeds are termed dehiscent. Those that do
not split open are called indehiscent.
Indehiscent, Dry Fruits
Indehiscent, dry fruits do not split at maturity.
Subclasses of indehiscent fruits:
Achene
Grain (caryopsis)
Nut
Indehiscent, Dry Fruits - Achene
Achene - single seeded, thin pericarp, seed coat is separate
from ovary wall.
Example: sunflower and strawberry “seeds”
Indehiscent, Dry Fruits - Grain
Grain (caryopsis) - single seeded, pericarp fused with the
ovary wall.
Example: corn, wheat
fused
Indehiscent, Dry Fruits - Nut
Nut - single seeded, with hard or bony pericarp, wholly or
partially surrounded by a husk of bracts.
Example: hazelnut, walnut
Dehiscent, Dry Fruits
Dehiscent fruits are characterized by the splitting of the pericarp
to release the seeds.
Subclasses of dehiscent fruits:
Legume
Capsule
Dehiscent, Dry Fruits - Legumes
Legume - usually dehisces along two sutures; from a simple pistil.
Example: beans, peas, soybeans
caylx
one folded carpel
seed/ovule
style
Unopened Legume
Legume Split Open
(1 carpel, 2 seams)
Dehiscent, Dry Fruits - Capsule
Capsule - usually from a compound pistil, usually many seeded.
Pericarp opens with pores or slits.
Example: okra (which we eat before maturity.)
seed
septa
locule
dehisces along locules
(loculicidal)
okra is a capsule
Fleshy Fruits
Fleshy fruits are fruits in which all or part of the pericarp is
fleshy and swollen at maturity.
Types of fleshy fruits:
Berry
Drupe
Hesperidium
Pome
Pepo
Fleshy Fruits - Berry
Berry - one to multiple seeds, mesocarp is fleshy, endocarp is
soft. Example: grape, tomato
Fleshy Fruits - Drupe
Drupe - usually one seeded, mesocarp fleshy, endocarp
usually hard. Example: peach, plum
Fleshy Fruits - Hesperidium
Hesperidium - special kind of berry with leathery rind and oil
glands dotting the surface. Example: lime, orange
Fleshy Fruits - Pepo
Pepo fruits are simple fruits that are berrylike with a hard
rind; almost always with three carpels and parietal
placentation. Examples: melon, squash
Fleshy Fruits - Pome
Pome fruits are simple fruits that are berrylike with most of
the flesh derived from a floral cup and receptacle.
Example: Apple, pear
(receptacle)
Other Fruit Types (Non-Simple)
Other fruit types:
Multiple
Aggregate
Accessory
Parthenocarpic
Non-Simple Fruits - Multiple
Multipe fruits are formed by the fusion of fruits of numerous
independent flowers.
Example: pineapple, fig
Non-Simple Fruits - Aggregate
Aggregate fruits are those formed from several separate ovaries
within a single flower.
Examples: raspberry, blackberry
Non-Simple Fruits - Accessory
Accessory fruits are those where the “fruit” part is derived from
something other than ovary tissue. A strawberry is a swollen
receptacle and the seeds on the surface are the true fruits, called
achenes.
Today’s Lab Activities
• You need to get information from the prop cards to add to your chart.
For each fruit you need to record if it is a monocot or dicot, family and
genus/species name, fruit type, origin and carpel number.
• For some, carpel number will be given and for others you will need to
determine the carpel number yourself by counting the carpels by either
counting locules or points of attachments for seeds in an open fruit.
• WARNING! If you have a severe allergy to poison ivy, you should not
eat mango, pistachios, or cashews unless you know you are not sensitive
to them
• Other than allergy concerns, you are encouraged to taste things that are
new to you by cutting small pieces to eat !! Have fun!