Plants and People

Reproductive Morphology: Flowers and Fruits

Why a Flower?

The Reproductive Structure of Flowering Plants: Perianth Petal: Corolla Sepal:Calyx

Flower Anatomy

Calyx

: the outer whorl of

sepals

; typically these are green, but are petal-like in some species.

Flower Anatomy

Corolla

: the whorl of

petals

, which are usually thin, soft and colored to attract animals that help the process of pollination. The coloration may extend into the ultraviolet, which is visible to the compound eyes of insects, but not to the eyes of birds.

Flower Anatomy

Androecium

(from Greek

andros oikia

: man's house): one or more

stamens

, each with a

filament

topped by an

anther

where pollen is produced. Pollen contains the male gametes.

Flower Anatomy

Gynoecium

(from Greek

gynaikos oikia

: woman's house): all the female parts—the

pistil(s) with ovule(s) inside

.

Flower Anatomy carpel

fertilization carpel structure

Evolution of the Carpel

See figures 3.1 and 3.2 in your book

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 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

septa

.

locule

(pl. = locules). The dividing walls are called the

ovule

transverse section

locule

longitudinal section single carpel 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

said to have a compound pistil.

and the flower is

Evolution of the fused carpel syncarpous

Placentation

basal placentation

locule, no septa. : attachment of ovules to the bottom of the ovary. One

apical placentation

: The attachment of the ovules is at the apex (top) of the ovary. One locule, no septa.

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

ovary (one locule, no septa) : ovules attached to a free-standing central column in a syncarpous, unilocular

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 D E F G

Flower Structure Variation

imperfect perfect imperfect

Flower Structure Variation

Ovary Position

A.

ovary superior, floral parts hypogynous

B.

ovary inferior, floral parts epigynous

C.

ovary half-inferior

D.

ovary superior, floral parts perigynous, hypanthium cup shaped

Flower Structure Variation

A flower having sepals, petals, stamens, and pistils is

complete

; if a flower is lacking one or more of these whorls, it is said to be

incomplete

.

no stamens present = incomplete incomplete complete

Inflorescences

An

inflorescence

is a group or cluster of flowers. It may be branched or unbranched. Modifications can involve the length, variations in the proportions, compressions, and swellings, and the order in which the flowers open.

Usually the modifications have been evolved to optimize the plant’s method of pollen dispersal.

Pollen Dispersal by Animals

Bees, Beetles, Bats, Birds, Butterflies, etc…

Symmetry

Flowers that are

actinomorphic

have "radial symmetry", meaning they can be divided into symmetrical halves by more than one plane passing through the axis, much as a pie can be cut into several equal and identical pieces.

Zygomorphic

flowers have "bilateral” symmetry, where flowers can be divided by only a single plane into two mirror image halves, much like a person's face.

Dicot versus Monocot

Dicot Monocot

Fruit and Seed Formation

A fruit develops from an

ovary

. A seed develops from an

ovule

.

Dry Fruits

Dry fruits

have the

pericarp

(fruit wall) 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 -

Achene

Achene

- single seeded, thin pericarp, seed coat is separate from ovary wall. Example:

sunflower

and

strawberry “seeds”

Indehiscent, Dry Fruits -

Grain

Grain (caryopsis)

ovary wall. Example: - single seeded, pericarp fused with the

corn, wheat, rice, oats, etc.

fused

Indehiscent, Dry Fruits -

Nut

Nut

- single seeded, with hard or bony pericarp, often wholly or partially surrounded by a husk of bracts. Example:

hazelnut, walnut, pecan

Dehiscent, Dry Fruits -

Legumes

Legume

Example: - usually dehisces along two sutures; from a simple pistil.

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 -

Berry

Berry

- one to multiple seeds, mesocarp is fleshy, endocarp is soft. Example:

grape, tomato

Fleshy Fruits -

Drupe

Drupe

- usually one seeded, exocarp a thin skin, 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 berrylike, with a hard rind; almost always with three carpels and parietal placentation. Examples:

melon, squash

Fleshy Fruits -

Pome

Pome fruits

have 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 achenes

.

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

Today’s Lab Activities

• You need to get information from the prop cards to add to your chart. For each crop, record if it is a

monocot

or

dicot

,

family

and

genus/species name

,

fruit type

,

origin

and

carpel number (for fruits.)

• 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!