Seeds and Fruits
Types & Dispersal
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Seeds and Fruit
• Fruits are formed by
seed plants to aid in
dispersing seeds
• A seed contains the
developing plant embryo
in a protective coat
(testa)
• Seeds form from ovules
fertilized in the ovary
• Ovaries with seeds ripen
into dry or fleshy fruits
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Parts of a Seed
External seed coat or testa
Developing plant embryo
Stored food called endosperm
Seeds may be in one part (monocot) or
two parts (dicots)
DICOT
MONOCOT
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Parts of a Seed
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Gymnosperm Seed
• A single fertilization produces the
diploid (2n) embryo
• The food source is the haploid
megagametophyte
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Flowering plant seed
In angiosperms (flowering plants) there is
DOUBLE _______________
Which produces a diploid ________(2n) and,
A triploid (3n) __________
Endosperm is the
food source
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Dicot vs. monocot seed
Dicot has two cotyledons
(like bean)
Endosperm (food) is kept
in the _________
Monocot has one
__________ which
absorbs the endosperm
tissue during
germination (corn)
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Fruit
In flowering plants – Fruit is a mature,
ripened o_____ that contains the seeds
Pericarp – the ovary wall
Fruit types
A. Simple
B. Aggregate
C. Multiple
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ovary
A. Simple fruit
A. Simple fruit – develops from a ______
ovary of a single flower.
Simple fruits can be either fleshy or dry when
mature
Simple fleshy fruit
1. __________
2. _________
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Simple fleshy fruit
1. Berry – entire fruit wall is soft
and fleshy at maturity. Inside is
slimy.
For example, grapes, tomato, etc.
2. _______________ is a berry
with tough, leathery rind (peel)
Examples: oranges, lemons,
other citrus.
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Simple fleshy fruit: drupe
3. _______ type – outer part of fruit wall is
soft and fleshy, inner part is hard and
stony
For example: ______________________
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Simple fleshy fruit: pepo
4. ________ – also a fleshy fruit with a tougher
outer rind
All member of the squash family: pumpkin,
melons, cucumbers
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Simple fleshy fruit: pome
5. Pomes: most of the fleshy part of pomes
develops from the enlarged base of the
perianth (corolla and calyx) that has fused
with the ovary wall
Pomes include ___________________
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Simple dry fruit: capsule
Simple dry fruits are dry (not fleshy) at maturity.
Simple dry fruits that open at maturity include:
capsules and legumes
Capsule – fruit is dry at maturity and splits open
along several seams
Example: Cotton
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Simple dry fruit: Legumes
Legumes are dry at maturity and split open
along _______ seams
Examples: pea pods, bean pods, peanut
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Simple dry fruits
Simple dry fruits that do NOT open at
maturity include
Caryopsis: seed coat is fused
to the ovary wall (cereal grains
like ____________________)
Nuts: single-ovary wall and
seed coat remain separate,
ovary wall is very hard
(acorns)
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B. _____________
__________ fruit develops from one flower with
many separate pistils/carpels, all ripening
simultaneously
Examples: strawberry, raspberries, blackberries
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C. Multiple fruit
Multiple fruit develops from ovaries of several
flowers borne/fused together on the same
stalk
For example: ____________
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What is the purpose of the fruit?
The main function of the fruit is to disperse the
seeds
Dispersal is important because
1. It spreads the progeny in order to colonize new
environments
2. Reduces ______________ for resources with
parents
3. Reduces the chances of predators destroying all
of the plant’s yearly seed production
Four types of seed dispersal:
A. Self dispersal
B. ______ dispersal
C. Water dispersal
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A. Self dispersal
Plants disperse their seeds by forceful ejection –
explosive fruits!
Witch hazel, squirting cucumber (jet propulsion)
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Self dispersal
The peanut plant sows
(buries) its own seeds!
Geocarpic: carpel grows
inside the earth (soil)
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B. Wind dispersal
Fruit and seeds may have special devices for
wind dispersal
Plumes catch wind currents: Dandelion
Trees take advantage of their great heights for
wind dispersal. Fruits with wings are used to
slow the descent to land: maple, ash fruit
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C. ___________ Dispersal
Fruits and/or seeds use flotation devices to
travel by water (in rivers, oceans, etc.)
Fruit may have air spaces and corky floats: for
example ________________
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D. Animal dispersal
Plants have _____________ with animals to
accomplish seed dispersal
Many plants depend on animals for seed
dispersal; they may offer a nutritional reward
Animals learn to recognize ripened fruit colors
Fleshy fruits eaten and dispersed
with feces
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Animal dispersal
Some dry fruit attach and cling to animals
(they hitchhike on the animals)
Some have Velcro-like hooks that cling to animal
fur (burdock, cockleburs)
Others have sticky substances that stick to host
(mistletoe)
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Further Study on Seed Dispersal
What carries the dandelion seeds for miles?
What feature of trees gives them a particular
advantage when dispersing seeds by air?
How does the squirting cucumber disperse its
seeds?
Although plants use wind and water, what do
most plants use as carriers for their seeds?
Blackberries on a tree do not ripen
simultaneously, why?
What plant do elephants help to disperse? How
do they do it? What percentage of these seeds
germinate in elephant dung? Why?
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