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Lecture 14: Seeds and Fruit

Seeds

Fruits

Fruit types

Seed dispersal Video: seed dispersal

Real fruit samples

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What is a seed?

A matured ovule, containing:

1. a plant __________

2. a food supply 3. covered by a _____________

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Embryo

The seed contains a well-formedmulticellular young plant embryo (germ)

Embryo is _________ (2n)

It will become a whole plant

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Nutritive tissue

Seed contains a food supply

Stored food contains enough energy for the

embryo to grow through the soil, when

seedling is unable to photosynthesize.

Food source can be the _________, which is

______ (_n)as a result of double fertilization

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Seed coat

A thick protective coatouter layer of the seed Formed from the _______________

Seed coat

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Gymnosperm seed

Single fertilization produces the diploid embryo(2n)

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 twocotyledons (like bean)

Endosperm (food) is

kept in the _________

Monocot has one

__________ whichabsorbs the endosperm

tissue during

germination (corn)

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Fruit

In flowering plantsFruit is a mature,ripened o_____ that contains the seeds

Pericarpthe ovary wall ovary

Fruit types

A. Simple B. Aggregate

C. Multiple

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A. Simple fruit A. Simple fruitdevelops from a ______

ovary of a single flower. Simple fruits can be either fleshy or dry when

mature

Simple fleshy fruit 1. __________

2. Hesperidium

3. __________ 4. Pepo

5. _________

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Simple fleshy fruit

1. Berryentire fruit wall is softand 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. _______ typeouter part of fruit wall issoft 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 pomesdevelops 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

Capsulefruit is dry at maturity and splits openalong several seams

Example: Cotton

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Simple dry fruit: Legumes

Legumes are dry at maturity and split openalong _______ seams

Examples: pea pods, bean pods, peanut

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Simple dry fruits

Simple dry fruits that do NOT open atmaturity include

Caryopsis: seed coat is fused

to the ovary wall (cereal grainslike ____________________)

Nuts: single-ovary wall andseed coat remain separate,ovary wall is very hard(acorns)

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B. _____________

__________ fruit develops from one flowerwith 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 theplants yearly seed production

Four types of seed dispersal:

A. Self dispersal

B. ______ dispersal

C. Water dispersal

D. _______ dispersal

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A. Self dispersal

Plants disperse their seeds by forceful ejectionexplosive 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 toslow 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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Video on seed dispersal Watch the video, take notes, answer these questions:

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?