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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
ovary
Fruit types
A. Simple
B. Aggregate
C. Multiple
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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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11. 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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12. 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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13. 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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14. 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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15. 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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19. 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
D. _______ 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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23. 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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26. 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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