Lecture 14: Seeds and Fruit Seeds Fruits Fruit types Seed dispersal Video: seed dispersal Real fruit...
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Transcript of Lecture 14: Seeds and Fruit Seeds Fruits Fruit types Seed dispersal Video: seed dispersal Real fruit...
Lecture 14: Seeds and Fruit
• Seeds
• Fruits
• Fruit types
• Seed dispersal
• Video: seed dispersal
• Real fruit samples
What is a seed?
• A matured ovule, containing:
• 1. a plant __________
• 2. a food supply
• 3. covered by a _____________
Embryo• The seed contains a well-formed
multicellular young plant embryo (germ)
• Embryo is _________ (2n)
• It will become a whole plant
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
Seed coat• A thick protective coat – outer layer of the seed
• Formed from the _______________
Seed coat
Gymnosperm seed
• Single fertilization produces the diploid embryo (2n)
• Food source is the haploid megagametophyte
Flowering plant seed
• In angiosperms (flowering plants) there is
• DOUBLE _______________
• Which produces a diploid ________(2n) and,
• A triploid (3n) __________
• Endosperm is the food source
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)
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
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. Hesperidium• 3. __________• 4. Pepo• 5. _________
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.
Simple fleshy fruit: drupe
• 3. _______ type – outer part of fruit wall is soft and fleshy, inner part is hard and stony
• For example: ______________________
Simple fleshy fruit: pepo
• 4. ________ – also a fleshy fruit with a tougher outer rind
• All member of the squash family: pumpkin, melons, cucumbers
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 ___________________
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
Simple dry fruit: Legumes• Legumes are dry at maturity and split open
along _______ seams
• Examples: pea pods, bean pods, peanut
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)
B. _____________• __________ fruit develops from one flower
with many separate pistils/carpels, all ripening simultaneously
• Examples: strawberry, raspberries, blackberries
C. Multiple fruit• Multiple fruit develops from ovaries of
several flowers borne/fused together on the same stalk
• For example: ____________
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
A. Self dispersal
• Plants disperse their seeds by forceful ejection – explosive fruits!
• Witch hazel, squirting cucumber (jet propulsion)
Self dispersal• The peanut plant sows
(buries) its own seeds!
• Geocarpic: carpel grows inside the earth (soil)
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
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 ________________
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
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)
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?