Lecture 14: Seeds and Fruit

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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-formed multicellular
  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 coat outer 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 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. Hesperidium
• 3. __________
• 4. Pepo
• 5. _________

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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 plants 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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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?