Transcript Seeds and Fruitm

Chapter 24.3
Seeds and Fruit
Why?
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The seeds and fruits formed
help ensure survival of the next
generation
Seed formation
After fertilization
 Zygote divides = embryo
 Triploid cell divides = endosperm
 Ovule wall = seed coat
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Fruit formation
Fruit – the structure that contains the
seeds of an anthophyte
 Fruit – the enlarged ovary
surrounding the seed
 Can be made up of other organs as
well.
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Fruits
Fleshy fruits – apples, grapes,
melons, tomatoes, cucumbers
 Dry fruits – peanuts, sunflower seeds,
walnuts.
 The ovary around the seeds hardens
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Seed dispersal
Fruits aid in dispersal
 Dispersal reduces competition
 Animals – digestion and/or carrying
the seed on the body
 Wind – dandelion, tumbleweed
 Water – coconut and water lilies
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Pictures – from flower to fruit
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http://www.cas.vanderbilt.edu/bioimages/page
s/fruit-devel.htm
What about seedless fruit?
Ex. Watermelon and bananas
 Triploid plants – prevents meiosis
from happening and no gametes are
produced
 So where do the plants come from if
there are no viable seeds?
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Bananas – vegetative reproduction
Watermelons – Cross a diploid with a tetraploid
to produce a triploid seed
Diploid (2) + Tetraploid (4) = 6 sets of
chromosomes
Divide 6 by meiosis to get 3 sets of
chromosomes.
Pollination triggers fruit formation – without
seeds.
The plants must be grown with a diploid variety
for pollen
Seed germination
Dormancy – the period of inactivity
in a mature seed
 Varies greatly between species
 Ends when the seed germinates
 Germination – the beginning of the
development of the embryo into a
new plant
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Germination
Water – activates the metabolism
 Some seeds have specific
requirements
 Ex. Animals digestive system,
freezing temps, extensive soaking
in saltwater, specific daylengths,
exposure to fire.
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Dicot germination
Radicle – embryonic root appears
first
 Hypocotyl – portion of stem nearest
seed
 Cotyledon – plants first leaves
 In monocots the cotyledon remains
below the surface
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Vegetative reproduction
A new plant is produced from a stem,
root or leaf
 This is essentially cloning –
producing new plants that are
genetically identical to their parents
 Tissue culture and/or cuttings.
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