Reproduction In Plants
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Transcript of Reproduction In Plants
Reproduction In Plants
Pollination • What are males gametes in plants? Where are
they?• Pollen grains on anthers
• What are the females gametes in plants? Where are they?• Ovule inside the stigma
• Pollination mixing of pollen grains with stigma to cause fertilization• What are the different methods of
pollination?1) Wind pollen designed to be carried by
breeze2) Pollinators pollen carried by birds, insects,
etc…
Fertilization 1) Pollen lands on stigma and chemical
signals cause pollen tube to grow down style to the ovary
2) Pollen tube reaches the ovule and deposits 2 male gametes; Inside ovary are 6 haploid cells (n) and 1 diploid nucleus (2n)
3) 1 male gamete fuses with 1 female gamete; this becomes the zygote (2n)
4) Second male gamete fuses with diploid endosperm nucleus; this becomes a 3n endosperm (food source for seed)
Seed Formation• After fertilization, the flower goes through a
total transformation:• All waste of energy stop; petals die, scent
stops, and nectar dries up• All reproductive parts break away was seed
forms• Ovule becomes seed of future plant• Ovary grows into fruit (in some plants)
• Parts of a Seed:1) Seed coat outer protective layer2) Food store storage of starch to power
growing seed3) Radicle grows into the plant’s first root4) Plumule grows into the plant’s first shoot
Seed
Seed CoatFood store
Radicle
Plumule
Pollination
Fertilization to Seed
CotyledonSepal Petal
Carpel Stamen
Ovary Style Stigma Filament
Anther
Pollen GrainPollination
Pollen tube growth
Male nuclei
Ovule
Male nuclei
Zygote
SeedRadicle
Food Store
Seed Dispersal • After a seed forms, it remains in a dormant
stage for months to years waiting for an environment to grow in• The embryo grows into the “fruit” and the
protective outer layer called a “pericarp”• Seeds rarely drop from their parent plant
and grow right there. Why?• Competition for resources in soil with parent
plant• Dispersal the spreading of seeds to new
areas away from the parent plant• Wind seeds designed to be carried by wind• Animal seeds designed to be carried or eaten
then excreted by animals
Wind vs. Animal Dispersal• What characteristics would a wind seed have:• Shape of seed is aerodynamic (works well in wind) so
seed can travel great distances• Fruit is dry so seed is as light as possible• Fruit is hard to protect the seed• Little energy in the fruit so it is less likely to be eaten
• What characteristics would an animal seed have:• Color/Shape/Scent is attractive to animals so they eat it• Fruit is fleshy, wet, and full of energy for the animal• Seed is heavily protected so to survive trip through
the animal’s digestive system; animal waste acts as fertilizer for soil seed grows in
• Seed may have spines/hooks that catch the animal’s fur
• Touch sensitive explosions
Seed Germination • After a seed as dispersed to a new area, if the area is
suitable to the seed, the seed will germinate (grow into a plant)• What is the first thing a seed needs?
• Water• What part of the plant must grow first then?
• The root; which come from the radicle (seed root)• Water is absorbed and taken to the seed which
causes the activation of enzymes.• What enzymes would we need to get energy to grow?
• Amylase break down starch food store; energy/cellulose
• Protease break down protein food store; amino acids for new cells
• Lipase break down fat food store; energy
The Steps of Germination 1) Seed grows radicle downward and absorbs water2) Water activates enzymes that breakdown the food
store to provide energy/nutrients for growth3) Radicle grows larger to absorb more nutrients from
the soil4) Plumule (first shoot) grows upward to break
through the top of the soil5) Plumule slowly opens up first leaves (from
cotyledons) and photosynthesis starts6) Energy from seed run out, but photosynthesis
powers the rapid growth of the rest of the plant• What factors will influence germination success:
• Nutrients/Water in soil• Depth of seed in soil• Looseness of soil; need oxygen for aerobic reactions• Temperature of environment
Radicle
Food Store
Plumule
Cotyledon
Leaves
Cotyledon
Plumule
Measuring Growth• What type of division powers plant growth?
• Mitosis• Where in the plant would mitosis be best seen?
• Tips of the roots and shoots• What are the two ways we can measure the growth
of a plant?• Weight the Wet Mass or the Dry Mass
• Wet Mass weigh the plant as is (subtract the weight of the soil)• Dry Mass dry the plant in an oven to remove all the
water and then weigh it; plant dies• Which is more accurate measure of growth?
• Dry mass; amount of water can fluctuate • Growth is the increase in size/weight caused by the bio-
material (not water) in an organism