Introduction to Plant Reproduction 23.1. Reproduction Sexual reproduction –Joining of an egg and...
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Transcript of Introduction to Plant Reproduction 23.1. Reproduction Sexual reproduction –Joining of an egg and...
Introduction to Plant Reproduction
23.1
Reproduction
Sexual reproduction
–Joining of an egg and sperm
Asexual reproduction
–A single organism replicating its genetic material to split into two identical organisms.
Vegitative Reproduction A form of asexual reproduction where
a new plant grows from parts of an existing plant.
Fast reproduction Examples:
– Strawberry runners– Moss fragmentation– Potato eyes and buds
Alteration of Generations
Alteration of GenerationsOf Nonseed Nonvascular Plants
Alteration of GenerationsOf Nonseed Vascular Plants
Alteration of GenerationsOf Naked Seed Vascular Plants
Alteration of GenerationsOf Flowering Seed Vascular Plants
Alteration of Generations
Fertilization: Nonvascular plants- Need a film of
water for the sperm to reach the egg.
Vascular plants- Do not need water for the sperm to reach the egg.
Alteration of Generations
As plants evolved, the sporophyte generation became larger:
Nonvascular plants- Sporophyte depends on the gametophyte for support and nutrition.
Vascular plants- Sporophyte lives independent of the gametophyte.
Moss reproductive cycle Gametophyte dominant
– Male= Antheridium
– Female= Archegonium
ArchegoniumAntheridium
Moss reproductive cycle Antheridium- Male produces
flagellated sperm that need water to get to the archegonium.
Chemotaxis- Female archegonium produces chemicals that attract/direct the sperm.
Moss reproductive cycle
Moss reproductive cycle Sporophyte- Depends on the
gametophyte for support and
nutrition. Protonema- Spores that land in a
favorable spot develop into a protonema (gametophyte
generation).
Fern reproductive cycle Sporophyte dominant Frond- feathery stems of a fern Sorus- underneath the frond
–Produces spores
Fern reproductive cycle Prothallus
– The fern spore grows into a prothallus when it lands on damp, rich soil.
– Heart shaped
– Contains Antheridia
& Archegonium
Conifer reproductive cycle
Sporophyte dominant Heterosporous- Produces two kinds
of spores that develop into male and female cones.
– Female cones
–Made of many scales
–2 ovules at the base of each scale
–Each ovule produces a Megaspore which develops into the female archegonia.
Conifer reproductive cycle
– Male cones
–Made of small scales that form microspores
–4 microspores develop into a single pollen grain
–Pollen grains are the
male gametophyte that
are transported on air
currents
Chapter 23.2
Flowers
The Parts of a Flower
• Most flowers have four parts:
• sepals,• petals,• stamens,• Carpels (pistils)
The parts of a flower• Sepals protect the
bud until it opens.• Petals attract
insects.• Stamens make
pollen.• Pistils (carpel)
grow into fruits which contain the seeds.
Stamen (male)
• Anther: pollen grains grow in the anther.
• When the grains are fully grown, the anther splits open.
• Filament: holds the anther
Pistil (female)
• Stigma• Style• Ovary
Stigma – sticky place for pollen to attachStyle – where pollen nuclei travels to reach the eggOvary – where egg is located
Modifications in Flowers Complete flowers – have all four
organs (sepals, petals, stamens, and pistils)– M orning glory and tiger lily
Incomplete flowers – lacks one or more of the four organs– Squash and corn
Tiger Lily – a complete flower
Female Squash Flower Male Squash Flower
Incomplete Flowers
Modifications in Flowers P erfect flowers- Have both stamens
and pistils (E x: Lily) Imperfect flowers- E ither have a
functioning stamen or pistil, but not bothE x : Cucumber, Squash
Pollination Mechanisms Animal pollination
– hummingbirds & bees transfer pollen from plant to plant
– Flowers are brightly colored or highly scented
Wind pollination– lightweight and are carried by wind– Small flowers with little color or scent
Self pollination– Able to pollinate flowers on same plant– Have both pistel and stamen
Pollinators
PHOTOPERIODICITY Plants flower based
on the number of hours of darkness they are exposed to
Short-day plants -
flower when days are short (fall, winter, spring)
Ex: Pansy,
Poinsettias
PHOTOPERIODICITY Long-day plants -
flower when days are long (summer)
Examples:
– Potatoes
– Clover
– Spinach
PHOTOPERIODICITY Intermediate-day
plants- Grow when darkness is about equal to daylight.E x : Sugar Cane
PHOTOPERIODICITY Day-neutral plants-
Hours of darkness does not effect flowering, as long as there is enough daylight to perform photosynthesis.
E x: Corn, tomatoes, cotton, roses
Chapter 23.3
Flowering P lants
Flowering Plant reproductive cycle
Sporophyte dominant Ovary- produces 4 megaspores, but 3
disintegrate and only one remains. Double fertilization – requires 2 sperm
to fertilize the egg and make a seed. Seed – embryo (cotyledons),
endosperm (food for embryo), seed coat (protect seed)
Flowering Plant Reproduction
4 kinds of fruit
1. Simple Fleshy fruits- contain one or more seeds.
Ex: Apples, Peach, grape, tomato, pumpkin
4 Kinds of fruit
2. Aggregate fruit- Most berries. Many female parts fuse to form one fruit.
Ex: Blackberries, strawberries, raspberries
4 Kinds of fruit
3. Multiple fruit- Flowers fuse to form one fruit.
Ex: Pineapples, figs
4 Kinds of fruit
4.. Dry fruit- Fruits that are dry.
Ex: Nuts, grains, seed pods
Seed Dispersal Water
– Coconuts Wind
– Dandelions Animals
– Fruits attract animals that will eat the seeds so that the seeds can be carried far away where it won’t have to compete with its parent.
Seed Germination Requires:
– Water (swells and breaks seed coat)– Oxygen (cell respiration as seed grows)– Optimal Temperature (each plant requires
a certain temperature to begin growth)
Seeds will lie dormant in their hard seed coats waiting for optimal conditions.