Transcript Reproduction

Reproduction
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Reproduction = producing a new copy of
something
Reproduction can be
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Asexual
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biological process by which an organism creates a
genetically similar copy of itself without the combination
of genetic material with another individual.
Sexual
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a biological process by which organisms create
descendants through the combination of genetic material.
These organisms have two different adult sexes, male and
female.
Asexual Reproduction in Plants
Natural Vegetative Reproduction
 Ch. 20 - Pgs 408-411
 Most plants reproduce sexually but
vegetative reproduction involving roots,
stems and leaves is also common.
 Cambium and epidermal tissues differentiate
to form a new plant
1. Bulbs
A short underground
stem surrounded by
thick fleshy leaves that
contain stored food.
 As the plant grows new
bulbs sprout from the
old one. Each bulb can
give rise to a new plant.
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2. Tubers
Underground storage stems from which
new plants can grow after a dormant
season.
 “Eyes” – indentations on a tuber that can
give rise to new plants.
 The new stem uses the stored food until in
can carry on photosynthesis.
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Mountain Buffalo
3. Stolons
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An above ground runner from which plants roots can grow to
start off a new plant.
Where buds from a runner touch the ground, new
independent plants can grow.
4. Rhizomes
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An underground runner that gives rise to new plants.
Rhizomes are usually thick, fleshy and stores food
Plants arise from nodes on the rhizome.
Artificial Vegetative Reproduction
 Common
in horticultural production
(fruits & vegetables).
 These techniques allow producers to
grow plants with desirable traits.
1. Cuttings (2 Types)
a)
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Stem Cuttings – a branch,
or slip, is cut from a plant
and placed in water or
moist sand. Usually the
bottom of the clipping is
dipped into hormones to
promote root
development. Which
hormones?
Common with geraniums,
roses, ivy and grapevines.
b)
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Leaf Cutting – A leaf or part of a leaf is placed in
water or moist soil. A new plant will arise from the
base of the leaf.
Common with African violet, snake plant and
begonias.
2. Layering
A stem is bent over so that part of it is
covered with soil. The covered part will
develop roots and the cut from the parent
plant and replanted as a new plant.
 Common with raspberries, roses and
honeysuckle.
 This also occurs naturally.
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Air Layering
Trench Layering
Tip Layering
3. Grafting
A stem or bud is removed from one plant and
permanently joined to the stem of a closely
related plant.
 The 2 parts are held together by tape, wax or
commercial grafting compounds.
 The part providing the root is called the stock
and the bud is called the scion.
 The scion will keep its characteristics on the
new root stock.
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Advantages of Vegetative
Propagation
 Decreases
variation in crops.
 Faster reproduction than by seed.
 Fruit will be produced faster through
grafting.
 Plants bearing seedless fruit can
reproduce by this method.
Sexual Reproduction in
Angiosperms
 Angiosperms
reproduce sexually
through flowers.
 Seeds are protected within the ovary
of the flower which develops into a
fruit.
Parts of the Flower
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The sepals are the green “leaves” that encase the flower
before it blooms. All of the sepals form the calyx at
the base of the flower.
All of the petals of the flower make up the corolla.
Parts of the Flower
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The anther and the filament make up the stamen =
male parts of the flower.
The anther produces the sperm which is encased in the
pollen for transport to the female flower parts.
Parts of the Flower
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The stigma, style and ovary make up the pistil = female flower
parts.
The stigma is where the pollen attaches; the style is the
structure the pollen tube must grow through to reach the
ovary which produces the egg. When the egg is fertilized it
creates the seed and the ovary becomes the fruit to protect the
seeds.
Fertilization of a Flower
Self – Pollination of Flowers
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Pollen is transferred from the anther to the stigma on the
same plant.
This is not ideal because the inbreeding limits them
genetically.
There are three common advantages:
A given genotype may be particularly adapted to an
environment. Self-pollination helps keep this trait
static.
Self-pollinating plants are not dependent on
pollination agents.
Self-pollination is an advantage when the number of
individuals is small or widely spaced.
Cross Pollination of Flowers
This process is by which a flower is fertilized by
the pollen from another plant of the same
species.
 The advantages of cross-pollination are genetic
in nature. This creates genetic diversity in the
plant population and reduces inbreeding.
 Mechanisms of cross pollination are insects,
wind, chemical suppressants, separate male and
female flowers or plants, animals and genetic
incompatibility
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Types of Fruit
1.
Simple Fruit – Fruit that develops
from a single ovary.
2. Aggregate Fruit
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Fruit is produced from a single flower that has
many ovaries.
3. Multiple Fruit
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Simple fruits of many flowers fuse together.
A – Jackfruit
B – Pineapple
C - Breadfruit
Structure of the Seed
Made up of the seed coat, embryo and
endosperm.
 All seed plants have at least one seed leaf or
cotyledon.
 Monocot seeds have an endosperm in which
food is stored for the developing embryo.
 Food is stored in the 2 cotyledons of dicot
seeds for the embryo.
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Structure of the Seed (cont.)
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Before the seed can germinate, water has to enter
the seed.
Water enter through a structure called the
micropyle. This is a small hole in the seed coat
that allows water to enter and allow for
germination.
Seeds can remain dormant for long periods of
time until conditions become right for
germination.
Structure of the Seed (cont.)
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In addition to the cotyledons, the embryo has 3
parts:
Epicotyl (Plumule)– The part of the embryo above
the point of attachment of the cotyledons. Gives
rise to the leaves and upper stem.
Hypocotyl – below the point of attachment but
above the radicle. Gives rise to the lower stem.
Radicle – lower part of the embryo. Forms the
roots of the plant.
epicotyl
radicle
Dispersal of Seeds
1. Water. eg. Water Lilly
2. Wind. eg. Dandelion
3. Animal fur. eg.
Cockleburr
4. Through animal
digestive tract spread
with feces. Eg.
Mountain ash, chokecherry, strawberry and
saskatoon berry