Transcript Chapter 24 Reproduction of Seed Plants

Chapter 24
Reproduction of Seed Plants
Sporophytes
Gametophytes are the
gametes (egg and sperm)
Sporophytes are the
plants
Gametophytes
Life Cycle of Gymnosperms
Turn to page 611, Figure 24-4
Life cycle of gymnosperms takes
place in cones which are produced
by the mature sporophyte plant.
Cone scale
Ovule
Pollen cones – produce male gametophytes
Seed cones – produce female gametophytes
Ovules
Ovules – found at the base of each scale, this
is where the female gametophyte develops
Fertilization and Development
Text page 611
Pollen tube – structure containing two
haploid sperm nuclei
Generally takes 2 years to complete
Pollen grain
has 2 nuclei!
Zygote – new diploid
sporophyte plant
Zygote grows into an embryo, and
becomes encased in a what will
soon become a seed.
Structure of flowers
Specialized leaves:
NOT involved in reproduction...
1. Sepals – outermost circle of floral parts;
protects flower bud
2. Petals – found just inside the sepal;
often brightly colored; attract insects
Text page 612
Structure in Flowers:
Reproduction
Specialized leaves:
ARE involved in reproduction...
3. Stamen – contains the male parts of
the flower
 Anther – oval sac producing pollen grains
 Filament – stalk that supports the anther
Structure in Flowers
Reproduction
Specialized leaves:
ARE involved in reproduction...
4. Carpel (Pistils) – makes up the female part
of the flower; stigma, style, and ovary
 Ovary – contains ovules where the
female gametophyte are produced
 Style – stalk leading to the ovary
 Stigma – top of the style; sticky
Flower variety
Flowers vary greatly in shape,
color, and size.
Flower Variety
The typical flower produces both
male and female gametophytes.
But, sometimes, male and
female gametophytes are
produced in separate flowers on
the same plant... Like on corn!
Tassel = flower that produces male gametophytes
Silk = style of a flower that contains the female gametophyte
Composite Flowers
Often called compound flowers
A simple flower has one reproductive system...
A compound flower is a whole colony of flowers
with their own petals, and multiple reproductive
systems.
A sunflower is not a single flower, but a
row of outer petals around many small flowers
Other examples:
•Dandelion
•Zinnia
•Aster
•Black-eyed Susan
•Chrysanthemum...
Life Cycle of Angiosperms
Reproduction takes place within the flower
Seeds develop inside protective
structures.
1. 4 haploid cells are produced in the anther
2. Each cell becomes a pollen grain
3. In the ovary, 4 haploid cells form, but three
disintegrate.
4. Remaining cell divides into 8 nuclei within a
membrane called a embryo sac. One of the 8
nuclei is the egg nucleus.
This is the gametophyte of the flowering plant
Pollination
Most angiosperms are pollinated by animals,
not wind...
Advantage?
Animals carry pollen from one flower to another.
What is the advantage to the animal?
http://www.ted.com/talks/louie_schwartzberg
_the_hidden_beauty_of_pollination?language
=en
Double Fertilization
Text page 616
A pollen grain lands on the stigma and begins to grow a pollen tube.
The pollen tube grows into the style, eventually reaching the ovary
and entering the ovule.
Two distinct fertilizations take place:
• sperm and egg nuclei fuse together  new plant embryo
• other nuclei form endosperm, a rich food supply for plant
Practice your flower parts!
24-2: Seed Development & Germination
Development of the seed was a major
factor in the success of plants on land
A seed enclosed within a fruit
offers something else...
A better start to its new life!
Seed & Fruit Development
Fruit – applies to any seed that is
enclosed within its embryo walls
Which of these foods are fruits?
As Angiosperm seeds
mature, the ovary walls
thicken to form a fruit
that encloses the
developing seeds.
Plant Ovary (fruit) Lab
Assignment:
Bring in a plant ovary for our lab.
You may choose any ovary, from the
grocery store or out of your yard.
We will dissect the plant ovaries...
and possibly eat a few 
Seed Dispersal
Dispersal by Animals:
Seeds are covered with a tough coating
enabling them to pass through the
digestive system unharmed
Seeds dispersed by
animals are typically
contained in fleshy,
nutritious fruits
Dispersal by Wind and Water
Seeds dispersed by wind or water are
typically lightweight, allowing them to
be carried in the air or to float on the
surface of the water
Seed Dormancy
Dormancy – time in which an embryo
is alive, but not growing
Environmental factors such as
temperature, and moisture can cause a
seed to end dormancy and germinate
Seed Germination
Germination – the early growth
stage of the plant embryo
Monocots
Usually, the single cotyledon
remains underground
Dicots (one of two ways)
• cotyledons emerge above ground and 
protect early leaves
• cotyledons remain below the soil,
providing food for the growing seedling
24-3: Plant Propagation & Agriculture
Seed plants are essential to human life
The earliest humans gathered plants
for food, shelter, and medicine
Vegetative Reproduction
Vegetative reproduction - the production of
new plants from horizontal stems, plantlets,
or underground roots
Stolen – long,
trailing horizontal
stems that
produce roots
Occurs when plants are
well adapted to an area
Can reproduce
very quickly!
Plantlets
Plant Propagation
When a plant has a desired
characteristic, we want copies.
There are a variety of methods...
Text p. 622
Cuttings – cut a length of stem
that
includes buds (meristematic tissue)
Plant Propagation
Other methods...
Text p. 623
To reproduce seedless or woody plants without
strong root systems, we use grafting or budding.
Grafts – stems are used
Budding – buds are used
Scion – the stem or bud of a plant
Stock – root plant to which scion is attached
Agriculture
Agriculture - the systematic cultivation of plants
Worldwide Patterns of Agriculture
North America has some of the richest,
most productive cropland in the world.
Most of the people in the world
depend on a few crop plants for
the bulk of their food supply...
• Wheat
• Rice
• Corn
Changes in Agriculture
Increases in crop yields has lowered
prices, and fed more people on less land.
As our population on Earth increases,
what else can we do?
Up?