Transcript Plant Life Cycles

Plant Life Cycles
Ch 6 section 1 and 2
What Are the Functions of Roots, Stems, and
Leaves?

Roots
-3 Main functions
-anchor the plant in the ground
-absorbs water and minerals from the soils
-sometimes stores food
Types of Roots

- Fibrous
 - consists of many similarly sized roots that form a dense tangled
mass.
 - remove lots of soil when pulled out of the ground
 - examples- grass, corn, onions

-Tap
- one long, thick main root
- smaller, roots branch off the main root
- hard to pull out of the ground
- examples- carrots, dandelions, cactus
Root Structure
 Root
cap- rounded and covers the tip of the root
 Root
hairs- grow out of the roots surface
Absorb
Help
water and minerals
anchor plant in soil
 Tissues
Xylem-
water and nutrients move through this
Phloem-
transfers food
Plant Structures
Root Structure
.
Stems
 Two Main functions

- carries substances between the plant’s roots
and leaves

- provides support for the plant and holds up
the leaves
Structure of the Stem

-can be either woody (hard and rigid) or herbaceous (contain no wood and are often
soft). Both contain phloem and xylem tissues


Woody Stems

Outer layer is bark (protective)

Cambium – creates new phloem and xylem
Annual rings

Represents a tree’s yearly growth

Made of xylem
 Xylem
that forms in the spring are large and have thin walls because of rapid
growth. Produce a wide, light brown ring
 Xylem
that forms in the summer grows slowly, are small and have thick walls.
Produce a thin, DARK ring

One pair of light and dark rings represents a years growth
 In
wet years the tree’s annual rings are wide. In dry years, the rings are narrow
Leaves

Capture the sun’s energy and carry out the food making process of photosynthesis.

Structure of a Leaf

Surface layer
 Stomata-
small openings that control the gasses entering and exiting the
leaf.
Inside the leaf

 Veins


containing xylem and phloem
The Leaf and Photosynthesis

Cells containing the most chloroplasts are found near the upper surface

Carbon dioxide enters through the stomata

Water travels from the roots through the xylem tissue
Controlling Water Loss

Transpiration- water evaporating from plant’s leaves

Prevented by closing the stomata
Plant Structures
Leaf Structure
Each structure helps a leaf produce food.
Plant Structures
Stomata
Stomata can slow water loss.
How Do Seeds Become New Plants

Seed Structure
3
main parts
 Embryo
 Young
 Has
plant that develops from a fertilized egg
the roots, stems, and leaves of new plant
 Cotyledons
 Food
 Seed
(seed coats)
is either stored here or outside the embryo
coat
 Outer
covering that protects the seed and food from
drying out
 Allows
the seed to remain inactive for long periods of
time

In many plants the seeds are surrounded by a fruit
Seed Dispersal

Scattering of seeds
 Methods
Animals
eat the fruit, the seeds pass through
digestive system and are deposited in new areas
Attach
to articles of clothing or fur with hook like
structures and fall off in a new area
Water

and wind dispersal
Seeds that are dispersed far away from parent plant has
a better chance for survival because there’s no
competition
Germination

Occurs when the embryo begins to grow again and pushes
out of the seed

Begins when the seeds absorbs water.

Roots grow downward first and then stem and leaves grow
upward.
What Are the Structures of a Flower?

Main Function of a flower is reproduction

-A typical flower contains
Sepals
Petals
Stamens
Pistils

The color, shape and scent of a flower attracts insects and
other animals that ensure that pollination occurs.

Pollination is transfer of pollen from male structures to
female structures
Sepals and petals
Sepals
enclose the
bud and protect the
developing floweroften green in color
Petals
are found
under the sepals and
are generally the
most colorful part of
the flower
Stamens
 Male
reproductive
part
Filament-
thin
stalk
Anther-
contains
the pollen- found
at the top of the
filament
-Pistils

Female reproductive part
 Stigma-
sticky tipcatches the pollen
 Style-
tube connecting
the stigma to the
ovary- pollen travels
down it
 Ovary-
hollow base
that contains the eggs,
protects the seeds as
they develop
Ch 6 Lesson 2
What are the Stages of a Plant’s Life Cycle?

Two Different Stages
 Sporophyte
First
stage where plant produces spores or seeds
(tiny cells) that can grow into new organisms

Gametophyte
 Second
egg.
stage that produces the sex cells; sperm or
Plant Reproduction
Plant Life Cycle
All plants go through two
stages in their life cycle.
Which are the sporophyte
and gametophyte stages?

Angiosperms are classified based on the length of their life cycle
 Annuals
 Flowering
plants that complete their life cycle within one growing season
 Examples-
marigolds, petunias, wheat, cucumbers
 Biennials
 Complete
 First
year- germinate and grow roots, very short stems and leaves
 Second
year- grow larger and produce flowers and seeds
 Examples
their life cycle in 2 years.
parsley, celery, and foxglove flowers
Perennials
 Flowering
 Flower
plants that live for more than 2 years
every year
How Do Plants reproduce?
 All
plants undergo sexual reproduction
that involves fertilization.
 Fertilization occurs when the sperm
enters the egg. The fertilized egg is
called a zygote
Asexual Reproduction

Doesn’t involve flowers,
pollination, or seeds

Can happen quickly

Can reproduce unfavorable traits
since there’s no new genetic
information being passed to
offspring
Non Vascular and Seedless Plants
 Release
spores, instead
of seeds, that grow into
gametophytes.
 When
the gametophytes
produce the egg and
sperm there must be
water available for the
sperm to swim to the
egg.
 Examples-
mosses,
liverworts, hornworts,
ferns, and horsetails.
Gymnosperms

Have reproductive structures called cones

Reproduction Steps
Cone Production



Covered in scales

Two types- male and female
Pollen Production and Ovule Development

Male cones produce pollen

Female cones produce ovules that contain an egg.
Female cones contain at least one ovule at the
base of each scale. The ovule later turns into a
seed
Pollination



Transfer of pollen to egg is done by wind.
Fertilization

Ovule closes and seals in the pollen.

Scales close and zygote develops
Seed Development

Female cones remain on the tree while seeds
mature

Cone grows in size, sometimes taking up to 2
years to mature

When mature, the scales open and release the
seed into the air
Angiosperms


Pollination

Flower is pollinated when pollen
lands on the stigma

Pollen travels down the style to the
ovary.

Zygote develops within the seed’s
embryo
Fruit Development and Seed
Dispersal

As the seeds develops the ovary
changes into fruit, which encloses
the seeds.