Transcript Introduction to Plants

Introduction to
Plants
Classification of plants
• Kingdom Plantae
– Phylums
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Lycodiophyta (Club Mosses)
Equisetophyta (Horsetails)
Psilotophyta (Wisk Ferns)
Polypodiophyta (Ferns)
Cycadophyta (Cycads)
Ginkgophyta (Ginkoes)
Pinophyta (Conifers)
Gnetophyta (Vessel-bearing Gymnosperms)
Magnoliophyta (Flowering Plants)
Facts…
• critical to other life on this planet because they
form the basis of all food webs
• Most plants are autotrophic
• earliest fossils found have been aged at 3.8
billion years
• scientific study of plants, known as botany
• identified about 350,000 extant (living) species
of plants
– ~258,650 are flowering and ~18,000 bryophytes
What are plants?
• Multi-cellular
organisms
• Make own food
(photosynthesis)
• Have chloroplasts
• Have rigid cell walls
made of cellulose
• Found all over the
world
Plants provide:
•
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Food
Oxygen
Medicines
Building
materials
• Textiles (fibers)
• Coloring
pigments
Plant Classification
Plants
With seeds
Gymnosperms
"naked seeds"
cones, no flowers
needle-like leaves
EX: Ginko
Without seeds
need water to
reproduce;
spores
Angiosperms
flowering plants
largest group
EX: conifers
Monocots
Mosses
Dicots
EX: grasses EX: orchids EX: oak tree EX: broccoli
Ferns
Liverworts
Horsetails
Plants Without Seeds
• Need water to reproduce
• Reproduce with spores
• Include
–Mosses
–Ferns
–Horsetails
–Bladderworts
Plants with Seeds
• 2 types
• Found all over the world
Gymnosperms
• Means “naked seed”
• Often have cones & needle-like
leaves
• Do not have flowers
–Ex: conifers, gingko
Angiosperms
• Flowering plants
• Largest group
– Moncots
– Dicots
Monocots
Dicots
Evolution
• Principal photosynthetic organisms were
microscopic cells floating below the surface of
the water, closer to the sun’s rays
• As they multiplied, depleted resources of the
open ocean, so colonies could be found nearer
to the shores, in order to get minerals and
nutrients from runoff
• About 650million years ago, diversity of these
organisms abounded on the rocky shores, and
some even integrated into multicelluar bodies
Evolution
• These new multicelluar photosynthetic
forms developed a cell wall due to the
rough waters of the rocky coastline
• As size increased, they developed internal
structures that linked the
photosynthesizing parts to the nonphotosynthesizing parts
Evolution to land..
• Oxygen & carbon dioxide not as abundant
in the water, as it is not as free circulating
as it is on land
• Critical factor to adapting to land is water
resources
• Development of root systems to be able to
keep plant stable on land and to seek out
water resources without moving
Warm UP
• What is a seed?
SEEDS
What is a Seed?
•A living organism that is dormant
•Has the new plant inside
•Part of the plants reproduction
• Develop in the pistil of the plant
– Develops from the ovule
• Living thing!
• Once fertilized zygote grows forming the
embryo of the seed
What does it mean to be
dormant?
Seeds are Dormant…
• they remain alive though metabolically
inactive and incapable of germination until
the proper conditions to awaken it.
• The seed is supplied all that it needs to
germinate.
• Seed dormancy is a mechanism that insures
the survival of the species. To "Mother
Nature", dormancy is a blessing that insures
the continuation of the species over time and
through periods of environmental stress.
Seed Dormancy
Mechanisms
Hardseededness
• Hardseededness is where the seedcoat
surrounding the seed is the physical
barrier to the uptake of water.
• Physical scaring; or freezing and thawing
may be needed to allow water uptake and
germination to proceed.
Impermeable Membranes
• Seed is impermeable to water uptake and
oxygen uptake.
• Generally, cool temperatures allow oxygen
to make its way into the seed while warm
temperatures prevent oxygen uptake.
– Since germination is fueled by the respiration
of stored food within the seed, without
oxygen, germination cannot occur.
Inhibitors and Promotors
• Dormancy due to inhibitors is based upon the
fact that germination and growth promoting
enzymes and hormones can be inhibited, thus
preventing germination.
• These inhibitors are found in the endosperm,
cotyledons, or other food storage tissue.
Sometimes these chemicals are found in the
outer coverings of the seed or fruit.
Light and its Role
• Many seed species with small seeds need light
to germinate. When buried deeply in the soil,
they lack the light and go dormant. This can be
seen in your garden where you think you have
gotten rid of the weeds and then you disturb the
soil. This disturbance brings seeds to the
surface where they are stimulated by the light
and begin to germinate.
Seed Diagram
Endosperm provides FOOD!
Hypocotyl
Epicotyl
Radicle
Seed Embryo
• Has parts of a complete plant
– Leaves
• Epicotyl, plumule
– Stems
• Hypocotyl
– Roots
• Radicle
– FOOD
• Endosperm, or cotyledon
Seed Embryo Anatomy
• Radicle : the lower end of the hypocotyl
that forms the first root of the plant.
– Emerges 1st at the start of germination
• Hypocotyl: develops into true stem
• Epicotyl/Plumule: first leaves!
Seed Embryo Anatomy
• Endosperm: provides food for growing
seed embryo
• Cotyledons: store food absorbed from the
endosperm when the seed was formed
• Seed Coat: surrounds the seed and
protects it from injury and dehydration
Germination
• Definition: process by which an embryo
plant inside the seed changes into a
developing seedling
– Crops grown from seeds: soybean, corn,
cotton and other vegetables !
Germination: Steps
• Step 1: Absorption of
Water and Oxygen!
– By Diffusion
– Pressure Builds
• Pressure in seed (and adult
plant) is called TURGOR
– Seed ruptures
• Step 2: Radicle Emerges
– First root/tap root
Germination: Steps
• STEP 3: After the root
absorbs water, an
embryonic shoot emerges
from the seed.
– This shoot comprises three main
parts: the cotyledons (seed
leaves), the section of shoot
below the cotyledons
(hypocotyl), and the section of
shoot above the cotyledons
(epicotyl).
– The way the shoot emerges
differs among plant groups.
What’s Required For
Germination?
• WATER!
• Optimum temperature
– 55 and 70 degrees F
• Oxygen
– Too much water can
suffocate the plant
• Some require Stratification
– A period of cold temperature
• Broken seed coat
– Digestive Bacteria, eaten by
an animal, Frozen then
thawed
WHAT TO COMPLETE…
• Seed Dissection Lab…
• Seed Planting.. You will get
some seeds and a cup. Soil is
available to plant your seeds.
Be sure to put your name on
your cup!
• P.577 foldable…
• All due by the end of the
period
Roots
What do they do for
the plant???
Are you Rooted?
• Roots help to keep plants in place.
• They spread out into the soil and
“attached” themselves to the particles of
the soil.
• Why do they reach and probe?
– To find nutrients and water, thus in the end
the plant gets anchored into the soil.
Are you Rooted?
• Plants get the water they need
for photosynthesis through their
roots.
• The roots have a type of cell
called a root hair cell - these
project out from the root into the
soil. Roots have a big surface
area and thin walls, which allow
water to pass into them easily.
• Note that root cells do not
contain chloroplasts, as they
are normally in the dark and
cannot photosynthesis.
Are you Rooted?
• The water absorbed by
the root hair cells
passes through the
plant in xylem tubes,
and eventually reaches
the leaves. If a plant
does not absorb
enough water, it will wilt
or go floppy. Without
water it may also not
photosynthesis quickly
enough, and it may die.
Root Hairs
• Water in the soil is
taken up by root hairs
and then passes from
cell to cell to the
xylem.
Types of Roots
Fibrous Roots
• Generally grasses
have this type of
root
• Many roots extend
into the soil from
base of plant
Tap Roots
• One or more large
roots extending
into the soil
• Smaller roots
branch off
Types of Roots
• Shallow roots
– Desert roots
– Quickly growing
plants
• Deep
underground
roots
– Areas with little
rainfall
• Deep and Shallow
Roots
– Takes
advantage of
underground
water sources
and occasional
showers.
Root Growth
What does it depend on?
• Amount of moisture in the soil
• Type of soil
• How quickly the plants grow and go to
seed
• Type of rainfall in that area
• Type of plant – prop roots are used to
help support the plant
Lastly…
• Roots are used as food storage for
plants. They store sugars and
starches to help plants over winter.
• Sugar storage in roots also help to
send up new shoots each spring, and
to regenerate stems and leaves that
were eaten or burned.
• Radishes, carrots, turnips – store
large amounts of food in the form of
starch in their roots. We eat these
roots as a source of energy.
Plant Functions
What do stems & leaves do for a
plant???
Stems
The stem is a part of the plant
that holds up other structures
such as the leaves and flowers.
This is important as the leaves
need to be held up to the sun
to get its light for
photosynthesis and the flowers
need to be held up to be
available for pollination.
Stems also carry water and
minerals up from the roots to
the leaves to help with
photosynthesis and take food
back down to be stored and
distributed to the plant as it
has need.
Stems
The tubes in the stem that take
the water and minerals up into
the plant are the xylem and the
tubes that carry the food back
down are called the phloem.
Transport of Materials
• Phloem (2)
– Carries sugars (food)
up & down in plant
• Xylem (1)
– Carries water &
mineral up from roots
to all parts of plants
Leaves
The leaf is a part of the plant that is
charge of making food for the
plant. This food making process is
called photosynthesis.
Parts of the leaf
• Petiole - a thin stalk
that connects the
blade of the leaf to the
plant's stem. These
veins are called
• Blade - a thin, flat part
of the leaf that extends
off the end of the
petiole. It is green as it
contains chlorophyll
which is necessary in
making the plant's
food.
Primary vein: is the main vein starting at the
base of the leaf. It is noticeably wide than
the other veins.
Secondary veins: veins usually branching
off the primary vein, are noticeably
narrower than the primary vein.
Leaf Cross Section
• Plants get carbon
dioxide from the air
through their leaves. The
carbon dioxide diffuses
through small holes in
the underside of the leaf
called stomata.
Leaf Cross Section
• The lower part of the
leaf has loose-fitting
cells, to allow carbon
dioxide to reach the
other cells in the leaf.
This also allow the
oxygen produced in
photosynthesis to
leave the leaf easily.
Leaf Cross Section
• A leaf usually has a large
surface area, so that it can
absorb a lot of light. Its top
surface is protected from water
loss, disease and weather
damage by a waxy layer.
• The upper part of the leaf is
where the light falls, and it
contains a type of cell called a
palisade cell. This is adapted
to absorb a lot of light. It has
lots of chloroplasts and is
shaped like a tall box.
Photosynthesis
• Leaves collect
sunlight, water and
carbon dioxide to
make sugar (food) for
the plant
• The chemical
equation for this
process is
• 6 H2O + 6 CO2
C6H12O6 + 6 O2
sugar
• Leaves break down
sugars to get energy
• This process releases
excess water as waste
• The chemical equation
is C6H12O6 + 6 O2
energy + 6 H2O + 6
CO2
sugar
To help plant grow
Energy released
Respiration
Transpiration
• Taking in CO2 and releasing O2 and H2O as
waste products after respiration
Angiosperms
• Monocots
–Has 1 food part
–Parallel veins
–Petals in groups
of 3, 6, 9
–Xylem & phloem
scattered
throughout stem
Angiosperms
• Dicots
–Have 2 food
parts
–Net-like veins
–Petals in groups
of 4 or 5
–Xylem & phloem
are ring-like in
stem