Plants
Ms. Luaces
Honors Biology
2.2 – Properties of Water
• Water is a neutral molecule and found over 75% of
Earth’s surface
– However, water is polar (a molecule in which the
charges are unevenly distributed)
2.2 – Properties of Water
• Polar molecules like water can attract each other –
known as hydrogen bonding
– This accounts for many of waters special properties
2.2 – Properties of Water
• Cohesion: attraction between
molecules of the same substance
– Why drops of water form beads
and why there is such a thing as
surface tension
• Adhesion: attraction between
molecules of different substances
– Causes the capillary action that
draws water out of roots up into a
plants stems and leaves
2.2 Properties of Water
• Water also has a high heat capacity – takes a large
amount of heat to cause the molecules to move faster
– This is why cells don’t overheat as they are carrying out the
bodies processes – the water is drawing the heat out (sweat!)
Chapter 22: Plants
• Plants have adapted so well to many environments that
they dominate much of the surface of the planet
– Include trees, shrubs, mosses, and even green algae!
22.1 – Characteristics of
Plants
• Plants are:
–
–
–
–
–
Kingdom Plantae
Multicellular
Eukaryotes
Have cell walls with cellulose
Autotrophs (photosynthesis)
22.1 – Characteristics of
Plants
• The lives of plants center on
the need for sunlight, gas
exchange, water and
minerals
– Sunlight: required for
photosynthesis so they’ve
developed broad, flat leaves
– Gas exchange: require carbon
dioxide and have to let go of
oxygen, so they’ve developed
special parts to deal with this
– Water and minerals: required
for photosynthesis and survival,
so they’ve evolved structures
that limit water loss and
increase the intake of water and
nutrients upwards from the soil
22.1 – The History &
Evolution of Plants
• Ancestors of land plants were water-dwelling without
leaves and roots: today’s algae
– At first, algae was in Protista, but because they have cell walls
and do photosynthesis, they are classified as plants
22.1 – The History &
Evolution of Plants
• Over time, the demands of life on land favored the
evolution of plants more resistant to the drying rays of
the sun, more capable of conserving water, and more
capable of reproducing without water.
22.2 Seedless Plants
• Algae: any photosynthetic eukaryote other than a land
plant
–
–
–
–
Mostly aquatic
Absorb moisture and nutrients directly from their surroundings
One of the first plants to evolve billions of years ago
Can form colonies – how first plants probably arose
22.2 Mosses and other
Bryophytes
• Bryophytes: higher degree of
cell specialization and one of
the first plants to become
established on land.
• Characteristics:
– Live in damp places with plenty of water
– Lack vascular tissue (roots and stems)
and lignin, and therefore cannot support
a tall plant body
– Include mosses, liverworts, and
hornworts
22.2 Vascular Plants
• Tracheophytes (vascular plants): have a transport
system with true vascular (roots and stems) tissue
• Characteristics:
– Contain cells called tracheids (water conducting cells)
– Contain xylem (carries water from the roots) and phloem
(transports solutions of nutrients and carbs)
22.2 Vascular Plants
• Vascular plants are split up into 2 categories:
– Seed Plants: the majority of plants on earth
– Seedless plants: ferns, mosses and horsetails
Let’s Practice!
• Study Workbook A Pgs. 17 #1-4 and Pgs.
253-255 SKIP #4-6
• Work with a buddy – one sheet of paper
• Question AND Answer
• You’ve got 40 minutes!!
22.3 Seed Plants
• Each and every seed contains a living plant ready to
sprout as soon as it encounters the proper conditions for
growth
• A seed is a plant embryo and a food supply, encased in
a protective covering
22.3 The Importance of
Seeds
• Unlike mosses and ferns, the gametes of seed plants do
not need standing water for fertilization
• Adaptations that allow seed plants to reproduce without
standing water include:
– a reproductive process that takes place in cones or flowers
– the transfer of sperm by pollination
– the protection of embryos in seeds
22.3 Seed Plants
Gymnosperms
Angiosperms
• Bear seeds directly on scales
of cones
• Male gametophyte is in pollen
grain
• Pollen is carried by wind
• Flowering plants
• Bear their seeds in flowers
inside a layer of tissue to
protect the seed
• Male gametophyte also in
pollen grain
• Pollen is carried by animals
22.3 Seed Plants
• Embryos can remain in dry conditions for weeks or even
years because of the tough seed coat that surrounds
and protects it
22.4 Flowering Plants
• Angiosperms
(flowering
plants) are the
most recent in
evolution of
plants
– Contain
ovaries, which
surround and
protect seeds
– Attract animals
such as bees to
carry pollen to
other flowers
22.4 Flowers & Fruits
• Fruit contains one or more ovaries with seeds inside the
walls
– Helps to disperse the seeds, especially when eaten by an animal
– Increase the range the plants inhabit (over hundreds of km)
22.4 Angiosperm
Classification
• Classified according to
the number of seed
leaves (cotyledons) in
their embryos
– One seed leaf –
monocots
– Two seed leaves – dicots
– ** Recent classification
has shown dicots go into
a variety of different
categories, and have
been expanded
– **Figure 22-22 is a good
reference!
23.1 Specialized Tissues in
Plants
• Plants move materials, grow, repair themselves, and
constantly respond to the environment. They do this with
3 principal organs that produce, store, and transport
nutrients:
– Roots
– Stems
– Leaves
23.1 Seed Plant Structure
• Roots:
–
–
–
–
–
Anchor plants
Absorb water and dissolved nutrients
Transport these materials to the rest of the plant
Store food
Hold the plant upright
23.1 Seed Plant Structure
• Stems:
– Support the plant body
– Transport nutrients
– Serve as a defensive system that protects the plant against
predators and disease
23.1 Seed Plant Structure
• Leaves:
– Main photosynthetic organ (absorbs sunlight and creates food)
– Protect against water loss
23.1 Plant Tissue Systems
• 3 main tissue systems:
– Dermal: covers the plant like skin
– Vascular: forms a system of pipe-like cells
– Ground: produces and stores food
23.1 Plant Tissue Systems
• Dermal Tissue: made of a single layer of cells called
epidermis
– Covered with a thick waxy layer (cuticle) which protects against
water loss
– The protective outer covering of a plant
23.1 Plant Tissue Systems
• Vascular Tissue: supports the plant body and transports
water and nutrients throughout the plant. Made up of 2
types of tissue:
– Xylem: transports water (also known as tracheids)
– Phloem: transports dissolved nutrients (also known as sieve
tube elements)
23.1 Plant Tissue Systems
• Ground Tissue: produces and stores sugars, and
contributes to physical support of the plant
– Edible portions of the plants
– Composed of parenchyma cells and contain many chloroplasts
for photosynthesis
23.1 Plant Tissue Systems
• Even the oldest trees produce new leaves because of
meristems: unspecialized cells in which mitosis
produces new cells that are ready for differentiation
– Only located at the tips of stems and roots (apical meristems)
– Act like stem cells of animals
– Gradually, the cells mature and specialize through a process
called differentiation
23.2 Roots
• Seeds put out their first root to draw water and nutrients
from the soil
– Adds length and surface area to take up water and nutrients
– 2 types of root systems: Taproot & Fibrous
23.2 Types of Root Systems
Taproot System
Fibrous System
• Primary root grows long
and thick
• Smaller branch roots from
the main root
• Ex: Oak, Dandelions
• Many equally sized roots
that grow separately from
the base of the stem
• No root is longer than
another
• Ex: Grasses
23.2 Anatomy of a Root
• A mature root has an
outside layer (epidermis),
and also contains vascular
tissue and a large area of
ground tissue
– Helps to transport water and
minerals
23.2 Anatomy of a Root
• Epidermis is involved in
protection and absorption
– Contains small projections
called root hairs that help
produce a large surface area for
absorption
23.2 Anatomy of a Root
• Ground Tissue moves
water and minerals
through the cortex
and stores the
products of
photosynthesis (such
as starch)
– Also contains a layer
called the endodermis
which works closely
with vascular tissue
23.2 Anatomy of a Root
• Vascular Tissue helps
absorb water and
nutrients through the
special channels
xylem and phloem
23.2 Anatomy of a Root
• Apical Meristem
contains the root
cap that protects
the growing region
of unspecialized
cells
23.2 Root Functions
• Roots support a plant, anchor it in the ground, store
food, and absorb water and dissolved nutrients from the
soil
– Ingredients of the soil help define what plants can flourish there
– In general, plants need large amounts of N, P, K, Mg, S, and Ca
23.2 Root Functions
• Active transport (where
the use of energy in the
form of ATP is used to
move materials across
membranes) help to
transport water by pressure
from the outside into roots,
up the stems and into the
leaves
– Root Pressure
23.3 Stems
• There are above and underground
(potatoes!) stems
• Aboveground stems have several
important functions:
– Produce leaves, branches, and flowers
– Hold leaves up to the sun
– Transport substances throughout the plant
23.3 Stem Structure &
Function
• Stems are important
water (xylem) and
mineral (phloem)
transport system
• They also function in
storage and aid in
the process of
photosynthesis
23.3 Stem Structure &
Function
• Stems contain all 3 tissue systems:
– Dermal: thick layer of cell wall and waxy covering
– Vascular: xylem and phloem
– Ground: specialized mesophyll cells to carry out
photosynthesis
23.3 Stem Structure &
Function
• Stems also
contain
nodes
(attach
leaves) and
buds (apical
meristems)
23.3 Growth of Stems
• The growth of most plants isn’t precisely
determined like our growth is
• Adding length to the plant is called primary
growth
– Occurs in all seed plants and is a result of
elongation of cells in the apical meristem
23.3 Growth of Stems
• Adding thickness is
known as secondary
growth
– Occurs mostly in pines
and dicots, not in
monocots
– Allows plants to grow
to great heights
because the width
supports the weight
23.3 Growth of Stems
• In conifers and dicots,
secondary growth
takes place in the
meristems called
vascular cambium
and cork cambium
– Vascular: produces
vascular tissue and
increases thickness
– Cork: produces outer
covering
23.4 Leaves
• Photosynthesis
uses CO2 & H20 to
produce sugar and
oxygen  The
structure of a leaf is
optimized to absorb
light and carry out
photosynthesis
23.4 Leaf Structure &
Function
• A leaf has a flat shape that helps
maximize light absorption – the blade
– Top and bottom surfaces are covered by
epidermis (dermal tissue) that have thick
outer walls that resist tearing and a waxy
cuticle to waterproof
23.4 Leaf Structure &
Function
• The vascular
tissue is made of
xylem and
phloem tissue
bundled in leaf
veins to transport
water and
nutrients
23.4 Leaf Structure &
Function
• Ground tissue makes up the area between
leaf veins – known as mesophyll
– Sugars produced here move to the leaf veins
for transport in the ________?
23.4 Leaf Structure &
Function
• Stomata are small openings in the epidermis that
allow CO2, H20 & 02 to diffuse in/out of the leaf
– Transpiration is the loss of water through the leaves
• Helps to keep it cool on hot days but can lead to water loss
23.4 Gas Exchange &
Homeostasis
• Photosynthesis
– 02  Leaves  CO2
• Plants use food (Cellular Respiration)
– CO2  Leaves  O2
• All through the stomata openings
23.4 Gas Exchange &
Homeostasis
• Plants maintain homeostasis by keeping
their stomata open just enough to allow
photosynthesis to take place but not so
much that they lose excessive water
– Guard cells surround the stomata and control
opening/closing
23.4 Gas Exchange &
Homeostasis
• When there is a lot of water, guard cells
will open the stomata
– Vice versa when there’s little water
– Typically, stomata are open during the day
(why?) and closed at night (why?)
23.4 Gas Exchange &
Homeostasis
• Wilting results from the loss of water
(therefore pressure)
– When it wilts, the stomata will close (why?)
23.5 Transport in Plants
• Remember that active transport and root
pressure cause water to move from soil
into plant roots
– Major force of water transport is provided by
transpiration
23.5 Water Transport
• Capillary action (combines cohesion and
adhesion forces) and transpiration work
together to move water through the xylem
tissues in the plant
23.5 Nutrient Transport
• Phloem transport
works through
pressure-flow
hypothesis
– Active transport
moves sugars
through phloem
– Water follows by
osmosis
Let’s Practice!
• Study Workbook A 23.3 & 23.4 Pgs. 276280
• 23.3 #1-5, 7, 10-15
• 23.4 # 1-17, 19
• Work in pairs, one sheet of paper,
answers only!
Study Workbook A
• Pg. 268 #9-13
• Pg. 284 ALL
• Pg. 288-289 #17-27
– YES, you must draw the flower and label the
parts!
• UNTIL EVERYONE HAS FINISHED, WE
CANNOT TAKE OUR TRIP!!
Rooftop Garden
• Sketch 2 of the plants and include their name
at the top of the page. Include the following:
–
–
–
–
How many nodes the plant has
What kind of root system is it
Leaf classification, arrangement, and shape
If there are any flowers, what kinds of pollinators
would be attracted?
– If you had to name the plant yourself, what name
would you come up with and why? (use Pg. 7 of
your packet)
Leaf Drawing Contest
• If you had gone on the Magic School Bus,
how would you have drawn the inside
structure of a leaf?
– Include in your sketch the following: the cuticle,
ground tissue (including mesophyll cells),
vascular system (both xylem and phloem), dermal
tissue, and stomata.
– Label all of the above parts
– The best sketch that has identified ALL the parts
above will get to choose from the coupon book 
Sample Sketch