Roots anchor the plant, absorb minerals and water,conduct water and
nutrients, and store food. These are two types of root systems.
- Taproot System:
This system consists of a single main vertical root with many smaller
side roots. Examples of this type of system are: carrots, turnips, and
dandelions. They serve as excellent reserves for food and anchor the
- Fibrous System:
This system consists of many small lateral roots that spread out just
below the soil's surface. The plants containing this type of root
system has excellent exposure to water in the soil. It helps anchor
the plant and helps prevent soil erosion.
roots are roots that grow from
plant structures other than the roots.
- Shoot System:
The shoot system consists of vegetative shoots which produce leaves
and floral shoots that end with the flower.
contain areas where side branches and leaves develop from. These areas
are called nodes. The area in-between the nodes are the inter
nodes. At the node axially buds are found. These buds contain
embryonic tissue which will allow the stem to grow. Lenticels
are small holes located on the stem. These holes allow air into the
stem while they are active. As the stem gets older they disappear.
Many stems end with a terminal bud. This bud allows the stem to
grow in length.
Leaves carry on photosynthesis. Their position and shape allow them to
absorb the maximum amount of sunlight as possible. The leaf consists
of the flattened portion called the blade, the edge or the margin, the
petiole, and the veins. Leaves can be classified based on the these
(flowering plants) can be classified into 2 main groups based on the
types of roots, stems, leaves, flowers, and seeds they contain.
One seed leaf
||Floral parts in
multiples of 3
Two seed leaves
bundles arranged in rings
||Floral parts in
multiples of 4 or 5
- Types of Plant Cells:
- Parenchyma Cells.
These cells are the most general of plant cells. They consist of thin
flexible cell walls. They contain a large central vacuole and can
carry out most of the metabolic functions of the plant. Mesophyll
cells of the leaf are parenchyma cells. The fleshy tissue of most
fruits also contain much parenchyma.
Cells. These cells have a much
thicker primary wall than the parenchyma cell. Grouped in strands or
cylinders they support young plants.
Cells. Function in support of
the plant. They contain a thick secondary wall containing lignin. For
all intent and purpose these cells function best when dead.
These are water conducting elements. These cells are dead and are
found along with vessel elements making up the plants xylem.
These function in carrying food throughout the plant. They are kept
alive and nourished by companion cells. These are found in the plants
- Tissue Types:
- Dermal Tissue.
generally a single layer of cells. They are tightly packed and covered
with a transparent, waxy, material called the cuticle.
- Vascular Tissue.
functions in support and transportation of food and water throughout
- Ground Tissue.
makes up the bulk of a young plant. It fills the space between the
dermal and the vascular tissues.
- Vascular Plants
- Tissues of vascular
plant leaves: Leaves are cloaked by a single layer of cells called the
epidermis. It protects the leaf from physical damage and
pathogens. A transparent, waxy, colorless cuticle coats the
epidermis. The stomata ( small holes) are located on the lower
epidermis of the leaf. The stomata allow gases and water vapor into
and out of the leaf. Each stoma is controlled by two bean shaped guard
cells. The palisade mesophyll is a layer of elongated cells
containing chloroplasts found just under the upper epidermis. The
majority of photosynthesis takes place within this area. Just below
the palisade mesophyll is an area of loosely packed parenchyma called
the spongy mesophyll. The spongy mesophyll contains air spaces
in which gases circulate. The petiole of the leaf connects the
blade with the stem. The vascular tissues pass through with the xylem
positioned in the top section of the vein while the phloem occupies
the lower section.
- Primary Growth:
Apical meristem is responsible for primary root and stem growth in
- Primary Root Growth:
is concentrated near the tip and results in the root growing in
length. The root tip contains 4 zones of development: The root cap,
which protects the area behind it and softens the soil ahead of it by
producing a polysaccharide. The apical meristem, is an area of
rapidly dividing cells. It will replace the cells of the root cap as
they wear away and push cells above them that will develop into the
main tissues of the plant. The zone of elongation, is an area
where the cells elongate 10 times their original length. This
elongation helps push the root into the soil. The zone of
maturation, is the area farthest from the root tip. Here the new
cells will specialize and carry out the functions of the epidermal,
ground, and vascular tissue. The primary tissues in a dicot root are
arranges in a central x pattern for the xylem with the phloem located
in each of the angles of the xylem. In a monocot the vascular tissues
are alternated in a circle.
- Primary Stem
Growth: begins at the tip of
the terminal bud in the area called the apical meristem. The cell
divisions are responsible for the stem's growth in length. The primary
vascular tissue in monocots takes on a scattered arrangement. In a
dicot, it takes a circular pattern.
- Secondary Growth:
Increases the girth of a stem it is caused by the vascular and cork
- Vascular Cambium:
meristematic parenchyma produces xylem on the inside and phloem on its
outer side. The secondary xylem accumulates and forms the wood. The
secondary phloem does not accumulate and is sloughed off with the
- Cork Cambium:
forms in the outer cortex. Produces cork and epidermal tissues.
- Wood has 2 zones:
Heartwood- the older (inner) layers of xylem blocked with
resins. It is non -functional in water transport. Sap wood-
outer xylem, vascular cambium, phloem and cork cambium. Conducts water
- Transport in Plants:
- Absorption of water
and minerals by roots: Water
and mineral enter through root epidermis, cross the cortex, pass into
the stele, and are carried upward in the xylem.
- Active accumulation
of Mineral Ions. The cells cannot get enough mineral ions from the
soil by diffusion alone. The soils solution is too dilute.
- ACTIVE TRANSPORT
of these ions must occur. Specific carrier proteins in the plasma
membrane attract and carry their specific mineral into the cell. A
Proton Pump: H+ is pumped out of the cell causing a change in pH and a
voltage across the membrane. This helps drive the anions and cations
into the cell. Water and minerals cross the cortex in one of 2 ways:
Via SYMPLAST which is the living continuum of cytoplasm connected by
PLASMODESMATA. Via APOPLAST which is nonliving matrix of cell walls.
At the endodermis the apoplastic route is blocked by the CASPARIAN
STRIP. this is a ring of suberin around each endodermal cell. Here
water and minerals MUST enter the stele through the cells of the
endodermis. Water and minerals enter the stele via symplast, but xylem
is part of the apoplast. Transfer cells selectively pump ions out of
the symplast into the apoplast so they may enter the xylem. This
action requires energy.
- ASCENT of XYLEM SAP:
- Water transported up
from the roots must replace water lost by transpiration.
- WATER POTENTIAL: Xylem
sap rises against gravity, driven by a gradient of water potential (*)
Water flows from an area of high * to an area of low *. Water
Potential is expressed in units of pressure: 1 bar = pressure needed
to push a column of water up 10 meters. 1 megapascal= 10 bars. Pure
water has * = 0. Addition of pressure increases *. Addition of solutes
- ROOT PRESSURE: When
transpiration is low, ions pumped into the stele decrease * and cause
water uptake by the stele. This uptake force is called root pressure.
Cannot keep pace with transpiration, can force water up only a few
- a). water leaves leaf
- b). this water loss is
replaced by evaporation from mesophyll cells, lowering their water
potential, causing them to take water from neighboring cells.
- c). Process continues
back to the tracheids causing water up take from the xylem sap.
- d). Water goes fro
tracheids to air following a water potential gradient.
- e). Cohesion and
adhesion of water. H bonds of water, hydrophilic walls of xylem and
small diameter of xylem aid in the movement of water up the tube.
- f). This pull decreases
water pressure in the xylem causing the roots to take water from the
- How Stomata Open and
- Turgid guard cells open
the stomata, while flaccid cells close them.
- The K+ ion is
responsible for the stomatal action.
- Uptake of K+ causes the
cell to become turgid- decreases water potential.
- Stomata open at dawn
because light induces the cells to take in K+. An internal clock
(circadian rhythm) will make them open even if in they are kept in the
- Guard cells will close
due to: a water deficiency, High temperatures due to an increase of
- Transport in PHLOEM:
- Translocation =
transport of the products to the rest of the plant by the phloem. Phloem
carries sucrose, minerals, amino acids, and hormones.
- SOURCE to SINK
- Source = origin of the
sugar Sink = Organ that consumes or stores the sugar.
- Flow is always from the
source to the sink.
- Phloem is loads by
- Click here to develop
the concept of Transpiration by completing the AP
Lab 9: Transpiration.
The angiosperm life cycle
includes alternation of generations. Here a multicellular haploid (N)
gametophyte generation alternates with a diploid (2N) sporophyte
- The sporophytes produce
the haploid (N) spores by meiosis.
- The sporophytes are the
large plants we see dotting our landscape.
- These spores will
undergo mitosis and become the male and female gametophytes.
- Gametes are produced by
the gametophytes through the process of mitosis.
- The gametes fuse and
develop into the multicellular sporophyte.
The flower is the sexual
reproductive part of an angiosperm. It consists of four whorls of modified
leaves : sepals, petals, stamens and carpals. The stamens are the male
reproductive parts which includes the sporangia that produces pollen. The
carpals are the female reproductive parts and includes the sporangia that
produces the egg.
Flowers are classified
according to the number and type of their structures.
- Complete flower. The
flower contains all four basic whorls of modified leaves.
- Incomplete flower. A
flower missing one or more of its parts.
- Perfect flower. A flower
containing both male and female parts. Could be complete or
- Imperfect flower. A
flower that is either male or female due to its missing of either
- Monoecious. Plants
having both male and female flowers on the same plant.
- Dioecious. Plants having
male and female flowers on separate plants.
- A pollen grain is an
immature male gametophyte.
- It is produced within
the sporangium of the anthers.
- The diploid microspore
mother cell will undergo meiosis and form 4 haploid microspores.
- The microspores nuclei
will undergo mitosis and produce a tube nucleus and a generative
- A thick wall forms
around the spore in a specific pattern, producing the pollen grain or
immature male gametophyte.
- The ovule is an immature
seed. It is formed within the ovary and contains the female
- The female gametophyte
is the embryo sac and forms in the following way.
- The megaspore mother
cell undergoes meiosis to form 4 haploid (N) megaspores.
- One of the 4 will
continue to develop, while the other 3 dissolve.
- The remaining megaspore
grows and its nucleus will undergo 3 mitotic divisions, forming 1
large cell with 8 haploid nuclei.
- This will develop into
the embryo sac. This sac contains a specific arrangement of these
nuclei in the following order: The egg cell is located near the
micropyle surrounded by 2 other cells called synergids. At the
opposite end 3 antipodal cells are found. In the center of the sac
will be found 2 polar nuclei.
Pollination is the
placement of the pollen on the stigma of the carpal. This pollen
transfer can be accomplished by wind, insects, built in mechanical
discharge, and man. Once the pollen lands on the stigma, a series of
chemical reactions takes place allowing the pollen grain to begin
producing a structure called the pollen tube. As this is happening,
the generative nucleus will divide and produce 2 sperm nuclei. This
pollen grain with the pollen tube and 3 nuclei is considered the
mature gametophyte. The pollen tube will work its way through the
style of the carpal and touch the micropyle of the ovule. Here the
sperm nuclei will enter the embryo sac and fertilize the egg and the
two polar nuclei; hence the term double fertilization. The fertilized
egg (2N) will develop into the immature seed plant, while the (3N)
central cell will develop into the endosperm or food storage area of
Structure of the
- The seed is protected by
the seed coat or testa.
- The micropyle is the
only opening into the seed. It is through here that the water will
enter to start germination.
- The seed contains stored
food in the form of seed leaves (cotyledons). Some seeds contain one (
monocots) while other contain 2 ( dicots).
- The embryo plant
contains several areas : the area above the attachment of the
cotyledons is the epicotyl. This will develop into the shoots and
leaves of the developing plant. The area below the attachment is
called the hypocotyl. This will develop into the roots of the plant.
The fruit of a flower
develops from the ovary. They protect the seeds and allow for their
dispersal. Fruits may be classified in many ways. Below find one of such
- Simple Fruits: These
fruits develop from a single ovary. Peach, cherry, soybean.
- Aggregate Fruits: These
fruits develop from a single flower with many carpals. Strawberry.
- Multiple Fruits: Fruit
develops from a group of tightly clustered flowers. Pineapple.