Transcript flowers

Plant Tissue and Growth
What organs do plants have?
Section 1: Plant Cell Structures
• The large central vacuole is surrounded by its own membrane and contains
water and dissolved substances.
o Its primary role is to maintain pressure against the inside of the cell wall, giving the cell shape and helping to
support the plant.
• The cell wall is located outside the cell membrane. It consists mainly of
cellulose and may also contain lignin, which makes it more rigid.
o The cell wall shapes, supports and protects the cell. It prevents the cell from absorbing too much water and
bursting. It also keeps large, damaging molecules out of the cell.
• Plastids are membrane-bound organelles with their own DNA. Ex:
Chloroplasts and chromoplasts.
o Chloroplasts contain the green pigment chlorophyll and carry out photosynthesis.
o Chromoplasts make and store other pigments, they give flower petals bright colors.
Plant Tissues
• Dermal Tissue – covers the outside of a plant in a single layer of cells called
the epidermis. It is like the plant’s skin.
o These cells secrete a waxy substance called cuticle, which coats, waterproofs, and protects the above-ground
parts of plants. This prevents water loss, abrasions, infections, and damage from toxins.
• Ground Tissue – makes up much of the interior of a plant and carries out
basic metabolic functions.
o In stems it provides support and may store food or water.
o In roots it may also store food.
• Vascular Tissue – runs through the ground tissue inside a plant.
o Consists of xylem and phloem, which transport fluids.
Vascular Tissue
• Xylem – a vascular tissue that
transports water and dissolved
minerals from roots to stems and
leaves.
o This type of tissue consists of dead cells that lack
end walls between adjacent cells.
o The side walls are thick and reinforced with lignin,
which makes them stiff and water proof.
Vascular Tissue
• Phloem – vascular tissue that
transports food (sugar dissolved in
water) from photosynthetic cells to
other parts of the plant for growth or
storage.
o This type of tissue consists of living cells that are
separated by end walls with tiny perforations, or
holes.
Growth of Plants
• Plants grow throughout their lives. Plants grow
through a combination of cell growth and cell
division.
o Cell growth increases cell size, while cell division (mitosis) increases the
number of cells.
o As plant cells grow, they also become specialized into different cell types
through cellular differentiation.
o Once cells differentiate, they can no longer divide.
• The key to continued growth and repair of plant
cells is meristem.
o Meristem is a type of plant tissue consisting of undifferentiated cells
that can continue to divide and differentiate.
o Meristem at the tips of roots and stems allows them to grow in length,
this is called primary growth.
o Meristem within and around vascular tissues allows growth in width,
this is called secondary growth.
Section 2: Plant Organs
• Plants have specialized organs
that help them survive and
reproduce in a great diversity of
habitats.
o Major organs of most plants include roots,
stems, leaves, and flowers.
o A plant has 2 organ systems:
• The shoot system – is above the ground
and includes the organs such as leaves,
stems, flowers and fruits.
• The root system – includes the parts of the
plant below ground, such as roots.
Roots
• Roots are important organs in
all vascular plants.
o Two types of roots:
• Primary roots grow downward
• Secondary roots branch out to the side.
Root Systems
• Two Basic Types: Taproot systems and
Fibrous systems
• Taproot systems – feature a single,
thick primary root, called the taproot,
with smaller secondary roots growing
out from the sides.
o The taproot may penetrate as many as 200 feet below
the ground surface.
o It can plumb very deep water sources and store a lot of
food to help the plant survive drought and other
environmental extremes.
o The taproot also anchors the plant very securely to the
ground.
Root Systems
• Two Basic Types: Taproot systems
and Fibrous systems
• Fibrous root systems have many
small branching roots, called fibrous
roots, but no large primary root.
o The huge number of threadlike roots increases the
surface area for absorption of water and minerals,
but fibrous roots anchor the plant less securely.
Root Structures and Functions
• The tip of the root is called the root cap.
o It consists of specialized cells that help regulate primary growth of the root at the tip.
o The root cap is primary meristem, where growth in length occurs.
• The rest of the root is covered with a single layer of epidermal cells.
o These cells may have root hairs that increase the surface area for the absorption of water and minerals from the
soil.
• Beneath the epidermis is ground tissue, which may be filled with stored
starch.
• Bundles of vascular tissue form the center of the root. Secondary meristem is
located within and around the vascular tissues.
Primary Functions of Roots
• Absorbing water and minerals
o Thin walled epidermal cells and root hairs are well suited to absorb water and dissolved minerals from the soil.
• Anchoring and supporting the plant
o Root systems help anchor plants to the ground, allowing plants to grow tall without toppling over.
o A tough covering may replace the epidermis in older roots, making them ropelike and even stronger.
• Storing food
o In many plants, ground tissues in roots store food produced by the leaves during photosynthesis.
Root Growth
• Roots have primary and secondary meristems
for growth in length and width.
• As roots grow longer, they always grow down
into the ground. Even if you turn a plant upside
down, its roots will try to grow downward.
• Specialized cells in root caps are able to detect
gravity. The cells direct meristem in the tips of
roots to grow downward toward the center of
Earth.
Stems
• In vascular plants, stems are the
organs that hold plants upright so
they can get the sunlight and air they
need.
• Stems also bear leaves, flowers,
cones, and secondary stems.
o These structures grow at points called nodes.
o At each node, there is a bud of meristem tissue that
can divide and specialize to form a particular
structure.
Stem Tissues and Functions
• A single-celled layer of epidermis protects
and waterproofs the stem and controls gas
exchange.
• In trees, some of the epidermal tissue is
replaced by bark. Bark is a combination of
tissues that provides a tough, woody
external covering on the stems of trees.
The inner part of bark is alive and growing;
the outer part is dead and provides
strength, support and protection.
Stem Tissues and Functions
• Ground tissue forms the interior of the stem. The large central vacuoles of
ground tissue cells fill with water to support the plant. The cells may also
store food.
• Bundles of vascular tissue run through the ground tissue of a stem and
transport fluids. Plants may vary in how these bundles are arranged.
Stem Growth
• The stems of all vascular plants get longer through primary growth. This
occurs in primary meristem at the tips and nodes of the stems.
• Most stems also grow in thickness through secondary growth. This occurs in
secondary meristem, which is located in and around the vascular tissues.
• Secondary growth forms secondary vascular tissues and bark. In many trees,
the yearly growth of new vascular tissues results in an annual growth ring.
Leaves
• Leaves are the keys not only
to plant life but to all
terrestrial life.
• The primary role of leaves is
to collect sunlight and make
food by photosynthesis.
Factories for Photosynthesis
Factories for Photosynthesis
• Mesophyll makes up most of the leaf’s interior. This is where photosynthesis
occurs. Mesophyll consists mainly of parenchymal cells with chloroplasts.
• Veins are made primarily of xylem and phloem. They transport water and
minerals to the cells of leaves and carry away dissolved sugar.
Factories for Photosynthesis
• The epidermis of the leaf consists of
tightly-packed dermal cells. They secrete
waxy cuticle to prevent evaporation of
water from the leaf.
• The epidermis has tiny pores called
stomata (singular, stoma) that control
transpiration and gas exchange with the
air.
Flowering Plants
• Angiosperms, or flowering seed plants,
form seeds in ovaries.
• As the seeds develop, the ovaries may
develop into fruits.
• Flowers attract pollinators, and fruits
encourage animals to disperse the
seeds.
Parts of a Flower
• A flower consists of male and
female reproductive structures.
• The main parts of a flower
include the stamen, pistil,
petals, and sepals.
Parts of a Flower
• The stamen is the male reproductive
structure of a flower. It consists of a
stalk-like filament that ends in an anther.
• The anther contains pollen sacs, in which
meiosis occurs and pollen grains form.
• The filament raises the anther up high so
its pollen will be more likely to blow in
the wind or be picked up by an animal
pollinator.
Parts of a Flower
• The pistil is the female reproductive structure of a flower. It
consists of a stigma, style, and ovary.
• The stigma is raised and sticky to help it catch pollen.
• The style supports the stigma and connects it to the ovary, which
contains the egg.
• Petals attract pollinators to the flower. Petals are often brightly
colored so pollinators will notice them.
• Sepals protect the developing flower while it is still a bud. Sepals
are usually green, which camouflages the bud from possible
consumers.
Major Tissues in Plants
Function
Dermal Tissue
Compares to the skin, or
epidermis in animals. Protects
plant and intermediates between
the plant and its environment.
Basic metabolic functions. Makes
up most of the interior of the
plant. Makes up most organs.
Transports water, minerals and
food throughout the plant.
Ground Tissue
Vascular Tissue
Organ
Functions
Root
Anchorage.
Absorption of water and dissolved minerals.
Storage (surplus sugars transported from
leaves)
Conduction
Stem
Conduction of water and sugars throughout
plant.
Support leaves and fruits.
Leaf
Perform photosynthesis
Regulate water loss of the plant
Abcission (leaf fall)
Flower
Contain reproductive organs
Attract pollinators
Produce fruit