Transcript BL 1021 – Unit 2-2

BL 1021 – Unit 2.2
Plant Physiology
2.2.1 Plant Cells
• Plant cells are eukaryotic, meaning that they
contain many organelles.
• The chloroplast is unique to plants. It is a specialized
organelle designed to capture sunlight energy and
use it to perform photosynthesis to create food for
the plant.
• The formula for photosynthesis is:
2.2.1 Plant Cells
• Plant cells also feature a large central vacuole. This
large body of water has several uses: regulatingosmosis, providing an emergency water supply and
providing firmness and stability to the plant.
• Plants also have a cell wall. This wall is made of
cellulose and strengthened by lignin. This gives
plants strength and structure, allowing them to grow
tall.
2.2.1 Plant Cells
2.2.2 Basic Plant Features
• Plants are true multicellular organisms. They have
division of labour performed by tissues, organs and
organ systems.
• Two major organ types – subterranean
(underground) and aerial (above-ground).
• Roots usually have fungi growing near/on them.
These work with the plants to break down certain
nutrients in the soil into forms the plant can use. This
combination is called mycorrhizae.
2.2.2 Basic Plant Features
• Leaves are the major site of photosynthesis.
• Leaves are also the site of gas exchange via the
stomata.
• Leaves are coated in waxy cuticle in order to
prevent water loss.
• Leaves and other extremities are supplied with
water and minerals via the xylem and wastes and
food made in photosynthesis is removed through
the phloem.
2.2.3 Organs of Angiosperms
• Flowering plants have 4 major organs.
• Roots
• Roots anchor a plant to the soil, preventing it from
being uprooting during winds.
• Water and minerals are absorbed from the soil by
roots.
• Roots store food for the plant.
• Roots have small projections called root hairs that
increase the reach and surface area of the roots.
2.2.3 Organs of Angiosperms
• Stems.
• Generally above ground.
• Support the upper leaves and flowers, putting them
in prime locations.
• Leaves attach at nodes. Leafless internodes exist
between the leaf-attachment nodes.
• Come in many types; some run straight up, other
along the ground, etc.
2.2.3 Organs of Angiosperms
• Leaves
• Leaves show a large amount of diversity, coming in
many shapes and sizes to suit the climate, wildlife
and other factors affecting the plant.
• Leaves are the primary site of photosynthesis and
gas exchange.
• Two parts of the leaf – the blade (the flat part) and
the petiole (the stalk that attaches to the node of a
stem).
2.2.3 Organs of Angiosperms
• Flower
• The site of sexual reproduction in plants.
• Contains both “male” and “female” apparatus –
capable of self-pollenation, but diversity is
increased when insects transfer pollen from flower
to flower.
• Flowers are brightly colored to attract insects to
them. Flowers also offer nectar that insects eat
while being covered in the flower’s pollen.
2.2.3 Organs of Angiosperms
• Parts of a flower:
• Petals – colorful to
attract insects
• Sepals – lower,
supporting green
leaves with
photosynthetic role.
2.2.3 Organs of Angiosperms
• Stamen – pollenproducing “male”
reproductive structures
• Carpel - “female”
reproductive structure,
containing the ovary.
This matures into fruit to
surround the seed after
fertilization.
2.2.4 Monocots and Dicots
• There are two major types of flowering plants. They
differ on many of their traits but the main difference
can be traced back to the seed leaves. A seed’s
first embryonic leaves known as cotyledons are
either singular or double.
• Plants with a single cotyledon are called
monocotyledons, or monocots.
• Plants with two cotyledons are called dicotyledons,
or dicots.
2.2.4 Monocots and Dicots
• At the seed level, monocots
have a “whole” seed while
dicots have a “split” seed.
• Dicot roots feature a large
singular root called a tap
root whereas monocots
have more branching roots
called fibrous roots.
• Vascular tubing in monocots
is scattered whereas it is
neatly arranged into a ring in
dicots.
2.2.4 Monocots and Dicots
• Monocot leaves have their
veins running parallel while
dicot leaves are branching.
• The floral petals in monocots
come in multiples of threes
whereas dicot petals come
in groups of four or five.
2.2.5 Roots and Shoots
• The root system of a
plant is exists below
ground mostly.
• This portion anchors the
plant, absorbs water
and nutrients, and
stores food.
2.2.5 Roots and Shoots
• The shoot system
makes up the aboveground portion – make
of leaves, stems, and
flowers.
• Leaves are placed into
a good location to
photosynthesize by the
stems.
• The flowers’ purpose is
reproduction.
2.2.6 Specialized Structures
• Some plants have uniquely-designed parts of their
anatomy that allows for additional functions.
• A runner is a special type of stem that runs
horizontally. They are capable of sprouting a new
plant out of them asexually to spread out over an
area. Strawberry plants have runners.
• Rhizomes work in a similar way, except
underground. The Iris plant can spread using
rhizomes.
2.2.6 Specialized Structures
• Tendrils are specialized leaves that allow plants to
latch on and climb. Sweet pea plants use tendrils to
grow upwards on their supports.
• Tubers are enlarged sections of stems or roots that
the plant stores extra nutrition in. This allows them to
survive seasons where photosynthesis would not
generate enough food. These structures are
capable of re-growing the plant.
• Potatoes are a tuber that develops from the stem
while sweet potatoes develop from the root.
2.2.7 Plant Cell Types
• There are five major types of plant cells.
• Parenchyma Cells
• Most common cell.
• Stay alive after they have matured. (Many other
cell types will die out after a certain period)
• If needed, may be able to convert into another
type of cell
• Are good food-storing cells (found in tubers).
• Used for photosynthesis as well.
2.2.7 Plant Cell Types
Collenchyma Cells
Have a singular, but think cell wall.
Found in the growing stems and petioles.
These cells elongate with the lengthening plant.
The strong fiber regions in celery contain these cells.
Sclerenchyma Cells
Have a secondary cell wall, strengthened with
lignin.
• Most die when matured but still offer a large
amount of stability and strength to the plant.
• Often used by people to form fibers (hemp, flax).
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2.2.7 Plant Cell Types
• Water-Conducting Cells
• Also contain a secondary lignin-strengthened cell
wall.
• Die when they mature, leaving only the cell wall.
This essentially leaves an open channel for water
flow.
• Long chains of these cells make up the xylem of the
plant. (other cells offer support and storage help)
2.2.7 Plant Cell Types
• Food-Conducting Cells
• Similar to water-conducting cells, but do not die at
maturity.
• Form the phloem of the plant. Again, other cell
types are associated with these cells to provide
helper roles.
2.2.8 Plant Tissues
• Plants have 3 major
tissue types that make
up all of the organs of
a plant.
• Dermal tissue acts like
skin to protect the
plant. These cells
secrete the waxy
cuticle and are the
location of the
stomata.
2.2.8 Plant Tissues
• Vascular tissue, like the
circulatory system in
animals, deals with the
movement of water,
nutrients and wastes
through the plant.
• Vascular tissue includes
the xylem and phloem.
• The most internal tissue.
• Some plants
(bryophytes) lack this
tissue.
2.2.8 Plant Tissues
• Ground Tissue makes
up the middle ground
of a plant.
• Young plants contain a
higher percentage of
this tissue.
• This tissue functions to
perform photosynthesis,
store foods and water,
and to provide
structure.
2.2.9 The Leaf
• The leaf contains structures for photosynthesis, gas
exchange, water transport and sugar transport.
• The topmost and bottommost surfaces are made of
the epidermis. This works much like the human skin.
The lower surface contains stomata – small
openings that allow gas into and out of the leaf
interior.
• Stomata are only on the underside to prevent
excessive water loss by evaporation caused by
sunlight.
2.2.9 The Leaf
• The mesophyll makes up the interior of the leaf.
• The upper mesophyll is called the palisade
mesophyll and contains highly-ordered cells.
• The lower mesophyll is much more unorganized and
less densely packed. As the cells are more spaced,
it is known as spongy mesophyll. This area works
somewhat like lung tissue in that it has lots of open
areas for air to flow around.
• Xylem and phloem run through the mesophyll
region, circulating water, nutrients and sugar.
2.2.9 The Leaf
2.2.10 Leaf Physiology
• The design of a leaf is such that it optimizes
photosynthesis and minimizes water loss
(transpiration).
• The epidermis is transparent, allowing light to easily
penetrate to the photosynthetic mesophyll cells of
the interior.
• Stomata allow air in and out. Being on the bottomsurface allows this to happen while minimizing
transpiration.
2.2.10 Leaf Physiology
• Xylem pumps in additional water gained from the
roots to the leaf. This makes up for water lost.
• The many gaps and holes in the leaf interior and in
the leaf’s cells allows for water gases to circulate
easily and reach all cells quickly.
• The waxy cuticle acts as a water barrier, preventing
transpiration.