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Plant Structure & Function
AP Biology
Plant Evolution
• _____________ancestor of all plants
• _____________mosses- were the
first land plants
• Next _________
tissues evolved to
carry water up the
stem and sugar down
the stem
• Next ___________
developed to assist in
plant ___________
• Lastly, ___________
developed to attract
pollinators
Plant Classifications
• Plants are grouped informally based on whether or not they
have ___________ tissue. Plants that don’t have vascular
tissue can’t grow ___________.
• Vascular tissue carries substances throughout a plant.
There are two types:
– ___________ - carries water and minerals
– ___________ - carries sugars
• Plants are also grouped based on what type of
___________ they produce. Seeds are plant ___________.
– ______________ - are conifers and have a “naked” seed
and are pollinated by wind
– ______________ - are flowering plants- seeds develop
inside an ovary and plants are pollinated by insects,
animals
Angiosperm Classifications
• Angiosperms are divided into two classes: the
___________ and the ___________ :
Characteristic
Description
Dicots
Monocots
Storage tissue- provides
nutrition to developing seed
2 cotyledons
1 cotyledon
The pattern of veins in
leaves
Netted
(branching)
Parallel
Number of petals, sepals,
stamens, and other flower
parts
In 4’s, 5’s, or
multiples thereof
In multiples of 3’s
Arrangements of bundles of
vascular tisse
(xylem/phloem) in stems
Organized in a
circle
scattered
Form of root
Taproot (large,
single root)
Fibrous system
(cluster of many
fine roots)
Monocots Vs. Dicots
Plant Tissues
• Plant tissues are divided into three groups:
– 1. ___________ tissues- include 3 kinds of cells that differ
mostly by the nature of their cell walls:
• ___________ cells- most common- thin cell walls- function in
storage, photosynthesis and secretion
• ___________ cells- thick but flexible cell walls, serve as
mechanical support
• ___________ cells- thicker cells walls, also give mechanical
support Plant tissues are divided into three groups:
– 2. ___________ tissue- the epidermis that covers the
outside of plants. Produces a waxy ___________ to protect
the plant from dessication (drying out).
– 3. ___________ tissue- carry substances and usually occur
together forming vascular bundles.
• ___________ carries water and minerals. Made of two types of
cells called vessel members and tracheids.
• ___________ carries sugar. Made of cells called sieve tube
members.
The Seed
• The seeds consists of an embryo, a seed coat, and some
kind of storage material.
• The storage material is either ___________ or
___________. Cotyledons are formed by digesting the
endosperm. Dicots have two cotyledons (peas) and
monocots only have one (corn).
• The embryo consists of the following parts:
– The top part of the embryo is the ___________ - it becomes
the ___________ tip.
– Attached to the epicotyl are young ___________ called
___________.
– Below the epicotyl and attached to the cotyledons is the
___________. It becomes the young ___________.
– The ___________ develops below the hypocotyl. It
develops into the ___________.
– A ___________ called the ___________ surrounds and
protects the epicotyl.
The Seed
Germination & Development
• Mature seeds can remain ___________ until specific
___________ cues are encountered: water,
temperatures, light, or seed coat
___________(animal digestive tract or fire).
• Water absorption causes ___________ to start
cellular respiration. It also causes the seed coat to
___________ and the growing tips of the ___________
to produce roots to anchor the seedling. Elongation
of the ___________ follows- forming the young
shoot.
Meristems
• ___________ are tissues that are actively dividing in
a plant- they allow the plant to grow. There are two
types:
• ___________ meristems- are responsible for up and
down growth (tips of roots and shoots). This type of
growth is called ___________ growth.
• In some plants there are also ___________
meristems- responsible for side to side growth, also
called ___________ growth. This allows plants to
become woody. There are two lateral meristems:
– ___________ cambium- gives rise to periderm- the outside
of woody plants
– ___________ cambium- gives rise to secondary xylem and
secondary phloem.
Meristems
Primary vs. Secondary Structure
Primary Structure of Roots
• ___________ - lines the outside of the root.
• ___________ - makes up the bulk of the root. Stores starch.
• ___________ - tightly packed cells that form the innermost portion of the
cortex
• ___________ cylinder- inside the endodermis. Contains xylem and
phloem
Dicot Root
Primary Structure of Stems
• Primary structures in the stem are very similar to the root, but the
___________ is lacking. Also:
– The epidermis is covered by a waxy coating.
– The cortex consists of various types of ground tissue that contain
___________.
– The vascular cylinder contains xylem, phloem.
Dicot Stem
Monocot Stem
Structure of the Leaf
• ___________ - protective covering. Covered by a cuticle of
wax. Reduces transpiration (water loss from the plant).
• ___________ ___________ - parenchyma cells with
numberous chloroplasts and large surface areas
specializaed for photosynthesis.
• ___________ ___________ - parenchyma cells loosely
arranged below the palisade mesophyll. Spaces between the
cells provide air chambers for carbon dioxide and oxygen.
• ___________ cells- epidermal cells that control the opening
and closing of stomata (holes in the leaf that allow for gas
exchange)
• ___________ bundles- consist of xylem and phloem
Structure of the Leaf
Structure of Flowers
• ___________ - male part
– ___________ - contains male
gametophyte (sperm)
– ___________ - holds up the
anther
• ___________ - female part
– ___________ - contains
female gametophyte (eggs)
– ___________ - tube leading to
ovary
– ___________ - opening to sty
• ___________ - attracts pollinators
• ___________ - mature ovary that
aids in seed dispersal
Transport of Water
• Water and minerals enter the
roots through root hairs by
___________. There are
two pathways through which
water can move to the center
of the root:
– ___________ route- water
moves through cell walls
from one cell to another
without ever entering the
cells.
– ___________ route- water
moves from one cell to
anotehr through
___________.
Transport of Water
• Three mechanisms are involved in the movement of
water and dissolved minerals in plants:
– ___________ - water moves from the soil to the root and
into xylem by osmosis. The concentration gradient is
maintained by moving water out of the root continuously
and by the higher mineral content in the plant.
– ___________ action- the rise of liquids in narrow tubes due
to adhesion.
– ___________ -tension theory• ___________ - evaporation of water from plants creates negative
pressure or tension.
• ___________ - water molecules being attracted to each other
Control of Stomata
• ___________ - openings in the
leaf that allow for exchange of
gases.
• Each stoma is controlled by
___________ cells. Water fills
these cells to allow them to
control stomata.
• Many factors control the
stomata:
– Stomata close when
temperatures are ___________
– Stomata open when carbon
dioxide concentrations are
___________ inside the leaf
– Stomata usually ___________
at night and open during the
day
Transport of Sugars
• ___________ is the movement of
carbohydrates through the phloem form
the sources (where its made) to the sink
(where its used or stored). It’s described
by the pressure-flow hypothesis:
– Sugars enter sieve tube members by
active transport. This develops a
concentration of solutes that’s higher
than the sink.
– Water enters sieve tube members as
a result of the solute concentration.
– Pressure in sieve tube members at
the source moves water and sugars.
– Pressure is reduced at the sink as
sugars are removed from the
phloem.
Plant Hormones
• ___________ - promotes plant growth. Is produced in
•
•
•
•
the tips of roots and shoots.
___________ - also promote cell growth, stem
elongation.
___________ - stimulate cell division. Stimulate organ
development. Stimulate lateral buds. Delay the
aging of leaves.
___________ - promotes ripening of fruit and
production of flowers.
___________ ___________ - a growth inhibitor.
Maintains dormancy of seeds.
Plant Responses to Stimuli
• ___________ - a growth pattern in response to
an environmental stimulus:
• ___________ - in response to light. Hormone
Auxin controls the plants growth.
• ___________ - in response to gravity by stems
and roots. Auxin and giberellins are involved.
• ___________ - in response to touch.
Photoperiodism
• Response of plants to changes in the ___________ relative time of day and night.
• Plants maintain a ___________ rhythm- a clock that
measures the length of day and night.
• Many flowering plants initiate flowering in response
to changes in the photoperiod:
– ___________ -day plants flower in the spring and early
summer when daylight is increasing.
– ___________ day plants flower in the late summer and
early fall when daylight is decreasing.
– ___________ ___________ plants do not flower in response
to daylight changes. It is some other cue, such as
temperature or water that triggers their flowering.