Download Botany Part II Plant Structure and Growth

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Monocots and Eudicots = Phylum ANTHOPHYTA
Both are MONOPHYLETIC = ONE common ancestor
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- Plants need resources from both the
air and soil, so the ROOT system
(ground) needs to work with the
SHOOT system (air)…they depend
on each other
Tissue  a group of cells,
consisting of one or more types,
which perform a specific function
(ex. ground tissue, vascular tissue,
etc)
Organ  several types of tissues
that work together to carry out
particular functions (3 main organs
in plants = roots, stems, leaves)
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Roots
- Function → anchor, absorb
water, store food
-Monocots = fibrous roots
-Dicots = taproots
- Roots may have root hairs to
increase the surface area and take
up water
- Adventitious roots are above
ground roots
-Have epidermal tissue but no
waxy cuticle
Adventitious Roots
of Ficus
Root
Hairs
Taproot – Ex. Carrot
Fibrous Root – Ex. Onion
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Shoots
-Stems and Leaves
- Can be:
-Vegetative (leaves)
- Reproductive (flowers)
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Stems
-Alternating system of nodes
(leaf attachments) and
internodes (between leaves)
- Axillary bud (angle at
leaf/stem) have potential to
bud
-Terminal bud → concentrated
growth; this inhibits the axillary
buds = APICAL DOMINANCE
The presence of a terminal bud is
responsible for inhibiting the
growth of axillary buds. If the
terminal bud gets removed
(pruning), then the axillary bud
will start to grow. Sometimes
gardeners cut the terminal bud off
so that the axillary buds will grow
and the plant will become fuller.
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COPY THIS INTO YOUR
NOTES!!!
Mesophyll Tissue 
- VERY photosynthetic
- Divided into spongy and
palisades mesophyll
-
Leaves
Main photosynthetic
organ in plants
Flattened blade and
petiole (stalk)
Waxy cuticle (helps
prevent water loss)
Some have special
functions
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3 Types of Plant Tissues:
- Dermal → outer layer;
“epidermis”
- Vascular → transport;
xylem and phloem
- Ground →
photosynthetic;
storage; support
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Dermal Tissue
-The dermal tissue is the
epidermis of the plant; it is
called the “skin of the plant”
- It is the outside layer of the
plant
- It is a single layer of cells
that are tightly packed
together
- It can secrete a waxy cuticle
(prevent dehydration)
Note the upper
and lower
epidermis
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Vascular Tissue
- Organized into veins
- Transports materials between
the roots and the shoots
- The vascular tissue of the root
or stem is called the stele
- 2 main parts:
- Xylem → transports water
“up”
- Phloem → transports food
to roots and nonphotosynthetic parts of the
plant; from “source to sink”;
transports up and down
In this picture,
the “S” stands
for phloem
(sieve tube
elements)
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Ground Tissue
- Neither dermal nor vascular
- Functions in photosynthesis,
storage, and structural support
- In eudicots (where the vascular
bundles are arranged in a ring)
it is divided into:
-Pith (internal to the vascular
tissue)
- Cortex (external to the
vascular tissue)
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There are 3 basic types of plant cells:
1. Parenchyma
2. Collenchyma
3. Sclerenchyma
Each cell type has structural adaptations in the cell contents (protoplast) and in the cell
wall.
Terms to know:
- Plasmodesmata → channels connecting cells
- Middle lamella → cements adjacent cell walls
- Primary wall → made as the cell grows
- Secondary wall → made after the growth stops
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Parenchyma
-Thin, flexible primary walls
- Most lack secondary walls
- “Typical cell” → generally the LEAST
specialized (all cells start out as parenchyma)
-Can dedifferentiate for plant tissue cultures
-Photosynthetic!!
- Perform most metabolic functions
-Do not usually do cell division (unless in
meristems), but retain the ability to divide and
differentiate
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Collenchyma
-Thicker, but uneven primary cell
walls
- Grouped together to support
young parts of shoots
-LACK secondary walls
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Sclerenchyma
-Function as SUPPORT
ELEMENTS in plants
- They have thick secondary walls
strengthened with lignin
-More rigid than collenchyma
-Mature cells cannot elongate
(b/c of rigid cell walls), so they
are present in cells that have
stopped growing
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Xylem
-Transports water and
dissolved materials “up”
from the roots
- There are two types of
water conducting
elements:
-Tracheids → long
and thin; their
secondary cell walls
have hardened with
lignin; they have pits
where water flows
through
-Vessel Elements →
wider and shorter;
thinner walls and
linked together
forming long tubes
(called xylem vessels)
-The cells that make up
xylem are DEAD at
maturity
Xylem
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Phloem
-Transports food to roots and
other non-photosynthetic parts
of the plant
- Moves sucrose and other
organic molecules through tubes
formed by chains of cells called
sieve tube elements →
- These sieve tube elements
are ALIVE at maturity
- The end of each element
has a sieve plate, which
has pores to allow
substances through
- They are associated with
non-conducting
companion cells that help
them move the materials
(via plasmodesmata)
- Used in
TRANSLOCATION (Bulk
Flow Movement)
Phloem =
Blue
(in this
picture)
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Meristems
-Perpetual embryonic tissue
in growth areas (makes more
cells!)
- Pattern of growth depends
on the locations of the
meristems
- There are 2 main types of
meristems:
-Apical Meristems
-Lateral Meristems
Meristems allow for
LIFELONG GROWTH!!!
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Apical meristems
are found at the tips
of roots and at the
buds of shoots.
These are for
PRIMARY growth
(LENGTH). They
give rise to the
primary plant body.
They allow roots to
extend through the
soil and the shoots
to increase their
exposure to light
and carbon dioxide.
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Lateral meristems are cylinders that run along the root/
shoot. They provide SECONDARY growth (THICKNESS) .
They add girth to the plant by making secondary vascular
tissue and periderm. These meristems are very important in
woody plants (trees, etc).
- There are two types of
lateral meristems: the
vascular cambium and the
cork cambium.
- The vascular cambium adds
layers of vascular tissue
called secondary xylem
(wood) and secondary
phloem.
- Plants with vascular
cambium with lignified
cell walls are called
woody plants (not
herbaceous)
- The cork cambium replaces
the epidermis with thicker,
tougher periderm.
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- Annuals  complete their life
cycle—from germination to
flowering to seed production
to death—in a single year or
less.
- Biennials  span two years,
with flowering and fruiting in
the second year
- Perennials  plants such as
trees, shrubs, and some
grasses that live many years
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- Roots show mostly PRIMARY GROWTH and produce the
epidermis, ground tissue, and vascular tissue.
- Water and minerals absorbed from the soil must enter the
plant through the epidermis, a single layer of cells covering
the root.
- Root hairs greatly increase the surface area of the epidermis.
- In angiosperm roots, the stele is a vascular cylinder with a
solid core of xylem and phloem.
- The ground tissue of roots consists of parenchyma cells.
- When plant stems are cut, roots will develop at the cut end
which is opposite the apical bud.
Root Cap →
protects meristem
Zone of cell
division → apical
meristem and its
derivatives
Quiescent Center
→ Cells that divide
more slowly than
meristem cells;
resistant to damage
Zone of elongation
→ cells elongate;
responsible for
pushing the root tip
Zone of
differentiation (aka
zone of maturation)
→ specialization;
complete
differentiation and
become distinct cell
types
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Stele – vascular bundle in the center of roots; produced by the procambium
There are 3 Primary
Meristems:
Protoderm – forms
the dermal tissue
(epidermis)
Procambium –
forms the stele
(vascular tissue in
the center of roots –
primary
xylem/phloem)
Ground – forms
ground tissue
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Secondary Growth –
Thickness
- Occurs in stems and
sometimes in roots, but rarely
in leaves
- TWO LATERAL MERISTEMS:
-Vascular Cambium →
makes secondary xylem
(WOOD) and secondary
phloem
-Cork Cambium → Makes
the tough covering for roots
and stems which replaces the
epidermis
-Periderm → layers of cork and
cork cambium
- Bark → refers to all tissue
external to vascular cambium
(secondary phloem, cork, cork
cambium)
IF there is
secondary
growth, the
plant is
considered to
be “woody”
not
“herbaceous”
KNOW THIS PICTURE AND THESE DEFINITIONS!!
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One of the major differences between plants and
animals is TOTIPOTENCY!
For plants growth and development is NOT
restricted to the embryonic/ juvenile
period but occurs throughout the life of the
plant; can develop into any part of the
plant; to get features from the juvenile
form, must take cuttings from areas formed
in that period
Growth = increase in size
Development = changes that
elaborate an organisms body
Plant Life Cycle:
Germ → Flower →Seed → Death
RECALL:
Annual = 1 year or less
Biennial = 2 years
Perennial = Lives many years
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Processes that are important to the development of plants:
1. Morphogenesis → development of body form and organization;
depends on pattern formation (specific structure in specific
location)
2. Differentiation → specialization of cells; depends on control of gene
expression (regulating transcription and translation)
3. Growth → includes both:
- Cell Division (can be symmetrical or asymmetrical)
- Cell Expansion (water accounts for 90% of expansion – fills
vacuoles)
Both of these contribute to plant form
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Terms to Know:
- Stomata
- Guard Cells
- Palisades Mesophyll
- Spongy Mesophyll
-Mycorrhizae (symbiotic fungus on
roots to help get water)
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