Download Plant Diversity

Note that the following is a rudimentary outline of the class lecture; it does not contain
everything discussed in class.
Plant Diversity
Cont.
Angiosperms
Angiosperm Advantages
Advance Vascular Tissue
Xylem
– support and water transport
– more efficient at water transport
– Support
Phloem
Sieve cells
Sieve tube members
Flowers
Fruits
Angiosperm Life Cycle
Sterile Flower Parts
– the outer most part of the flower, leaf-like and green
– usually delicate in texture; often colored
Lecture 3 - Plant Diversity
– often larger than sepals; may be shed soon after the flower opens
– the swollen tip of the stalk supporting the flower
Female Flower Parts
– the female reproductive part of the flower, occupies a central position.
– The female parts may consist of a single carpel or several carpels.
Each carpel consists of three parts:
–
the pollen receptive part at the summit, which may be single, lobed or
branched
–
the stalk like portion below the stigma
–
the enlarged portion at the base which contains one or more ovules or
immature seeds
Male Flower Parts
– the male reproductive part of the flower, occupies a position inward from the
petals.
Each stamen consists of two parts
– the sac-like part that contains the pollen
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Lecture 3 - Plant Diversity
– the stalk that connects the anther to the floral axis or some other part
Development of Male Gametophyte
Development of Female Gametophyte
Pollen Tube Growth & Double Fertilization
Angiosperm Pollination
Flower characteristic feature of Angiosperms
– functions in the facilitation of
– often possible to tell how plant is pollinated by
– method by which a
is carried to
of carpel
Angiosperms - great diversity of pollination vectors
Pollination Vectors
- pollination by insects
–
flowers
sweet scents; blue, dark pink, yellow-red, or purple
aggregated in head of many small long tubed flowers
flower may have recessed parts to preclude all but long-tongued
pollinators and protect ovule from herbivory
– Bee; Moth; Fly; Beetle flowers all have special features
Other animals Wind;
Angiosperm Pollination
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– mutual evolutionary influence between two species (the evolution of two species
totally dependent on each other)
– Each of the species involved exerts selective pressure on the other, so they
evolve together
– extreme example of
Pollen Tube Growth & Double Fertilization
Eudicot Plant Embryo Development
- primary meristem that gives rise to epidermis
- differentiates into the pith and cortex
- primary meristem that gives rise to vascular tissue.
Relationship between Pea Flower and Fruit
Fruit Type
fruit
– 1 carpel involved
– simple or compound carpel
fruit
– more than one carpel per flower
fruit
– more than one flower (rare)
Fruit Function
Seed
– "
" hidden among foliage to discourage animal consumption
– contains
– seeds mature, fruit "
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and other organic acids - fruit unpalatable
" tannins and other undesirables broken down
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Lecture 3 - Plant Diversity
–
broken down to sugars (sweetens fruit); fruit
Seed
Seed and Fruit Dispersal
Four main types
Wind
– Air borne
–
plants; wings; whole plant blown across ground or ice
Animal
– on outside of animal
carried
; hooks or spines; seed sticky when wet
carried
; fruit large and fleshy or seed large –
carried by mammals or birds
– eaten by animal - passing through
Seed and Fruit Dispersal
– Plants overhanging water bodies
– floating fruit or seed
– discharge of fruit or seed
Typical Seeds
– embryonic leaves
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– stem of embryo located between the cotyledons and plumule
– stem of embryo located between the cotyledons and radicle
– embryonic root
Endosperm
– thin specialized cotyledon
– sheath enclosing and protecting plumule
– sheath covering radicle
Seed Adaptations
Mature seed - dehydrated – very
metabolic rate; growth and development
Conditions for Breaking Dormancy
– Variable
– Some only need suitable environment
– Some need pretreatment - specific environmental cue causes break in
dormancy
E.g.
– Desert plants, need substantial
– Plants in areas with frequent natural fires, need
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– Plants from cold climates; need
– Some seeds have thick seed coats – need
Seed Adaptations
Length of seed
– Few days to decades or more
– Dependent on species and environment
– Most seeds are viable
– Seed bank in soil in case of
– e.g.
Seed Germination
The
– first organ to emerge from germinating seed
Many eudicots
– hook forms in
– growth pushes hook above ground
– cotyledons are pulled out of ground
– turn green and become
Seed Germination
– Use a different method for breaking ground when they germinate
Corn and other grasses
– The
– pushes upward through soil and into air
– shoot grows straight up through tube of
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Feature MONOCOT EUDICOT
No. cotyledons
Leaf venation
1
2
parallel
Vascular bundles
central bundles
scattered
peripheral rings or arranged in circle
Growth form
mostly herbaceous
herbaceous or __________
Mature root system
FIBROUS, several
one central __________
wholly adventitious
primary and/or adventitious
Vascular cambium
Leaf petioles
No. floral parts
Examples:
yes
usually
absent present
multiples of _
4's or 5's
grasses (incl. cereals),
palms, lilies, pineapple,
cacti, sunflowers,
most Angiosperm trees
NOTE: no vascular cambium means limited SECONDARY GROWTH
Tissue Systems
Each plant organ
– has all three
Tissue Types
Dermal Tissues
protect the soft tissues of plants and control interactions with the plants' surroundings
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Lecture 3 - Plant Diversity
– primary growth
– secondary growth
Epidermis
A single layer of closely packed cells covering the younger parts of a plant
Secretes a waxy layer (
) that inhibits water loss
Most epidermal cells lack chloroplasts
hair-like projections
– lower water loss by decreasing the flow of air over the plant surface
– prevent herbivory by storing substances that are harmful to animals
– increase water uptake by increasing surface area of cell
– contain chloroplasts and regulate gas exchange between the inside of leaf and
surrounding air
Periderm
Replaces epidermis in older stems and roots that undergo secondary growth
Provides protection while permitting gas exchange
– outer layer of periderm
– produced from cork cambium
– cell walls are impregnated with
(a waxy material)
– cells dead at maturity
– lateral meristem
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Lecture 3 - Plant Diversity
– blister-like breaks in the surface of the cork layer
Tissue Types
Ground Tissues
occupy the space between dermal tissues and vascular tissues
responsible for most of plant’s metabolic functions
In roots, ground tissue (
) may store sugars or starches to fuel the spring
sap flow
In leaves, ground tissue is the
(photosythetic layer)
–
–
–
Parenchyma
Structure
– the cells are
– each cell contains a nucleus, cytoplasm and a large central vacuole
– cell surrounded by a relatively
cellulose wall, very weak and flexible; no
walls
–
at maturity
Location
– occur in many places in plants
– stem and root cortex; stem pith (centre of stem); leaf mesophyll; flesh of fruits
(e.g.,
)
– usually a continuous mass or in vertical or horizontal
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Lecture 3 - Plant Diversity
Function
– in photosynthesis, storage, secretion of materials, water movement and food
transport
Collenchyma
Structure
– typically elongate cells
– primary cell wall unevenly thickened cellulosic walls
– i.e. strong & thick but flexible (
) walls
– plastic nature necessary because it occurs in organs that constantly
with growth
–
at maturity
Location
– occurs in bands of cells beneath the epidermis in stems and petioles
– found only in young organs as organ matures
becomes
Function
– mechanical tissue; structural support of young, actively growing plants
– easily stretched during growth, can elongate
Sclerenchyma
Structure
– various shapes –
secondary wall thick, often heavily
– Water and dissolved substances do not pass through (or very slowly) the
wall
–
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at maturity
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Lecture 3 - Plant Diversity
Location
– found in mature organs that have
Function
– structural support and
to plant body
Types of Sclerenchyma
- short cells
– brittle and inflexible
– groups of layers of sclereids form protective layers
– e.g.
– long, slender cells; pointed tip, unbranched, narrow
, extremely
thick secondary wall
– found in places where
–
and
is important
cells continue to lengthen after rest of organs ceased to elongate great length
– e.g.
Tissue Types
Vascular Tissues
: phloem & xylem
surrounded by
+/-
– water-conducting & supporting functions
– food-conducting
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Xylem
Structure
– complex tissue
–
- principal conducting cells; hollow elongated cells with
thickened secondary walls - dead at maturity
– Other cell types:
and
Function
– principle water conducting tissue
– produced during both primary and secondary growth
Types of Tracheary elements
– generally long and thin with tapered ends
– contain pits in their walls through which water and nutrients can move
– have imperforate (closed) end walls
– found in vascular plants such as
– elongated shape but not as long or thin as
– have perforate (open) end walls; joined together end-to-end in long tubes called
_____________________
–
(wider than
) permit faster flow through the
xylem
Phloem
Structure
– complex tissue
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–
; elongated cells join end-to-end to form tubes
– narrower than vessel elements
– are living at maturity; but lack nuclei or other organelles
– Other cell types:
and
Function
– principle
– produced during both
conducting tissue
and
growth
Types of Sieve Elements
– tapered; have narrow pores
– accompanied by
which perform sieve cells’ metabolic
activities
– found in
– flat-ended, line up in tubes; joined at tends by sieve plates
– associated with
(specialized
cells)
perform metabolic activities
– found in
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