Studied by 2 peopleThe Plant Body
two organ systems
The Shoot
The Root
The Shoot
Aerial (above-ground) component of the plant
The organs in this system are Stem (and its branches) and leaves
Composed of repeating module called a phytomer
Phytomer
consists of a leaf, the portion of the stem which the leaf is attached (node) and the surrounding stem (internode), and the bud
Include Leaf, Stem and Bud
Node
the portion of the stem to which the leaf if attached
Leaf
primary organ of photosynthesis
Bud
contains shoot meristem cells
Stem
organ of support; vascular tissue
The Root
the below-ground component of the plant. The organs in this system are the foots and repeating units called lateral roots
Root Functions
Secures the plant in place
Absorb water and minerals from the soil
Store photosynthetic products
Parts of the Leaf
petiole and sheaths, blade, compound leaves
Taproot
type of root system
large trees need these for stability
Fibrous
type of root system
common in monocots esp. grasse
Adventitious
type of root system
roots that arise from tissue other than the radicle
How many tissue systems are there in plants?
3
Dermal, Ground and Vascular
Dermal Tissue System
forms the outer covering of the plant
Ground tissue system
carries out photosynthesis, stores photosynthetic products, and helps support the plant
Vascular Tissue System
conducts water and solutes throughout the plant
Characteristics of plant cells
cell walls - primary, secondary and middle lamella
Plasma membrane
Large Vacuoles
Chloroplasts (plastids)
Starch grains can be present
Plasmodesmata
Primary Cell Wall
flexible, cellulose
Secondary Cell Wall
cellulose, lignin, other components
Middle Lamella
Pectin-rich layer that cements together cell walls of adjacent cells
Plasmodesmata
small tubes joining plant cells
Cytoplasmic channels that pass through pores in primary and secondary cell walls
Living bridges between cells allowing molecules to pass from cell to cell
Provide cell to cell communication
Parenchyma
least specialized plant cells ‘workhouse cells’
Primary walls thin and flexible, no secondary walls
Large vacuoles - water and solute storage
ALIVE at functional maturity
regeneration of more specialized cells in case of damage
Functions: Metabolism, Photosynthesis, Starch Storage, in stems and roots, abundant in fleshy parts of fruit
Totipotent
stem cells of plants
Collenchyma
Thick primary walls
usually grouped in strands of cylinders
can elongate and expand with stem and leaf growth
ALIVE at functional maturity
Function: flexible support for herbaceous and young woody plants
Sclerenchyma
thick secondary walls
two types (Fibers and Sclereids)
strengthened by lignin
cannot elongate with growth
Function: support
Often lack protoplasts at maturity
DEAD at functional maturity
Fibers
Type of Sclerenchyma
long slender and tapering in bundles (rope, flax)
Sclereids
type of sclerenchyma
(stone cells); short, irregular shape
makes hard seed coat and nut shells
Gritty texture in pears
Cells in Vascular Tissue
Xylem and Phloem (together in vascular bundles)
Xylem
Tracheids and Vessel Elements; Sclerenchyma
Water conducting cells - from roots to leaves
Pits in secondary walls
Dead at functional maturity
secondary walls often deposited in spiral or ring patterns
Tracheids
type of Xylem
Angiosperms = Hardwood
Gymnosperms = Softwood
Gymnosperms and Angiosperms
Long thin cells with pits and tapered ends
Water moves from tracheid to tracheid through the pits in the cell wall
Vessel Elements
type of Xylem
Angiosperms
wider, shorter, less taper than tracheids
end walls perforated - form long tubes or pipes constructed of vessel elements end to end
Phloem
‘Food’ conducting cells - from leaves to roots but also elsewhere in the plant
In chains like pipes joined together
Alive at maturity although sieve tube elements lack nucleus, ribosomes and vacuoles
Companion Cells
Companion Cells
alongside each sieve tube member
Plasmodesmata connect sieve tube member to companion cell, companion nucleus serves sieve tube member
Dermal Tissue
comprised of epidermis, cuticle and root hairs
Epidermis
single layer of tightly packed cells
Root Hairs
specialized epidermal cells for water and mineral absorption
Meristems
specialized bundles of undifferentiated cells
can give rise to any and all of the cell types in plants
tissue found in both shoot and the root
two types; apical and lateral
Apical Meristem
Dome shaped
all types of tissues (epidermal, ground vascular) are derived from ______
Axillary buds develop from meristematic tissues at base of leaf primordia
Lateral Meristems
responsible for secondary (outwards) growth
2 types
Vascular Cambium
Cork Cambium
Vascular Cambium
in stems and roots of perennials and woody trees
increase tree girth
form xylem to inside, phloem to outside
Cork Cambium
Produced Bark
Primary Growth in Roots 3 Regions plus Root Cap
1) Zone of Differentiation (Maturation) - root hairs. vascular tissue
2) Zone of Elongation
3) Zone of Division - Meristem produces cells to either side
4) Root Cap - protective layer of cells, continuously sloughed off
The Leaf
primary organ of photosynthesis
occur in any tissue or organ where chloroplasts are present, but are in HIGHEST concentration in the leaf
The Veins
a bundle of vascular tissue that deliver water and nutrients to the leaf cells (xylem), and remove sugars to distribute throughout the body of the plant (phloem)
Tricomes
are specialized hair-like extensions of the epidermis that reduce air flow around the leaf, helping to reduce water loss throughout the stomata
Epidermis
secrete waxy cuticle
Stomata, and trichomes are usually on the lowest
Stomata
pores in a leaf, mostly on the undersurface
each pore is surrounded by a pair of guard cells
pores that regular gas exchange
Take in CO2 and releasing O2
Close to prevent water loss
Guard Cells
change shape to open or close the stoma
Mesophyll
ground tissue in plant leaves
two layers
the upper/palisade
lower/spongy
Palisade Mesophyll
is made up of elongate cells with a high density of chloroplasts
this layer performs most of the photosynthesis in the leaf
Spongy mesophyll
made up of smaller, irregularly shaped, loosely packed cells
The loose packing of these cells helps with both gas exchange and catching any photons the palisade miss
Vascular Bundles
continuous with stem and roots
contain both xylem and phloem
structural support and transport
Chloroplasts
cellular organelles that conduct photosynthesis
circular genome (endosymbiotic origin)
outer and inner membrane
Contain stroma, thylakoid and granum
Stroma
dense fluid
Granum
stack of thylakoids
Thylakoid
light-dependent reactions take place
Contain chlorophyll
Chlorophyll A
absorbs blue and red light
Accounts for most of the photon capture by chloroplasts
Chlorophyll B
absorbs aqua and orange light
Carotenoids, Xanthophylls and Anthocyanins
absorb other wave lengths
Overall photosynthetic efficiency of the plant
Chlorophylls
reflect green wavelength
that’s why ‘grass is green’
Absorption Spectrum
plot of light energy absorbed against wavelength
Action spectrum
plot of the biological activity of an organism against wavelength
First step of Photosynthesis
Light dependent reaction
Captures light energy as chemical energy; produces oxygen, splits water oxygen
In those photons of specific wavelengths are absorbed by photosynthetic pigments are used to create ATP and NADPH
One photon = 3ATP, 2NADPH and 1 O2
Second Step of Photosynthesis
The calvin cycle
can occur in light or in the dark
energy from the light reaction is used to create an organic (sugar) colecule
Photosynthetic products → sugars are usually stored in plants as starch
Photosynthesis
Occurs in Chloroplasts
Uses CO2 and H2O
Produces O2 and Glucose
Requires energy input
Respiration
occurs in mitochondria
uses O2 and Glucose
Produces CO2 and H2O
Produces Energy (ATP)
Note 
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