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General characteristics of plants
Multicellular
Sessile, anchored in place
Autotrophic (self-sustaining)
Able to perform sexual reproduction
Cellulose-rich cell walls
Adapted to life on land
Land plants evolved from ancestral aquatic green algae
Bryophytes:
Mosses, Hornworts, Liverworts
Lycophytes:
Fern allies
Pteridophytes:
Ferns
Gymnosperms:
Non-flowering Open seeded plants
Angiosperms:
Flowering plants
Plants have names: Rules of Plant Nomenclature
Genus name starts with an uppercase letter
Specific epithet starts with a lowercase letter
AND:
By looking at the name, one can tell that Linnaeus
(L.= Linnaeus) named the coffee plant for us.
ex: Coffee is “Coffea arabica L.”
Ethnobotany:
Studying how plants were used in
traditional societies in the past
Economic Botany:
Studying how modern
industrialized societies use plants
for-profit (e.g. agricultural crops etc.)
The most commonly used crop plants in ancient societies were;
Cereals – fruits/seeds of grass family plants
Legumes – Bean family plants
Cereals:
Have high carbohydrate
Easy to harvest and
store long-term when dry
However, poor in some
essential nutrients
Legumes:
Rich in proteins. Provide
essential amino acids lacking
in cereals.
Dry seeds are easy to store
long term
Primary metabolites:
Major biomolecules critical for
life of the plant, such as;
proteins, carbohydrates, fats
Secondary metabolites:
compounds with accessory
functions, not critical for the life of the plant,
such as;
terpenes
phenolics
alkaloids
Important terpenes from plants
Many perfumes come from flowers.
Carotene is the precursor
for vitamin A, Rubber is a terpene used for tires,
balloons and numerous other
parts or devices we use every day
Important phenolics from plants
Many pigments/coloring and
flavors like;
Vanilla from vanilla bean
Hot capsaicin from chili peppers
Tannins are good anti-oxidants
in tea & red wine
Lignins in plant cell walls make
the wood
Important alkaloids from plants
Some plant alkaloids affect the
the nervous system of animals
Examples: narcotics, caffeine
Many have therapeutic or medicinal uses
examples: codeine, morphine, quinine
Levels of organization within a plant:
Cells → Tissues → Organs → Organ systems
Organelles Specific to Plant cells:
Chloroplasts, vacuoles, cell walls, and plasmodesmata
Most plant cells do NOT contain:
Flagellum, centriole, and lysosomes
Role of vacuoles and cell walls on turgor pressure in
plant cells:
When the vacuole has a high
solute concentration, water
moves in by osmosis
Creates a turgor pressure
on the cell wall
Keeps the cells turgid, and
tender parts rigid
If the solution around the cell is hypertonic
water moves out of the vacuole by osmosis → causes plasmolysis
plasmolysis
plasma membrane comes off the cell wall (occurs in hypertonic solutions), plant wilts in tender parts
Vacuoles play many important roles in plants:
turgor pressure, stores nutrients and waste materials, stores toxins for defense, stores calcium ions, sometimes contains colored substances (gives plants colors)
Plastids are unique to plant cells:
Chloroplasts, Amyloplasts, Chromoplasts
Chloroplasts for
Amyloplasts for
Chromoplasts for
Photosynthesis
Starch storage
Give color to tissues
Two types of Plant cell walls:
Primary cell walls
Secondary cell walls
In older tissues (for example: woody stems) several layers of
lignin containing secondary cell walls are present
Plant Tissues
Groups of cells with a common function
Could have live cells, dead cells, or both
live cells in a tissue communicate through Plasmodesmata
Tissues are of two types:
meristematic tissues
non-merstematic tissues: complex v. simple
Meristematic tissues
All other tissue types arise form meristematic tissues. These are the sites of mitotic cell division.
Three types of meristems;
Apical, Lateral, and Intercalary
Apical meristems
at growing tips of roots
and shoots, increase length/height in all plants
Lateral meristems
in dicots, at mature areas
of the plant body, increase width/girth
Intercalary meristems
in monocots, at nodes or
at leaf bases
Apical meristems are
Primary meristems, Present at every tip of a shoot or root and at axillary buds
near leaf bases
Cells derived from the meristem differentiate to form the rest of the tissues of the plant body (three kinds)
Dermal tissue, Vascular tissue, and Ground tissues
Dermal tissues
protective layer
Vascular tissues
conductive tissue
Ground tissues
fill up the space
Meristem tissues (picture)
Lateral meristems + Intercalary meristems are
Secondary meristems (Lateral only appear in woody dicots) (Intercalary only appear in monocots)
Lateral meristems (function)
Increase in girth of stem and roots.
Intercalary meristems (function)
Present at nodes in most grasses increasing the length of internodes
Cell division by mitosis
occurs in meristems
Mitosis (order)
Prophase, Metaphase, Anaphase, Telophase, Cytokinesis
Mitosis in plants is used for:
growth and development, asexual reproduction, and healing wounds
Plant Tissues (non-meristematic)
Generated as a result of meristem activity and
subsequent differentiation of cells.
Two types of plant tissues;
simple tissues - only one kind of cells
complex tissues - two or more kinds of cells
simple tissues
parenchyma, collenchyma, sclerenchyma
complex tissues
dermal tissue, vascular tissue, ground tissue
Parenchyma cells
Composed of relatively unspecialized living cells,
Characteristics:
-very thin cell walls
-loosely packed cells
-varying shapes
-alive at maturity
Appearance of parenchyma
Functions of parenchyma:
Different functions, depending on the location
i,.e. storage of food
photosynthesis
storage of chemicals
synthesis of chemicals
Collenchyma cells
Composed of more specialized living cells
Characteristics:
irregularly thickened cell walls
tightly packed cells
elongated cell shape
alive at maturity
Function of collenchyma tissue:
provide strength to young, tender parts that need to bend and elongate
Sclerenchyma cells:
Very specialized, dead cells
Two types:
sclerenchyma fibers (elongated cells with
tapering ends, strong, flexible)
sclereids (variable shapes, not elongated)
sclerenchyma fibers
Fibers have very thick cell walls
=>For strength
sclereids
Sclereids give the gritty
texture to fruits
Also found in seed coats
Xylem tissue for
transport of water, Vessel elements, tracheids and
xylem sclerenchyma fibers are dead cells with lignified cell walls
Phloem tissue for
transport of food,
-Only phloem sclerenchyma fibers
are dead cells
-Sieve tubes have lost their nucleus
but still alive with cytoplasm
-Companion cells regulate the
activities of sieve tubes
Xylem and phloem together
make
vascular bundles
Vegetative organs
leaves, stems, roots, embryo
Complex tissues:
Composed of two or more types of cells that perform a common function. (Dermal tissue, vascular tissue)
reproductive organs
stamens and pistils
The plant body consists of two systems:
root systems
shoot systems
What is Growth?
Growth = irreversible increase in the size of the body
- adding new cells and tissues by cell division
- increasing cell size by expansion
continuous – happens throughout the plant life
Thus; different from animal growth
Plant growth happens in
two ways:
Primary growth
Secondary growth
Primary growth (def.):
seen in non-woody parts
Secondary growth (def.):
forms woody stems and roots
Primary growth happens in-
tender parts
- Due to cell division at primary (apical) meristems
and subsequent cell expansion
- Cell expansion increases both lengths
and girth of the primary plant body
Primary growth (tree diagram)
Leaf primordia →
leaves
Apical meristem (turns into) →
unchanged
procambium →
vascular tissue
axillary bud →
branches
protoderm →
epidermis
ground meristem →
pith and cortex
growth and development of plant dia.
Animal hormones:
-substances produced at one location, and transported to another location for action
- specific action
- act at very minute concentrations.
How are plant hormones different? (from animal)
-Act locally or at distant locations
- Action is not very specific
- Required concentration varies
Too high concentrations of plant hormones may exert
opposite effects
Growth promoting hormones:
Auxins
Cytokinins
Gibberellic acid
Brassinosteroids
Growth inhibitory hormones:
Abscisic acid
Ethylene
Defensive hormones:
Salicylic acid
Jasmonic acid
Auxin function:
Produced in young plant organs (mostly in young shoots & some in root tip)
Involves in almost all aspects of plant growth and
development
cell division
cell expansion
development
stress response
and many more...
Cytokinin function:
-cell division
- Anti-aging effects
- Inhibition of lateral roots
- Promotion of axillary shoots
auxin vs. cytokinin
Gibberllins (GA function)
Works with auxin to promote cell
elongation
Promotes flowering
Stimulates seed germination
Breaks seed and bud dormancy
Seeds are dormant until soaked
Soaking ---> burst of Gibberellin production ---> mobilize nutrients
in endosperm
Abscisic acid (ABA) function:
inhibits the growth of axillary buds, and dormant seeds. Mostly comes into play during winter (plant dormancy period) where days are shorter and nights are longer. Also called the “stress hormone”, ex, plant during drought (produced in drying roots, travels to shoots)
Ethylene function:
A gaseous hormone for ripening and senescence.
Ethylene promotes the formation of an abscission layer in fruits and leaves, helping ripe fruits or yellowing leaves to drop from the plant
Salicylic acid and jasmonic acid
mainly involved in damage/disease response
Help reduce the damage by herbivores, bacteria, and fungal pathogens
Help plants acquire resistance against pathogens and herbivores
tropism
Directional growth towards or away from an
environmental factor
nastic movements
Non-directional movements
photoperiodism
Measure the nature of light, and day length to
program development
statoliths
sense and inform the root where gravity is
Developmental responses
Plants regulate their development according to the
environmental signals
phytochrome
measures the length of the night (the dark period)
Hypersensitive response - HR
(death of local tissue) Prevent the spreading of
pathogen within the plant
Systemic Acquired Resistance = SAR
Salicylic acid and Jasmonic acid work together in inducing defense responses
Note 
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