BIO 2410 (Intro Botany) Exam 1

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:

1. Primary cell walls

2. 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:

1. root systems

2. 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:

1. Primary growth

2. 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