Homework to be emailed to
valenciabiologyhw@gmail.com
1.
From a diagram of an idealized flower, correctly label the following structures
and describe their function
a.
sepals
b.
petals
c.
stamen: filament and anther
d.
pistil: stigma, style, ovary, carpal, ovule
2.
Distinguish between monoecious and dioecious
3.
Distinguish among generative nucleus, tube nucleus, and sperm nucleus in
developing pollen grain
4.
Outline the process of double fertilization and describe the function of
endosperm
5.
Describe several functions of fruit and explain how fruits form
Flowers
Angiosperm Reproduction and Biotechnology
Angiosperm
Evolution
•
Clarifying
the origin and diversification of angiosperms
– Poses
fascinating challenges to evolutionary biologists
•
Angiosperms
originated at least 140 million years ago
– And
during the late Mesozoic, the major branches of the clade
diverged from their common ancestor
Fossil
Angiosperms
•
Primitive
fossils of 125-million-year-old angiosperms
– Display
both derived and primitive traits
Flowers
•Modifications in reproduction were key adaptations enabling
plants to spread into a variety of terrestrial habitats.
• Water has been replaced by wind and animals as a means for
spreading gametes.
•· Embryos are protected in seeds.
•Vegetative reproduction is an asexual
mechanism for propagation in many environments.
Flowers
•The angiosperm (flowering plant) life cycle includes alternation
of generations during which multicellular haploid
gametophyte generations alternate with diploid sporophyte
generations
Flowers
•The angiosperm (flowering plant) life cycle includes alternation
of generations during which multicellular haploid
gametophyte generations alternate with diploid sporophyte
generations
Flowers
•‘Gametophytes produce gametes (sperm and
egg) by mitosis. The gametes fuse to form a zygote which develops into a multicellular sporophyte.
Flowers
•The sporophyte
is dominant in the angiosperm life cycle with the gametophyte stages being
reduced and totally dependent on the sporophyte.
An
“Evo-Devo” Hypothesis of Flower Origins
•
In
hypothesizing how pollen-producing and ovule-producing structures were combined
into a single flower
– Scientist
Michael Frohlich proposed that the ancestor of
angiosperms had separate pollen-producing and ovule-producing structures
Angiosperm
Diversity
•
The
two main groups of angiosperms
– Are
monocots and eudicots
•
Basal
angiosperms
– Are
less derived and include the flowering plants belonging to the oldest lineages
•
Magnoliids
– Share
some traits with basal angiosperms but are more closely related to monocots and
eudicots
•
Exploring
Angiosperm Diversity
Evolutionary
Links Between Angiosperms and Animals
•
Pollination
of flowers by animals and transport of seeds by animals
– Are
two important relationships in terrestrial ecosystems
Evolutionary
Links Between Angiosperms and Animals
•
:
Human welfare depends greatly on seed plants
•
No
group is more important to human survival than seed plants
Products
from Seed Plants
•
Humans
depend on seed plants for
– Food
– Wood
– Many
medicines
Threats
to Plant Diversity
•
Destruction
of habitat
– Is
causing extinction of many plant species and the animal species they support
•
Overview:
To Seed or Not to Seed
•
The
parasitic plant Rafflesia arnoldii
– Produces
enormous flowers that can produce up to 4 million seeds
•
: Pollination enables gametes to come
together within a flower
•
In angiosperms, the dominant sporophyte
–
Produces spores that develop within
flowers into male gametophytes (pollen grains)
–
Produces female gametophytes (embryo
sacs)
•
: The reproductive adaptations of
angiosperms include flowers and fruits
•
Angiosperms
– Are
commonly known as flowering plants
– Are
seed plants that produce the reproductive structures called flowers and fruits
– Are
the most widespread and diverse of all plants
Characteristics
of Angiosperms
•
The
key adaptations in the evolution of angiosperms
– Are
flowers and fruits
Flowers
•
The
flower
– Is
an angiosperm structure specialized for sexual reproduction
•
A
flower is a specialized shoot with modified leaves
– Sepals,
which enclose the flower
– Petals,
which are brightly colored and attract pollinators
– Stamens,
which produce pollen
– Carpels,
which produce ovules
Flower
Structure
•
Flowers
– Are
the reproductive shoots of the angiosperm sporophyte
– Are
composed of four floral organs: sepals, petals, stamens, and carpels
•
Many variations in floral structure
–
Have evolved during the 140 million years
of angiosperm history
Flowers
•More About
Flowers
•Several variations on the basic flower structure have evolved
during the angiosperm evolutionary history.
•Complete flower = A flower with sepals, petals, stamens
and carpels.
•Incomplete flower = A flower that is missing one or more
of the parts listed for a complete flower (e.g. most grasses do not have petals
on their flowers).
Flowers
•Perfect flower = A flower having both stamens and carpels (may be incomplete by lacking either sepals or petals).
•Imperfect flower = A flower that is either staminate (having
stamens but no carpels) or carpellate
(having carpels but no stamens) - a unisex
flower.
Flowers
•Monoecious = Plants having both staminate flowers
and carpellate flowers on the same individual plant.
•Dioecious = Plants having staminate flowers and carpellate flowers on separate individual plants of the
species.
Gametophyte
Development and Pollination
•
In angiosperms
– Pollination
is the transfer of pollen from an anther to a stigma
– If
pollination is successful, a pollen grain produces a structure called a pollen
tube, which grows down into the ovary and discharges sperm near the embryo sac
Flowers
•‘
Mechanisms
That Prevent Self-Fertilization
•
Many
angiosperms
– Have
mechanisms that make it difficult or impossible for a flower to fertilize
itself
•
The most common anti-selfing
mechanism in flowering plants
–
Is known as self-incompatibility, the
ability of a plant to reject its own pollen
•
Researchers are unraveling the molecular
mechanisms that are involved in self-incompatibility
•
Some
plants
– Reject
pollen that has an S-gene matching an allele in the stigma cells
•
Recognition
of self pollen
– Triggers
a signal transduction pathway leading to a block in growth of a pollen tube
•
:
After fertilization, ovules develop into seeds and ovaries into fruits
Double
Fertilization
•
After
landing on a receptive stigma
– A
pollen grain germinates and produces a pollen tube that extends down between
the cells of the style toward the ovary
•
The
pollen tube
– Then
discharges two sperm into the embryo sac
•
In
double fertilization
– One
sperm fertilizes the egg
– The
other sperm combines with the polar nuclei, giving rise to the food-storing
endosperm
From
Ovule to Seed
•
After
double fertilization
– Each
ovule develops into a seed
– The
ovary develops into a fruit enclosing the seed(s)
Endosperm
Development
•
Endosperm
development
– Usually
precedes embryo development
•
In
most monocots and some eudicots
– The
endosperm stores nutrients that can be used by the seedling after germination
•
In
other eudicots
– The
food reserves of the endosperm are completely exported to the cotyledons
Embryo
Development
•
The
first mitotic division of the zygote is transverse
– Splitting
the fertilized egg into a basal cell and a terminal cell
The
Angiosperm Life Cycle
•
In
the angiosperm life cycle
– Double
fertilization occurs when a pollen tube discharges two sperm into the female
gametophyte within an ovule
– One
sperm fertilizes the egg, while the other combines with two nuclei in the
center cell of the female gametophyte and initiates development of food-storing
endosperm
•
The
endosperm
– Nourishes
the developing embryo
Flowers
•‘Embryo Development (Embryogenesis)
During embryogenesis: ·
The zygote's first mitotic division is
transverse, creating a larger basal cell and a smaller terminal cell.
• The basal cell divides transversely to
form the suspensor, which anchors the embryo and transfers nutrients to
it from the parent plant.
•·
Flowers
•‘· The terminal cell divides several time to
form a spherical proembryo attached to
the suspensor.
•Cotyledons appear as bumps on the proembryo and the embryo elongates. = The apical meristem of the embryonic shoot is located between the
cotyledons.
Flowers
•Where the suspensor (the opposite end of the axis) attaches is
the apex of the embryonic root with its meristem.
•= The basal cell gives rise to part of the root meristem in some species.
•After germination, the apical meristems
at the root and shoot tips will sustain primary growth.
Flowers
•‘=
The embryo also contains protoderm, ground meristem and procambium.
•· Two features of plant form are established
during embryogenesis. = The root-shoot axis with meristems
at opposite ends.
Flowers
•‘A radial pattern of protoderm,
ground meristem, and procambrium
ready to produce the dermal, ground, and vascular tissue systems.
Flowers
•‘Structure of the Mature Seed
•In mature seeds, the embryo is quiescent until germination.
•· The seed dehydrates until its water
content is only 5-15% by weight.
•· The embryo is surrounded by endosperm,
enlarged cotyledons, or both.
•The seed coat is formed from the
integuments of the ovule.
Flowers
•Below the cotyledon attachment point, the embryonic axis is
termed the hypocotyl, which terminates
in the radicle, or embryonic root.
•Above the cotyledons, the embryonic axis
is termed the epicotyl, which
terminates in the plumule (shoot tip
with a pair of tiny leaves).
Flowers
•Fleshy cotyledons are present in some dicots
before germination due to their absorption of nutrients from the endosperm.
•In other dicots,
thin cotyledons are found and nutrient absorption and transfer occurs only
after germination.
Flowers
•‘A monocot seed has a single cotyledon
called the scutellum.
•· The scutellum
has a large surface area and absorbs nutrients from the endosperm during germination.
•The embryo is enclosed in a sheath
comprised of the coleorhiza (covers the
root) and the coleoptile (covers the
shoot).
Seed
Germination
•
As
a seed matures
– It
dehydrates and enters a phase referred to as dormancy
Seed
Dormancy: Adaptation for Tough Times
•
Seed
dormancy
– Increases
the chances that germination will occur at a time and place most advantageous
to the seedling
•
The
breaking of seed dormancy
– Often
requires environmental cues, such as temperature or lighting cues
From
Seed to Seedling
•
Germination
of seeds depends on the physical process called imbibition
– The
uptake of water due to low water potential of the dry seed
•
The radicle
–
Is the first organ to emerge from the
germinating seed
•
In many eudicots
–
A hook forms in the hypocotyl,
and growth pushes the hook above ground
•
Monocots
–
Use a different method for breaking
ground when they germinate
•
The coleoptile
–
Pushes upward through the soil and into
the air
Flowers
•Evolutionary adaptations in the process
of germination increase the probability that seedlings will survive
•Seed germination represents the continuation of growth and
development which was interrupted when the embryo became quiescent at seed
maturation.
Flowers
•‘· Some seeds germinate as soon as they
reach a suitable environment.
•• Other
seeds require a specific environmental cue before they will break dormancy.
•
Flowers
•‘Seed Dormancy
•The evolution of the seed was an important adaptation by
plants to living in terrestrial habitats.
•· The environmental conditions in terrestrial habitats fluctuate
more often than conditions in aquatic habitats.
Flowers
•‘Seed dormancy prevents germination when
conditions for seedling growth are unfavorable.
•It increases the chance that germination
will occur at a time and place most advantageous to the success of the
seedling.
Flowers
•‘Conditions for breaking dormancy vary
depending on the type of environment the plant inhabits.
•· Seeds of desert plants may not germinate
unless there has been heavy rainfall (not after a light shower).
•· In chaparral regions where brushfires are
common, seeds may not germinate unless exposed to intense heat, after a fire
has cleared away older, competing vegetation.
Flowers
•‘Other
seeds may require exposure to cold, sunlight or passage through an animal's
digestive system before germination will occur.
• Dormant seeds may remain viable for a few
days to a few decades (most are viable for at least a year or two).
Flowers
•‘This
provides a pool of ungerminated seeds in the soil
which is one reason vegetation appears so rapidly
after environmental disruptions.
Flowers
•‘. From Seed to Seedling
•The first step in seed germination in many plants is imbibition (absorption of water).
•· Hydration causes the seed to swell and
rupture the seed coat.
•· Hydration also triggers metabolic changes
in the embryo that cause it to resume growth.
Flowers
•‘· Storage materials of the endosperm or
cotyledons are digested by enzymes and the nutrients transferred to the growing
regions of the embryo.
•For example, the embryo of a cereal grain
releases a hormone (a gibberellin) as a messenger to
the aleurone (outer layer of endosperm)
to initiate production of
Flowers
•‘(Xamylase and other enzymes that digest starch
stored in the endosperm
• The radicle
(embryonic root) then emerges from the seed.
•The next step in the change from a seed to a seedling is the
shoot tip breaking through the soil surface.
•In many dicots,
a hook forms in the hypocotyl
Flowers
•‘=> Growth pushes the hypocotyl above ground.
•· Light stimulates the hypocotyl
to straighten, raising the cotyledons and epicotyl.
•The epicotyl
then spreads the first leaves which become green and begin photosynthesis.
Flowers
•‘Germination may follow different methods
depending on the plant species.
•In peas, a hook forms in the epicotyl
and the shoot tip is lifted by elongation of the epicotyl
and straightening of the hook.
•= The cotyledons remain in the ground.
Flowers
•‘In monocots, the coleoptile
pushes through the soil and the shoot tip grows up through the tunnel of the
tubular coleoptile.
•Only a small fraction of the seedlings will survive to the
adult plant stage.
•· Large numbers of seeds and fruits are produced
to compensate for this loss.
Flowers
•‘This
utilizes a large proportion of the plant's available energy.
Seed structure
Seed maturation
•
Takes place in the fruit on the parent plant
•
Endospermous seeds: Retain the endosperm tissue, which eventually dies
but it is surrounded by a layer of living cells, the aleurone
layer.
•
Non-endospermous seeds: The endosperm tissue is absorbed by
the cotyledons. These then become the food reserve for the seed.
Dormancy
•
Metabolism falls
•
Number of organelles per cell falls
•
Dehydration – water content falls
•
Vacuoles in cells deflate
•
Food reserves become dense crystalline bodies
Maintaining dormancy
•
Physical barriers
The seed coat (testa) is
waxy = waterproof and impermeable to oxygen
•
Physical state – dehydrated
•
Chemical inhibitors present e.g. salts, mustard oils, organic
acids, alkaloids
•
Growth promoters absent
Seed viability
•
Viability:
When a seed is capable of germinating after all the necessary environmental
conditions are met.
•
Average life span of a seed 10 to 15 years.
•
Some are very short-lived e.g. willow (< 1 week)
•
Some are very long-lived e.g. mimosa 221 years
•
Conditions are very important for longevity
•
Cold, dry, anaerobic conditions
•
These are the conditions which are maintained in seed banks
Germination: The breaking
of dormancy
The growth of the embryo and its penetration
of the seed coat
Germination
Stages leading to cell
division
The control of food
reserve hydrolysis
•
Control by growth promotors such as gibberellin and growth inhibitors such as abscisic acid
•
These directly affect the genes for enzyme synthesis or the activity of
the enzymes themselves
•
The growth substances are affected by environmental factors (e.g.
light, temperature, humidity)
The control of food
reserve hydrolysis
•
Negative feedback control of enzymes
•
The action of the enzyme also limited by substrate
•
Once all the starch in an amyloplast is
hydrolysed the enzyme stops work
Therefore the release of the stored food is adjusted
to suite the demand
The mobilisation of food reserves
•
The food reserves are stored as large insoluble macromolecules
•
They are hydrolysed
using enzymes to smaller soluble molecules for transport
Flowers
•The ovary develops into a fruit adapted
for seed dispersal
•
•A
fruit develops from the ovary of the flower while seeds are developing from the
ovules.
•A fruit protects the seeds and aids in
their dispersal by wind or animals.
Flowers
•· In some angiosperms, other floral parts
also contribute to formation of what we call fruit:
•The core of an apple is the true fruit.
•The fleshy part of the apple is mainly
derived from the fusion of flower parts located at the base of the flower.
Flowers
•A true fruit is a ripened ovary.
•· Pollination triggers hormonal changes
that cause the ovary to grow.
•The wall of the ovary thickens to become the pericarp.
•Transformation of a flower into a fruit
parallels seed development and is called fruit set.
Fruits
•
Fruits
– Typically
consist of a mature ovary
•
Can
be carried by wind, water, or animals to new locations, enhancing seed
dispersal
Couroupita guianensis
Cannon Ball Tree
The amazingly complex flower of the Cannonball Tree is also heavenly scented -
a cross between a fine expensive perfume and a wonderful flower scent
•
Fruits are classified into several types
– Depending
on their developmental origin
•
Fruits are classified into several types
– Depending
on their developmental origin
•
Many flowering plants clone themselves by
asexual reproduction
•
Many angiosperm species
–
Reproduce both asexually and sexually
•
Sexual reproduction
–
Generates the genetic variation that
makes evolutionary adaptation possible
•
Asexual reproduction in plants
–
Is called vegetative reproduction
Flowers
•‘In
most plants, fruit does not develop without fertilization of ovules. (In parthenocarpic plants, fruit does develop
without fertilization.)
Flowers
•‘Depending upon their origin, fruits can
be classified as:
•I. Simple fruits.
•• Fruit
derived from a single ovary. For example, cherry (fleshy) or
soybean (dry). 2. Aggregate fruits.
•Fruit derived from a single flower with
several separate carpels. For
example, a strawberry.
Flowers
•‘. Multiple
fruits.
•Fruit derived from an inflorescence or
separate tightly clustered flowers. For example, pineapple.
Flowers
•‘Fruits ripen about the time seeds are
becoming fully developed.
•· In dry fruits, such as soybean pods, the
fruit tissues age and the fruit (pod) opens and releases the seeds.
•• Fleshy
fruits ripen through a series of steps guided by hormonal interactions.
Flowers
•‘The fruit becomes softer as a result of
enzymes digesting the cell wall components.
•Colors usually change and the fruit becomes sweeter as organic
acids or starch are converted to sugar.
•These changes produce an edible fruit
which entices animals to feed, thus dispersing the seeds
ADAPTATION FOR SEED
DISPERSAL
The success of a plant not only depends on the production of
seed but on the dispersal of that seed. If the seeds germinated near the parent
plant they would compete.
Some Australian plants produce substances which inhibit the
growth of seedlings so seeds that fall beneath the parent plant are doomed.
Many mechanisms of seed
dispersal are evident among Australian plants that have fruit around the seed,
for example:
Wind Dispersal
- winged seeds e.g. Hakea, Banksia;
- parachute seeds e.g.
Dandelion;
- feathery seeds e.g.
Clematis.
Animal Dispersal - birds especially
carried in the
gut:
- colourful
ripe fruit to attract birds;
- succulent fruits
with hard seeds inside e.g. Geebung;
- sticky fruits -
mistletoes.
carried on the outside:
- burrs e.g. Burr
medic;
- hooks e.g. Bathurst Burr;
- clinging
hairs e.g. many grasses
- spines e.g. Bindii, Cats
Head, Calthrop, Galvanised
Burr.
-glue e.g. Paspalum
grass
Mechanisms
of Asexual Reproduction
•
Fragmentation
– Is
the separation of a parent plant into parts that develop into whole plants
– Is
one of the most common modes of asexual reproduction
•
In
some species
– The
root system of a single parent gives rise to many adventitious shoots that
become separate shoot systems
Vegetative
Propagation and Agriculture
•
Humans have devised various methods for
asexual propagation of angiosperms
Clones
from Cuttings
•
Many
kinds of plants
– Are
asexually reproduced from plant fragments called cuttings
Grafting
•
In
a modification of vegetative reproduction from cuttings
– A
twig or bud from one plant can be grafted onto a plant of a closely related
species or a different variety of the same species
Test-Tube
Cloning and Related Techniques
•
Plant
biologists have adopted in vitro methods
– To
create and clone novel plant varieties
•
In
a process called protoplast fusion
– Researchers
fuse protoplasts, plant cells with their cell walls removed, to create hybrid
plants
•
Plant biotechnology is transforming
agriculture
•
Plant biotechnology has two meanings
–
It refers to innovations in the use of
plants to make products of use to humans
–
It refers to the use of genetically
modified (GM) organisms in agriculture and industry
Artificial
Selection
•
Humans
have intervened
– In
the reproduction and genetic makeup of plants for thousands of years
•
Maize
– Is
a product of artificial selection by humans
– Is
a staple in many developing countries, but is a poor source of protein
•
Interspecific
hybridization of plants
–
Is common in nature and has been used by
breeders, ancient and modern, to introduce new genes
Reducing
World Hunger and Malnutrition
•
Genetically
modified plants
– Have
the potential of increasing the quality and quantity of food worldwide
The
Debate over Plant Biotechnology
•
There
are some biologists, particularly ecologists
– Who
are concerned about the unknown risks associated with the release of GM
organisms (GMOs) into the environment
Issues
of Human Health
•
One
concern is that genetic engineering
– May
transfer allergens from a gene source to a plant used for food
Possible
Effects on Nontarget Organisms
•
Many
ecologists are concerned that the growing of GM crops
– Might
have unforeseen effects on nontarget organisms
Addressing
the Problem of Transgene Escape
•
Perhaps the most serious concern that
some scientists raise about GM crops
– Is
the possibility of the introduced genes escaping from a transgenic crop into
related weeds through crop-to-weed hybridization
•
Despite
all the issues associated with GM crops
– The
benefits should be considered
Basis of regulation:
à
Process of biotechnology poses no special risks.
à
Foods derived from biotechnology should be regulated in the same way as
traditional foods.
Therefore:
à
The same laws are applicable.
à
Three federal agencies have responsibility:
àUS Department of Agriculture (USDA)
àEnvironmental Protection Agency (EPA)
àFood and Drug Administration (FDA)
à
Basis of regulation:
Protecting the US agriculture from agricultural pests and noxious weeds
(Federal Plant Pest Act)
à
Gm plants:
All plants carrying DNA from an organism considered to be a plant pest (Agrobacterium, CaMV) are defined
as “regulated articles”.
à
Stepwise procedure for deliberate release of gm plants:
àField trial authorisation (physical confinement),
àDetermination of non-regulated status (required for
unrestricted release and movement in the US).
à
A petition for nonregulated status must
consider:
àharm to other organisms (beneficial & non-target org.),
àincrease in weediness,
àadverse effects on the handling, processing
or storage of commodities,
àthreat to biodiversity.
à
No tests requirements laid down in the Federal Plant Pest Act.
à
Generally performed tests to exclude toxic effects:
àdata from field experiments on the lack of toxic effects
on animals (counting),
àcomparison of the nutritional composition with a
conventional counterpart.
61 gm plants are no longer regulated by USDA
(August 2003). These include:
à10x maize (HT, IR),
à10x tomatoes (PQ),
à 4x soybeans
(HT),
à 4x oilseed
rape (HT),
à 3x cotton
(HT),
à 3x potatoes (IR, VR).
àBasis of regulation:
Manufacture, sale and use of pesticides; environmental safety as well as
tolerance levels for presence in foods
àGm plants:
Substances produced in a living plant to control pests
(plant-incorporated protectants [PIPs])
(e.g. Bt-toxins, viral proteins)
àIn general, the data requirements for a registration
of PIPs are based on those for microbial pesticides.
à
These general data requirements include:
àproduct characterisation,
àmammalian toxicity (acute oral toxicity),
àeffects on non-target organisms (avian,
aquatic species, beneficial insects, soil organisms),
àallergenicity potential (AA sequence homology, heat / processing
stability, in vitro digestibility in gastric fluids),
àenvironmental fate, and, if appropriate,
àinsect resistance management.
à
The exact data requirements for a registration are developed on a case-by-case
basis.
8 plant-incorporated protectants
(PIPs) have been
registered by EPA (June 2003):
àBt Cry IA(b)
in maize (2x),
àBt Cry IA(c) in cotton,
àBt Cry IIIA in potato,
àBt Cry 1F in maize,
àBt K Cry IA(c) in maize
(2x),
àPotato Leaf Roll Virus replicase
in potato (Monsanto)
àBasis of regulation:
- Whole foods are under post-market authority.
- A premarket-approval is only necessary when
substances are added to foods
that are not
“generally recognised as safe” (GRAS) Þ Food
additive petition.
àGm plants:
- No pre-market approval necessary.
- All food crops on the market have undergone
voluntary consultations.
- Responsibility (liability) rests with the companies.
àNevertheless, the FDA developed guidance documents for
the industry.
US regulation:
different GMOs
Trait / Organism Agency reviewed for:
Insect Resistance / USDA safe to grow
food crop EPA safe for the environment and
human consumption (PIPs)
FDA safe to eat (except for PIPs) and wholesomeness
Herbicide tolerance / USDA safe to grow
food crop EPA use of the companion herbicide
FDA safe to eat and wholesomeness
Modified oil content / USDA safe to grow
food crop FDA safe to eat and wholesomeness
Modified flower colour USDA safe to grow
ornamental crop
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The
18th century, Pharmacognosy
•
Johann Adam (1759-1809)
•
Linnaeus (naming and classifying
plants)
•
At
the end of the 18th century, crude drugs were still being used as
powders, simple extracts, or tinctures
The
era of pure compounds
(In 1803, a new era in the history of medicine)
•
Isolation
of morphine from opium
•
Strychnine
(1817)
•
Quinine
and caffeine (1820)
•
Nicotine
(1828)
•
Atropine
(1833)
•
Cocaine
(1855)
•
In the 19th century, the
chemical structures of many of the isolated compounds were determined
•
In the 20th
century, the discovery of important drugs from the animal kingdom, particularly
hormones and vitamins.
microorganisms have
become a very important source of drugs
Definitions
•
Pharmacognosy:
It is the science of biogenic or
nature-derived pharmaceuticals and poisons
•
Crude drugs:
It is used for those natural products such
as plants or part of plants, extracts and exudates which are not pure compounds
•
Ethnobotany:
It is a broad term referring to the study of
plants by humans
•
Ethnomedicine:
It refers to the use of plants by humans as
medicine
•
Traditional medicine:
It is the sum total of all non-mainstream
medical practices, usually excluding so called “western” medicine
•
Natural
products: they
can be
• Entire
organism (plant, animal, organism)
• Part
of an organism (a leaf or flower of a plant, an isolated gland or other organ
of an animal)
• An
extract or an exudate of an organism
• Isolated
pure compounds
Types
of drugs derived from plants
•
Herbal drugs, derived from specific parts
of a medicinal plant
•
Compounds isolated from nature
•
Nutraceuticals,
or “functional foods”
II. Value of natural
products
•
Compounds from natural
sources play four significant roles in modern medicine:
• They
provide a number of extremely useful drugs that are difficult, if not
impossible, to produce commercially by synthetic means
• Natural
sources also supply basic compounds that may be modified slightly to render
them more effective or less toxic
3. Their
utility as prototypes or models for synthetic drugs possessing physiologic
activities similar to the originals
4. Some
natural products contain compounds that demonstrate little or no activity
themselves but which can be modified by chemical or biological methods to
produce potent drugs not easily obtained by other methods
Baccatin
III ®
Taxol
III. Production of natural
drug products
• Collection
(wild)
• Cultivation
(commercial), collection, harvesting, drying, garbling, packaging, storage and preservation e.g.
ginseng, ginkgo, peppermint
• Fermentation (Recombinant DNA
technology or Genetically engineered drugs)
• Cell-culture
techniques
• Microbial
transformation
• Biologics
(prepared from the blood of animals)
IV. The role of natural
products in drug discovery
•
Combinatorial chemistry
•
High-throughput screening of natural
products
•
Combinatorial biosynthesis
•
Ethnopharmacology
V. General principles of botany:
morphology and systematics
•
How
to define a pharmaceutical plant-derived drug from the botanical point of view ?
a
botanical drug is a product that is either:
Derived from a plant and
transformed into a drug by drying certain plant parts, or sometimes the whole
plant, or
•
Obtained from a plant, but
no longer retains the structure of the plant or its organs and contains a
complex mixture of biogenic compounds (e.g. fatty and essential oils, gums,
resins, balms)
•
isolated
pure natural products are thus not “botanical drugs”, but rather chemically
defined drugs derived from nature.
u
the following plant organs are the most important, with the Latin
name that is used, for example in international trade, in parentheses:
•
Aerial parts or herb (herba)
•
Leaf (folia)
•
Flower (flos)
•
Fruit (fructus)
•
Bark (cortex)
•
Root (radix)
•
Rhizome (rhizoma)
•
Bulb (bulbus)
•
The
large majority of botanical drugs in current use are derived from leaves or
aerial parts.
•
A
plant-derived drug should be defined not only in terms of the species from
which it is obtained but also the plant part that is used to produce the dried
product. Thus, a drug is considered to be adulterated if the wrong plant parts
are included (e.g. aerial parts instead of
leaves)
Taxonomy
•
It is the science of naming organisms and
their correct integration into the existing system of nomenclature
•
The names of species are given in
binomial form: the first part of the name indicates the wider taxonomic group,
the genus;
the second part of the name is the species.
Papaver somniferum
L.
•
Species:
somniferum,
here meaning ‘sleep- producing’
•
Genus:
Papaver
(a group of species, in this case poppies, which are closely related)
•
Family:
Papaveraceae
(a group of genera sharing certain traits)
•
L.:
indicates the botanist who provided the first
scientific description of the species and who assigned the botanical name
Morphology of higher plants
1. Flower
•
It is the essential reproductive organ of
a plant.
•
For an inexperienced observer, two
characteristics of a flower are particularly noteworthy: the size and the color
•
Although the flowers are of great
botanical importance, they are only a minor source of drugs used in phytotherapy or pharmacy e.g. chamomile, Matricaria recutita
L. (Asteraceae )
2. Fruit and seed
•
The lower plants, such as algae, mosses
and ferns, do not produce seeds
Gymnosperm and Angiosperm
•
Gymnosperm:
they are characterized by seeds that are
not covered by a secondary outer protective layer, but only by the testa – the seed’s outer layer
•
Angiosperm: the
seeds are covered with a specialized organ (the carpels) which in turn develop into the pericarp.
•
Drugs from the fruit thus have to be
derived from an angiosperm species
•
Fruits and seeds have yielded important phytotherapeutic products, including:
Ø Fruit
Caraway, Carum
carvi L. (Umbelliferae)
Ø
Seed
(white) mustard, Sinapis alba L. (Brassicaceae)
3. Leaves
•
The function of the leaves,
as collectors of the sun’s energy and its assimilation, results in their
typical general anatomy with a petiole (stem) and a lamina (blade)
•
A key characteristic of a species is the
way in which the leaves are arranged on the stem, they may be:
• Alternate
• Distichous
• Opposite
• Decussate
• Whorled
•
The
form and size of leaves are essential
characteristics e.g. oval, oblong, obovate, rounded, linear, lanceolate,
elliptic, spatulate, cordate,
hastate or tendril
•
The
margin of the leaf is another characteristic feature e.g. entire, serrate, dentate, sinuate, ciliate or spinose
•
Numerous
drugs contain leaf material as the main component. e.g.
Deadly nightshade, Atropa belladonna L. (Solanaceae)
4. Bark
•
The
bark as an outer protective layer frequently accumulates biologically active
substances e.g.
Red cinchona, Cinchona
succirubra L.
(Rubiaceae)
•
No
stem-derived drug is currently of major importance
5. Rhizome and root drugs
•
Underground organs of only a few species
have yielded pharmaceutically important drugs e.g.
•
Sarsaparilla, Smilax regelii (Smilacaceae)
•
Korean ginseng, Panax
ginseng (Araliaceae)
6. The bulbs and exudates
•
Garlic, Allium
sativum L. (Liliaceae)
•
Aloe vera
L. (Asphodelaceae)
Medicinal
Chemistry
Urgent
need to study medicinal plants
•
To rescue knowledge in imminent danger of
being lost
Inventory by
WHO found 20,000 plant species in use for medicine in 90 countries
Only 250 of
those species are commonly used or have been checked for main active chemical
compounds
Urgent
need to study medicinal plants
•
The utility of plants in current therapy
There has
been a rush to develop synthetic medicines based on plant medicines, but often
the synthetic medicines don’t work as well as the original plant medicines.
For example –
quinine and malaria
Efficacy
of Quinine
•
Quinine is traditional and effective
preventative of malaria
•
Synthetic preventatives such as chloroquine, maloprim, and fansidar have largely replaced the use of quinine
•
Many strains of Plasmodium have
developed resistances to the synthetics and the synthetics are more toxic. It is recommended that people do not take fansidar for more than 3 months due to potential liver
damage.
Malaria
Cycle
Anopheles
freeborni mosquito – intermediate host
and vector for Plasmodium sp.
Historical
distribution of Malaria
Red
areas show countries with malaria today
One
of the sources of
Quinine – Cinchona succirubra
Cinchona
pubescens
Timeline
of Quinine Use
•
1633, a Jesuit priest named Father Calancha described how to use quinine bark to cure fevers
•
1645 Father Bartolome
Tafur took some bark to Rome and many of the clergy
used it
•
Cardinal John de Lugo wrote a pamphlet to
be distributed with the bark - use of the bark became so widespread that in the
papal conclave of 1655 no one died of malaria
•
1654 – English aware of use of quinine
bark
•
1735, a French botanist named Joseph de Jussieu journeyed to South America and found and described
the tree that is the source of the bark - he sent samples to Sweden where in
1739, Carl Linneaus named the tree genus Cinchona
Timeline
of Quinine Use
•
20 to 40 species of Cinchona - the
species are very hard to tell apart and the species will hybridize, so the
exact number of species is unknown – mostly understorey
trees
•
1820 the French chemists Joseph Pelletier
and Joseph Caventou isolated the alkaloid quinine
from the bark and identified it was the active ingredient in Peruvian bark
•
1861, an Australian named Charles Ledger
obtained seeds from an Aymara Indian named Manuel Incra
•
by
1930, the Dutch orchards in Java produced 22 million pounds of quinine, 97% of
the world’s market
Chemical
structure of quinine
Properties
of Quinine
•
Quinine itself is an odorless white
powder with an extremely bitter taste
•
It can be used to treat cardiac
arrhythmias as well as malaria - it is also used as a flavoring agent
•
Quinine prevents malaria by suppressing
reproduction of the Plasmodium and also helps prevent some of the fevers
and pain associated with malaria
Quinine
fluoresces under UV light
Raymond
Fosberg in the
field in 1948
Cinchona
bark drying in the sun in Ecuador, 1944
Urgent
need to study medicinal plants
3. To find new
molecular models in plants
Many times we
can take a plant chemical and modify it or make synthetic copies of it that are
very valuable to us.
Lippia
dulcis – sweetener
from
Pre-Columbian America
Lippia
as a sweetener
•
In
Pre-Columbian America, several plants of the genus Lippia
were used as sweeteners. (F. Verbenaceae – the verbenas).
•
In
the 20th century, L. dulcis was chemically
analyzed and a new sweetener was found, hernandulcin, that is 800 to 1000 times sweeter than sucrose.
Urgent
need to study medicinal plants
4. The wide use of plants in folk medicine
One positive
aspect of the use of medicinal plants is their low cost compared to the high
price of new synthetic drugs that are totally inaccessible to the vast majority
of the world’s people. Another benefit
is that most medicinal plants don’t have the kinds of harmful side effects seen
with synthetic drugs.
Plants
and Human Cosmologies
Cosmologies
Cosmologies
are branches of philosophy which deal with the origins and structures of the
universe - religions that explain how the universe formed and our place within
it are one kind (a very powerful kind) of cosmology
The
Oak of Guernica
Basque
coat of arms with
Oak of Guernica
Oak
of Guernica by Wordsworth - 1810
•
THE OAK OF GUERNICA
The ancient oak of Guernica, says Laborde in his
account of Biscay, is a most venerable natural monument. Ferdinand and
Isabella, in the year 1476, after hearing mass in the church of Santa Maria de
la Antigua, repaired to this tree, under which they swore to the Biscayans to
maintain their "fueros" (privileges). What
other interest belongs to it in the minds of this people will appear from the
following.
SUPPOSED ADDRESS TO THE SAME
OAK of Guernica! Tree of holier power
Than that which in Dodona did enshrine
(So faith too fondly deemed) a voice divine
Heard from the depths of its aerial bower--
How canst thou flourish at this blighting hour?
What hope, what joy can sunshine bring to thee,
Or the soft breezes from the Atlantic sea,
The dews of morn, or April's tender shower?
Stroke merciful and welcome would that be
Which should extend thy branches on the ground,
If never more within their shady round
Those lofty-minded Lawgivers shall meet,
Peasant and lord, in their appointed seat,
Guardians of Biscay's ancient liberty.
Guernica
by Picasso
Moses
and The Burning Bush
The
sacred Maori Waka Huia
The
sacred Maori Waka Huia
Miro tree –
Podocarpus ferruginea