Botany session 1

© Copyright PCNM 2011
Botany and Pharmacognosy
Session 1

This Session
During this session we will
cover:
Introduction to Botany &
Pharmocognosy

Introduction
• Pharmacognosy is the study of medicines derived from natural
sources. The study of drugs from plants includes the subjects of
botany, chemistry and pharmacology.
• Botany includes the identification and naming of plants, their
genetics and cultivation.
• Chemical studies include the isolation, identification and
quantification of constituents in plant materials.
• Pharmacology is the study of the biological effects the chemicals in
medicinal plants have on cell cultures, animals and humans.

Plant Diversity
• Plants are living organisms classified as belonging to the Kingdom
Plantae. This includes trees, herbs, grasses, vines, ferns, mosses
and green algae.

What Is Botany?
• Botany is a science that deals with plants. It includes the study of
the internal and external structures of plants as well as of their
diverse functions.
• Botany can be studied from the ëpureí and from the ëappliedí
aspect.
• Pure botany is the study of plants.
• Applied botany is the study of the uses of plants.

The Importance of Plants
• Green plants contain a substance, chlorophyll, especially in their
leaves. Chlorophyll converts energy from sunlight into the sugar
glucose, using carbon dioxide and water from the environment. This
process is called photosynthesis. Glucose is then converted into
starch for storage in the plant. Thus green plants make their own
food, and are known as autotrophs (self-feeders).

The Importance of Plants
• Nearly all other forms of life on earth are dependent upon green
plants.
• Plants are direct food sources for many animals. Other animals eat
animals which have eaten plants.
• Animals, including humans, are heterotrophs. Heterotrophs obtain
energy from organic molecules that are made by autotrophs.

Types of Plants
• There is a huge variety of green, chlorophyll-containing plants in the
world. These range from the single-celled fresh water alga called
Chlamydomonas to the giant Sequoia or redwood trees growing up
to 95m high and 17m in diameter. These are found growing on the
Western Slopes of the Sierra Nevada in California.
• Plants can be classified as vascular or non-vascular. Non-vascular
plants do not possess xylem or phloem, specialised tissue for
internal transport of water.
• Xylem (Greek: xylon meaning wood). The basic function of xylem is
to transport water, but it also transports some soluble mineral
nutrients from the roots to other parts of the plant.

Types of Plants
• Phloem is the living tissue that carries
organic nutrients, especially sucrose, to all
parts of the plant when needed.
• Unless they are aquatic, ie living in water,
non-vascular plants are unable to grow to a
large size.
• Aquatic non-vascular plants include some
green algae. Non-aquatic non-vascular
plants are called Bryophytes, and include
mosses, liverworts and hornworts.
• Most of the larger plants we encounter
contain a vascular system of xylem and
phloem.

Types of Plants
• Vascular plants belong to three main groups, angiosperms,
gymnosperms and ferns.
• Angiosperms are the flowering plants, eg a daisy
• Gymnosperms bear cones where the seeds develop, eg a pine tree
• Ferns are sorus-bearing plants. A sorus is a cluster of sporangia.
Sporangia are structures which produce and contain spores. A
spore is a reproductive structure that is adapted for dispersal away
from the parent plant, and is also adapted for surviving for extended
periods of time in unfavourable conditions.
• Spores also form part of the lifecycle of many bacteria, algae, fungi
and even some single-celled animals called protozoans.
• Plants with vascular systems are sometimes referred to as ëhigher
plantsí.

Types of Plants
• Botany has identified about 350,000
species of plants that are extant. Extant
means they are still alive today.
• A species can be defined as a group of
organisms capable of interbreeding to
produce fertile offspring. A horse and a
donkey can mate and give birth to a
viable offspring, a mule or a hinny, but
these are always sterile and unable to
breed. Horses therefore, are a species,
as are donkeys, but mules and hinnies
are not.

Types of Plants
• Each species is placed within a particular genus on the premise that
the species is more closely related to other species within its genus
than to species in other genera.
• All species are given a binomial (two part) name
consisting of the generic name and specific name.
• The specific name is sometimes referred to as the
specific epithet.

Types of Plants
• An example of this is the widely used medicinal herb the purple
coneflower, Echinacea purpurea. The genus is Echinacea, the
species is purpurea. There are eight other echinaceas , all a little
different to Echinacea purpurea; eg Echinacea pallidum which has
pale or white flowers rather than purple like E. purpurea. However all
the species have the central spiny flower head which gives the
name Echinacea to the genus, (Greek; echinos, meaning
hedgehog). All the species have their individual differences but
share the characteristics of the genus.
• Note that the genus is always capitalised while the species name is
always begun with a lowercase letter.

Types of Plants
• Genera are organised into families, which can be considered major
groups of organisms with identifying characteristics. The Echinacea
are daisy flowers so they are placed in the daisy family, the
Asteraceae. This family is sometimes called the Compositaceae
family. All the genera and species in the family Asteraceae are daisy
flowers of some sort, and therefore share the identifying daisy
characteristics of that family.
• Note that family names always end in -aceae

Types of Plants
• Families are grouped into Orders. The members of an order can
appear very diverse but they share certain important characteristics.
In the animal world there is an order Carnivora. The animals in the
different families in this order can look very, very different from each
other. As an example, in the order Carnivora there are the cat
family, the dog family and the bear family, all very different animals.
However they all eat meat; that is they are carnivorous.

Types of Plants
• Our Echinacea example is
classified in the order Asterales.
There are eleven families in this
order and approximately 27,500
species. Of course they may look
very different, one from the other,
but they share the characteristics
of the Asterales order. One of
these characteristics is that they
contain a constituent called inulin.
Inulin is an important soluble fibre
in human diets and provides food
for the very important bacteria
living in our large intestines.

Types of Plants
• Orders are grouped into Classes. An example of a class is
Mammalia which contains all the mammals. Mammals can look very
different but they all share certain characteristics not found in other
organisms, and which have been inherited from a common ancestor.
Dogs and cats are both in the class Mammalia, as are sheep,
horses, humans and whales. They look sufficiently different to be
easily identified but they all share the mammalian characteristics of
having hair covering and of giving birth to live offspring which they
feed on milk.

Types of Plants
• Echinacea are in the class Eudicot,
although in botany class is often
replaced by the word ëcladeí.
Eudicots are dicotyledons, that is
when the seed germinates it first
produces two baby or seed leaves
which are different in appearance to
the true leaves produced as the
seedling grows.

Types of Plants
• Classes are further grouped into Phyla or Divisions. A phylum or
division groups together organisms depending on their general body
plan. The actual organisms can, at least superficially, look very
different. As an example, spiders and crabs are both in the phylum
Arthropoda. They look very different but they share certain
characteristics, especially that they have external skeletons,
segmented bodies and jointed appendages. In botany a phylum is
usually referred to as a Division. Echinacea are in the division
Angiospermae.
• There are eleven divisions of plants, but for our purposes we will
consider five main divisions.

Types of Plants
• Angiospermae contains all the angiosperms. The name comes from
the Greek: angion meaning a small container; sperma meaning
seed. The seeds of angiosperms are completely covered.
Angiosperms are flowering plants. There are approximately 200,000
species of angiosperms.
• Gymnospermae contains the gymnosperms. These are plants that
produce their seeds in cones. The name comes from the Greek:
gymnospermos meaning naked seed. The seeds are not completely
enclosed like those of the angiosperms but develop on the surfaces
of leaf or stalk-like appendages in the cones. Gymnosperms include
conifers, cycads and Ginkgo. There are about 900 species of
gymnosperms.

Types of Plants
• Pteridophytae contains the pteridophytes, ferns and fern-like plants.
These are vascular plants; that is they have xylem and phloem but
they do not produce flowers or seeds. Instead they reproduce by
spores. There are 11,000 species of ferns and their allies.
• Bryophytae is the division containing the bryophytes; mosses and
liverworts, Bryophytes reproduce by spores but they do not contain
vascular tissue. They are land plants. Most bryophytes need to live
in moist, shaded areas as they do not possess vascular systems for
internal water transport. There are about 24,000 known species of
mosses and liverworts.

Types of Plants
• Chlorophyta is the division where we find the green algae. Green
algae are nearly all aquatic plants, capable of photosynthesis but not
possessing roots, stems, true leaves or vascular tissue. They have
simple reproductive structures. A few green algae are terrestrial,
living in moist places on land. There are about 18,000 species of
green algae.
• There are several other phylogenetic groups of algae but they are
not considered true plants. One of these of interest to us is
Cyanobacteria which contains the blue-green alga, including
spirulina.

Types of Plants
• All the plant divisions listed
above are classified as
belonging to the kingdom
Plantae. The kingdom which
contains all the animals is
called Animalia
• One other group of interest to
us is that containing the fungi.
Fungi used to be classified as
plants but are now allocated
their own kingdom, Mycetae.
There are at lest 75,000
species of fungi.

Types of Plants
• We can now completely classify our Echinacea plant:
• Kingdom: Plantae
• Division: Angiospermae
• Class: Eudicot
• Order: Asterales
• Family: Asteraceae
• Genus: Echinacea
• Species: purpurea

Types of Plants
• This enables anybody throughout the
world to know exactly which plant is
being referred to. An example of the
importance of this is in the chemical
differences between species.
Alkamides found in echinacea are
chemicals that have modulatory
effects on the human immune system.
Alkamides are found in Echinacea
angustifolia and E. purpurea but not in
E. pallida. An herbal preparation from
E .pallida therefore would not have
the same effect on the immune
system as preparations from
E.angustifolia or E.purpurea.

Types of Plants
• In general, when a plant is being referred to it is only called by its
genus and species names. Sometimes the family will be noted, but
rarely will any higher classification be used.
• Take note:
• Family names always end in Öaceae
• The Genus is always capitalised
• The species is always begun with a lowercase letter

Checkpoint!

Angiosperms
• Most of the plants used for food and medicine are flowering plants.
• Angiosperms are very widely distributed throughout the world, being
found from the poles to the tropics, and in a wide variety of habitats.
• Most angiosperms are terrestrial, although some are aquatic. There
are even epiphytes which live in the air, supported by other plants.
Many species of orchids are epiphytes.
• Angiosperms exhibit a very varied morphology. They may be
grasses, tiny alpine flowers, palm trees, shrubs or huge trees. Some
are twining plants and others can climb.
• The most important characteristics of angiosperms are:
• They produce flowers
• The seeds are completely covered by the fruit coat.

Angiosperms
• Angiosperms are classified according to their form. The
classifications are as follows:
• Herbaceous or woody
• Herb, shrub or tree
• Annual, biennial or perennial
• Deciduous or evergreen
• Succulent or non-succulent
• Herbaceous: Soft and green, with little or no woody tissues. These
plants are often non-woody plants which die down to ground level
each year.
• Woody: hard and firm because of the presence of woody tissues,
e.g. the trunk of a tree is really a woody stem.

Angiosperms
• Herb: a flowering plant of small or relatively small size whose aerial
shoots last only as long as is necessary to develop the flowers and
fruits. By this definition we can see that trees are not herbs even
though we can use them medicinally.
• Shrub: A woody plant which usually remains low. It produces shoots
or trunks from the base and usually does not have a distinct single
trunk.
• Tree: A woody plant with a distinct trunk. Branches arise from the
trunk to form a crown or canopy. Branches do not ordinarily arise
from the base of a tree. Trees are often taller than shrubs.

Angiosperms
• Annual: a plant which completes its
life cycle in a single growing season.
In this season it germinates from a
seed, flowers, fruits and then dies. It
survives the unfavourable season
only as a seed. Western Australian
wildflowers are often annuals,
completing their entire lifecycle in the
few weeks between the winter rains
and the hot, dry summer. Their
seeds then remain dormant until the
autumn or winter rains begin. Many
of our grain crops such as wheat,
oats and rice are annuals.

Angiosperms
• Biennial: a plant that completes its lifecycle in two years. It will only
flower in the second year. In the first year it is entirely vegetative,
forming leaves and sometimes a swollen food storage root. Food
from the storage root is used in the next years growth, when flowers
and seeds are produced. After this the plant dies. A carrot is an
example of a biennial. The next generation develops from the seeds
produced. In many places biennials have a dormant period during
the unfavourable season, but in mild climates there may be a long
growing season and no dormant period.

Angiosperms
• Perennial: A plant which lives for more than two years.
• Herbaceous perennials are non-woody plants that do not die down
during unfavourable seasons. Some persist with reduced growth but
retain some leaves, such as grasses. In others the above-ground
parts die at the end of the growing season but the plant survives as
dormant underground organs, eg asparagus, rhubarb. These
dormant underground organs, such as bulbs, corms and rhizomes
contain food for rapid growth and flowering in the following season.
These storage organs are produced each year and are the means
by which many herbaceous perennials survive unfavourable
seasons.

Angiosperms
• Deciduous: Deciduous trees and shrubs
shed all their leaves annually in a short
period of time. In cool and temperate
climates the leaves are shed in autumn,
in the tropics the leaves are shed before
the hot dry season. Flowering
sometimes occurs during the deciduous
phase. This aids pollination. When the
leaves drop, growth ceases or is
reduced. When conditions are more
favourable new leaves and branches are
rapidly produced. Jacaranda, peach,
almond and mulberry are examples of
deciduous trees.

Angiosperms
• Evergreen: Evergreen trees and shrubs retain most of their leaves
throughout the year. Leaves are shed in small numbers throughout
the year, when they become old or cease to function properly.
Eucalyptus, grevillea and camellias are evergreen.
• Succulent: Juicy, fleshy, soft and thick. A succulent plant is one with
thick plant parts for water storage. Cacti are succulent.
• Non-succulent: There are no specialised adaptations for water
storage. Many plants are non-succulent. Examples are wheat,
lettuce.

Angiosperms
• Angiosperms can also be grouped according to their water needs.
They can be xerophytes, hydrophytes or mesophytes.
Xerophytes:
• Xerophytes are plants adapted to survive in dry habitats. Many
plants of the Australian desert are xerophytes, e.g. Spinifex.
Xerophytes are able to survive long spells without rainfall or artificial
watering because they possess one or more of the following
characteristics.
• Ability to recover from partial drying out
• Ability to store water in plant tissues such as the roots, leaves and
stems. Plants with this ability have already been described as
succulents.

Angiosperms
• Deep root systems to be able to reach water
• Ability to reduce water loss by one or more of the following:
• Leaves which are shed during the dry season. The boab tree of
northern Australia stores water in its swollen trunk but also
sheds its leaves during the dry season.
• Waxy leaves. The leaves are covered by a waxy cuticle which
lessens water loss. Larrea tridentate, the creosote bush of the
deserts of USA have waxy leaves
• Reduced leaf area, such as needle- shaped leaves e.g. the
Rottnest Island pine, or feathery leaves e.g. the Californian
poppy. Some plants have lost their leaves altogether and rely on
their green stems to carry put photosynthesis, eg most cacti. In
most cacti the leaves have evolved into spikes which do not
carry out photosynthesis

Angiosperms
• Sunken stomata. Stomata (singular: stoma) are microscopic-
sized pores on the surface of land plants. They are surrounded
by a pair of specialised epidermal cells called guard cells. These
act as valves that open and close the pores in response to given
environmental condit ions. Carbon dioxide and oxygen can enter
the plant through stomata, oxygen produced by photosynthesis
is released from the plants through stomata, and water vapour is
released through stomata the loss of water vapour through
stomata is called transpiration. During dry conditions the stomata
can be closed to reduce the loss of water vapour. This prevents
the plants from dehydrating and wilting. Sunken stomata are
below the surface cells of the epidermis; this reduces water loss.
Pine trees have sunken stomata. They also have waxy leaves
with reduced surface area.

Angiosperms
• Leaves that can curl up or fold during very dry times. Many
grasses have this ability
• Silvery- grey leaves. These reflect light and heat. The globe
artichoke, the Senecio daisy plant called Dusty Miller and the
Stachys plant known as lambsí ears all have grey leaves.

Angiosperms
• Hydrophytes.
• Hydrophytes are plants of wet habitats, living either in water or in
very wet soil.
• Hydrophytes typically contain aerenchyma, tissue with a lot of air
spaces.
• Aerenchymy are found throughout the plant but especially in the
leaves and the roots. Aerenchymy enable gas exchange between
the roots and the stems of plants in wet areas. Plants without any
aerenchymy die when they are submerged in water as insufficient
oxygen reaches the root. Sedges, bulrushes and the maize plant all
have aerenchymy.

Angiosperms
• Some hydrophytes float on the surface of water and their roots are
not anchored, e.g. duckweed, Lemma sp.
• Some are completely submerged. The common aquarium plants
elodea (Canadian pondweed) and eelgrass (Vallisneria sp) are
examples of plants which are rooted in the bottom of the lake or
stream and all their other parts are also under the water.
• Some hydrophytes are rooted under the water but their leaves,
flowers and fruits are above water. A well known example is the
water lily, Nymphaea sp.
• Some hydrophytes can live where they are not permanently
submerged but where the soil is very wet. Mangrove trees,
Rhizophora sp, live in swampy land on tidal coasts.

Angiosperms
• Hydrophytes are characterised by the following:
• A thin cuticle. Because they are in wet situations these plants do
not need to conserve water
• Stomata with inactive guard cells so that the stomata are open
most of the time
• An increased number of stomata
• A less rigid structure as water pressure supports them
• Flat leaves on surface plants for flotation
• Air sacs for flotation
• Smaller roots; water can diffuse directly into leaves
• Feathery roots; the roots do not have to be able to support the
plant
• Specialised roots able to take in oxygen

Angiosperms
• Mesophytes:
• These are plants that grow under average conditions of water
supply, avoiding extremes of moisture and of drought. The majority
of flowering plants are mesophytes. They generally do not have any
specific internal structures or morphological adaptations, although
they often have broad, flat and green leaves.
• They have larger, thinner leaves than xerophytes, with a greater
number of stomata on the underside of their leaves, and need to
have a more or less continuous supply of water.

Summary
Today we have covered;
• An Introduction to Botany &
Pharmocognosy

Next Session
We will cover:
Angiosperm morphology
Stems
Roots

Preparation
Brief Notes
• Don’t forget to log on to the LMS and download and print off your
brief notes and handouts for the next session.

Botany session 1

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