Botany session 2

© Copyright PCNM 2011
Botany and Pharmacognosy
Session 2

Review
Last week we covered:
An Introduction to Botany &
Pharamcognosy

This Session
During this session we will
cover:
Angiosperm morphology
Stems
Roots

• Morphology is the outer form of the flowering plant. It covers the
external structure of plant parts, such as leaves, roots, stems, buds,
flowers, fruits and seeds

Monocotyledons and Dicotyledons.
• Cotyledons are parts of the embryo within the seed of a plant. Upon
germination they become the embryonic first leaves of a seedling.
The number of cotyledons possessed by an angiosperm is one
characteristic used to classify them. Species with one cotyledon are
called monocotyledons, and those with two are termed dicotyledons.
• Cotyledons are quite different in appearance to the true leaves of
the seedling which only develop after the seed has germinated.

Monocots and dicots have other
distinguishing features.
• Feature Monocotyledon Dicotyledon
• Leaf structure Parallel veins Network veins
• Roots Fibrous roots Tap roots
• Stem Soft Hard
• No. of cotyledons 1 2
• Number of petals Divisible by 3 Divisible by 4 or 5
• Type of plant Mostly grasses Herbaceous or
and similar Woody; herbs, Shrubs
or tree

Basic Plant Organisation
• Angiosperms are, like all other living things, made up of cells.
• A number of cells of the same type grouped together and concerned
with the same function form a tissue.
• Two or more tissues closely associated and performing a major
function form an organ.
• Organs may be grouped into organ systems.
• The organs that make up flowering plants are roots, leaves, buds,
flowers, fruit and seeds.
• Each organ of a plant has one or more functions to perform so that
the plant as a whole can survive and produce its own kind.

The principal functions
• Roots
• provide anchorage
• absorb oxygen, water and
minerals from the soil
• store food which has been
manufactured by other parts of
the plant
• conduct absorbed materials
and stored food to the stem
• are sometimes involved in
asexual reproductive
processes

• Stems
• support the leaves and flowers
• transport water and minerals from
the roots to the leaves
• transport food manufactured in the
leaves to other parts of the plant
• store food and water
• take part in asexual reproduction
• photosynthesise food if the stems
are green

• Leaves
• manufacture sugars by
photosynthesis
• assist in maintaining
the water balance of
the plant
• leaves of some plants
take part in asexual
reproduction, food
storage, climbing and
insect trapping

• Flowers
• contain the structures for
sexual reproduction for the
production of fruit and seeds
• attract pollinators
• Fruit
• protects seeds
• provides various means of
dispersing the seeds to
locations favourable for their
growth

The Angiosperm Life Cycle
• A typical angiosperm undergoes these events in the life cycle.
• 1. Under suitable conditions a seed germinates to produce a
seedling
• 2. The seedling grows into a mature plant
• 3. Flowers form on the plant
• 4. Pollen grains form in the anthers, egg nucleus forms in the
ovules of the flower
• 5. Pollen grains are transferred from the anther to the stigma in
the process called pollination. The pollen grain produces a pollen
tube which grows down the style to enter an ovule in the ovary
The pollen tube discharges sperm nuclei into the ovule. A sperm
nucleus unites with an egg nucleus to form a zygote in the
process called fertilisation.

• 6. after fertilisation the flower
withers, except for the ovary. A
fruit and seeds form. Note that
in angiosperms the seeds are
fully protected enclosed within
the fruit.
• This process is sexual
reproduction.
• The sexual reproduction of any
organism, whether animal or
plant, is defined as the union of
two gametes or gametic nuclei
resulting in the formation of a
zygote. The zygote is the
beginning of the formation of a
new individual

• A gamete is a reproductive cell. It has only one set of chromosomes.
It is said to be haploid. In plants the male gametic nuclei are the
sperm nuclei produced in the germinating pollen grain. The female
gametic nucleus is the egg nucleus produced in the ovule. The
zygote is formed from the fusion of the sperm nucleus and the egg
nucleus. Thus the zygote has two sets of chromosomes. It is said to
be diploid.
• The most important feature of sexual reproduction is that the
offspring are usually different from one another and from their
parents. This is termed variability.
• In plant and animal breeding when the parents are genetically
similar the offspring are also genetically similar. These individuals
form a pure line.

• Asexual reproduction results in offspring which are identical to the
parent and to one another.
• Asexual reproduction is any form of reproduction that does not
involve the fusion of haploid gametes or gametic nuclei. New plants
are produced from parts of the parent plant which already have two
sets of chromosomes. Such parts include stems, leaves and roots.
No pollination or fertilisation processes are involved.
• In botany, asexual reproduction is often referred to as vegetative
reproduction.. It is very important in the lives of many flowering
plants.

• Vegetative reproduction can occur naturally or artificially through
manipulation by humans.

Natural
• Many angiosperms have modified structures which can store food
which can help a plant survive unfavourable periods and then
provide for rapid growth when growing conditions are once again
favourable. These structures are modified stems or roots. New
plants can also arise from these structures. For example, the tuber
of a potato is an underground stem and the tuber of a sweet potato
is a swollen root. These possess ëeyesí from which new individuals
can grow.
• Plants such as onions and daffodils produce bulbs. Bulbs are
thickened, fleshy usually subterranean buds, growing roots from the
underside and stems, flowers and foliage from the crown. Bulbs can
split into two bulblets which will grow to produce identical daughter
plants. Some bulbs produce tiny bulbils from their base. These will
all grow into plants identical to the parent plant. Note that bulbous
plants can also reproduce sexually to produce seeds.

Natural
• Other bulb-like structures which reproduce asexually are corms.,
such as found in the gladiolus and the crocus. Corms are
underground sections of stem, consisting of fleshy tissue with a bud
at the top. Tiny cormels are produced at the base of the corm.
These will eventually grow to a mature plant identical to the parent.
• Rhizomes are underground stems. They possess nodes from which
roots and shoots can grow, forming a new individual. The ginger
plant has rhizomes.
• Stolons are above ground stems which grow out from the parent
plant and produce roots and leaves to form a new plant.
Strawberries reproduce asexually using stolons.
• Some plants can reproduce asexually by producing new plants from
the parent leaves. Begonias are an example of this.

Artificial
• Using various techniques man can increase the numbers of a plant
by asexual means. Stem cuttings, root cuttings and even leaf
cuttings all produce plants identical to the parent. Adventitious roots
grow from the end of the cutting and a new plant is formed.
• Micro-propagation is used commercially to produce large numbers
of plants from a small piece of tissue. Vegetative buds of a plant
such as an orchid are divided into individual cells. These are
cultured under special conditions in a laboratory. The cells divide
and produce new plants, each identical to the parent plant. Each
culture can produce many new plants, often thousands at a time,
which are identical to the parent plant. Note that this is NOT genetic
engineering.
• The benefits of artificial or tissue culture reproduction is that large
numbers of plants with special characteristics can be produced in a
short period of time.

Checkpoint!

Roots
• The root systems of many plants seem to be disproportionately
extensive. However, root systems need to be large enough to meet
the requirements of all the aerial parts of the plant so that it can
survive and reproduce.
• The major functions of the roots are:
• Anchorage and support. Plants need to be firmly anchored in the
soil so that the above ground parts of the plant are supported
and the plant does not blow over in normal strength wind
• Absorption. The roots need to be able to absorb from the soil
oxygen, water and minerals in solution.
• Translocation. The roots need to be able to conduct absorbed
materials to the stem to reach the rest of the plant.
• Storage. Roots can store water, nutrients and carbohydrates,
especially at times when the plant is dormant.

Kinds of Roots
• Taproot system.
• When a seed from a dicotyledon
germinates a single root grows
vertically down into the soil. Lateral
roots arise from this primary root, and
smaller roots arise from these lateral
roots but the primary root remains the
largest and dominant root, the taproot.
Taproots are capable of growing deep
down into the soil some taproots are
modified to store food, as seen in the
carrot and other root vegetables.

Kinds of Roots
• When a monocotyledon seed
germinates a single root first appears.
This is then followed by lateral roots
called seminal roots. This juvenile root
system is soon replaced by a number of
roots growing from the base of the stem
of the plant. These are adventitious
roots. Smaller roots then develop from
these adventitious roots. The end result
is a tuft of shallow roots of similar size
arising from the base of the stem. This
fibrous root system, shallower than the
tap root system, is found in monocots
such as grasses, lilies and palm trees.

Kinds of Roots
• Adventitious roots.
• An adventitious root is one which grows from some part of the plant
other than a pre-existing root.
• Adventitious roots form the main roots of the fibrous root system
because they arise directly from the base of the stem.
• Adventitious roots can grow out from the stems of climbing plants,
giving extra support to the plant. These roots are also able to absorb
water and mineral salts, and can replace a root system should it be
destroyed Climbing ivy develops these roots. Corn and maize plants
grow prop roots from the stem just above ground level. These grow
down into the soil to provide additional support. Some plants
produce adventitious roots from leaves. New plants of African violets
can be propagated in this way.

Kinds of Roots
• Many plants can be grown from
cuttings. This involves the
development of adventitious roots.
The new plants are complete
plants but have an adventitious
root system, even if they are
dicotyledons. A dicot grown from a
cutting will develop several large
lateral roots but not a dominant
taproot. Note that this adventitious
root system is not the same as the
fibrous root system of a
monocotyledon.

General Root Structure
• Mature roots are generally
coloured brown. Young roots are
white and do not contain
chlorophyll, with the rare
exception of the aerial roots of
some orchids.
• Roots do not bear leaves although
they may have adventitious buds
Note that when we come to
discuss stems we will see that an
underground stem has scale
leaves and axillary buds.

• Young roots form at the extremities of older roots.
• The root cap is located at the root tip. Its function is to protect the
delicate apical meristem from damage as the root grows through the
soil. The outer part of the cap is continually worn away by the
abrasive action of soil particles. The apical meristem produces new
cells to replace these old ones.
• The apical meristem is made up of cells capable of dividing to
produce new cells. Some of these new cells replace old root caps
cells, others remain in the meristem and still others add to the region
of elongation.

• The region of elongation lies behind the
meristem. As the cells in this region
mature to full size they push the apical
meristem and root cap down into the soil.
• Roots become longer as a result of cell
division in the apical meristem and the
enlargement/elongation of cells in the
region of growth.

• Root hairs are tiny, finger-like outgrowths from the cells of the outer
covering of the root, the epidermis. They are located just behind the
region of elongation. They are not found in the root tip or in older parts
of the roots. The region where the root hairs grow looks fuzzy
• The function of root hairs is three-fold:
• They grow out from the root in between soil particles. Their cell
walls adhere to soil particles, which helps to keep the plant firmly
rooted in the soil.
• Thee second function is absorption of water, oxygen and nutrients
in solution. The root hairs greatly increase the surface area of the
root tip because there are millions of root hairs in a root system
• Their third function is to reduce soil erosion from wind or rain
because the cell walls adhere to soil particles which do not easily
wash off.

• Roots exhibit positive geotropism. This means they grow down
towards the centre of the earth. Shoots exhibit opposite behavior,
growing up away from the earth. It is believed that roots and shoots
act like this under the influence of plant growth- regulating hormones
called auxins.

Soil
• Soil is the natural environment for most roots.
• Soil is composed of:
• Particles of sand, silt and clay
• Soil dwelling organisms
• Organic substances from partially or completely decomposed
plant and animal material
• Air
• Water with nutrients in solution.

Soil
• Sand and silt are formed by the weathering (physical break-up) of
rock.
• Sand particles range in size from 2mm to 0.02 mm diameter.
• Silt particles are smaller than sand particles.
• Clay is composed predominantly of minerals formed as products of
secondary, chemical weathering. The rock minerals undergo a
chemical change before becoming clay minerals. Clay particles are
very small, 0.00005mm and smaller. Clay usually contains
aluminium silicate.

Soil
• In between the particulate matter making up soil are pore spaces.
There are larger macropores which hold air and smallmicropores
containing water. Air provides the oxygen required by roots for
respiration to produce energy for growth, and the water held in the
micropores is the most important source of water for plants.
• Soil with a combination of macro and micropores provides the best
medium for root growth. Roots cannot grow in water-logged soil as
there is insufficient air in the macropores. Equally, water cannot
grow in soil without water. Roots generally grow towards moisture,
as is evidenced by roots clogging up drainpipes!

Modified Roots
• The roots of some plants have functions beyond those of anchorage
and absorption. Many plants have roots modified for food storage.
When a root is modified for food storage it is known as a tuber.
Tubers are found in biennial and perennial plants. Plants with
taproots modified as tubers include root vegetables such as carrots,
turnips, radish and beetroot. Plants with tuberous adventitious roots
include the sweet potato, the dahlia and the day lily.
• Some plants produce aerial roots which grow from above ground
stems. Some climbing plants use aerial roots for attachment or
support. Climbing ivy is an example. Other plants produce aerial
roots which can absorb moisture from rain. Some orchids have
thickened, whitish aerial roots which absorb and store moisture.
Crucifix and vanda orchids produce aerial roots with green tips
which can carry out photosynthesis.

Modified Roots
• Prop roots are adventitious roots which arise from nodes above the
ground. They then grow down into the soil where they branch
extensively and provide additional support. These roots can also
absorb water, nutrients and oxygen. Some mangrove trees produce
prop roots as do pandanus, some palms and maize.
• Mangrove trees growing where they are regularly underwater
develop respiratory roots. These grow from underground roots but
grow vertically up out of the water. These roots are called
pneumatophores and they absorb oxygen for the plant.

Modified Roots
• Plants from the Fabaceae family develop nodules on their roots.
These nodules are formed by Rhizobium bacteria which are able to
fix nitrogen so that it can be absorbed by plants. Nitrogen is
essential for plant growth as it makes plants green, thus enabling
photosynthesis to take place. Plants cannot absorb gaseous
nitrogen but can absorb the mineral form of nitrogen converted by
these bacteria. Many Australian plants are able to fix nitrogen, an
essential function as Australian soils are of very poor quality.
• Banksia, Grevillea and Hakea are members of the Proteaceae
family They develop dense clusters of tiny lateral feeder roots.
These proteoid roots increase the surface area of root hairs so that
more nutrients can be absorbed from the very infertile soils found in
much of Australia.

Modified Roots
• Some plants are parasitic, that is they obtain nutrients and water,
and sometimes food, from another, host, plant. The roots of parasitic
plants develop suckers called haustoria which attach to the roots of
host plants from which they absorb water or nutrients. The do not
take up substances directly from the soil. The WA Christmas tree,
Nuytsia floribunda, is a parasite.
• Some plants are stem parasites. Their roots do not enter the soil but
attach to the stem of the host plant. The haustoria penetrate the
bark of the host stem and absorb nutrients and water. In many
instances the parasite kills part or all of the host plan

Stems
• Functions:
• To conduct water and dissolved mineral salts from the roots to the
leaves
• To carry manufactured sugars from the leaves to other parts of the
plants in the process of translocation.
• To hold leaves in a suitable position for maximum photosynthesis
• To hold the flowers up to allow easier pollination
• Stem structure.
• Young stems are usually herbaceous, that is green and soft.
• As a perennial stem matures it becomes thicker and harder, and
develops bark. Woody tissues develop inside. These increase
the girth of the trunk and support the canopy. Stems can become
very large in this way especially in trees.

Stems
• Young stems usually have a smooth surface or are covered in hairs.
• Lenticels are small pores which develop on some stems to allow
oxygen to penetrate into deeper tissues. Lenticels are seen mainly
on cool temperate trees and shrubs which need to survive cold wet
soils during winter. Australian native plants do not usually have
lenticels, so they are very susceptible to death from waterlogging.
Many mangroves contain lenticels and can survive periodic
inundation.
• Stems bear leaves and buds. The place where leaves attach to the
stem is called a node. The area between two nodes is the internode.
• Organs which may be attached to stems are leaves, buds, flowers
and fruit.

Buds
• A bud is an undeveloped, immature shoot or flower.
• Vegetative buds develop into leafy shoots. Floral buds develop into
single flowers or inflorescences. An inflorescence is a group of
flowers.
• A mixed bud grows to become a leafy flowering branch or shoot. The
Australian bottlebrushes, Callistemon species, bear mixed buds.
• Buds are also named according to the position they occupy on the
plant. A terminal bud is located at the apex (top) of a stem. An axillary
or lateral bud is located in the axil of the leaf. The axil is the angle
between a leaf and a stem.
• If a stem ends in a vegetative bud it can continue to grow, and is said
to have indeterminate growth. When a stem ends in a floral bud,
further growth ceases. This stem shows determinate growth. Some
stems may end in a mixed bud, such as is seen in Callistemon.

Adventitious Buds
• An adventitious bud is one which arises on any part of a plant other
than the normal terminal or axillary positions. A few plants develop
buds on roots, as in sweet potatoes, or on the edge of leaves.
Kalanchoes develop buds on their leaves, hence one of their
common names, Mother of thousands, as adventitious buds on roots
or leaves can grow into new plants when conditions are favourable.
• The spider plant, Chlorophytum cosmosum, has adventitious buds in
the inflorescence stalks which develop into tiny plants.
• These adventitious buds are examples of vegetative propagation.

Epicormic growth
• Adventitious buds are also found in the trunks and branches of
many shrubs and trees endemic to fire prone regions. Endemic
means native to a particular region. After fire, these buds develop
epicormic growth, which is the development of new shoots along the
trunk and mature branches where new shoots would not normally
develop. Some trees and shrubs develop lignotubers, and after fire
the buds on the lignotuber can re-shoot. A lignotuber is a starchy
swelling of the root crown found in some plants from fire prone areas
.Lignotubers will be examined in more detail later in this session.
The lignotuber contains buds from which new shoots can develop.
• Note: if a tree is not correctly pruned but simply lopped, it can
develop epicormic growth from below the cuts. The branches that
develop are weak and subject to wind damage, so can be
dangerous.

Modified Roots
• Vegetative buds consist of many tiny, immature leaves wrapped
around an apex of young dividing cells called the apical meristem.
The outermost leaves are often thicker and tougher, and may be
coloured brown or black. These are the bud scales and they protect
the bud from disease, extremes of temperature and damage from
birds and insects. A Brussels sprout is a large vegetative bud and a
cabbage head is a giant vegetative terminal bud.
• Most vegetative buds grow into new shoots. A terminal bud grows to
extend the height of a plant and an axillary bud grows into a leafy
branch. Some vegetative buds grow to form tendrils and leaves.

Modified stems
• Stems can be modified for several
purposes:
• Vegetative reproduction
• Storage of water, nutrients and food
• Protection of dormant buds in
adverse seasons
• Protection against grazing animals
• Climbing

Stems for vegetative reproduction
• Stolons and runners are slender
stems that grow horizontally just
above the ground. A stolon has
longer internodes than a runner,
and only alternate nodes develop.
The terminal bud touches the soil,
develops adventitious roots and
then grows into a new,
independent plant. Strawberry
plants reproduce vegetatively by
stolons.
• Runners develop adventitious
roots at every nodule. Lawn
grasses such as kikuyu and
buffalo spread by runners.

• Rhizomes are horizontal underground stems. They store food which
has been translocated from the above-ground leafy shoots. Along the
rhizome are brown reduced leaves called scale leaves. These scale
leaves have axillary buds which develop into lateral shoots in the leaf
axils. There is a terminal bud which develops into a leafy shoot.
Adventitious roots develop at the nodes. Ginger, bamboo and mint
have rhizomes, as do the Western Australian native kangaroo paw and
blue lechenaultia.

• Suckers are underground shoots
which develop into new plants. A
sucker comes from a root. Roots
do not normally develop buds but
some species have the ability to do
so if the roots have been damaged
in some way. When stimulated by
damage to the root, the meristem
tissue in the root divides to produce
a shoot. Plants which produce
suckers include poplars, the
powton tree, wisteria, members of
the rose family, including some old
varieties of fruit tree rootstock, and
the herb Taraxacum -dandelion.

• Stem tubers are the swollen ends of
underground stems. The ends of the
roots of the potato plant swell to form
a swollen tuber. The eyes of the
potato stem tuber are made up of
scale leaves and axillary buds. Each
eye can produce a new shoot in the
following year, using the food stored
in the tuber. Jerusalem artichokes,
the Gloriosa lily from Africa, and the
donkey orchid from Western Australia
all produce stem tubers.

• A corm is formed by the enlargement of an underground stem base.
In a young corm, leaf bases form protective scales around the corm.
In an older corm only leaf base scars are seen forming circles
around the corm. Axillary buds are found in the axils of these leaf
bases, and a terminal bud is present at the upper end of the corm. In
spring the food stored in the corm enables the terminal bud to grow
quickly into a flowering shoot above the ground. Later in the season
the leaves send food down below ground but it is not stored in the
old corm. Instead it goes to the base of the stem immediately above
the old corm; this stem base then swells and forms a new corm on
top of the old shrivelled corm. The problem of new corms developing
on top of the old corm and therefore being too close to the soil
surface is solved by the new corm producing contractile roots. Parts
of these roots contract and pull the corm deeper underground.
Gladioli, the autumn crocus and the saffron crocus all produce
corms.

• A bulb is a condensed shoot. The stem of the shoot is very short
and never grows above the soil. Food is stored in the fleshy leaf
bases, which are very close together and wrap around one another.
The outermost leaf bases are dry and scaly. There is a terminal bud
which grows rapidly into a flowering shoot when conditions are
favourable. Axillary buds in the axils of the leaf bases may grow into
new plants. During the growth season some of the food made in the
leaves above ground is sent underground to the leaf bases. This
provides energy for growth in the axillary bud to form a new bulb,
another form of vegetative reproduction. Onions, garlic and other
members of the Allium family produce bulbs. Oxalis is the only
dicotyledon plant to produce true bulbs.

Cladodes and Phylloclades
• In some plants the stems are modified to resemble leaves. They are
green when young so can photosynthesise like true leaves. True
leaves may be absent except on very young stems, or they may be
modified into scales or spines. Flowers may grow from the edges or
even out of the flat surface of the stem.
• A cladode is a stem with limited terminal growth, often for only one
or two internodes. Short cladodes may branch out from the node on
the main stem. Asparagus produces short cladodes, as does the
Australian native she-oak, Allocasuarina.
• A phyllocladode is a stem which can keep on growing, showing
regular nodes and internodes. Buds develop in the nodes and along
the stems, and may result in flowers or lateral branches. The
zygocactus, Schlumbergera, bears phyllocladodes. The true leaves
are modified into fine spines which surround the base of the floral
buds

• Some plants store water in an enlarged swollen stem. This enables
them to survive drought or the tropical dry season. The boab tree
from the north west of Western Australia, Adansonia gregorii, and
the ponytail palm, Beaucarnea recurvata, from Mexico, store water
in this way.
• A lignotuber is a large underground modified stem. Lignotubers are
a feature of many Australian native trees and shrubs. They store
food and are fire and drought resistant. If the main trunk of the tree
is destroyed by fire, wind damage or drought, the dormant
adventitious buds in the lignotuber will develop. The resulting re-
growth will be as a multi-stemmed tree rather than a single trunk.

• Spines, thorns and prickles are modified sharp structures found on
certain plants. A spine is a modified leaf, such as found on cacti.
• Prickles are modified hairs, for example, rose prickles.
• A thorn is a modified shoot. It develops from a bud in a leaf axil. In
some species this bud develops into a short shoot with its own
leaves and with the terminal bud replaced by a strong, sharp thorn.
It is suggested that thorns are defence mechanisms developed
especially by plants growing in sandy soil which does not provide
adequate resources for fast regeneration. Plants with thorns include
lemon trees and bougainvillea.
• Prickles develop out of the surface cells of a stem. They are found
along the internodes, not just at a node as with spines and thorns.
As already mentioned, roses bear prickles, not thorns.

• A tendril is a structure modified for climbing. Tendrils may develop from
leaflets, buds, and from the central stalk-the rachis- of an inflorescence.
Remember that an inflorescence is a cluster of flowers on a stem.
• Tendrils from buds develop in the leaf axil, as seen in passionfruit.
Peas have tendrils that develop from modified leaves that emerge from
a leaf node.
• The tendrils of grape vines are also modified buds. The leaves are
arranged alternately along the stem with a bud developing from the
same node. Some of these floral buds develop into bunches of grapes
while others are modified to develop into tendrils to support the vine.
• The internodes of some thin, flexible stems also twine around support
to climb. Jasminum polyanthum, pumpkins and cucumbers are twiners.

• Modified stems can be identified by the following characteristics they
possess:
• A leaf-like structure such as scale leaves or leaf bases or the scars
where they have been
• Nodes and internodes
• A terminal bud
• Axillary buds in the axils of leaf-like structures

Advantages of food storage in modified
stems
• Food storage in modified stems such as rhizomes, corms and stem
tubers makes it possible for there to be very rapid growth under
favourable conditions, such as the warmer, longer days of spring.
Plants that can grow early are then able to flower and set seed
before there is competition from other plants for water, mineral salts
and light. This can be used to manís advantage, for example
growing a crop of potatoes from pieces of potatoes containing eyes,
rather than growing them slowly from seed. It also means the same
strain of potato can always be produced.
• Plants with underground food stores are able to be persistent, that is
they can survive and grow even if their aerial shoots are destroyed
for some reason. This does have the disadvantage of making weeds
with underground food stores extremely difficult to eradicate, such
as oxalis.

Non-modified stems for propagation
• Modified stems enable vegetative reproduction to occur in nature.
Man can replicate plants vegetatively by taking cuttings of stems
which would not normally reproduce.
• Softwood cuttings are the young, soft tip shoot growth. Lavender,
sage and rosemary will propagate readily from soft tip cuttings.
• Semi-hardwood cuttings are taken from young growth several
months old and just beginning to mature. Shrubby plants such as
hibiscus and camellia are propagated in this way. Rosemary can be
propagated in this manner.
• Hardwood cuttings are taken from mature growth a year old, often
from a deciduous plant. Rootstocks of roses and fruit tress are
obtained this way. The bay tree is also propagated from hardwood
cuttings.

Summary
Today we have covered;
Stems
Roots

Next Session
We will cover:
• Leaves

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 2

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