Download Artificial reproduction/propagation

Artificial reproduction/propagation
This technique is the creation of new life by other than the natural means
available to an organism. Examples include artificial insemination, in
vitro fertilization, cloning and embryonic splitting, or cleavage.
Cutting plants' stems and placing them in compost is also a form of
artificial reproduction. We can grow many plants from one plant by using
the man-made methods. The process of growing many plants from one
plant by man-made methods is called artificial propagation of plants. A
number of methods of artificial propagation of plants are used in
agriculture (for raising crops), and horticulture (cultivation of vegetables,
fruits and flowers). The three common methods for the artificial
propagation of plants are:
1. Cuttings,
2. Layering, and
3. Grafting.
We will now describe all these methods, one by one. Let us start with the
cuttings method for the artificial propagation of plants.
1. Cuttings :
A small part of a plant which is removed by making a cut with a sharp
knife is called a 'cutting'. A cutting may be a piece of stem, root or even
a leaf. While making a cut, care should be taken to see that there are some
buds on it.
In this method, a cutting of the parent plant (say, of stem or shoot) having
some buds on it is taken and its lower part is buried in the moist soil. After
a few days, the cutting develops roots; shoot, and grows into a new plant.
Cuttings are a means of asexual reproduction in plants. The new plant
formed from a cutting is exactly similar to the parent plant.
The plants like rose, Bougainvillea, Chrysanthemum, grapes, sugarcane,
bananas, and cactus, etc. can be grown by means of cuttings. For example,
rose plants and chrysanthemums are propagated (or reproduced) by
means c cuttings from stems (or shoots) as follows: A piece of stem (or
side shoot) having bud is cut from an existing rose plant with the help of
a knife. The lower part of this cutting is buried in moist soil. After a few
days, the end of cutting buried in soil develops roots and later on grows
to become a new rose plant. An advantage of cuttings method is that by
using this method we can produce many new plants from just one plant
quickly, without waiting for flowers and sexual reproduction.
2. Layering :
In this method, a branch of the plant is pulled towards the ground and a
part of it is covered with moist soil leaving the tip of the branch exposed
above the ground. After some time, new roots develop from the part of
the branch buried in the soil. The branch is then cut off from the parent
plant. The part of the branch which has developed roots grows to become
a new plant (just like the parent plant). Jasmine plant (chameli) is
propagated or produced by the layering method.
We can see from that one left side branch and one right side branch of the
parent jasmine plant have been buried in moist soil. The parts of branches
which are buried in soil grow their own roots. When this happens, the
branches of the parent plant connecting the newly formed plants are cut
off so that the newly formed plants may grow on their own and develop
into mature plants (like the parent plant).
Many plants like strawberry and raspberry are propagated by the natural
layering method. The natural layering occurs because these plants form
runners (which are soft horizontal stems running above the ground).
Wherever the ends of such runners touch the ground, new plants are
formed at those places. In this way, many more strawberry or raspberry
plants are formed from" the parent plant in a natural way.
The layering method is used for the propagation (or reproduction) of
plants like : Jasmine, Strawberry, Raspberry, Lemon, Guava, Hibiscus
(China rose), Bougainvillea and many slender ornamental plants.
3. Grafting :
Grafting is a method in which the cut stems of two different plants (one
with roots and other without roots) are joined together in such a way that
the two stems join and grow as a single plant. This new plant will have
the characteristics of both the original plants.
(i) The cut stem of a plant (or tree) having roots (and fixed in soil) is
called stock. Stock is the lower part of a plant (or tree) having the roots.
(ii) The cut stem of another plant (without roots) is called scion. Scion is
the upper part of a plant which may have leaves on it (but no roots).
In carrying out grafting, two plants (or trees) are chosen which are to be
used as scion and stock. First, the stem (or branch) is removed from the
plant chosen to be made scion (for its desirable characteristics) by making
a slanting cut. This gives us the scion with a slanting cut. The stem of
second plant (or tree) to be used in grafting is also cut in a slanting way.
The lower part of this plant (or tree) is stock. It has also a slanting cut.
The scion is placed over the stock. The cut surfaces of the scion and stock
are fitted together and bound tightly with a piece of cloth and covered
properly with polythene sheet (so as to prevent harmful infection by
bacteria or fungus, and loss of water and plant sap from the cut and joined
ends of stock and scion).
While joining the scion to the stock, care should be taken to make sure
that the cambium layer of scion is in contact with the cambium layer of
stock (because the cambium layer in the stem is responsible for growth).
The cut soon heals and the stock and scion of two plants grow together
and become one plant. The scion continues to produce its original leaves,
flowers and fruits but it gets water and minerals for making food from the
chosen stock. So, the fruits will have the characteristics of both the plants
(from which scion and stock have come).
Grafting is used to breed fruit trees and flowering bushes. Apple, peach,
apricot and pear trees are often grafted. We will now describe some of
the advantages of the grafting method of artificial propagation.
(i) Grafting enables us to combine the most desirable characteristics of
the two plants (scion and stock) in its flowers and fruits.
(ii) By grafting method, a very young scion (shoot part of a plant) .can be
made to flower and produce fruits quite fast when it is grafted to the stock
(stem having roots) of a mature plant.
(iii) It enables us to obtain flowers and fruits having different desired
characteristics by grafting scions from different varieties of plants on the
same stock. Many varieties of mango have been produced by grafting
method.
(iv) Grafting can be used to produce varieties of seedless fruits.
Artificial vegetative propagation is usually used for the propagation (or
reproduction) of those plants which produce either very few seeds or do
not produce viable seeds. Some examples of such plants which are
reproduced by artificial vegetative propagation methods are: Banana,
Pineapple, Orange, Grape, Rose, etc.
Cutting (plant)
A magnolia stem cutting has been coaxed to form new
roots, and is now a complete plant.
A plant cutting is a piece of a plant that is used
in horticulture for vegetative (asexual) propagation.
A piece of the stem or root of the source plant is
placed in a suitable medium such as moist soil. If
the conditions are suitable, the plant piece will
begin to grow as a new plant independent of the
parent, a process known as striking. A stem cutting
produces new roots, and a root cutting produces new stems. Some plants
can be grown from leaf pieces, called leaf cuttings, which produce both
stems and roots. The scions used in grafting are also called cuttings.
Technique[edit]
Softwood cuttings of elm (Ulmus) are kept
under a water mist to prevent them from
drying out while they form roots.
Cuttings from a variety of succulents.
Some plants form roots much more easily
than others. Stem cuttings from woody plants are treated differently,
depending on the maturity of the wood:
 Softwood cuttings come from stems that are rapidly expanding, with
young leaves. In many species, such cuttings form roots relatively
easily.
 Semi-hardwood
cuttings come from stems that have completed
elongation growth and have mature leaves.
Hardwood cuttings come from fully matured stems, and are often
propagated while dormant.
Most plant cuttings are stem pieces, and have no root system of their own,
they are likely to die from dehydration if the proper conditions are not
met. They require a moist medium, which, however, cannot be too wet
lest the cutting rot. A number of media are used in this process, including
but not limited to soil, perlite, vermiculite, coir, rock wool,expanded clay
pellets, and even water given the right conditions. Most succulent cuttings
can be left in open air until the cut surface dries, which may improve root
formation when the cutting is later planted.
In temperate countries, stem cuttings may be taken of soft (green or semiripe) wood and hard wood which has specific differences in practice.
Certain conditions lead to more favorable outcomes for cuttings; timing,
size, location on the plant, and amount of foliage are all important.
In temperate countries, stem cuttings of young wood need to be taken in
spring from the upper branches, while of hardened wood need to be taken

in winter from the lower branches. Common bounds on the length of stem
cuttings are between 5–15 centimetres (2.0–5.9 in) for soft wood and
between 20–25 centimetres (7.9–9.8 in) for hard wood. Soft wood
cuttings do best when about two thirds of the foliage removed, while hard
wood stem cuttings need complete foliage removal.
The environment for cuttings is generally kept humid—often attained by
placing the cuttings under a plastic sheet or in another confined space
where the air can be kept moist—and partial shade to prevent the cutting
from drying out. Cuttings in the medium are typically watered with a
fine mist to avoid disturbing plants. Following the initial watering, the
aim to keep the soil moist but not wet and waterlogged; the medium is
allowed to almost dry out before misting again.
A rooting hormone may be administered to "encourage" growth and
maturity in plants determined[clarification needed] to be unlikely to grow.
Though not essential, several compounds may be used to promote the
formation of roots through the signaling activity of plant hormone auxins,
and is helpful with especially hard plantspecies.[clarification
needed] Among the commonly used chemicals is indole-3-butyric
acid (IBA) used as a powder, liquid solution or gel. This compound is
applied either to the cut tip of the cutting or as a foliar spray. Rooting
hormone can be manufactured naturally, such as soaking the yellowtipped shoots of a weeping willow tree in water or to preparing a tea from
the bark of a willow tree. Shoots or bark do better when soaked for 24
hours prior to using.[1] Honey, though it does not contain any plant
hormones, can also aid in rooting success through its antiseptic
quality.[citation needed]
Types of cuttings[edit]
For cuttings used in viticulture, see Propagation of grapevines.
Scheme of appropriate type of stem cuttings according to season, based on
several[which?] sources.[2] Key: eq.:equinox, sol.: solstice, HW: hardwood,
SR: semi-ripe, SW: softwood.
Many vegetative parts of a plant can be used. The most common methods
are:
 Stem cuttings, in which a piece of stem is part buried in the soil,
including at least one leaf node. The cutting is able to produce new
roots, usually at the node.
 Root cuttings, in which a section of root is buried just below the soil
surface, and produces new shoots
 Scion cuttings are used in grafting.
 Leaf cuttings, in which a leaf is placed on moist soil. These have to
develop both new stems and new roots. Some leaves will produce one
plant at the base of the leaf. In some
species, multiple new plants can be
produced at many places on one leaf, and
these can be induced by cutting the leaf
veins.
Although
some
species,
such
as willow, blackberry and pelargoniums can be grown simply by placing
a cutting into moist ground, the majority of species require more
attention. Most species require humid, warm, partially shaded conditions
to strike, thus requiring the approach above to be followed. Particularly
difficult species may need cool air above and warm soil. In addition, with
many more difficult cuttings, one should use the type of cutting that has
the most chance of success with that particular plant species.[3]
Improving results[edit]
Rose cuttings under plastic bottle greenhouse
Softwood stemcuttings of Buxus sempervirens
There are ways of improving the growth of stem cutting propagations.
Intensifying light allows cuttings to root and sprout faster, though the heat
thus
generated
could
cause
the
propagation
material
distress.[4] Azalea cuttings can be mildly heated in water to disinfect it
from the fungus pathogen Rhizoctonia, and this could potentially be used
for other plants.[5]
Providing the right soil[edit]
Depending on the type of soil being used, several additives may need
adding to create good soil for cuttings. These additions may include:
chalk; to increase the pH-value of the soil; a pH of 6-6.5 is to be
maintained
organic substance/humus; to increase nutrient load; keep to a bare
minimum though
sand or gravel; to increase the soil's water permeability
For example, with plain potting soil, a third of the container should be
filled with sand, to make suitable soil for cuttings.
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
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Providing the right humidity[edit]
A white plastic greenhouse, used to keep the cuttings humid
Although several options can be used here, usually semi-white plastic is
used to cover the cuttings. The soil below and from the cuttings
themselves is kept moist, and should be aerated once in a while to prevent
formation of molds. A plastic bottle can be used as a small greenhouse to
provide the right humidity level.