Conservation of
Medicinal Plants
Objectives
At the end of this
lecture, student will be able to
• Discuss the objectives and methods of conservation of
medicinal plants
• Discuss methods of in situ and ex situ conservation of
medicinal plants
Conservation
of Medicinal Plants
• All cultures from ancient times to the present day have
used plants as a source of medicines
• As per WHO, 80% of the world’s population depend on
traditional medicine for their primary health care needs
• The greater part
of traditional therapy
involves the use
of plant extracts or their active
principles ignoring the fact that these plants will not be available on a
continuing basis
• However, one need to ensure concerted efforts to make the plants available on a continuing
basis in spite of facing the following threats
• Threats posed include increasing demand, a vastly
increasing human population and extensive destruction of plant-rich habitats
such as the tropical forests, wetlands, Mediterranean ecosystems and parts of
the arid zone
• Today many medicinal plants face extinction or severe
genetic loss, but detailed information is lacking
• For most of the endangered medicinal plant species no
conservation action has been taken to ensure sufficient materials to the gene
banks
• Now a days too much emphasis has been put on the potential
for discovering new wonder drugs, and too little on the problems involved in
the use of traditional medicines by local populations
• In the light of this situation, WHO, IUCN, WRI and WWF in
consultation with each other have framed certain guidelines in 1988 to conserve
medicinal plants
• The aim of these WHO Guidelines is to provide a framework
for the conservation and sustainable use of plants in medicine
Conservation of Medicinal
Plants
In situ conservation
Ex situ conservation
CONSERVATION
OF POPULATIONS OF MEDICINAL PLANT SPECIES IN NATURAL HABITATS
In situ
conservation
• In situ conservation means ensuring that the populations
of species of plants and animals continue to grow and evolve in the wild – in
their natural habitats
• in situ conservation is achieved by
• setting aside areas as nature reserves and national parks
(collectively termed “Protected Areas”)
• by ensuring that as many wild species as possible can continue
to survive in managed habitats, such as farms and plantation forests
In this regard the
policy creation includes
• Identifying which of the protected areas are most
important for medicinal plants;
• Targets and techniques for recording and monitoring
medicinal plants in protected areas;
• Techniques and procedures for collection of medicinal
plants within protected areas;
• A legal mechanism to ensure that benefits reach local
people
• Training of park managers about medicinal plants,
including their uses;
• Public education about medicinal plants in protected areas
The methods adopted
includes the following assessments
• The Parks Department should assess the extent to which the
protected areas system covers the medicinal plants of the country
• It should then create new protected areas and extend
existing ones to ensure that all the medicinal plants of the country are
conserved
• The Parks Department should devise economic and social
incentives for maintaining natural habitats and wild species
• Park managers should ensure that the conservation and
exploitation of medicinal plants are incorporated into site management plans
• Species that are heavily depleted by over-collection
should be re-introduced into areas where they once grew wild
• This can be achieved by park departments extending their
help to encourage the process of cultivation of the medicinal plants
• They can also provide seeds and saplings for local people,
and can even set up small medicinal plant nurseries in suitable areas
Ex situ
conservation
• Ex situ conservation means, conservation of the medicinal
plants outside their habitat unlike in situ
• Ex situ conservation has the advantage that it is usually
easier to supply plant material for propagation, for re-introduction, for
agronomic improvement, for research and for education purposes
• The disadvantages of ex situ conservation are that the
sample of the species conserved ex situ may represent a narrower range of
genetic variation than that which occurs in the wild
• Species conserved ex situ can also suffer genetic erosion
and depend on continued human care
• For this reason, ex situ conservation must not replace,
but should complement, in situ conservation
• Most important of all, ex situ conservation should not be
used as a reason for failing to safeguard representative samples of the
medicinal plants and their habitats in nature
• Priority for ex situ conservation should be given to
species whose habitats may have been destroyed or cannot be safeguarded
• It should also be used to bulk up populations of depleted
or even locally extinct plants for restocking in nature
• In some countries it may be appropriate to conserve all
medicinal plants ex situ
• Relating to ex situ conservation of medicinal plants, it
is particularly important to conserve a broad genetic base, to permit
improvement in the cultivated material
• When collecting the plant material for ex situ
conservation, care should be taken not to put the survival of the wild
population at risk
Techniques adopted
for conservation
1. Germplasm
technique
• Germplasm technique means use of seeds in live gene banks
• The advantage of this in vitro or reduced growth storage
method includes
• The need for lesser space in growth rooms for maintaining
thousands of genotypes
• Absence of diseases and pest attack in culture vessels
• eliminates the need for long and frustrating quarantine
procedures during movement and exchange of germplasm
Disadvantages of
Germplasm technique
• Some crops do not produce viable seeds
• Some seeds remain viable for a limited duration only and
are recalcitrant to storage
• Seeds of certain species deteriorate rapidly due to seed
borne pathogen
• Some seeds are very heterozygous not suitable for
maintaining true to type genotypes
2. Cryopreservation
technique
• “Cryopreservation” is defined as the viable freezing of
biological material and their subsequent storage at ultra-low temperatures
(-196C)”using liquid nitrogen
Cryopreservation
procedures
• Three different procedures have been used for
cryopreservation of plant cells:
A. Two-step freezing
B. Vitrification
C. Encapsulationdehydration.
• Two-step freezing:
incubation of cells in a mixture of
cryoprotectants (total concentration of 1–2M), which causes moderate
dehydration of the cells, followed by a slow freezing step (for example,
1°C/min down to app –35°C).
• Vitrification:
based on severe dehydration at non-freezing temperatures by direct exposure to
concentrated cryoprotectants (total concentration ranging from 5–8M), followed
by rapid freezing
• Encapsulation-dehydration:
Cells are encapsulated in alginate beads, cultured on medium with increased
sucrose concentration, air-dried using silica gel or the airflow of a flow
cabinet and directly transferred to liquid nitrogen
3. Tissue culture
technique
• Plant tissue culture is a practice used to propagate
plants under sterile conditions, often to produce clones of a plant
• Different techniques in plant tissue culture may offer
certain advantages over traditional methods of propagation, including:
• The production of exact copies of plants that produce
particularly good flowers, fruits, or have other desirable traits.
• To quickly produce mature plants the production of
multiples of plants in the absence of seeds or necessary pollinators to produce
seeds.
• The regeneration of whole plants from plant cells that
have been genetically modified.
• The production of plants in sterile containers that allows
them to be moved with greatly reduced chances of transmitting diseases, pests,
and pathogens
• The production of plants from seeds that otherwise have
very low chances of germinating and growing, i.e.: orchids and nepenthes.
• To clean particular plant of viral and other infections
and to quickly multiply these plants as ‘cleaned stock’ for horticulture and
agriculture
Tissue culture
techniques
A. Cell suspension technique
B. Zygotic embryo technique
C. Adventitious bud technique
D. Gene bank technique
Cell suspension
Technique:
• Pre-treatment:
The cell suspension is inoculated at high density into standard medium
containing 6% mannitol and cultured under standard conditions.
• The suspension is harvested when the cell will be dividing
rapidly and chilled on ice.
• Cryopreservation:
A double strength cryoprotectants solution (1M dimethylsulfoxide (DMSO) + 1M
glycerol + 2M sucrose) was prepared and one volume ofcryoprotectants solution
is added to one volume of cell suspension and the mixture is incubated on ice
for 1hr.
• The mixture is dispensed as 1 ml aliquots and the ampoules
are cooled until they reach – 35oC
• Storage: The
ampoules are stored in or over liquid nitrogen.
• Thawing: The
ampoules are dropped into sterile water at about 40oC with a ratio of 4
ampoules to 150 ml water
• Re- growth: The
cells in suspension are transferred to several layers of 5 cm filter paper on
the surface of a 9 cm agar plate containing a growth medium and are incubated
under standard conditions.
• The cells and upper layers of filter paper are then
transferred to fresh medium, until after 5 – 6 days, the cells alone are
transferred to agar medium
Zygotic embryos
Technique:
• Pre-growth: The
embryos are excised aseptically from the seeds then in an open petridish, are
exposed to a sterile airflow in a laminar flow cabinet for 3h
• Cryopreservation:
The embryos contained in plastic ampoules are immersed in liquid nitrogen
• Thawing: The
plastic ampoules are transferred to a water bath at 37 – 38oC then
placed on moist sterile filter paper in petri dishes for 10 days
• Re growth:
After 10 days in the absence of medium the embryos are added to a standard
growth medium to stimulate growth into plants
Adventitious buds
technique:
• Pre growth:
uniformed nodes (5 mm in length) containing an adventitious bud are removed
from stem sections of plants
• Nodes are placed on agar medium containing 0.7 M sucrose
and incubated under standard conditions or two days then transferred to a nylon
membrane contained in a dish.
• Cryopreservation:
Nodes are transferred to plastic ampoules then immersed in liquid nitrogen and
stored under liquid nitrogen.
• Thawing: Nodes
are thawed in a water bath at 25oC
• Re-growth: Because of their size, nodes can be
transferred individually to a standard growth medium and the adventitious bud
is stimulated to develop as a shoot
Gene bank
technique
• A Gene bank conserves genetic wealth through seeds,
vegetative propagules, tissue culture, embryos, gametes or cells, DNA etc
• The importance of gene banks has been recognized since
long and they have been in existence in various parts of the world for a long
time
• The purpose of the Gene Bank
• To undertake and promote long-term conservation of plant
genetic resources employing ex-situ conservation for seeds, in-vitro cultures
and cryopreservation techniques and assist in in-situ conservation efforts
• To act as the repository of collected material, elite
material and endangered material, as also a regional repository of duplicate
collections as a part of the global system
• To monitor and maintain the existing collections,
facilitating the organisation of regeneration program
• To ensure availability of exotic and indigenous germplasm
through periodic seed increase for evaluation, utilization and conservation
• To conduct research related to medium and longterm
conservation of germplasm
• To develop and operate a database and information network
system on forest genetic resources
• To
support/assist in organization
of post-graduate education
and short/medium-term training courses on Forest germplasm activities at
national, regional, and international levels.
Summary
• All cultures from ancient times -plants as a source of
medicines
• WHO- 80% of the world’s population depend on traditional
medicine
• Threats -increasing demand, a vastly increasing human
population and extensive destruction of plant-rich habitats
• WHO, IUCN, WRI and WWF – guidelines in 1988 to conserve
medicinal plants
• In situ and ex situ conservation
• In situ conservation – Natural habitat, protected areas,
national parks
• Ex situ conservation
• Germ plasm technique – use of seeds in live gene banks
• Cryopreservation technique – Liquid nitrogen, -1960C,
two step freezing, vitrification and encapsulation-dehydration
• Tissue culture technique – Cell suspension, zygotic
embryo, adventitious bud technique