Extrinsic factors affecting cultivation and collection of medicinal plants-By Dr. Preeti Verma

Prepared by,
Dr. Preeti D. Verma
Asst. Professor, Department of Pharmacognosy
L. M. College of Pharmacy, Ahmedabad.
CULTIVATION, COLLECTION,
PROCESSING AND STORAGE OF
CRUDE/HERBAL DRUGS
1

Wild
Species
Cultivated
Species
Crude Raw
Material for
Herbal
Drugs
2Prepared by Dr. Preeti Verma for academic purpose only, LMCP
• Some cases: Pharmacopoeias specify cultivation
methods for the medicinal and aromatic plants.
Such as Fennel, ginger, cinnamon & opium
• Opium: only official growers may legally
produce herbs.
• Other herbs: Senna, Tragacanth, etc, may be
collected from wild or cultivated species.

Disadvantages of Wild plant Collection
• Sparse distribution e.g. Sceletium tortuosum
• Potentially difficult to transport herb to area of
processing
• Difficult access (e.g. Forests, Mountains etc)
• Collector ignorance  admixture of other plants,
collection of undesired plant parts or stage of
development or during an incorrect season  loss of
medicinal activity.
• Damage to natural environment  Extinction of a
spp.

Advantages of Cultivated Herbs
1. It ensures Quality and Purity of Medicinal plants. Hence,
collection of crude drugs from cultivated plants give Better
therapeutic quality.
• Only desired spp. are collected  uniform quality.
• Herb collectors – trained
• Better control of soil quality, pests & plant disease.
• Collection, transport & access to processing facilities is improved.
2. Ensures regular Constant & Regular (Controlled) Supply of crude
drugs.
3. Leads to Industrialization (e.g. Tea and Poppy).
4. Permits application of Modern Technological aspects, like
Mutation, Polyploidy & Hybridization.

Plant Variation
• Ideally: correct cultivation & harvesting is
aimed at producing high quality, healthy herbs.
• Complicated: All natural products: variation
between individual plants.
– Plant morphology (size, etc)
– Content of medicinal actives (active constituents)
– WHAT BRINGS ABOUT THIS VARIATION?

Variation Factors
– Environmental (Exogenous) Factors
(Geographical, seasonal, intra-day variation, etc)
– Genetic (Endogenous) Factors
– Post-Cultivation Factors (Processing methods –
e.g. Drying & Storage Methods, etc)

Factors affecting Cultivation of Medicinal Plants
Factors
Extrinsic/
Exogenous
Intrinsic/
Endogenous

1. Altitude & Latitude
2. Temperature
3. Water
4. Edaphic Factor: Soil &
Soil Fertility
5. Fertilizers and Manure
6. Climate/ Season
7. Wind
8. Light, Length of Day &
Radiation
9. Propagation method
10. Biotic Factors: Pests,
Weeds, etc.
11. Allelopathy
I. Extrinsic/Exogenous Factors

II. Intrinsic/Endogenous Factors
1. Plant Growth Regulators (Hormones)
2. Polyploidy
3. Mutation
4. Hybridization
5. Chemical Races (Chemodemes)

I.
Extrinsic Factors

1. ALTITUDE & LATITUDE

1. ALTITUDE & LATITUDE
 Tea, Cinchona and Eucalyptus are cultivated at an altitude of
1000-2000 m, While Senna can be cultivated at lower level.
 In case of Cinchona succirubra, the plants grow well at low levels
but produce practically no alkaloids.
 The bitter constituents of Gentiana lutea increase with altitude.
 The alkaloids of Aconitum napellus and Lobelia inflata decrease
with altitude.
 The oil content of Thyme and Peppermint decrease. Other oil
producing plants may reach a maximum at certain altitudes.
12
Prepared by Dr. Preeti Verma for academic purpose only, LMCP

1. ALTITUDE & LATITUDE (contd.)
 Flower production is also affected by location (altitude):
E.g. Pyrethrum gives the best yields of flower-heads and pyrethrins
at high altitudes, on or near the equator. It is therefore produced
in East Africa and South America.
13

Examples of medicinal and aromatic plants indicating the altitude for their
successful cultivation:
Plant Altitude for Drug Cultivation (meters)
Tea 1000-1500
Coffee 1000-2000
Cinchona 1000-2000
Camphor 1500-2000
Cardamom 600-1600
Cinnamon 250-1000
Saffron upto 1250
Clove upto 900
14

2. TEMPERATURE

2. TEMPERATURE
• Major factor controlling the growth, development and
metabolism of plants.
• It control the rate of photosynthesis and rate of respiration
in the plants.
• Each plant is specialized to adapt to its native natural
environment.
• Plants are frequently able to exist in a considerable range
of temperature.

Plant
Optimum temperature of drug
cultivation (0F)
Tea 70-90
Coffee 55-70
Cinchona 60-75
Examples of ranges of temperature necessary for luxuriant
growth of certain medicinal plants:

18
• But, Excessive temperature,
as well as, frost affects the
quality of medicinal plants
adversely.
E.g. Camphor and Coffee cannot withstand frost.

Prepared by Dr. Preeti Verma for academic
purpose only, LMCP
19
E.g.
 Formation of Volatile oils appear to be enhanced at higher
temperatures, although very hot days may lead to an
excess physical loss of oil.
 Growing peppermint in shade rather than the sun.

E.g.
 For saffron cultivation, we need an explicit climatological summer
and winter with temperatures ranging from no more than 35oC or
40oC in summer to about –15 oC or –20 oC in winter. That's
why saffron can be cultivated in dry, moderate and continental
climate types but not in tropical or polar climate types. Its Maximum
vegetative growth takes place during winter. Such weather is
prevalent in parts of Karnataka, Himachal Pradesh and Jammu and
Kashmir.
20

E.g.
 The mean optimum temperature for Nicotine production in
Nicotiana rustica is 20o C (lower at 12 oC and at 30 oC).
21

E.g.
 Fixed oils produced at low temperatures contain fatty acids with a
higher content of double bonds than those formed at higher
temperatures.
22

3. WATER

3. WATER
• Paramount requirement in the physiology of plant.
• Universal Solvent: Dissolves all the mineral content
in soil & acts as a medium by which solutes enter the
plant.
• Raw material in Photosynthesis.
• Maintains temperature & affects the rate of
biochemical reactions.

Sources of Water:
1. Rainfall or Irrigation
2. Atmospheric moisture or Humidity.
25

(A) Rainfall or Irrigation:
Important effects of rainfall on vegetation must be considered
in relation to:
• annual rainfall
• its distribution throughout the year.
• effect on humidity
• effect on water holding properties of the soil.
26

27
Irrigation

E.g.
 Variable results : Production of volatile oils under different
conditions of rainfall are sometimes coupled with the
development of glandular hairs.
 Ginger : requires heavy rainfall.
 Senna: cannot tolerate heavy rainfall.
 Cardamom: 150-600 cm.
 Cinnamon: 200-300 cm.
 Continuous rain can lead to a loss of water soluble substances
from leaves and roots by leaching [e.g. in some plants producing
alkaloids (esp. of Solanaceae family), glycosides and volatile oils].
This could account for low yields of some active constituents in
wet seasons from plants whose general condition appears to be
good. 28Prepared by Dr. Preeti Verma for academic purpose only, LMCP

(B) Atmospheric moisture or Humidity
• Invisible water vapour content of the air is usually
expressed as Humidity.

• As Humidity increases : Rate of Evaporation
(Transpiration) decreases (the vapor pressure between
the atmosphere and moist surface is lowered).
• E.g. Some desert plants take water directly from the air
when humidity rises above 85%.
• Eg. Pyrethrum requires dry weather for cultivation (no
humidity)

 Except the Xerophytic plants like Aloe, Acacia, Ephedra,
etc., most of the plants need either proper arrangements for
irrigation or sufficient rainfall for their favourable
development.
E.g.
With Cassia angustifolia (Tinnevelly senna),
Short term drought increases concentration of Sennosides A &
B, but in the longer term causes loss of leaf biomass.

4. Climate

Climate
 Climate : Tropical , Sub-tropical , Temperate, Cool and Cold.
 Cultivation of medicinal plants in climate different from that of
their natural habitats presents several problems.
33
E.g. Astragalus species which
yields Tragacanth gum
ceases to produce gum when
transferred to Northern region.

 But many a times some species grow and
develop satisfactory under new climatic
conditions. E.g. Papaver.
 Digitalis produces higher content of
glycosides when cultivated in Himalaya
than the original plants grown in
Germany.
34

Collection Season
• Active constituents of herbs are affected by the
seasons (due to climate, rainfall, day-length etc).
• Medicinal plants should be therefore collected in the
season in which their active constituents are
highest.
• E.g. Rhubarb (laxative) contains high anthranol in
winter. This is then oxidized to anthroquinones in
summer.

5. Wind

Wind: Important ecological factor.
Effects:
37
Pollination
Cause Mechanical Injury:
Drives dust, snow & cause abrasive
effect on plants.

purpose only, LMCP
38
Increase transpiration (Modifies Humidity)

Distribute weeds
39

Source of many diseases like rust.
40

6. Light, Length of Day
& Radiation

 Development of plants vary in amount and intensity they
require.
 The wild grown plants meet the required conditions & so
they grow well. But during cultivation, we have to fulfill
those requirements.

 In cloudy weather, amount of carbohydrates produced in leaf
decreases since photosynthesis is light dependent.
 The quantity of active constituents in some medicinal plants is
affected.

E.g.
 Cinchona give higher content of alkaloids in full
sunshine.
 Long exposure of Datura stramonium var tatula to
intense light increase hyoscine content quickly.
 Leaves of Belladonna grown in sunshine contain 3-4
times more alkaloids than the plant grown in shade.

Day-length
• Mentha piperita (Peppermint) :
– Long day: menthone, menthol & menthofuran traces
– Short day: menthofuran = main component
• Some spp: produce more active constituents at night
E.g. Nicotiana (Tobacco)
• Some spp: produce more active constituents in morning
E.g. Opium
• Foxglove produces more actives during the day than at night.

Radiation
• Type of radiation plants receive is also important.
• E.g. Ocimum basilicum – plants grown in glass houses
have less phenols & terpenoids in the leaves (flavonoids,
volatile oils).

7. EDAPHIC FACTOR:
SOIL & SOIL FERTILITY

EDAPHIC FACTORS: SOIL & SOIL FERTILITY
Defn: Soil is the superficial layer of the earth crust and
typically made up of Minerals, Organic materials as well as
Living organisms.

• It is the mineral matter, which makes a lot of difference in
various forms of soil. Mineral matter may be coarse
gravel, coarse sand or in the form of finest particles of
clay and silt.
• Air and water give rise to pores.
• Dark, organic matter in the
soil that forms when plant
and animal matter decays,
constitute the organic
matter/ humus (contains
useful nutrients)

Clay is one of the highly withered portions of the soil,
consisting of finest particles.
This provides the soil adhesive and cohesive properties
and also hold plant nutrients with the result that
nutrients are not lost through leaching.
Soil fertility: The capacity of soil to supply plant nutrients
in quantities and proportions required and
to provide a suitable medium for plant growth
is known as soil fertility.

Functions:
 Soil is the most important natural resource as it
supports growth of all plants. Soil provides:
1. Mechanical anchorage
2. Water supply
3. Essential plant Food elements/ nutrients
 Plants absorbs minerals from the soil and convert
them in to the complex organic compounds such as
cellulose, lignin, starch, sugar, fat and proteins.

Plant growth depends upon:
o Nature of soil particles
o Physical arrangement of soil particles
o Organic matter content of soil and
o Living organisms in soil.
 Plants and soil are strongly influenced by each
other.

Types of Soils
I. Depending upon the size of mineral matter (soil particles):
Type of soil Particle size (diameter)
1 Fine clay Less than 0.002 mm
2 Coarse clay or silt 0.002 to 0.02 mm
3 Fine sand 0.02 to 0.2 mm
4 Coarse sand 0.2 to 2 mm

Prepared by Dr. Preeti Verma for academic purpose only, LMCP 54

Type of soil Percentage of Clay
1 Clay More than 50% of clay
2 Loamy 30 to 50% of clay
3 Silt loam 20 to 30% of clay
4 Sandy loam 10 to 20% of clay
5 Sandy soil More than 70% sandy soil
II. Depending upon the percentage of soil covered by clay :

III. Depending upon the percentage of organic matter in soil:
Type of soil Percentage of Organic Matter
1 Rich More than 1.5%, up to 5%
2 Intermediate 0.5% to 1.5%
3 Poor Less than 0.5%

IV. Other types of Soils:
Type of soil Content Characteristic
1 Calcareous
More than 20%
of lime
White
2 Laterite Fe, Al2O3 Reddish-brown to Yellow
3 Plat 80-90% Humus Dark, Porous & Light
Chalky soil  poor Digitalis growth

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58

Properties of Soils
A. Physical Properties : “Particle size”
• Variation in particle size results in different types of soil,
ranging from clay via sand to gravel.
• Particle size is one factor influencing Water-holding
capacity.
Some plants (e.g. Althaea officinalis) which produce
mucilage as a water retaining material contain
less mucilage when grown on soil with a high moisture
content. 59

• Water holding capacity of soil :
 Rainfall on coarse soil – penetrates almost immediately –
so that none is lost as runoff.
 The rate of infiltration of water into a heavy soil is very
slow because runoff is greater there.
• Relative resistance To root penetration:
Soil with high silt and clay retard the growth of root.
Basic soil type is modified by presence of Humus, Organic
fertilizers, Chalk, Lime, etc.
Fine soil is rich in humus. 60

B. Chemical Properties :
“pH of Soil”
 pH of soil decides favorable growth of plants and presence
of microorganisms.
 The maximum availability of plant nutrients is in the pH
range of 6.5 to 7.5.
 To bring the pH to Neutral :
Acidic soils can be limed or
Alkaline soils can be made acidic by adding sulphur
compounds. 61

E.g.,
• Particular species have their own soil pH tolerance.
E.g., Datura stramonium 6.0-8.0
• Tobacco, Cinchona, Tea and Potato grow well only in acidic
soils.
• Acidic soils are not suitable for leguminous plants due to poor
development of nodular bacteria.
• Acidic pH solubilizes more iron.
• Groundnut, Sunflower, Cotton and Rice grow better in alkaline
soils only.
• In Alkaline soils, phosphorus is converted to insoluble forms of
calcium phosphate and so it can not be made available to plants.
62Prepared by Dr. Preeti Verma for academic
purpose only, LMCP

“Nutrients of Soil” : Inorganic & Organic
For vegetative growth
Nutrients
Primary Secondary
N, P & K Mg, Ca, S
Trace elements: Cu, Fe, Na, Cl, Mn, B, Mb, Zn
E.g. Trace amount of Mg is necessary for successful production of
Digitalis purpurea. 63

C. Microbial and Microbiological Properties :
 Rhizobium, Azotobacter bacteria helps in Nitrogen
Fixation.
 Production of growth stimulating substances,
 Improvement of soil aeration.
 Proper mixing of nutrients.
 Agrobacterium are finding application in production of
Hairy root culture. 64

Soil fertility :
 It is the capacity of soil to provide nutrients in adequate
amounts and in balanced proportion to the plant.
 If cropping is done without fortification of soil with plant
nutrients, soil fertility gets lost.
 It is also diminished through leaching or erosion.
 Soil fertility can be maintained by crop rotation, by addition
of animal manure or by application of chemical fertilizers.

8. Fertilizers

Fertilizers :
Chemical compounds given to plants to promote growth;
Usually, applied through the soil for uptake by plant roots.
Basic needs for growth and development of plant are
• Water
• Mineral matters
• carbon-dioxide
• sunlight
Secondary
Metabolites, like
Alkaloids
Glycosides
Volatile oils
Resin
Primary
metabolites, like
sugar, proteins
and fixed oils

FERTILIZERS
Chemical fertilizers
& Synthetic fertilizers
Manures Biofertilizers

a. Manures :
Supply almost all nutrients
required by plant. So,
increase crop prouctivity.
E.g. Farm Yard Manure,
Castor seed cake, Neem and
Karanj seed cake, etc…
Biological origin Fertilizers

Castor seed cake

b. Biofertilizers :
Consist of different types of micro-organisms or lower
organisms that enriches the soil nutrients.
It mostly included those which fix the atmospheric nitrogen into
soil so that plant can use them.
E.g. Rhizobium, Azotobacter, etc.
Biological origin Fertilizers

c. Chemical fertilizers :
Primary nutrients (Macronutrients) like N , P & K.
Secondary nutrients (Micronutrients) are Mg, Ca, S etc..
Trace elements required are Cu, Mg, Fe, B, Mb, Zn etc
E.g . Urea and Potash.

73
• The effect of nitrogen containing nutrients on alkaloid
production has received considerable study (Solanaceous drugs,
Nicotiana, Opium); generally nitrogen fertilizers increase the
size of the plants and the amounts of alkaloids produced.
• Nitrogen fertilization has been shown to increase the silymarin
content of the fruits of Silybum marianum grown on fortified soil.
• The effect of potassium on alkaloid production shows no
consistent trend, but an interesting example is the increase in
putrescine (1,4-Diaminobutane) production in barley grown
on a potassium deficient medium, where it is possible that the
organic base has been formed to act as a substitute for potassium
ions.

74
Elements of Fertilizers: Functions, Deficiency Symptoms and Forms
Element
of
fertilizer
Function Deficiency
symptoms
Forms in which
available
Nitrogen 1. Promotes
vigorous
vegetative
growth
2. Builds up
plant
proteins and
chlorophyll.
3. Improves the
quality of leaf
drugs.
Pale yellow
appearance
of the plant,
shunted
growth, less
flowering,
pre-mature
shedding of
leaves
Compounds providing
nitrogen to the plant
(nitrogenous fertilizers)
are namely ammonium
sulphate, ammonium
chloride, ammonium
nitrate sulphate
(ANS), calcium
ammonium nitrate
(CAN) and urea

75
Phospho
rus
1. Being active
part of the
nucleus of the
plant cell, it is
essential for
plants growth.
2. Stimulant of
seed and fruit
formation and
also a
stimulant of
root
development.
3. Brings early
maturity of crops
1. Shunted
root growth.
2. Delays
maturity and
retards the
plant growth in
general
Phosphorous
containing
fertilizers (i.e.
Phosphatic
fertilizers) are of
two types-
Water soluble
phosphate: Single
super phosphate,
triple super
phosphate
Water insoluble
phosphate : Di-
calcium
phosphate.

76
Potassiu
m
1. Mainly responsible
for resistance of
plants against
disease and adverse
climatic conditions
2. Starch and sugar
formation is
enhanced and their
movements in plant
parts are
regularized.
1. Scorching and
browning of
tips of leaves.
2. Shrivelled
seeds, fruits,
shunted growth
Potassiu
m
chloride

77
Sulphur Synthesis of various proteins and oils,
formation of nodules and
chlorophyll.
Leaves turn to
yellowish-green
colour.
Water wettable
sulphur
Magnesium 1. Essential constituent of green
plant pigment chlorophyll.
2. Helps in carrying the
phosphorus and other plant
nutrients.
3. Essential for oil and fat formation
in plants.
1. Discoloration of
leaves and leaves
to curve upwards.
2. Susceptible to
fungal growth.
Magnesium
sulphate
Calcium 1. Promotes root formation and
responsible for hardness of plant
tissue.
2. Detoxicating agents for organic
acids in plants (by way of
formation of calcium oxalate
and calcium carbonate).
3. Translocation of carbohydrates
necessary for mitosis.
1. Drying of plants,
weaken the stem
structure, falling of
buds and
blossoms.
2. Root growth
retarded.
3. Hooking of the
leaf-tips.
Calcium
ammonium
nitrate(CAN)
Zinc Formation of growth hormones like
Indole acetic acid, essential part oa
most of enzymes, helps in utilization
of phosphorus and nitrogen in
plants.
1. Various symptoms
in different plants.
In general plants
are shunted.
2. Yellow colored
spots develop on
leaves.
Zinc sulphate
or Zinc oxide

78
Copper Activator for many plant activities
such as development, reproduction and
formation of vit. A.
Visible in certain
plants.. Brown spots on
citrus fruits, yellowing
of younger leaves in
maize.
Copper sulphate
Manganese Involved in plant respiration process,
catalyst for several enzymatic and
physiological reactions in plants. Also
in synthesis of chlorophyll.
Interveinal, chlorosis
leaves turn to yellow
color.
Manganese
sulphate
Iron Necessary for synthesis and
maintenance of chlorophyll, as
enzyme components
Interveinal, chlorosis of
young leaves,
yellowish green color
of leaves.
Ferrous sulphate
Boron Regulates potassium-calcium ratio
uptake and utilization of calcium in
plant. Involved in lignin, protein
synthesis.
Terminal buds turn to
light green in colour,
death of growing
plants.
Borax
Molybdenum For nitrogen utilization and nitrogen
fixation.
Mottling of lower
leaves, marginal
necrosis, in folding of
leaves.
Sodium
molybdate,
Ammonium
molybdate,
Molybdate
trioxide

9. Propagation

80

TYPES PROPAGATION
Sexual Asexual / Vegetative
(Through Seeds) (Through other vegetative parts)
E.g. Senna E.g. Bulb - Garlic
Neem Corm - Saffron
Tuber - Potato, Dioscorea
Rhizome - Ginger
Sucker – Mint
By grafting, cutting or tissue culture
Seedless fruits can be propagated vegetatively.
81

82

83
 Seeds are long-lived.
 Cheaper & comparatively easy to raise.

Propagation through other vegetative parts of plant:
E.g.
• Bulb – Garlic
• Corm – Saffron
• Tuber - Potato, Dioscorea
• Rhizome - Ginger
• Sucker – Mint
• Stem cutting- Rose
• Leaf - Bryophyllum

88

10. Biotic Factors:
Pests & Pest Control

Pests and pest control :
PEST : Any undesirable plant or animal species detrimental to
human or human concern (agriculture or livestock).
PESTICIDES : Chemicals of synthetic or natural origin, which are
effective in small concentration and used to control pests.
91

Pest types :
1. Insects :
E.g. Flea beetle, termites
(Odontotermis), Phytomyza
(leaf miner flies) are insects
which attack Mentha species.
Other insects are Ants,
caterpillar larvae, aphids,
grasshopper, etc.
92
Flea beetle Aphid
Caterpillar
GrasshopperPhytomyza

Pest types (contd.) :
2. Non-insects pests :
Vertebrates : rats, monkeys, birds, rabbit, etc…
Invertebrates : crabs, snails, nematodes, etc.
93
ROOT-KNOT DISEASE ON ROSES
CAUSED BY NEMATODE
Meloidogyne hapla
Chitwood
CARROT

Pest types (contd.) :
3. Bacteria, Viruses, Fungi, Moulds
4. Weeds : Undesired plant.
94

Methods of pest control
a. Mechanical method:
Manual labour along with
different devices for
collection and destruction
of pest.
E.g., hand picking,
burning, trapping of pests.
95
Farmer Hand Pick Colorado
Beetles from potato plants
Eco-friendly Solar Powered Pest
and Insects Control Traps

Methods of pest control (contd.)
b. Agricultural method:
• Advanced plant breeding
technique capable of inducing
genetic manipulation resulting
in production of pest resistant
species.

b. Agricultural method (contd.):
Ploughing - Which should be sufficiently deep so as to eradicate
weeds and early stages of insects.
97

c. Biological control :
• Combating the pest (esp. insects) with other living
organisms (mostly parasites).
E.g. Australian lady beetle ‘lady bug’ feed on damaging
insects called ‘cottony cushion scale insect’ on Citrus crop.

c. Biological control (contd.):
• Pheromones: Chemical substances produced & released by
some insects or animals, which affect the behaviour of other
animals. (to communicate with each other esp. Sex
Pheromones)
E.g., 7,8-epoxy-2-methyloctadecane
(sex pheromone from Gypsy-moth)
used for its control. 99
Pheromone
Trap

d. Chemical control : Use of chemicals: Pesticides
Pesticides can be grouped according to the types of pests which
they kill:
 Insecticides - insects
 Herbicides - plants
 Rodenticides - rodents (rats and mice)
 Bactericides - bacteria
 Fungicides - fungi
 Nematicides - Nematodes
 Larvicides - larvae

Chemical control
101

 Rodenticide : Warfarin, Chlorphacinone, Diphacinone,
Bromethalin, Strychnine
 Insecticide: D.D.T., Benzene hexachloride (BHC),
Gamaxine, Parathione, Malathione,
Nicotine, Pyrethroids (inorganic and organic),
Rotenoids.
 Fungicides : Captan, Sulfur, Mancozeb; Mefenoxam
 Herbicides : 2,4-dichloro phenoxy acetic acid (2,4-D),
Atrazine, Glyphosate, Simazine

11. Allelopathy

Allelopathy
 It is a biological phenomenon by which a living organism
produces one or more specific biomolecules that influences
the growth, survival and reproduction of other organisms.
 It can harm or give benefit to another organism.
 Allelopathy is a chemical process that a plant uses to keep
other plants out of its space.

 Allelopathic plants and plant material :
 Restrict or promote germination or growth of other plants
through releasing chemicals.
 Influence active constituents
 Affect leaf development and shedding
 Affect maturation of fruits, etc.
 When the organisms depend upon each other for survival, it is
called symbiosis. e.g. Belladonna when grown with Artemisia
absinthium shows better growth and high amount of alkaloids.
 When one plant causes destruction of other, it is called
antibiosis. e.g. Belladonna is strongly inhibited when grown
with Custard apple plant. 105

106

1) Leptospermone is an allelochemical in lemon bottlebrush
(Callistemon citrinus).
It was found to be too weak herbicide.
However, a chemical analog of leptospermone (mesotrione,
tradename Callisto) was found to be an effective herbicide to
control broadleaf weeds in corn but also seems to be an effective
control for crabgrass in lawns.
2) Eucalyptus leaf & root exudates are allelopathic for certain soil
microbes and plant species.
3) The tree of heaven (Ailanthus altissima) produces allelopathic
substances in its roots that inhibit the growth of many plants. 107

1) Leptospermone is an allelochemical in lemon bottlebrush
(Callistemon citrinus). It was found to be too weak herbicide.
However, a chemical analog of leptospermone (mesotrione,
tradename Callisto) was found to be an effective herbicide to
control broadleaf weeds in corn but also seems to be an effective
control for crabgrass in lawns.
108
Leptospermone
Mesotrione

12. Others

Other factors
• Effects of Exogenous factors may affect plants
growing in isolation differently than plants growing
in communities
– E.g. Camphor trees: produce > camphor when
growing alone than those growing in groups.
• Ergot: alkaloid content differs according to the host
(specific rye spp. or other type of cereal e.g. barley or
oats)

Extrinsic factors affecting cultivation and collection of medicinal plants-By Dr. Preeti Verma

Extrinsic factors affecting cultivation and collection of medicinal plants-By Dr. Preeti Verma

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