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Cytokinin induce cell division especially in carrot root tissue, pea callus etc Cytokinin may also induces cell enlargement in the leaves of Phaseolus vulgaris, pumpkin cotyledons etc.
Pre-sowing treatment of seed with growth regulators has been reported to enhance seed emergence. In tomato, pre sowing seed treatment with 100 ppm IAA, IBA and NAA enhanced the seed germination .
Induction of flowering which otherwise fails to flower has also been reported with the use of various growth regulators.
Poor fruit set is a major problem in tomato, brinjal and chillies which is frequently caused by adverse weather conditions during flowering.
Ethephon, an ethylene releasing compound, has been reported to induce ripening in tomato and pepper. (Prajapati, 2015)
Role of growth regulators in enhancing the productivity of vegetables
ROLE OF GROWTH REGULATORS IN ENHANCING THE
PRODUCTIVITY OF VEGETABLES
Course Title : Master’s Seminar
Course No. : VSC-591
AZIZ-UR-RAHMAN “JABARKHAIL” (A-2015-30-074)
Definition and History of growth regulators(GR’s)
Classification and Functions of growth regulators(GR’s)
Role of GR’s in Vegetable Crops
Constraints in the use of growth regulators
A growth regulator is
•An organic compound,
•Can be natural or synthetic,
•It modifies or controls one or more specific
physiological processes within a plant but the sites of
action and production are different.
If the compound is produced within the plant, it is called
as plant hormone.
Both internal plant hormones and lab created hormones are called
plant growth regulators.
Definition of growth regulators (GR’s) by different Scientists
Phillip (1971) defined growth hormone as substances which are synthesized in
particular cells and are transferred to other cells where in extremely small
quantities influence the developmental process.
Phill Olaiya (2013) stated that bio-regulators are endogenous or synthetically
produced substances that can control one or more specific biochemical and
physiological functions of many species probably by their influence on gene
and enzyme interactions.
Prajapati et al., (2015) stated that although, photosynthesis supplies the carbon
and respiration supplies the energy for plant growth, a group of chemicals
produced by plants known as plant growth regulators control the growth and
development of plant.
Auxin was the first hormone to be discovered in plant and at one time
considered to be only naturally occurring plant growth hormone. (Prajapati et
Three types of plant hormones Auxins, Gibberellins and Cytokinins and
these were discovered in the early decades of the twentieth century, in 1930’s
and in 1960's respectively.(Thomas, 1956)
History of Growth Regulators
Classification of growth regulators (GR’s)
NATURAL GR’s SYNTHETIC GR’s
2,4- D, NAA, IBA, 2,4,5T,
Maleic hydrazide etc.
• Also produced
spontaneously in the
plant body, but their
function is not
1. ON THE BASIS OF ORIGIN
• Produced by some
tissues in plant.
• Also called
• Produced artificially and
similar to natural
hormone in physiological
Major group of plant growth regulators
Plant Growth Promoters
The word Auxins has been derived from a Greek word auxein-
It was first isolated from human urine.
These are generally produced by the growing apex of stem and
roots of the plants..
This was the first group of plant hormones discovered.
Types of Auxin:
I. Natural Auxin
II. Synthetic Auxin
IBA, NAA, 2,4-D
( Meena, 2015 ) 8
It causes cell elongation by loosening of the cell wall
Promotes secondary growth of stem through cambium activity
Promotes callus and root formation in cutting
Restores apical dominance
Induction of flowering
Increases fruit setting and size
Delays leaf abscission
Prevention of premature drop of fruits
Develops parthenocarpic fruits
Acts as herbicide at higher concentration
Inhibition of prolonged dormancy
Inhibiting aging processes in tissues.
FUNCTIONS OF AUXINS
Second most important growth hormone.
Gibberellins are named after the fungus Gibberella fujikuroi ,
which causes rice plants to grow abnormally tall .
(Kurosawa et al., 1930)
Gibberellin produced in the shoot apex mainly in the leaf
primordial (leaf bud) and root system, hence they translocates
easily in the plant in both directions.
Now 135 different Gibberellins are available.
The most commonly occurring gibberellins is GA3.
( Meena, 2015) 10
It induces maleness
Promotes growth of dwarf plants
Possesses pollenicide effect
Replaces chilling and light requirements of plants
Promotes seed germination
Used for breaking of dormancy
Delays senescence of Fruits
Enhances seedless fruits
For stem elongation
Accelerates flowering in long day plants
Intensifies transpiration, photosynthesis and respiration.
FUNCTIONS OF GIBBERELLINS
They were first isolated from coconut milk.
They are synthesized in root apex, endosperm
of seeds, young fruits, where cell division takes
Induce flowering in short day plants.
Dormancy of certain light sensitive seeds such as lettuce can also be broken
by kinetin treatment.
Delays leaf senescence.
Inhibit apical dominance and help in growth of lateral buds. Therefore, it is
also known as anti-auxins.
Functions of Cytokinin
Ethylene is a colourless gaseous hormone.
Found in ripened fruits, flowers and leaves and nodes of stem.
Synthesis of ethylene is inhibited by carbon dioxide and requires oxygen.
Induces ripening of fruits.
Promotes abscission and senescence of leaf,
Induction of Femaleness:
cucumber, squash, melon.
It stimulates the formation of adventitious
Functions of Ethylene
(Meena, 2015) 15
It is also known as dormins, which acts as anti-Gibberellins.
It is synthesized in leaves of wide variety of plants.
Responsible for closing stomata during drought conditions, hence acts as plant
Induces senescence of leaves, abscission of leaves, flowers and fruits.
It induces dormancy of buds and seeds as opposed to Gibberellins, which
It inhibits seed germination and development.
ABA also plays important role in controlling stomata opening and closing.
Functions of Abscisic Acid
• Brassinosteroids have been recognized as a sixth class of plant hormones.
• Brassinolide was the first identified brassinosteroid and was isolated from
extracts of rapeseed (Brassica napus) pollen in 1979.
• It stimulate cell elongation and division, resistance to stresses.
• They inhibit root growth and leaf abscission.
Other Plant Growth Regulators
Morphactins are the group of substances which act on morphogenesis and
modulate the expression of plants.
Role of morphactins
Seed germination- inhibition.
Growth of seedlings- inhibit.
Stem elongation- dwarfing effect.
Commercial uses of bio- regulators in
COMMERCIAL USE OF PLANT
GROWTH REGULATORS IN
In tomato, pre sowing seed treatment with
100 ppm IAA, IBA and NAA enhanced the
seed germination. (Olaiya et al.,2009)
In muskmelon, soaking of seeds in ethephon
at 480 mg/litre of water for 24 hours
improves germination in muskmelon at low
temperature. (Meena, 2015)
Pre-sowing treatment of seed with GA3 and KNO3 @ 50 ppm enhanced the
germination of endive and chicory, respectively. (Tzortzakis, 2009)
IAA, NAA @ 20 ppm enhances seed
germination in okra. (Khan et al., 2013)
Seed dormancy is main problem in Potato and Lettuce.
Chemicals which have been reported to break the rest period are GA3,
Ethylene chlorhydrin and Thiourea.
Lettuce is another vegetable in which treatment with GA3 or cytokinin has
been reported to break seed dormancy induced by high temperature.
Soak the tubers in 1% aqueous solution of Thiourea for 1 hour or solution
containing 5-10 ppm GA3 for 10- 20 minutes can be used to break the
dormancy of potato. (Byran , 1989)
Breaking the dormancy in potato comprise the vapour heat treatment with
ethylene chlorhydrin (1 litre per 20 q) followed by dipping in thiourea (1%
sol.) for 1h & finally in GA (1 mg/l) for 2 seconds.
NAA 50 ppm has been reported to induce early
flowering in paprika. ( Kannan et al., 2009)
Plants sprayed with 300 ppm GA3 were earliest to
flower and recorded highest number of fruits and yield
per plant in tomato.
Application of GA@50 mg/l to young leaves of non-
flowering varieties of potato, when floral buds had
just formed, resulted in flower induction in all varieties.
Gibberellic acid has been reported to induce early
flowering in lettuce. ( Sharma et al.,1992)
The treatment with growth regulators has
been found to change sex expression in
cucurbits, okra and pepper.
GA3 (10-25 ppm), IAA (100 ppm) and
NAA (100 ppm) when sprayed at 2-4 leaf
stage in cucurbits, then they have been
found to increase the number of female
flowers. ( Hume et al., 1983 )
Whereas, GA3 (1500-2000 ppm), silver
nitrate (300-400 ppm) and silver
thiosulphate (300-400 ppm) sprayed at 2-4
leaf stage induces male flower production
in cucurbits. (Hatwal et al., 2015)
Plant growth regulators helps to
stimulate the fruit development
without fertilization ( Parthenocarpy).
2,4-D at 50 ppm when applied at
anthesis showed better performance
over other in parthenocarpic fruit
development in kakrol.
( Choudhury et al., 2007)
Seed treatment with 2,4-D @ 2-5ppm
gives early fruit set and leads to
parthenocarpy in tomato.
( Meena, 2015)
Staminate flowers were induced in parthenocarpic line of cucumber through
use of plant growth regulator GA3@ 1500 ppm and silver nitrate @ 200-
300ppm by four sprays at 4 days interval.
In brinjal, application of 2,4-D at 2.5ppm in lanolin paste to cut end of
styles or as foliar sprays to freshly opened flower cluster has been reported to
induced parthenocarpy. (Singh and Ram, 2004)
Poor fruit set is a major problem in tomato, brinjal
and chillies which is frequently caused by adverse
weather conditions during flowering.
Plant growth regulators such as PCPA (20-25 ppm)
and 2,4,-D (1-5 ppm), Kinetin (5 ppm), NAA (10
ppm) and GA3 (10 ppm) reported to enhance fruit
set under both normal and adverse weather
conditions, when applied at flowering stage in
tomato, brinjal and chillies (Prajapati et all. 2015).
Stimulation of fruit Set
Bioregulators have also been used for
maintenance of gynoecious lines in cucurbits.
Growth regulator like GA3 (1,500-2000ppm) and
chemical like silver nitrate (200-300ppm) induces
the male flowers on gynoecious cucumber .
Exogenous application of silver thiosulphate
(300-400ppm) induces the male flower in
gynoecious muskmelon .
( Meena, 2015 )
Hybrid seed production
Some PGR’s possesses gametocidal action to
produce male sterility which can be used for F1
hybrid seed production.
MH at 100 to 500 ppm appeared most effective
in inducing a high level of male sterility in
eggplant, okra, peppers and tomato, without
detrimental influence on female fertility.
(Saimbhi et al., 1978)
A high concentration of gibberellic acid (2%)
was found to act as a gametocide for the
common onion (Allium cepa L.), when sprayed in
the beginning of the bolting process.
(Meer et al., 1973)
Application of ethephon at 1000 mg/l at turning stage of earliest fruits
induced early ripening of fruits thus increasing the early fruit yield by 30-35%.
Post-harvest dip treatment with ethephon at 500-2000 mg/l has also been
reported to induce ripening in mature green tomatoes. (Gould, 1992)
Spraying with 60 ppm GA3 10 days before transplanting increased the yield per ha
of variety Roma. ( Naeem et al., 2001)
Spray with 6ppm 2,4-D gave highest yield of tomato. ( Patel et al., 2014)
Foliar sprays of 2,4-D @4 ppm gave the highest yield of brinjal.(Patel et al., 2012)
Seed treatment with 10ppm GA3 or IAA gave the highest yield in brinjal. (Sharma
et al., 1992)
Foliar sprays of 2 ppm 2,4-D, 40 ppm NAA and 10 ppm GA3 gave 28.75%,
13.61% and 2.30% higher fruit yield over control, respectively.(Choudhaury et al., 2006)
Spraying plants with 10 ppm NAA gave significantly highest fruit yield (277.8
g/plant). ( Sultana et al., 2006) 33
Crops Effect on Quality
15 Foliar spray Muskmelon Improve rind
5-15 Foliar spray Cauliflower,
Increases head or
50 Foliar spray Lettuce and
Increases dry matter,
protein and ascorbic
PCPA 50 Foliar spray Tomato Increases sugar and
EFFECT OF GROWTH REGULATORS ON QUALITY OF VEGETABLE
CCC 250 Foliar spray Potato Increases TSS and vitamin-C
content in tuber
Cytozyme 1% Foliar spray Garden pea Increases vitamin-C, reducing
sugars and total sugars
Ethephon 250 Foliar spray Tomato Increases TSS
NAA 50-70 Seed
Chilli Increases amino acid and vitamin-
C content in fruits
(Bahadur and Singh, 2014) 38
Cycocel (CCC) 250-500 Foliar spray Cucurbits,tomato,
Flowering, sex expression,
Acetic acid (PCPA)
50 Foliar spray Tomato Fruit set and Yield
Ethephon (CEPA) 100-500 Foliar spray Cucurbits, okra and
Flowering, fruiting, sex
expression and yield
2000 Post- harvest Tomato, chillies Fruit ripening
Gibberellic acid (GA) 10 Foliar spray Water melon,
Sex expression, fruiting
10-15 Foliar spray Okra, tomato,
Seed germination, fruit set
List of plant growth regulators and their important uses in vegetable
Growth and yield
10-20 Foliar sprays Chillies and Tomato Flower drop, fruit set and yield
25-30 Seed/ foliar Okra ,Tomato,
Seed germination, growth and
25-100 Seed/ foliar Tomato, Okra Germination, growth and yield
Silver nitrate 500 Foliar spray Cucumber Induction of male flower in
Silver thiosulphate 400 Foliar spray Musk melon Induction of male flower in
25-50 Foliar sprays Cucurbits Flowering, sex expression and
Tricontanol 2 Foliar sprays Chillies and Peas Fruit set and yield
Source :Chadha and Kalloo,1993 40
Growth substances should be sprayed preferably in the evening hours.
Avoid to spray in windy hours.
Spray should be uniform and wet both the surface of leaves.
Use growth substances at an appropriate stage of plant growth is of great
Chemical should be completely dissolved before application.
Precaution in Growth Regulator Application
Use always fresh solution of chemicals.
Use PGR’s strictly at recommended concentration.
Solution should always be prepared in distilled water only.
Fine spray can be ensured by hand automizer. It is most economical and
effective method of spray.
Wash the machine/pump after each spray.
Repeat the spray within eight hours, if chemical is wash out due to rain.
The difference in sensitivity of each plant species or even cultivars to a given
chemical treatment prevent easy predication of the biological effects.
The cost of developing new plants growth regulator is very high, due to which
they are very much costly.
Screening for plant growth regulatory activities entails high costs and is very
Constraints in the use of growth regulators
Some synthetic plant growth regulators cause human health hazards e.g.
Lack of basic knowledge of toxicity and mechanism of action.
Inadequate market potential.
Lack of support from agricultural researchers in public and private sectors.
Difficulty in identification of proper stage of crop at which the growth
regulators should be applied.
Most of the biological processes associated are polygenic, so gene transfer may
be difficult and hence the use of PGR’s may be beneficial for short
PGR’s provide an immediate impact on crop improvement programmes and
are less time consuming.
Applications of PGR’s must lead to quantifiable advantages for the user.
Industries involved in development of PGR’s should be well informed about
the latest scientific development in production of PGR’s.
Plant growth regulators should be recognized as more than academic
They are not only interesting but profitable to use to grower, distributor and
More research is needed to develop simple, economical and technical viable
production systems of PGR’s.
Plant growth regulators has an immense potential in vegetable production to
increase the yield, quality, synchronization in flowering, earliness, cold and high
temperature fruit setting, sex modification, increase post-harvest life and
resistance to biotic and abiotic stresses of vegetables to better meet the
requirements of food supply in general. But more research is needed to develop
simple, economical and technical viable production system of bio-regulator.
Bio-regulators must be toxicologically and environmentally safe.
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role of growth regulators in enhancing the productivity of vegetables