Transcript Role of Plant Growth Regulator in Horticulture Nursery

Introduction
•
Plant Growth Regulator (PGR) also called as bio-stimulants or
bio-inhibitors, are
organic
compounds,
other
than
plant
nutrients, that modify physiological processes in plant. PGR acts
inside plant cells to stimulate or inhibit specific enzyme or
enzyme systems and help regulate plant metabolism.
•
PGR naturally produced in plants which control the growth and
other physiological functions, slightly away from its place of
production and active in very minute quantities.
Common PGR
Name of PGR
(Hormones)
Example / Trade Name
Auxins
IAA, IBA, NAA
Gibberellins
GA1, GA2, GA3,..…GA60
Cytokinenins
Kinetin, Zeatin
Ethylene
Ethylene
Abscissic Acid (ABA)
Phaseic Acid, Dormins
Inhibitor
Cycocel, MH-40
Role of Auxins
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Cell Enlargement: It stimulates cell enlargement and stem growth.
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Cell Division: It stimulates cell division in cambium and is used in tissue
culture plant production in combination with Cytokinin.
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Vascular Tissue Differentiation: It stimulates differentiation of phloem
and xylem.
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Root Initiation: It stimulates root initiation on stem cuttings. It is used in
tissue culture plant propagation for development of roots.
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Apical Dominance: It suppresses the apical shoot growth and promotes
the growth of lateral buds.
Role of Gibberellins
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Stem growth: Gibberelic Acid (GA) causes hyper elongation of stems by
stimulating both cell division and cell elongation. This produces taller
plants.
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Bolting in Long Day Plants: GA cause stem elongation in response to
long days.
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Induction of Seed Germination: GA activates germination of seeds
which otherwise require cold (stratification) or light to induce germination.
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Enzyme Production during Germination: GA stimulates the production
of enzymes like amylase in germinating cereal grains.
Role of Cytokinins
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Cell Division: Applications of Cytokinin along with auxins induce cell
division in tissue culture.
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Morphogenesis: In tissue culture, Cytokinin promote shoot initiation.
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Growth of Lateral Buds: Cytokinin applications can cause the
release of lateral buds from apical dominance.
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Leaf Expansion: Resulting solely from cell enlargement.
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Chloroplast
Development:
Application
of
Cytokinin
leads
to
accumulation of chlorophyll and promotes conversion of leukoplasts
into chloroplasts.
Role of Abscissic Acid (ABA):
• Stomata Closure: Water shortage brings about increase in ABA
level, leading to stomata closure as a response to water stress.
• Growth Inhibiters: ABA inhibits shoot growth but has less effect
on root growth.
• GA Counteracts: ABA counteracts the effect of gibberellins on
a-amylase synthesis in germinating cereal grains.
• Induced Dormancy: ABA affects induction or maintenance of
dormancy in seeds.
Role of Ethylene
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Fruit Ripening: Ethylene in the form of gas helps ripe fruits in natural
conditions.
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Induction Of Femaleness: Promotes production of female flowers in
cucurbits (cucumber, squash, melon) to increase the yield.
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Flower Opening: Promotes of flower initiation and controlled ripening
in pineapples.
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Leaf and Fruit Abscission: Accelerates fruit abscission for
mechanical harvesting in fruit crops like grapes, cherries, and citrus.