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Growth Stimulants, Retardants, and Rooting HormonesGrowth Stimulants, Retardants, and Rooting Hormones
Growth regulatorsGrowth regulators
Hormones
Organic chemicals that act and interact to affect growth rate
Auxins – accelerate growth by stimulating cell enlargement
Hormones
Organic chemicals that act and interact to affect growth rate
Auxins – accelerate growth by stimulating cell enlargement
GibberellinsGibberellins
Stimulate growth in stem and leaf by cell elongation
Stimulates premature flowering, growth of young fruits and breaking of dormancy
Stimulate growth in stem and leaf by cell elongation
Stimulates premature flowering, growth of young fruits and breaking of dormancy
CytokininsCytokinins
Stimulate cell division
Work along with auxins
Will not work without auxins present
Stimulate cell division
Work along with auxins
Will not work without auxins present
InhibitorsInhibitors
Abscisic Acid and Ethylene Gas
inhibits seed germination
Inhibits stem elongation
Hasten ripening of fruit – ethylene gas
Abscisic Acid and Ethylene Gas
inhibits seed germination
Inhibits stem elongation
Hasten ripening of fruit – ethylene gas
Auxins and Gibberellins promote cell enlargement
Cytokinins stimulate cell division
Auxins and Gibberellins promote cell enlargement
Cytokinins stimulate cell division
Growth HormonesGrowth Hormones
Organic chemicals produced by actively growing plant tissue
Shoot tips and young leaves
Move throughout the plant and can be found in most tissues
Organic chemicals produced by actively growing plant tissue
Shoot tips and young leaves
Move throughout the plant and can be found in most tissues
These chemicals react with one another in a very complex system in the plant
In some cases a concentration of one hormone stimulates growth and a different concentration restricts growth
These chemicals react with one another in a very complex system in the plant
In some cases a concentration of one hormone stimulates growth and a different concentration restricts growth
Apical DominanceApical Dominance
Dominance of the terminal bud
Apical dominance exists there
Terminal bud secretes chemicals that inhibit or prevent the growth of axillary buds on the same shoot
Dominance of the terminal bud
Apical dominance exists there
Terminal bud secretes chemicals that inhibit or prevent the growth of axillary buds on the same shoot
Apical DominanceApical Dominance
Axillary buds are found in the axil – angle between a leaf and the stem.
Causes the plant to grow tall and not branch
Once the plant reaches flowering age and the terminal bud becomes a flower, the chemicals are no longer secreted
Axillary buds are found in the axil – angle between a leaf and the stem.
Causes the plant to grow tall and not branch
Once the plant reaches flowering age and the terminal bud becomes a flower, the chemicals are no longer secreted
Apical DominanceApical Dominance
The plant then starts to send out side branches
This allows the plant to grow above competing plants
Once height and access to sunlight are secured, the plant spreads out over its competitors
The plant then starts to send out side branches
This allows the plant to grow above competing plants
Once height and access to sunlight are secured, the plant spreads out over its competitors
Apical DominanceApical Dominance
Pinching off terminal buds removes the hormone and causes branching to happen faster
Common practice in greenhouses and nurseries to produce bushier plants with many flower buds
Pinching off terminal buds removes the hormone and causes branching to happen faster
Common practice in greenhouses and nurseries to produce bushier plants with many flower buds
StimulantsStimulants
Allow plants to grow taller
Most common is Gibberellic Acid (GA)
Causes stems of plants to stretch out
Nodes are farther apart
Allow plants to grow taller
Most common is Gibberellic Acid (GA)
Causes stems of plants to stretch out
Nodes are farther apart
Growth StimulantsGrowth Stimulants
Natural growth stimulants have been found in alfalfa
It causes stimulation of growth
It is the alcohol called Triacontanol
Stimulation is brought about by mulching plants with alfalfa hay
Natural growth stimulants have been found in alfalfa
It causes stimulation of growth
It is the alcohol called Triacontanol
Stimulation is brought about by mulching plants with alfalfa hay
Or watering plants with a “tea” made from soaking alfalfa feed pellets in water
Amount needed is very small
Also sold commercially
Or watering plants with a “tea” made from soaking alfalfa feed pellets in water
Amount needed is very small
Also sold commercially
Chemical RetardantsChemical Retardants
Chemicals are used to retard growth of plants causing them to be shorter and more compact
Plants are more attractive and the plants themselves are stronger
Used commercially
B-Nine is commonly used on Azaleas
Chemicals are used to retard growth of plants causing them to be shorter and more compact
Plants are more attractive and the plants themselves are stronger
Used commercially
B-Nine is commonly used on Azaleas
Newest uses of Plant Growth Retardants (PGR) is the application to lawns
After first mowing in the spring “Limit” is applied and absorbed by the roots
Restricts growth for 6-8 weeks
Newest uses of Plant Growth Retardants (PGR) is the application to lawns
After first mowing in the spring “Limit” is applied and absorbed by the roots
Restricts growth for 6-8 weeks
“Embark” is absorbed by the leaves and also restricts growth
PGR’s absorbed by the leaves move to the growing point where it interrupts cell division, stem elongation and seed head formation
Roots continue to grow
Applied after first or second mowing
“Embark” is absorbed by the leaves and also restricts growth
PGR’s absorbed by the leaves move to the growing point where it interrupts cell division, stem elongation and seed head formation
Roots continue to grow
Applied after first or second mowing
SumagicSumagic
New growth retardant
Reduces height of plants by inhibiting production of GA
Chemical is taken up by leaves and moves through the plant to the terminal bud
New growth retardant
Reduces height of plants by inhibiting production of GA
Chemical is taken up by leaves and moves through the plant to the terminal bud
Used to control growth of shrubbery and hedges
PGR Atrimmic applied after pruning can last an entire season
Reduces or eliminates the need to prune
Used to control growth of shrubbery and hedges
PGR Atrimmic applied after pruning can last an entire season
Reduces or eliminates the need to prune
AtrimmicAtrimmic
A systemic
Penetrates the plant, enters the plant sap, and moves through the plant
Blocks plant hormones that stimulate growth
Applied as a foliar spray
A systemic
Penetrates the plant, enters the plant sap, and moves through the plant
Blocks plant hormones that stimulate growth
Applied as a foliar spray
Rooting HormonesRooting Hormones
Important when propagating plants by cutting
Helps cuttings to develop more roots faster than without a rooting hormone
Indoleacetic Acid (IAA) naturally occurring, causes roots to form on plant stems
Important when propagating plants by cutting
Helps cuttings to develop more roots faster than without a rooting hormone
Indoleacetic Acid (IAA) naturally occurring, causes roots to form on plant stems
IBA – Indolebutyric AcidIBA – Indolebutyric Acid
Most widely used rooting hormone
Most effective rooting hormone
Most widely used rooting hormone
Most effective rooting hormone
Rooting HormonesRooting Hormones
Either mixed with talc and used as a powder or dissolved in water and used as a wet dip
Liquid can be slightly more effective
All rooting hormones should contain a fungicide
Either mixed with talc and used as a powder or dissolved in water and used as a wet dip
Liquid can be slightly more effective
All rooting hormones should contain a fungicide
FungicideFungicide
Helps prevent cuttings from rotting Helps prevent cuttings from rotting
Dwarfing RootstockDwarfing Rootstock
Used in fruit trees
Shorter trees enable you to pick fruit without using a ladder
First research done to prevent apple trees from growing very tall
Trees growing from certain types of roots didn’t grow as tall
Used in fruit trees
Shorter trees enable you to pick fruit without using a ladder
First research done to prevent apple trees from growing very tall
Trees growing from certain types of roots didn’t grow as tall
These trees also bore fruit at an earlier age
Complete series of rootstock known as malling rootstock developed in England
Controls size and rate of growth or apple trees
These trees also bore fruit at an earlier age
Complete series of rootstock known as malling rootstock developed in England
Controls size and rate of growth or apple trees
Stock has also been developed for peach and pear trees as well
Dwarf trees can be purchased commercially
Stock has also been developed for peach and pear trees as well
Dwarf trees can be purchased commercially
Chemical Blossom SetChemical Blossom Set
Used on tomato blossoms early in the season
Causes earlier development of fruit
Causes seedless tomatoes to set on first blossoms and results in tomatoes ready to eat as much as 10 days earlier than normal
Used on tomato blossoms early in the season
Causes earlier development of fruit
Causes seedless tomatoes to set on first blossoms and results in tomatoes ready to eat as much as 10 days earlier than normal
Plant BiostimulantsPlant Biostimulants
Natural products
Organic
Work to stimulate soil microbial activity and improve soil cation exchange capacity, stimulate plant growth and promote disease resistance
Natural products
Organic
Work to stimulate soil microbial activity and improve soil cation exchange capacity, stimulate plant growth and promote disease resistance
Humic AcidHumic Acid
Product of rotting organic matte is an example of a soil microbial stimulant
Product of rotting organic matte is an example of a soil microbial stimulant
Root growth biostimulantsRoot growth biostimulants
Improve water and nutrient uptake
Increase number of fibrous roots
High levels found in kelp plants
Improve water and nutrient uptake
Increase number of fibrous roots
High levels found in kelp plants
BiostimulantsBiostimulants
Greatly reduce the need for fertilizers, especially N
Saves money, reduces pollution
Greatly reduce the need for fertilizers, especially N
Saves money, reduces pollution
MethanolMethanol
A form of alcohol
Speeds plant growth
Research in California showed an increase in plant yield of 36-100%
Works by blocking photrespiration
Plants use water for growth rather than transpiring it into the air
A form of alcohol
Speeds plant growth
Research in California showed an increase in plant yield of 36-100%
Works by blocking photrespiration
Plants use water for growth rather than transpiring it into the air
MethanolMethanol
Works best on plants frown in full summer sun
Water use reduced by as much as 50% in some plants
Works best on plants frown in full summer sun
Water use reduced by as much as 50% in some plants
AllelopathyAllelopathy
Production of a chemical compound in one plant that slows or stops the growth of another plant
Natural herbicide
Black Walnut, Millet
Production of a chemical compound in one plant that slows or stops the growth of another plant
Natural herbicide
Black Walnut, Millet
