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Plant Growth Regulators

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					Plant Growth Regulators


   Why is the use of plant growth
   regulators important?
Key Questions

   What are two groups of plant growth regulating
    compounds?
   What is the difference between synthetic growth
    regulators and plant hormones?
   How do plant hormones control apical dominance?
   What are the benefits of using plant growth regulators?
   What are the different types of rooting compounds?
   How do you use plant growth regulators control the size
    of flowering plants?
   What is the impact of growth regulators on turf
    maintenance companies?
   When should growth regulators be applied?
   What are gibberellins and anti-gibberellins?
What are the two groups of plant growth
regulating compounds?

   Natural vs. Synthetic
       Natural- found naturally in plants
       Synthetic- human made


   Both groups regulate or influence:
       Cell division
       Cell differentiation
       Root and shoot growth
       Senescence (plant aging)
   Promoters vs. Inhibitors
       Promoters- cause faster growth
       Inhibitors- reduce growth
What is the difference between synthetic
growth regulators and plant hormones?
        Hormones
         plant produced natural compounds that inhibit or
          promote plant growth


        Major classes of plant growth regulators
         (hormones) are:
    1.    Auxins
    2.    Gibberellins
    3.    Cytokinins
    4.    Abscisic acid
    5.    Ethylene
Auxins
   Growth promoting chemicals

   Promote cell division and cell elongation

   Primary plant auxin is indoleacetic acid (IAA)

   Common synthetic forms of auxins are indolebutyric acid (IBA)
    and naphthaleneacetic acid (NAA)

   Useful in phototropism, geotropism, apical dominance, and root
    formation
     Phototropism- plant growth toward a light source

     Geotropism- plant growth in response to gravitational forces

     Apical dominance- terminal buds prevent the development of
       lateral buds on plant stem
Gibberellins

   Also known as Gibberellic acid or GA

   Growth promoting chemicals

   Stimulate stem growth through cell elongation
    and cell division

   Commercial supplies obtained from the
    fungus Gibberella fujikuroi
Cytokinins

   Promote cell division and delay leaf aging

   Used as a growth promoter in tissue culture

   Slows the process of senescence (biological
    aging) by preventing the breakdown of
    chlorophyll in leaves
Abscisic acid (ABA)

   Only natural plant growth inhibitor

   Growth inhibitor that closes the stomates of plants
    under water stress

   Counteracts the effects of auxins and gibberellins

   Cycocel and B-Nine are two synthetic ABA type
    growth inhibitors commonly used
Ethylene

   Gas that forms in tissue undergoing stress

   Important in the fruit-ripening process and
    early petal drop of flowers
How do plant hormones control apical
dominance?
   Apical dominance
       Controlled by auxins where the terminal bud inhibits the
        development of lower lateral buds
       In greenhouses, we pinch the terminal bud out of a plant so
        that the plant branches out and becomes bushy


   Phototropism
       Controlled by auxins, which is a plant’s response to grow
        toward light


   Geotropism
       Plant growth response to gravity
What are the benefits of using plant
growth regulators?
   Benefits
       Promote and accelerate root formation on cuttings

       Keep fruit on trees longer to allow further ripening achieved
        by the application of auxin

       Thin blossom clusters and increase berry size in grapes-
        achieved by the application of gibberellic acid

       Increase size and crispness of stalks of celery- achieved by
        the application of GA

       Control the size of plants
What are the different types of rooting
compounds?
   Rooting compounds
       Indoleacetic acid (IAA)- naturally occurring auxin
        that produces bushy, stunted root systems

       Indolebutyric acid (IBA)- synthetic form of auxin
        that produces strong, fibrous root systems

       Napthaleneacetic acid (NAA)- synthetic form of
        auxin similar to IBA
How do you use plant growth regulators control
the size of flowering plants?
        Leggy
         Condition when greenhouse plants grow too tall to make
          desirable flowering potted plants


        Growth regulators used in producing flowering
         plants
    1.    Arest
    2.    B-nine
    3.    Cycocel
    4.    Florel
    5.    Phosfon
    6.    IBA and NAA
   Increase the number of flower buds formed

   Improve the number of flower buds formed

   Improve the longevity and quality of cut flowers

   Control vegetative growth and reduce mowing
    frequency in turfgrass

   Reduce or eliminate unwanted sprouts and suckers

   Reduce pollen, for people with allergies, by
    eliminating flowers on some trees, which also can
    control unsightliness and odor caused by falling fruit

   Control the growth of shrubs and hedges
What is the impact of growth regulators
on turf maintenance companies?
        Growth regulators used on turf:
    1.    Cutless
    2.    TGR
    3.    Primo
    4.    Maintain CF 125
    5.    De-Cut
    6.    Retard
    7.    Slo-Gro
    8.    Posan
   Regulators reduce amount of mowing needed

   Reduces number of mowings per year
       Reduces labor and machinery costs


   Growth regulators beneficial to:
       1. Lawn care operators
       2. Cemetery managers
       3. Golf course superintendents
When should growth regulators be applied?

   Timing of application can affect how various
    regulators do their job & their affect on non-targeted
    plants
       Ex. Embark should be applied after spring “green-up but
        before seedhead emergence

   Some chemical may be washed away if applied
    before a rain or watering

   Be sure to read the label to find out when to apply!!!
       If a crop is edible, how would application affect harvest
        date?
What are gibberellins and anti-gibberellins?

   Gibberellins- promote plant growth

   Anti-gibberellins- counteract the effect of
    naturally occurring gibberellins
       Can reduce the rate of growth in shade trees
       Used be utility companies to control trees that
        may grow into utility lines
       How else could anti-gibberellins be used?

				
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