Plant Growth Regulators
Plant Growth Regulators are naturally occurring or synthetic compounds that affect plant growth and development
3 Types of Chemical Plant Growth Regulators Growth-inhibiting chemicals Growth-promoting chemicals Root-promoting chemicals
Plant Hormones “Chemical Messengers” Auxins Cytokinins Gibberellins Ethylene
Rooting Hormones Auxin, which stimulates rooting, is the main component IAA (indoleacetic acid) IBA (indolebutyric acid) NAA (naphthaleneacetic acid)
Rooting Hormones Combination of IBA and NAA Powder Formulations Hormodin Hormo-Root Rhizopon AA Liquid Formulations Woods Rooting Compound Dip’ N Grow
Liquid Hormones
Powder Hormones
Cytokinins Responsible for shoot initiation Present in rapidly dividing tissue Benzyladenine (BA) synthetic cytokinin increases offset formation in hosta
Gibberellic Acid (GA) Promotes cellular elongation (stretched internodes) Increases fruit set Pro-Gibb: Enlarges flowers and elongates peduncles (stems supporting flowers)
Ethylene Gas Affects cell division and development Cause flowering Causes fruit ripening Causes leaf abscission
Plant Growth Retardants (PGRs) are any chemicals that slow cell division and elongation in shoot tissues
Why Control Growth? Blow-over Plants out-grow pots Watering becomes difficult Increased shipping costs Leggy, low quality plants
Methods of Growth Control Pruning costly and time consuming Genetics not always available consumers wary of GMOs
Methods of Growth Control Environmental controls Low fertility Negative DIF (Temp) Water Stress Brushing, vibrations, and other mechanical disturbances
Many growers find chemical plant growth retardants to be an effective and inexpensive method of growth control
How do they work? Gibberellin Biosynthesis Inhibitors Release of Ethylene
Notice branching effects
Notice height control
Synergistic effects of two PGRs
Increasing PGR Effectiveness In Non-responsive Perennials
Additional Benefits: Control production schedule Increase branching Induce flowering Drought tolerant Pollution tolerant
Additional Benefits: Intensely green foliage Resistant to mechanical damage Protection from some pests (whiteflies) Overall higher quality and aesthetic value
PGRs for use in Greenhouses: B-Nine Cycocel Bonzi Sumagic Florel A-Rest
Chemical PGRs B-Nine (Daminozide) Cycocel (Chlormequatchloride) labeled for annuals and herbaceous perennials low activity (relatively safe) Cycocel (Chlormequatchloride) not labeled on many crops causes yellowing above 1500 ppm
Chemical PGRs B-Nine/Cycocel tank mixes Synergistic combination Cycocel 800-1,500 ppm B-Nine 800-5,000 ppm
Chemical PGRs A-Rest (Ancymidol) intermediate activity broad label
Chemical PGRs Bonzi (Paclobutrazol) Sumagic (Uniconazole) broad spectrum label high activity Sumagic (Uniconazole) most active PGR
Chemical PGRs Florel, Ethrel, Pistill, (Ethephon) causes plant to release ethylene narrow-spectrum label
PGR Efficacy Application timing Dosage Target tissue foliage/stems substrate
PGR Efficacy Environmental Conditions Application Technique environment at application status of plant post-application treatment Application Technique
Application Chemical must be accurately measured ALWAYS wear long sleeves, pants, gloves, and shoes with closed toes when mixing and applying PGRs!!!!!!
Media Drenches specific volume/pot
Foliar Sprays Specific volume/area (0.5gallons/ 100ft2)
PGR overdose Example: Bonzi overdose on pansies Ways To Reverse gibberellins (Pro-Gibb) high-N nutrition
QUESTIONS?