Plant Growth Regulators Growth Retardants Virginia Tech Blacksburg VA Growth Retardants Cell elongation inhibitors Retard growth by inhibiting the production of the plant hormones cause cell expansion Therefore, plants are shorter Growth Retardants Inhibit cell expansion Shoot Apex + (Gibberellic Acid) Metabolic Brian Whipker, NCSU O CH 2 New cell HO H CO H COOH 4 NC STATE UNIVERSITY Research Metabolic Chemical chain of events, which leads to the production of Knowing the pathway provides a better understanding of how s work. Cell Elongation Inhibitors Group A (chloromequat) Group B (N - containing heterocyclic compounds) A-Rest/Abide (ancymidol) [pyrimidine] Topflor (flurprimidol) [pyrimidine] (paclobutrazol) [triazole] Unicon (uniconazole) [triazole] Group C (daminozide) February 2011 1
12 -aldehyde Growth: Shoots Leaves Roots 12 -aldehyde Group B Ancymidol Unicon Topflor Group A Growth: Shoots Leaves Roots 12 -aldehyde Growth: Shoots Leaves Roots 12 -aldehyde Group C Tank Mix: Synergy? 12 -aldehyde Ancymidol Unicon Topflor Rudbeckia triloba 1000 ppm 2000 ppm 3000 ppm 4 WAT, moderate response to alone i 000 2 C l 4000 ppm February 2011 2
Rudbeckia triloba Lavandula angustifolia Silver Edge 5000/ 1000 5000/ 2000 5000/ 3000 5000/ 4000 / Tank Mix, 4 WAT 2500x3 5000x3 TankMix or / (5000/1500 ppm) tank mix sprays, 8WAT Other Effects of s Brian Whipker, NCSU HO O CO H H 4 COOH CH 2 NC STATE UNIVERSITY Research Greener Leaves treated leaves are darker green Suggests a higher chlorophyll content Cells smaller, so chlorophyll more concentrated Increased chlorophyll production because of blocked pathway Why greener leaves? 12 -aldehyde Phytyl Chlorophyll Greener Leaves February 2011 3
Reduced Water Stress Blocked pathway increases abscisic acid production and Interferes with the breakdown of abscisic acid Abscisic Acid Stomatal Closure Reduced Water Loss Why less water stress? 12 -aldehyde Phaseic Acid Abscisic Acid Reduced Water Stress Water Use (grams/day) 125 100 75 50 25 0 Mean Daily Water Use Colt Cherry Rootstocks Source: Asamoah and Atkinson, 1985. 0 butrazol Treatment 55% Disease Suppression Applying paclobutrazol to trees reduced the incidence of fungal diseases. Thought due to the inhibition of sterol production in fungi. Sterols essential constituents of membranes. Same mode of action as sterol biosynthesis inhibitor class of fungicides. Squalene Lanosterol Campesterol Chloesterol (in fungi) 12 -aldehyde Why less disease? = butrazol blocked Mycelial Growth Rate (mm/day) Disease Suppression (butrazol) 1.5 0.5 1 0 Verticillium dahliae Growth Inhibition 32% Label 1:50 1:100 1:200 0 butrazol Concentration Source: Jacobs and Berg, 2000. February 2011 4
Disease Suppression Disease Suppression Phaseic Acid Abscisic Acid Super Plants!!! Squalene Lanosterol Campesterol Chloesterol (in fungi) Shorter 12 -aldehyde Phytyl Chlorophyll Greener Healthier Tougher Benefits of Growth Retardants plant height/size space used per plant Buffer period of growth control Can meet shipping height reqmnt Can ship more plants per load Benefits of Growth Retardants Improve plant quality Deeper color Strengthen stems Plant height impacts perceived quality (balance) February 2011 5
Benefits of Growth Retardants May increase disease resistance Increase stress resistance Have less shrinkage (production losses) Have longer shelf life (production and retail) Benefits of Using s Growers using s: Reduce cost of production Reduce shrinkage Can ship more plants per load s higher quality and more saleable plants Benefits of Using s Growers using s Growth Retardants Make more money!!! s NO Soil Activity Typically short-term responses Uptake by leaves; good coverage required Daminozide WSG (OHP) Dazide (Fine Americas) s LIMITED Soil Activity Some root uptake Primarily foliar applications; good coverage required Chlormequat Cl (not labeled for chemigation) (OHP) Chlormequat E-Pro (Etigra LLC) Citadel (Fine Americas) February 2011 6
Labeling includes outdoor use. Guidelines Sprays only Limited to 3 applications per crop 12 hour REI (same as greenhouse use) Mechanical (tractor) multi-nozzle sprayer applications on gravel/landscaped fabric cannot exceed 1 acre of plants per mixer/loader/applicator/day. Veronica x Sunny Border Blue effective on a wide variety of perennials Multiple applications required at 7 to 14 day intervals 5000 x 2 Coreopsis grandiflora Sunray Phytotoxicity 100 ppm Crop specific responses 5000 ppm x 2 200 ppm 5000 ppm Chlorotic halos on geranium Minimal with rates below 750 ppm / Tank Mix on Tango Helenium Coppelia 2500/750 ppm 2500/1000 ppm 2500/1250 ppm 2500/1500 ppm Significant reductions in stem height Improved plant form 2500x3 5000x3 TankMix or / (5000/ 1500 ppm) tank mix sprays, 6WAT February 2011 7
Perovskia atriplicifolia : 5000 x3, good control / Tank mix, multiple applications 5000 ppm Tank mix 5000/1500 Gaura lindheimeri Siskiyou Pink 5000 ppm / 5000/1500 ppm For many plants, width more important than height s Soil ACTIVE Veronica Icicle Taken up by shoot and root tissues Typically more potent than foliar only 6 WAT Ancymidol (labeled for chemigation) A-Rest (SePRO) Abide (Fine Americas) Topflor (flurprimidol) (SePRO) (labeled for chemigation) 2 ppm 4 ppm 6 ppm 8 ppm Abide drenches at 2 fl.oz. per quart pot Plant ht: 10 inches vs. 8 ppm drench 4 inches Delphinium Blue Bird Delphinium elatum Blue Bird 4 WAT 2 ppm 4 ppm 6 ppm 8 ppm Abide drenches 10 fl.oz per trade gallon pot 13 inches vs. 8 ppm drench 7 inches 15 ppm 30 ppm 45 ppm 60 ppm Topflor foliar spray, 4 WAT, linear response February 2011 8
Erysimum linifolium 30ppm 60ppm 90ppm Topflor foliar spray, 6 WAT, persistent 120ppm s Soil ACTIVE butrazols labeled for chemigation much more potent than ancymidol & daminozide Uniconazoles not labeled for chemigation 8-10x more potent than paclobutrazols Primary uptake by stems and roots s Soil ACTIVE butrazols Paczol (OHP) Bonzi (Syngenta Professional Products) Piccolo (Fine Americas, Inc.) Florazol (Prokoz) Downsize (Greenleaf Chemical) s Soil ACTIVE Uniconazoles Sumagic (Valent USA) Concise (Fine Americas, Inc.) Phlox subulata Apple Blossom Alcea Chaters Double 40 ppm 80 ppm 120 ppm 160 ppm, 6 WAT, moderate control of plant width 40 ppm 80 ppm 120 ppm 160 ppm sprays, 2 WAT, multiple applications necessary for long term control February 2011 9
Veronica repens Sunshine Veronica x Sunny Border Blue 40 ppm 80 ppm 120 ppm 160 ppm, 6 WAT, excessive control 100 ppm 200 ppm / 5000/1500 ppm overdose Tank Mix excellent control, 1x Rudbeckia Herbstonne Relative Activity Sumagic 45 ppm Sumagic 90 ppm 5000ppm Sumagic: ~45 ppm : good control, 5000x3 Ancymidol Daminozide Chlormequat Daminoz + Chlormeq Unicon Topflor More Sedum Matrona 6 WAT Width control NR to or tank mix 0 40 80 120 160 0 15 30 45 Sumagic 60 Topflor 0 30 60 90 120 For more information 540-231-7906; jlatime@vt.edu http://www.hort.vt.edu/floriculture http://www.gpnmag.com February 2011 10