Abstract
Ranunculus asiaticus L. ‘Tecolote Giant White’ and Anemone coronaria L. ‘The Bride’ tubers were forced as spring pot crops in 1983 and 1984. Daminozide, ancymidol, and flurprimidol were used as preplant tuber dips or as foliar sprays. Foliar sprays were applied when the flower buds had grown to plant canopy height. A. coronaria ‘The Bride’ was not responsive to growth retardant treatment. Foliar application of ancymidol at 0.5 mg a.i./plant and daminozide as a 0.5% foliar spray were effective with R. asiaticus ‘Tecolote Giant White’ in reducing peduncle height without delaying time to anthesis. Daminozide as a 0.5% solution tuber dip provided an inadequate reduction in peduncle length at anthesis for either species. When ancymidol was used as a 1-min preplant tuber dip in the range of 10–25 mg a.i./liter of solution, excessive stunting and delay of anthesis resulted. Flurprimidol in the range of 3.0–10.0 mg a.i./liter as a preplant tuber dip and in the range of 0.1–10.0 mg a.i./plant as a foliar spray was effective in reducing peduncle length at anthesis. However, plants were considered unmarketable because of a slight delay in reaching full bloom and extreme growth reduction. Chemical names used: α-cyclopropyl-α-(4-methoxyphenyl)-5-pyrimidinemethanol (anycmidol); butanedioic acid mono(2,2-dimethylhydrazide) (daminozide); and α-(1-methylethyl)-α-[4-(trifluoromethoxy)phenyl]-5-pyrimidinemethanol (flurprimidol).
Abstract
The growth retardants 2,3:4,6-bis-O (1-methylethylidene)-O (-L-xylo-2-hexulofuranosonic acid) (dikegulac), α-cyclopropyl-α-(p-methoxyphenol)-5-pyrimidine methanol (ancymidol), α-(l-methylethyl)-α-[4-(trifluoromethoxy)phenyl]-5-pyrimidine methanol (flurprimidol) and hand shearing were tested for their effectiveness in reducing total shoot elongation and increasing lateral branch of container-grown Ilex ×meserveae S.Y. Hu cv. Blue Princess. Greatest shoot reduction (44% over a period of 9 months) was achieved by 1.5 and 3.0 mg/pot flurprimidol soil drench treatments. Ancymidol sprays and drenches were less effective, with the maximum reduction (29%, at 5 months) due to 3.0 mg/pot drench. A single spray application of 0.39% dikegulac resulted in the largest increase in lateral branching: 200% over untreated plants and 100% over hand-sheared plants. All dikegulac-treated plants exhibited varying symptoms of phytotoxicity that increased with rate and number of applications.
A common cultural practice in greenhouse production is to apply plant growth retardants (PGRs) to produce uniform, compact, and marketable plants. Plant growth retardants can be applied in several ways, including foliar sprays, substrate drenches
conditions such as temperature and light levels ( Moe et al., 1992b ). Fig. 1. Poinsettia ‘Classic Red’ height response to plant growth retardant (PGR) applications (spray with a mixture of daminozide and chlormequat chloride or drench with paclobutrazol) and
Twenty species of perennials were trialed to determine the effectiveness of five growth retardants on final plant height and flowering. Growth retardant treatments consisted of five sprays: 100 ppm ancymidol, 1500 ppm chlormequat, 5000 ppm daminozide, 30 ppm paclobutrazol, or 15 ppm uniconazole. Also included for comparison were two drenches of 15 ppm paclobutrazol or 7.5 ppm uniconazole. Spray treatments consisted of one application every 10 days until anthesis. Drench treatments consisted of one application only. Data for days to visible bud and anthesis, bud number, and final height were collected. Plant response varied significantly between growth retardant treatments. Sprays of ancymidol, chlormequat, daminozide, paclobutrazol, and uniconazole effectively controlled the height of 4, 3, 13, 4, and 12 species, respectively. Daminozide and uniconazole were the most effective sprays at controlling height on a broad range of species. However, daminozide delayed anthesis compared to control treatments of at least 5 species. Drench treatments of paclobutrazol and uniconazole were effective on 14 and 15 species, respectively. The number of responsive species increased significantly when paclobutrazol was used as a drench rather than a spray. All species tested were responsive to at least one growth retardant treatment.
Abstract
The effects of growth retardant succinic acid 2,2-dimethylhydrazide (SADH) on tomato transplants were evaluated in 9 field experiments. Two or more applications of 5,000 ppm of SADH at the seedling stage offers promise in scheduling tomato harvest by decreasing early yield.
, diameter, and dry weight, where GI = [height + (diameter 1 + diameter 2)/2 + dry weight]/3. Models represent plants grown with or without a plant growth retardant (PGR) drench of 4 mg (1.4 × 10 −4 oz) a.i. paclobutrazol per pot. The intersection of the two
growth retardants are frequently used in bedding-plant production to restrict growth of plants, as they can be easily applied without adversely affecting other crops in the same environment. Plant growth retardants are often applied as foliar sprays, but
Trials involving growth retardants applied in subirrigation water were conducted to evaluate the potential for this method of application and to determine critical concentrations for production of several floriculture crops. Eight concentrations of paclobutrazol or ancymidol ranging from 0 to 0.1 mg·liter–1 were applied continuously (from planting) to five crops. Based upon regression equations, paclobutrazol concentrations resulting in 20% size reduction were 0.005, 0.024, 0.017, >0.1, and >0.1 mg·liter–1 for begonia, chrysanthemum, impatiens, petunia, and salvia, respectively; for ancymidol, respective concentrations were 0.003, 0.01, 0.10, >0.1, and 0.058 mg·liter–1. A second set of trials compared the efficacy of a one-time vs. continuous application of paclobutrazol via subirrigation starting at 2 to 3 weeks after planting. For begonia, a one-time subirrigation application of 0.01 mg·liter–1 paclobutrazol resulted in 30% size reduction, while 0.003 mg·liter–1 applied continuously resulted in 20% size reduction. For impatiens, a one-time subirrigation application of 0.1 mg·liter–1 paclobutrazol resulted in 31% size reduction while 0.03 mg·liter–1 applied continuously resulted in 40% size reduction.
Plants of Euphorbia pulcherrima Wind. `Glory' were grown under total irradiances of 13.4, 8.5, or 4.0 mol·m-2·day-1 and sprayed with water (control), 2500 mg daminozide/liter + 1500 mg chlormequat chloride/liter (D + C), 62.5 mg paclobutrazol/liter, or 4, 8, 12, or 16 mg uniconazole/liter to ascertain plant developmental and postproduction responses to treatment combinations. Anthesis was delayed for plants grown under the lowest irradiance. Anthesis was delayed by the D + C treatment, whereas other growth retardant treatments had no effect on anthesis date. Irradiance did not affect plant height at anthesis, but all growth retardant treatments decreased height over control plants. Inflorescence and bract canopy diameters were decreased at the lowest irradiance level. Growth retardants did not affect individual inflorescence diameters, but all, except paclobutrazol and 4 and 8 mg uniconazole/liter, reduced bract canopy diameter compared with control plants. Plants grown under the lowest irradiance developed fewer inflorescences per plant and fewer cyathia per inflorescence. Cyathia abscission during a 30-day postanthesis evaluation increased as irradiance was decreased; cyathia abscission was unaffected by growth retardant treatment. Leaf abscission after 30 days postanthesis was lowest for plants grown under the lowest irradiance. At 30 days postanthesis, all growth retardant treatments increased leaf abscission over controls. Results indicate that irradiance and growth retardant treatments during production can affect poinsettia crop timing, plant quality at maturity, and subsequent postproduction performance. Chemical names used: 2-chloroethyl-N,N,N-trimethylammonium chloride (chlormequat chloride); butanedioic acid mono (2,2-dimethyl hydrazide) (daminozide); β-[(4-chlorophenyl) methyl]- α -(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol), (E)-1-(p-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-l-penten-3-ol (uniconazole, XE-1019).