Indonesia

Chrysanthemum or mums (Dendranthema grandiflora) have been grown in gardens for hundreds of years but only in last decade scientists emphasized on making them better plants for home garden, rather than for cut flower industry. Pot mums are versatile, attractive, and can be marketed almost in any size and container type. In order to maintain their height, compactness it is necessary to use plant growth retardants. Plant growth retardants are commonly used to inhibit stem elongation of many ornamental plants. Plant growth retardants act by inhibiting cell division in the sub apical meristem of the shoot. They are commonly used in the production of bedding plants to control plant growth and habit during production and to improve plant appearance and quality during marketing. The type of growth inhibition is, in part, dependent on the concentration of growth retardant applied and species. At low concentrations, growth retardants typically reduce cell elongation, whereas at high concentrations the reduction is increasingly due to a reduced cell division. There are several plant growth retardants like Paclobutrazol, Ancymidol, Sumagic, A-Rest, Daminozide, Cycoceal. Plant growth retardants in ornamental plants are commonly applied to limiting stem elongation and produce more compact, sturdy potted plants without changing developmental patterns or evoke phytotoxic effects. Growth retardants also enhance stress tolerance, green colour of the foliar and postharvest longevity. These growth retardants may be applied as foliar spray, drench at different concentrations according to the variety.

This study was conducted to test the potential of paclobutrazol and uniconazole used at the propagation stage as a plant growth retardant (PGR) of kalanchoe cultivars Rako and Gold Strike. Three node terminal cuttings were soaked in 500 mL of 0.05, 0.25, or 0.50 mg·L-1 paclobutrazol or uniconazole solution for 2 h. After soaking treatment, the cuttings were rooted in a fog tunnel with mean daily air temperature of 18.2°C and RH of 66%. Three replicates per treatment and eight plants per each replicate were used. All cuttings rooted well in all treatments. At all applied concentrations, plant height and stem internode length decreased significantly in both cultivars. Uniconazole was more effective than paclobutrazol at similar concentrations in suppressing stem growth. Both PGRs affected the number of leaves when compared with the control. Leaf area was significantly changed by different cultivars and PGR types, but not by the concentrations of PGR. While leaf chlorophyll concentration increased with an increase in the concentration of PGRs. The number of florets was increased in all PGR treatments when compared with the control. Consequently, soaking cuttings in PGR solutions seems to have a potential to reduce stem elongation of kalanchoe. This method of PGR treatment could become an environmentally friendly method in commercial productions, because of low PGR concentration needed and controlled application.

Production of poinsettias ( Euphorbia pulcherrima ) often involves intensive use of plant growth retardants (PGRs) to regulate height. Height control is necessary for visual appeal and postharvest handling. Since PGRs do not always provide consistent height control and can have unwanted side effects, there is interest in alternative methods of height control. Since turgor potential drives cell expansion, and thus stem elongation, drought stress has potential for regulating plant height. Through soil moisture sensor-controlled irrigation, the severity of drought stress can be both monitored and controlled. The objective of our study was to compare poinsettia ‘Classic Red’ height control using PGRs (spray, mixture of daminozide and chlormequat at 1000 mg·L −1 each and drench, 0.25 mg·L −1 paclobutrazol) with the use of controlled water deficit (WD). Graphical tracking of plant height, using a final target height of 43.5 cm, was used to determine when to apply PGR or controlled WD. In the WD treatment, substrate volumetric water content (θ) was reduced from 0.40 to 0.20 m 3 ·m −3 when actual height exceeded the expected height. PGR applications (spray or drench) reduced poinsettia height to 39 cm, below the final target level of 43.5 cm. WD resulted in a height of 44.5 cm, closest to the target height, while control plants were taller (49.4 cm). There was no effect of PGR drenches or WD on bract size, while spraying PGR reduced bract size by ≈ 40%. Bract chroma was unaffected by WD or PGR treatments. There was no difference in shoot dry weight between PGR- and WD-treated plants. Lateral growth was reduced by the PGR treatments, but not by WD. These results indicate that controlled WD can be used to regulate poinsettia height.

Beyond the inhibitory action against the gibberellin biosynthesis, some plant growth retardants (PGRs) can play an important role in regulating plant responses to abiotic stress through the induction of different tolerance mechanisms. The aim of the present study was the exploitation of the potential of PGRs in enhancing the resistance to drought stress in Stevia rebaudiana Bert. Therefore, the effects of three PGRs on stevia plants grown under drought stress condition were investigated. Stevia plants were first subjected to water stress and, second, treated with PGRs to detect PGRs effect on biometric, productive and phytochemical characteristics of drought stressed-plants. The control plants were uniformly irrigated at 3-day intervals, while water-stress conditions were imposed by watering the plants at 12-day intervals. Subsequently, the Chlorocholine chloride (CCC, as Copalyl diphosphate synthase inhibitor and Kaurene synthase inhibitor), Paclobutrazol (PBZ, as Kaurene oxidase inhibitor) and Daminozide (DAM, as anti-gibberellins) were applied in drought stressed-plants. The CCC and DAM were sprayed on stevia shoots, while PBZ was drenched. The obtained results showed that leaf dry weight of stevia plants was significantly reduced by drought stress, but this parameter increased as a consequence of CCC and PBZ treatments. Drought stress also caused a significant reduction in total steviol glycoside (SVglys) content. This reduction was more pronounced in drought stressed-plants treated with CCC, while PBZ was able to counteract the SVglys reduction, with SVgly content similar to that observed in the control. Similarly, PBZ was able to increase the soluble sugar production and total antioxidant capacity in the leaves of stressed-stevia plants. These findings suggested that CCC and, in particular, PBZ had a protective effect on stevia growth under drought stress by induction of antioxidant defenses and soluble sugar production. CCC seems to inhibit gibberellin biosynthesis, preventing the SVglys production, while DAM and PBZ, as gibberellin inhibitors, didn't have a negative effect on SVglys production in drought stressed-plants. This observation seems to emphasize their role in limiting the rate of target enzymes of CCC in SVglys biosynthetic pathway. Moreover, the induction of glucose production, as a substrate for SVglys biosynthesis, could be a convincing evidence for SVglys promotion in PBZ treated-plants.

The effects of the plant growth retardants, uniconazol at 1.25 and 2.5 ppm and paclobutrazol at 12.5 and 100 ppm and root pruning on the growth and yield of tomato plants cultured hydroponically at high temperature during summer were studied.1. Growth of tomato seedlings was suppressed by the plant growth retardants, especially with 100 ppm paclobutrazol or by root pruning.2. All of plant growth retardants decreased the number of nodes to the first truss and advanced anthesis.3. When plant growth retardants were applied to 2-leaf-old seedlings, stem retardation was significant to the 2nd truss.4. Plant growth retardants advanced harvest of the 1st truss.5. Fruit Brix and mean fruit weight were not influenced by the treatments.6. Total yield of 1st and 2nd truss was slightly increased by root pruning.7. Early fruit yield was increased by the plant growth retardants.

Dwarfed stature is a desired trait for modern orchard production systems. One effective strategy for dwarfing cultivation is exogenously applying plant growth retardants (PGRs) to plants. However, for many economic fruit trees, the current knowledge on the regulatory mechanisms underlying the dwarfing effect of PGRs is limited, which largely restricts the agricultural application of PGRs. In this study, we exogenously applied three kinds of PGRs [paclobutrazol, daminozide (B9), and mannitol] to the seedlings of pomegranate (Punica granatum L.) and performed comparative transcriptome analysis to elucidate the molecular features of PGR-induced dwarfing in pomegranates. Our results showed that all the three PGRs could significantly suppress plant growth of pomegranate. The inhibition of auxin biosynthetic processes, as well as auxin-mediated shoot development, may be considered as the main reason for the dwarfing. Besides that, different PGRs were also found to induce dwarfing via specific mechanisms, for example, cellular response to strigolactone was particularly suppressed by the application of paclobutrazol, while the level of carbohydrate homeostasis and metabolism were downregulated in conditions of either B9 or mannitol treatments. Furthermore, exogenous PGR application was supposed to cause adverse impacts on the normal physiological process of pomegranate seedlings, which may bring extra burden to pomegranate plants. These novel findings unveiled the genetic basis underlying the dwarfing in pomegranates, which provides deeper insights into PGR-mediated dwarfing cultivation of pomegranates.

Growth response of Perovskia atriplicifolia (Russian sage) treated with several plant growth retardants (PGRs) was determined under three production regimes: 1) small plants in 10 cm (4 in) pots grown in a greenhouse and half transplanted into the landscape at 6 weeks after treatment (WAT), and 2) large plants grown in 3.8 liter (#1) pots in a greenhouse or 3) in an outdoor nursery. Plants in 3.8 liter (#1) pots were not transplanted into the landscape. Treatments included Cutless at 50, 100 and 150 ppm; Sumagic at 20, 40 and 60 ppm; B-Nine/Cycocel tank mixes at 2,500/1,500, 5,000/1,500 and 7,500/1,500 ppm; Pistill at 500 and 1,000 ppm; and a non-treated control. All PGRs controlled plant growth through 6 WAT in the greenhouse and 2 weeks after planting. At this time (8 WAT), plants treated with the most effective rate of Cutless (150 ppm), Sumagic (20, 40, or 60 ppm), B-Nine/Cycocel tank mixes (5,000 ppm/1,500 ppm), and Pistill (500 or 1,000 ppm) were 32%, 32%, 25%, and 32% smaller in 10 cm (4 in) pots and 21%, 22%, 22%, and 16% smaller in 3.8 liter (#1) pots, respectively, compared to non-treated controls. Treatment effects were non-significant by 4 weeks after plants grown in the greenhouse in 10 cm (4 in) pots for 6 weeks were transplanted into the landscape (10 WAT). Plants in 3.8 liter (#1) pots in the greenhouse were significantly smaller, excluding those treated with Pistill, than non-treated controls at 12 WAT; at this time, the most effective rate of Cutless (150 ppm), Sumagic (40 ppm), and B-Nine/Cycocel tank mixes (5,000 ppm/1,500 ppm) suppressed growth 21%, 23%, and 26%, respectively. For 3.8 liter (#1) pots in the nursery, Cutless suppressed growth 5–11% at 2 WAT only, and the most effective rate of Sumagic (60 ppm) reduced growth 7% at 4 WAT, but not thereafter. The most effective rates of B-Nine/Cycocel (7,500 ppm/1,500 ppm) and Pistill (1,000 ppm) suppressed growth 13% and 10%, respectively, at 8 WAT. Results suggest that PGR effectiveness is less outdoors under nursery conditions than in the greenhouse, particularly for Cutless and Sumagic. The duration and magnitude of B-Nine/Cycocel treatment effects suggest that this PGR combination may provide the most effective growth control of Russian sage under nursery conditions.

WVirwille and Mitchell reported that applications of 2'-isopropyl-4'(trimethylammonium chloride) -5'methylphenyl piperidine-1-carboxylate (Amo 1618) (fig 1, I) to several types of flowering plants led to an abnormal growth habit characterized by shorter stems and internodes (17). Amo 1618 is one of the most active of several carbamate esters containing a quarternary ammonium group which produce this effect (12). Cathey has recently reviewed the physiological effects of these and other plant growth retardants (2). Sachs et al. (15) have shown that application of Amo 1618 leads to a drastic reduction of mitotic activity in the subapical meristem of vegetative, rooted cuttings of Chrysanthemum morifolium. In this case, as in numerous other instances reported in the literature, added gibberellins partly or completely overcome the action of plant growth retardants. [see (2) for a review]. Kende, Ninnemann and Lang (11) have provided evidence for the proposal that at least some of these plant growth retardants may function by inhibiting the production of gibberellins in the plant. This proposal was based initially on their demonstration that the addition of Amo 1618 at 100 ug per ml or of f-chloroethyltrimethylammonium chloride (CCC) at 300 ,ug per ml to the culture medium of Fusarium moniliforme Sheld. leads to a complete inhibition of gibberellin production without affecting mycelial growth (11). Several tvpes of evidence were presented to show that CCC inhibited the biosynthesis of gibberellins rather than causing destruction of preformed gibberellins (13). More recently Baldev et al. have also shown Amo 1618 to be an inhibitor of the accumulation of substances with gibberellin-like activity in developing pea seeds (1). The evidence to be discussed in this paper shows that an enzymic reaction resulting in the production of (-)-kaurene (fig 1, Ia) in a flowering plant system is inhibited in the presence of Amo 1618 or certain other plant growth retardants. (-)-Kaurene is a probable intermediate in the biosynthesis of gibberellins. Not only did Cross et al. (5, 6) isolate this compound from culture filtrates of F. noniliforme along with gibberellins, but they also demontrated in these cultures a conversion of (-) -kauretne labeled with C14 in the exocyclic methylene group to C14-gibberellic acid (fig 1, III) labeled in the same positioni (4). Recently we have confirmed this finding with C'4-labeled (-)-kaurene (9). The substrate in this case was derived from 2-C14-mevalonate in the endosperm nucellus of Echinocystis macrocarpa Greene (wild cucumber) seed. Furthermore, Phinney et al. (14) have reported that (-)-kaurene promotes growth of the dwarf-5 mutant of Zea mays, an effect qualitatively indistinguishable from that induced by an added gibberellin. This evidence considered together strongly supports the idea that (-)kaurene is an intermediate in gibberellin biosynthesis. Thus, an inhibition of (-)-kaurene synthesis would result in an inhibition of gibberellin synthesis. The endosperm of E. macrocarpa seed, a source knowln to be relatively rich in gibberellins and gibberellin-like substances (3,8,16), was used in the studies reported in this paper as a source of enzymes which catalyze the formation of (-)-kaurene. (-)kauren19-ol (fig 1, IIb) and trans-geranylgeraniol (fig 1, IV) from mevalonate (7, 9). Since these diterpenoid metabolites are involved in the gibberellin biosynthesis pathway, a study of the effects of Amo 1618 and other growth retardants on their formation was undertaken.

본 연구는 기내 배양한 나도 풍란에 식물생장억제제인 Uniconazole, Ancymidol, Paclobutrazol의 종류별, 농도별 처리가 식물체내 내생 GA 유사물질의 활성 및 ABA 유사물질의 함량의 변화에 미치는 영향을 알아보기 위하여 실시되었다. 지상부인 잎에서는 Uniconazole 0.05 mg/L, Ancymidol 0.1 mg/L, Paclobutrazol 0.3 mg/L 처리 시 ABA 유사물질의 함량은 대조구보다 낮았으며, GA유사물질의 활성은 대조구 보다 높거나 비슷한 수준이었다. 하지만 처리농도가 높아짐에 따라 ABA 유사물질의 농도는 높아졌으나, GA 유사물질의 활성은 비교적 억제되었다. 지하부인 뿌리에서는 Uniconazole 0.05, 0.2mg/L, Ancymidol 0.2 mg/L, Paclobutrazol 0.1 mg/L 처리에서 ABA 유사물질의 함량이 대조구보다 낮았고, 그 이상의 농도에서는 높았다. GA 유사물질의 활성은 비교적 저 농도에서는 높았으나, 고농도 처리에서는 저 농도와 비교하여 활성이 억제되었다. This experiment was conducted to identify the effect of several plant growth retardants on endogenous ABA-like substance content and GA-like substance activity in seedlings of Sedirea japonica cultured in vitro. When seedlings of Sedirea japonica were treated with low concentration of 0.05 mg/L Uniconazole, 0.1 mg/L Ancymidol and 0.3 mg/L Paclobutrazol, the content of ABA-like substances of the leaf was lower than that of the control. However, the activity of GA-like substances was similar or higher in treated seedlings. In the mid and high concentrations of three kinds of growth retardants, the ABA-like substance content was increased, but GA-like substance activity was inhibited. The content of ABA-like substances in the root was lower in 0.05 and 0.2 mg/L Uniconazole, 0.2 mg/L Ancymidol and 0.1 mg/L Paclobutrazol treatments than that of the control, but in the mid and high concentration treatments, the content was increased. GA-like substance activity in low concentration was increased but in the mid and high concentration, the activity was inhibited compared with low concentration treatment.

Plant growth retardant as one of plant growth regulator can inhibit the cell division, elongation and growth rate in shoot apical meristem (SAM), which can be reversed by gibberellin regulate the product of photosynthesis transfer to the root and rhizome part. As commonly used plant growth retardant, paclobutrazol, uniconazole, chlorocholine chloride, mepiquat chloride, choline chloride and daminozide are used to promote the growth of root and rhizome, call as "zhuanggenling", "pengdasu", "pengdaji" etc. Single or recombination of plant growth regulator is registered as pesticide, and called as pesticide "zhuanggenling" in this paper. Growth regulator which registered as a foliar fertilizer or fertilization was called agricultural fertilizer "zhuanggenling" in this paper. The author investigate the usage of "zhuanggenling" in the root and rhizome of medicinal plants cultivation from 2012 to 2014 in Sichuan province, Huangyuan town, Mianyang (Ophiopogonis Radix); Pengzhou Aoping town (Chuanxiong Rhizoma); Pengshan Xiejia town (Alismatis Rhizoma); Jiangyou Taiping town and Zhangming town (Aconiti Lateralis Radix Praeparata); Yunnan Wenshan (Notoginseng Radix et Rhizoma); Henan province, Wuzhidafeng Town (Rehmanniae Radix, Achyranthis Bidentatae Radix, Dioscoreae Rhizoma); Gansu Min county (Codonopsis Radix, Angelicae Sinensis Radix); Gansu Li county (Rhei Radix et Rhizoma). The result showed that "zhuanggenling" were applied in the most medicinal plant cultivation except Rhei Radix et Rhizoma. It has been applied widespreadly in Ophiopogonis Radix, Alismatis Rhizoma, Achyranthis Bidentatae Radix, Codonopsis Radix; Rehmanniae Radix, commonly in Angelicae Sinensis Radix application, and occasionally in Chuanxiong Rhizoma, Aconiti Lateralis Radix Praeparata, Notoginseng Radix et Rhizoma and Dioscoreae Rhizoma. In 53 collected sample from plantation areas, fifteen (28%) were pesticide "zhuanggenling", thirty-eight (72%) were pesticide "zhuanggenling". UPLC analysis results showed that 38 farmers fertilizer "zhuanggenling" content of 6 kinds of plant growth retardant. It is regarded that fertilizer "zhuanggenling" was dominant in medicinal plant cultivation, and that the plant growth retardant is added widespreadly in farm fertilizer "zhuanggenling". All evidence proves conclusively that "zhuanggenling" have been used in the proper way, whereas some others have been misused or even abused in the use regarding to type, number, use frequency. The root or rhizoma are increased to 20%-200%. But there is lack of evaluation to appraise the quality of medicinal materials from the aspects of research or industry. "zhuanggenling" has become a important Chemical control material besides fertilizer, insecticidal sterilization of pesticide

St. Augustinegrass [(Stenotaphrum secundatum (Walt.) Kuntz.] is the preferred warm‐season turfgrass for Florida's commercial and residential landscapes with an estimated 0.7 million hectare under growth and management. Limited published information is available on St. Augustinegrass response to plant growth retardants (PGRs). A 2‐yr study was implemented to monitor St. Augustinegrass turf quality, lateral stolon growth, percent cover, mowing frequency, cumulative turfgrass clippings, and seedhead suppression following PGR application. Treatments were applied on 23 June 1995 and 22 June 1996 as a single application (SIA) at label use rate (LUR) or as twin split applications (TSA) at half LUR each: the sequential application was only used when mowing interval equaled the untreated. The PGRs and rates were flurprimidol [α‐(1‐methylethyl)‐α‐[4‐(trifluoro‐methoxy)phenyl]‐5‐pyrimidine‐methanol] and paclobutrazol [(+/−)‐(R*,R*)‐β‐[(4‐chloro‐phenyl)methyl]‐α‐(1,1‐dimethylethyl)‐1H‐1,2,4‐triazole‐1‐ethanol] at 1.12 kg ha−1 for SIA and 0.56 kg ha−1 for TSA, trinexapac‐ethyl [4‐(cyclopropyl‐α‐hydroxymethylene)‐3,5‐dioxocyclohexane carboxylic acid ethylester] and mefluidide [N‐[2,4‐dimethyl‐5‐[[trifluoromethyl)sulfonyl]amino]phenyl]acetamide] at 0.28 kg ha−1 for SIA and 0.14 kg ha−1 for TSA, and imazapic [(±)‐2‐[4,5‐dihydrol‐4‐methyl‐4‐(1‐methylethyl)‐5‐oxo‐1H‐imidazol‐2‐yl]‐5‐methyl‐3‐pyridine‐carboxylic acid] at 0.028 kg ha−1 for SIA and 0.014 kg ha−1 for TSA. Responses were observed for a 12‐wk period following initial application, and turf quality was acceptable (>7) for all PGRs. Turf quality for imazapic was generally better than the untreated for Weeks 6 to 10. Greatest control of lateral stolon growth 10 wk after initial application was achieved with TSA of imazapic (68%) and mefluidide (61%). Percent cover 12 wk after initial application was lowest for SIA and TSA imazapic (66 and 53%, respectively). Greatest reduction in mowing frequency was provided by trinexapac‐ethyl (50%), while flurprimidol and mefluidide reduced mowing frequency by 26 and 20%, respectively. The only PGR that reduced cumulative turfgrass clippings (CTC) was trinexapac‐ethyl (63%). Greatest seedhead inhibition during peak production (about 35%) was provided by imazapic and mefluidide. The two most effective PGRs were trinexapac‐ethyl (reduced mowing frequency and CTC) and imazapic (controlled lateral stolon growth and seedhead production), while mefluidide demonstrated some potential. Combinations of these products could be examined in future studies.

Petunia (Petunia × hybrida) plants are treated with plant growth retardant (PGR) to inhibit stem growth. However, the effects of PGR differ depending on the PGR type, direction of use, and plant species or cultivars. In red petunias, PGR treatment inhibits coloration. Here, we investigated the effects of gibberellin (GA) and four PGRs, namely, daminozide (SADH), trinexapac-ethyl (TNE), paclobutrazol (PBZ), and prohexadione-calcium, on four Petunia cultivars with different coloration patterns: ‘Baccara Red’, ‘Red morn’, ‘Red picotee’ and ‘Star Red and White’). The SADH, TNE, and PBZ treatments effectively inhibited stem growth in all four cultivars. The SADH treatment affected the corolla coloration of the ‘Star Red and White’ (star type color pattern) and ‘Red Picotee’ (picotee type color pattern), however, did not affect ‘Baccara Red’ and ‘Red Morn’ (gradation coloration pattern) cultivars. These results suggest that the effects of SADH treatment on corolla coloration differ depending on the cultivar. We elucidated that the alteration in coloration by SADH in ‘Star Red and White’ and ‘Red Picotee’ was caused by GA activity suppression. However, the corolla coloration of ‘Red Morn’ was not affected by SADH or GA. These findings indicated that variations in GA activity may result in different coloration patterns. This study demonstrated that treatment with four types of PGRs inhibited stem elongation and affected flower coloration patterns in petunia. Additionally, GA may play a role in the formation of petunia bicolor patterns.

Plant growth retardant (PGR) refers to organics that can inhibit the cell division of plant stem tip sub-apical meristem cells or primordial meristem cell. They are widely used in the cultivation of rhizomatous functional plants; such as Codonopsis Radix, that is a famous Chinese traditional herb. However, it is still unclear whether PGR affects the medicinal quality of C. Radix. In the present study, amino acid analyses, targeted and non-targeted analyses by ultra-performance liquid chromatography combined with time-of-flight mass spectrometry (UPLC-TOF-MS) and gas chromatography-MS were used to analyze and compare the composition of untreated C. Radix and C. Radix treated with PGR. The contents of two key bioactive compounds, lobetyolin and atractylenolide III, were not affected by PGR treatment. The amounts of polysaccharides and some internal volatiles were significantly decreased by PGR treatment; while the free amino acids content was generally increased. Fifteen metabolites whose abundance were affected by PGR treatment were identified by UPLC-TOF-MS. Five of the up-regulated compounds have been reported to show immune activity, which might contribute to the healing efficacy (“buqi”) of C. Radix. The results of this study showed that treatment of C. Radix with PGR during cultivation has economic benefits and affected some main bioactive compounds in C. Radix.

In one experiment conducted in 1998 and two in 1999, Coreopsis rosea ‘American Dream’, or pink coreopsis, were treated with four plant growth retardants (PGRs): B-Nine from 2500 to 7,500 ppm, Cutless from 25 to 150 ppm, Sumagic from 10 to 40 ppm, and Bonzi from 25 to 100 ppm. The study was conducted to determine whether PGRs could be used to suppress growth of pink coreopsis without delaying flowering or causing phytotoxicity. Application of B-Nine, Cutless, or Sumagic suppressed plant growth 13–31% at first flower and when plants were marketable (one-third of flowers open) in all experiments and improved plant quality compared to controls. Plants treated with B-Nine, Cutless, or Sumagic had quality ratings 52–67% higher than those of control plants when marketable; treated plants appeared denser and more floriferous. Time to first flower and to a marketable stage were minimally affected by PGR application, and no phytotoxicity was observed. Bonzi did not significantly control growth or affect flowering of pink coreopsis in any of the three experiments.

Plant growth retardant (PGR) substrate drenches (in milligrams active ingredient) of ancymidol at 0.25, 0.5, 1, 2, or 4; paclobutrazol at 1, 2, 4, 8, or 16; and uniconazole at 0.25, 0.5, 1, 2, or 4 were applied to pampas grass (Cortaderia argentea Nees) to compare their effectiveness at chemical height control during greenhouse forcing and evaluate the residual effect on plant growth in the landscape. Cortaderia argentea plant height exhibited a quadratic dose response to paclobutrazol and uniconazole, while ancymidol-treated plants showed a linear dose effect. During greenhouse production, all rates of uniconazole reduced plant height by 56% to 71% compared to the untreated control, whereas paclobutrazol and ancymidol treatments reduced plant height by 14% to 61% and 0% to 34%, respectively. Severe height retardation was evident at 2 mg of uniconazole. By week 5 in the field all plants treated with uniconazole, paclobutrazol doses of 4, 8, or 16 mg, and with 4 mg of ancymidol were shorter than the untreated control. By week 24 in the field, all plants exhibited similar heights except plants treated with uniconazole at 1, 2, or 4 mg remained shorter than the untreated control. In conclusion, each PGR was effective in controlling plant height of Cortaderia argentea during greenhouse forcing. Furthermore, plants treated with low to moderate rates of ancymidol or paclobutrazol grew out of the regulating effect by week 5 in the landscape. These results demonstrate that PGR can be effectively and economically employed in the production of Cortaderia argentea.