Efeito de reguladores vegetais sobre o crescimento e o florescimento de grama-esmeralda - Plantas Daninhas (2024)

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Planta Daninha, Viçosa-MG, v. 31, n. 3, p. 695-703, 2013695Effect of plant regulators on growth and flowering of ‘Meer’ ...1 Recebido para publicação em 11.7.2012 e aprovado em 26.1.2013.2 Engo. Agro., Prof., Dr., Universidade Federal de Mato Grosso – UFMT, Avenida Governador Jaime Campos, 6390 – Barra doGarcas-MT, 78600-000, <sidneimarchi.ufmt@gmail.com>; 3 Engo. Agro., Prof., Dr., Faculdade de Ciências Agronômicas –FCA/UNESP, Dep. de Produção Vegetal-Agricultura, Fazenda Experimental Lageado, s/n, Caixa Postal 237, 18610-307 Botucatu-SP;4 Engo. Agro., Prof., Dr., Centro de Ciências Agrárias, Universidade Estadual do Oeste do Paraná, Caixa Postal 91, 85960-000Marechal Cândido Rondon-PR; 5 Engo. Agro., Dr., Syngenta Proteção de Cultivos Ltda., Avenida das Nações Unidas, 18001 –2o andar, 04795-900 São Paulo-SP.EFFECT OF PLANT REGULATORS ON GROWTH AND FLOWERING OF‘MEYER’ ZOYSIAGRASS1Efeito de Reguladores Vegetais sobre o Crescimento e o Florescimento de Grama-EsmeraldaMARCHI, S.R.2, MARTINS, D.3, COSTA, N.V.4, and SILVA, J.R.V.5ABSTRACT - This trial aimed to evaluate the effect of sequential applications of differentplant regulators over growth and flower rachis emission of ́ Meyer´ zoysiagrass (Zoysia japonica).The study was conducted on 15-month old green turfgrass under a randomized completeblock design with four replications. The following plant regulator and doses were tested:trinexapac-ethyl (113+113, 226+113, 226+226, 452+113, 452+226, 452+452, 678+339 e904+452 g a.i./ha-1), prohexadione-calcium (100+100 e 200+200 g a.i. ha-1) and bispyribac-sodium (40+40 e 60+60 g a.i. ha-1), as well as an untreated control. The turfgrass was mowedagain at 3.0 cm aboveground and the second plant regulator was applied when ‘Meyer’zoysiagrass was between 5.0 and 6.0 cm high. The effect of the treatments was visually ratedfor visual injury, plant height, height and number of flower rachis, and total dry mass productionof clippings. Only bispyribac-sodium had visual symptoms of injury on ‘Meyer’ zoysiagrass,and no intoxication was observed at 28 days after the second application (DAAB). Thesequential applications of trinexapac-ethyl, prohexadione-calcium and bispyribac-sodiumreduced by more than 80% the total clipping dry mass produced by ‘Meyer’ zoysiagrass. Allthe plant regulators tested also showed promising results in reducing the height and emissionof rachis, especially when trinexapac-ethyl was applied at the doses 452+452, 678+339 and904+452 g a.i. ha-1. ‘Meyer’ zoysiagrass turfgrass can be handled with the sequential applicationof a plant regulator, which reduces the need for mowing over a period up to 110 days after theapplication of the second plant regulator, and it also avoids deleterious visual effects overturfgrass.Keywords: Zoysia japonica, trinexapac-ethyl, prohexadione-calcium, bispyribac-sodium, sequential application.RESUMO - Este trabalho teve o propósito de avaliar o efeito da aplicação sequencial de diferentesreguladores vegetais sobre o crescimento e a emissão de hastes florais da grama-esmeralda (Zoysiajaponica). O estudo foi instalado em um gramado com 15 meses, no delineamento de blocoscasualizados com quatro repetições, e os reguladores de crescimento e doses testados foram:trinexapac-ethyl (113+113, 226+113, 226+226, 452+113, 452+226, 452+452, 678+339 e904+452 g i.a. ha-1), prohexadione-calcium (100+100 e 200+200 g i.a. ha-1) e bispyribac-sodium(40+40 e 60+60 g i.a. ha-1), além de uma testemunha sem aplicação de regulador de crescimento.Quando os tratamentos atingiram altura entre 5,0 e 6,0 cm, o gramado foi novamente aparado a3,0 cm de altura, sendo em seguida realizada a aplicação da segunda dose dos reguladores. Oefeito dos tratamentos foi avaliado quanto à fitointoxicação, por meio de avaliação visual, altura deplantas, altura e emissão de hastes florais e produção de massa seca de aparas. Apenas o bispyribac-sodium apresentou sintomas visuais de injúria, não se verificando mais intoxicação aos 28 dias apósa segunda aplicação (DAAB). As aplicações sequenciais do trinexapac-ethyl, prohexadione-calcium ebispyribac-sodium apresentaram reduções acima de 80% na quantidade total de massa seca deaparas produzidas pela grama-esmeralda. Todos os reguladores de crescimento também demonstraramMARCHI, S.R. et al.Planta Daninha, Viçosa-MG, v. 31, n. 3, p. 695-703, 2013696ser promissores em relação ao retardamento do crescimento e da emissão das inflorescências, comespecial destaque para o trinexapac-ethyl aplicado nas doses de 452+452, 678+339 e904+452 g i.a. ha-1. Gramados formados com grama-esmeralda podem ser manejados com a aplicaçãosequencial de regulador vegetal, com a redução da necessidade de cortes por um período de até110 dias após a aplicação, além de não causar efeito deletério no aspecto visual sobre o gramado.Palavras-chave: Zoysia japonica, trinexapac-ethyl, prohexadione-calcium, bispyribac-sodium, aplicação sequencial.INTRODUCTIONGood turfgrass maintenance provides asafe and comfortable place for leisure andsports activities, reduces air heating, releasesoxygen and captures atmospheric CO2, thusmitigating the greenhouse effect, and it alsoreduces the exposure of the soil to erosion.Turfgrass can be used for different purposesin different locations, such as residentialareas, industrial and urban areas, slopes andhillsides and road beds. However, it is best usedin sports activities, especially in soccer, golfand baseball fields.There are dozens of species and varietiesof grass for various purposes (Arruda &Henriques, 1995). The most used in Brazil are:Bahia Grass (Paspalum notatum), Americancarpet grass (Axonopus compressus) St.Augustine grass (Stenotaphrum secundatum),Korean Velvet grass (Zoysia tenuifolia),Bermudagrass (Cynodon dactylon) and,particularly, ’Meyer’ zoysiagrass (Zoysiajaponica).’Meyer’ zoysiagrass, originally fromJapan, is also known as wild zoysia, zoysiagrass or simply zoysia. It is a herbaceousrhizomatous creeping perennial grass. Itranges in height from 10 to 15 cm, and it hasnarrow and small leaves arranged in short andthick stems. It looks like a perfect lawn whenmown frequently (Lorenzi & Souza, 2001).One of the advantages of using ‘Meyer’zoysiagrass is the formation of a beautiful lawnat intermingling of penetrating stolon whichroots easily. It has great beauty, tender leavesand resistance to trampling; it is the mostversatile type of grass (Alvarez & Henriques,1995). However, regardless of the type of useor the choice of species, the major expenditurein the cost of turfgrass maintenance is theuse of mowing to maintain proper height(Freitas et al., 2002). The successive mowingoperations on the turfs are basically relatedto plant growth and grass flowering, especiallybetween October and March (Kissmann &Groth, 1992).Turfgrass leaves are expected to grow upto a certain limit, beyond which the lowerleaves are subject to self-shading and becomechlorotic, acquiring yellowish spots aftermowing. Another factor that changes thevisual quality of turfgrass is the intense flowerstem emission, which usually has shades ofcolors that differ from the color of leaves.Moreover, both the leaves as the flower stemscan reach excessive heights, which affect thepractice of sports and the comfort of users.Thus, expenditures on successive mowingoperations as well as aesthetic appeal call foralternatives to mechanical management, andone of them is to use plant growth regulators.The use of growth regulators is a commonpractice in the management of several speciesof grass in the United States, especially TypeI regulators, i.e., inhibitors of cell division, suchas mefluidide and maleic hydrazide, andType II regulators, which are inhibitors ofcell elongation, such as trinexapac-ethyl,paclobutrazol and prohexadione-calcium(McCullough et al. 2004; Ervin & Zhang, 2007).Particularly, Type II regulators are compoundsable to modifythe concentration of hormonesin plants and to promote smooth expansionsof leaf area and the development of sidestructures without incurring undesirableincreases in the top growth of grass species(McCullough et al. 2004).However, growth regulators can producesome undesirable effects if not used carefully.The occurrence of visual injury, therebychanging the visual quality of the turf, is oftenreported. Leaf injury varies according toenvironmental conditions: in temperateregions, dark green spots are observed(Ervin & Koski, 2001; Heckman et al., 2005,McCullough et al., 2006), while discolorationPlanta Daninha, Viçosa-MG, v. 31, n. 3, p. 695-703, 2013697Effect of plant regulators on growth and flowering of ‘Meer’ ...characterized by yellowing leaves is seen intropical regions (Heckman et al., 2001,McCullough et al., 2005, McCarty et al., 2011).Besides reducing plant growth, Type Igrowth regulators are also effective insuppressing floral emissions. In contrast, TypeII inhibitors are ineffective in suppressing theemission of flower stems (Johnson, 1990; Fry,1991; Mittlesteadt et al. 2009).Low-dose single applications usually resultin low levels of injury associated with shortperiods of growth control in height andreduction of inflorescence. In contrast, highdoses provide better results for longer periods,but with higher levels of injury. This imbalancebetween efficiency and injury can be solvedwith sequential applications involving well-adjusted doses (fa*gerness & Yelverton, 2000;Lickfeldt, et al., 2001, McCarty et al., 2004;Waltz Jr. & Whitwell, 2005; Ervin & Zhang,2007; McCullough et al., 2007).Thus, this study aimed to verify the effectof the sequential application of differentdoses of growth regulators trinexapac-ethyl,prohexadione-calcium and bispyribac-sodiumon growth and flowering of ’Meyer’ zoysiagrass.MATERIAL AND METHODSThe study was conducted in theexperimental area of the Center for AdvancedResearch in Weed Science - NuPAM,Department of Plant Production, owned by theFaculty of Agricultural Sciences of Botucatu/UNESP, whose geographic coordinates are:22º07’56" S latitude and 74º66’84" W longitude,and altitude of 760 meters. The turf,approximately 15 months old, was formed from’Meyer’ zoysiagrass in area which receivedoverhead irrigation. The soil was classified asa red Alfisol, clayish texture, moderate degree,dystrophic (Embrapa, 2006). After applicationof 2.6 t ha-1 lime, a chemical analysis revealedthe characteristics shown in Table 1.During development, the turf was kept atan average height of 3.0 cm aboveground bysuccessive mowing with an engine-poweredmechanical mower, equipped with a rotarycutting blade and a special device to collectclippings.The treatments, shown in Table 2, werearranged in a randomized complete blockdesign with four replications. The total areaof each plot was 1.5 m wide and 2.5 m long,totaling 3.75 m2. Besides the control plot, astrip of 0.5 m2 was maintained along theexperimental blocks as lateral control, so thatthe injury caused by growth regulators couldbe better monitored.Applications were made with a CO2pressurized backpack sprayer containing abar with two flat spray tips VS TP 80.02,interspaced at 50 cm. The entire assemblywas maintained at a constant pressure of2.0 bar, so that the solution volume wasequivalent to 200 L ha-1.Table 1 - Attributes for chemical characterization of the soil in the experimental area in the layer of 0-200 mmpH CaCl2 C org. P Ca Mg K Al H+Al CTC V Fe2O3(0,01 mol L-1) (g kg-1) (mg kg-1) (mmolc kg-1) (g kg-1)5.9 15 12 27 13 9.6 0.3 32.9 82.9 60 176Dose (g i.a.ha-1)Treatment 1stApplication2ndApplication\1 Total1. trinexapac-ethyl 113 113 2262. trinexapac-ethyl 226 113 3393. trinexapac-ethyl 226 226 4524. trinexapac-ethyl 452 113 5655. trinexapac-ethyl 452 226 6786. trinexapac-ethyl 452 452 9047. trinexapac-ethyl 678 339 10178. trinexapac-ethyl 904 452 13569. prohexadione-calcium 100 100 20010. prohexadione-calcium 200 200 40011. bispyribac-sodium 40 40 8012. bispyribac-sodium 60 60 12013. Control - - -Table 2 - Growth regulators and doses used in the first andsecond applications on ‘Meyer’ zoysiagrass1/ Second application when the average height of the treated areawas between 5 and 6 cm in height.MARCHI, S.R. et al.Planta Daninha, Viçosa-MG, v. 31, n. 3, p. 695-703, 2013698The first application was made at the endof November, with partly cloudy skies, airtemperature of 26.3 oC, relative air humidityof 69% and wind gusting to 9.0 km h-1, SEdirection. During application, the plots wereprotected laterally with screens of plasticcanvas, in order to avoid spraying theregulators onto adjacent parcels. Altogether,the experiment was conducted from Novemberto early May – a period favorable to plant andreproductive growth of ’Meyer’ zoysiagrass inthe area where the study was undertaken.When the treatments ranged between 5.0and 6.0 cm in height, the turf was mowed toapproximately 3.0 cm, and then the seconddose of growth regulators was applied. Theclippings were collected, placed in paper bagsand maintained in a forced air circulationincubator at 65 oC to achieve constant drymass for dry matter determination.Ratings of injury and growth reductionwere made weekly until mid-April, at whichtime both the control and the treated areasshowed no change in height over time becauseof the decrease in temperature and length ofdaylight, phenomena which are typical of fallin the region where the study was conducted.The injuries caused by the treatmentswere visually rated according to a scale of 0%- 100%, where 0 represents no injury and100 represents plant death. The reduction ingrowth was assessed by direct measurementof plant height with a ruler graduated incentimeters. Height and number ofinflorescences were measured by sampling anarea of 0.25 m2 in the center of the plots, beforethe turf was mowed for reapplication, and alsoat the end of the trial period, in order to obtainthe total dry mass of clippings (TDMC), whichis represented by the sum of the dry mass ofboth clippings. The results were submitted toanalysis of variance by the F-test; in case ofsignificance, the means were compared byTukey’s test at 5% probability.RESULTS AND DISCUSSIONFigure 1A shows the average heights of’Meyer’ zoysiagrass evaluated at seven daysafter application of the regulators (DAA), whenit was observed that none of the treatmentshad reached a height of 5.0 cm, and at 14 DAA,when height ranged between 5.0 and 6.0 cmin all the treatments where regulators hadbeen applied (Figure 1B), thus allowing formowing and application of the second dose.The resumption of growth in height is acommon event for most tropical grasses. Thisis because non-structural carbohydrates likeglucose, fructose, sucrose and starch can bestored and used as backup energy for stresstolerance, dormancy recovery and regrowthafter shoot removal (Waltz Jr. & Whitwell,2005). In this study, the rapid resumption ofgrowth in height was due, especially, to theredistribution of nonstructural carbohydratesthat were stored in the rhizomes and stolonsFigure 1 - Graph of the average height of ‘Meyer’ zoysiagrass obtained at 7 (A) and 14 (B) days after the first application (DAA)of growth regulators.ControlControlPlanta Daninha, Viçosa-MG, v. 31, n. 3, p. 695-703, 2013699Effect of plant regulators on growth and flowering of ‘Meer’ ...of ’Meyer’ zoysiagrass immediately after theleaves were mowed for application of growthregulators (McCarty et al ., 2004; Waltz Jr. &Whitwell, 2005; Ervin & Zhang, 2007;McCullough et al., 2007). It should be noted thatsingle doses of Type II growth regulatorspromote not only the obvious reduction in theconcentration of gibberellins, but also anincrease in the total chlorophyll b in the leavesup to two weeks after application.Thus, theleaves are more efficient at capturing lightenergy, and, hence higher CO2 fixationand higher production of non-structuralcarbohydrates occur (Ervin & Koski, 2001;Ervin & Zhang, 2007).In Table 3, it can be seen that none of thetreatments involving trinexapac-ethyl andprohexadione-calcium caused injuries onleaves of ’Meyer’ zoysiagrass at 7, 21 and28 days after the second application (DAAB).The second application of bispyribac-sodium at 40 and 60 g a.i. ha-1 resulted ininjuries of 56 and 59%, respectively, at 7 DAAB.These injuries were characterized byyellowing of leaves - a characteristic symptomof ALS inhibiting herbicides. However, thelevels of injury regressed considerably in theevaluation performed at 21 DAAB, with fullrecovery of turf coloring at 28 DAAB (Table 3).The use of type II growth regulatorsgenerally provides visual symptoms ofphytotoxicity when applied in grams(Heckman, et al. 2001; McCullough et al. 2005;McCarty et al. 2011), a similar effect causedby the use of ALS inhibiting herbicides(McDonald et al. 2006).Some research has shown that thedeleterious effects of injury caused bytrinexapac-ethyl and bispyribac-sodium maybe rapidly reversed with the use of anadditional source of iron or nitrogen, whichplay an important role in the formation ofchlorophyll, which gives back the grass leavestheir green coloring (Johnson, 1997, Zhanget al. 2002; Ervin et al. 2004; McDonald et al.2006). In this study, the rapid recovery of’Meyer’ zoysiagrass is probably associated withthe high amount of iron available in theexperimental area, given that the chemicalanalysis revealed a content of 176 g kg-1 of ironoxide (Fe2O3).Plant growth of ’Meyer’ zoysiagrass wassignificantly modified by growth regulators,and the effects on plant height extended up to110 days after the second application period.The assessments were discontinued at110 days after second application because theplant development stays stabilized on controltreatment as a result of weather and seasonconditions (temperature and luminositydecreased). It should be noted that the entireperiod between the first application of growthregulators and the final evaluation comprised124 days.Table 4 shows that trinexapac-ethyl wasthe main regulator of the development of’Meyer’ zoysiagrass, because all the dosesapplied were able to reduce plant height,regardless of when the rating was made.Height growth was reduced by more than 53%,compared to the growth observed in the control,even when the lowest sequential dose wasused: 113 +113 g a.i. ha-1.The trinexapac-ethyl doses in sequentialapplications of 452+226, 452+452, 678+379and 904+452 g i.a ha-1 were the most effectiveTable 3 - Means of the signs of injury observed in ‘Meyer’zoysiagrass after the second application of growth regulatorsInjury (%) – DAAB1/Treatment7 212/ 28trinexapac-ethyl 113+113 0 a 1.0 a (0) 0trinexapac-ethyl 226+113 0 a 1.0 a (0) 0trinexapac-ethyl 226+226 0 a 1.0 a (0) 0trinexapac-ethyl 452+113 0 a 1.0 a (0) 0trinexapac-ethyl 452+226 0 a 1.0 a (0) 0trinexapac-ethyl 452+452 0 a 1.0 a (0) 0trinexapac-ethyl 678+339 0 a 1.0 a (0) 0trinexapac-ethyl 904+452 0 a 1.0 a (0) 0prohexadione-calcium 100+100 0 a 1.0 a (0) 0prohexadione-calcium 200+200 0 a 1.0 a (0) 0bispyribac-sodium 40+40 56 b 1.3 a (1) 0bispyribac-sodium 60+60 59 b 3.8 a (4) 0Control 0 a 1.0 a (0) 0F Treatment 803.07* 1.66NS -F Block 0.55NS 1.20NS -DMS 3.82 1.50 -CV (%) 17.23 47.93 -1/ DAAB = days after the second application. 2/ Means transformedto √Y+1.0. Original means between brackets. NS – non-significant.* significant at 5% probability. Means followed by the same letterin the column do not differ by the Tukey’s test at 5% probability.MARCHI, S.R. et al.Planta Daninha, Viçosa-MG, v. 31, n. 3, p. 695-703, 2013700in retaining the vertical growth of ’Meyer’zoysiagrass, since an increase of only 0.3 cmwas observed between the assessments at 7and 110 days after the second application. Itshould be noted that the increases found inother sequential applications of trinexapac-ethyl ranged between 0.7 and 1.8 cm (Table4).The prohexadione-calcium used in thesequential application of 200+200 g a.i. ha-1was effective in reducing the vertical growthof ’Meyer’ zoysiagrass at 63 DAAB, whilebispyribac-sodium at the doses of 40+40 and60+60 g a.i. ha-1 reduced the height of ’Meyer’zoysiagrass only until 28 DAAB (Table 4).Although these three treatments have shownstatistically lower height than that of thecontrol throughout the trial period, it wasobserved that the height of ’Meyer’ zoysiagrassobtained at 110 DAAB was almost twiceas much as the one observed at 7 DAAB,representing a 43% reduction compared withthe height of the control.In contrast, calcium-prohexadione insequential applications of 40+40 g a.i. ha-1 wasvirtually ineffective for retaining the verticalgrowth of ’Meyer’ zoysiagrass, providing only a23.5% reduction in the height of the turf, andthus statistically similar to the height of thecontrol in most of the assessments made(Table 4). The reduction in top growth observedin ’Meyer’ zoysiagrass corroborates thedata obtained by Ervin et al. (2002), Beam(2004) and Costa et al. (2009). Additionally,Ervin et al. (2002) commented that thesequential application of trinexapac-ethyl isa management practice of Z. japonica,especially in areas with low light condition.Table 5 shows that only the prohexadione-calcium applied in the sequential dose of100+100 did not reduce inflorescence height,which was statistically similar to the control.All other treatments showed significantreductions in the height of inflorescences,with special emphasis on the highest doses oftrinexapac-ethyl (452+452, 678+339 and904+452 g a.i. ha-1), which showed statisticallylower heights than the one obtained in thecontrol.Johnson (1994) suggests that for a growthregulator to be commercially acceptable, itmust reduce the emission of the flowerTable 4 - Mean height values of ‘Meyer’ zoysiagrass obtained after the second application of the growth regulatorsGrass height (cm) – DAAB1/ ReductionTreatment7 14 21 28 63 110 (%)2/trinexapac 113+113 3.0 A 3.0 a 3.3 a 3.4 A 4.0 ab 4.8 ab 64.7trinexapac 226+113 5.6 A 5.9 ab 6.0 ab 6.0 Abc 6.4 abc 6.3 ab 53.6trinexapac 226+226 3.0 A 3.1 a 3.2 a 3.3 A 3.8 ab 4.3 a 73.6trinexapac 452+113 3.1 A 3.3 a 3.2 a 3.3 A 4.2 ab 4.3 a 68.4trinexapac 452+226 3.0 A 3.0 a 3.2 a 3.3 A 3.3 a 3.6 a 73.5trinexap 452+452 3.0 A 3.0 a 3.6 a 3.6 A 3.7 ab 3.6 a 73.5trinexapac 678+339 5.0 A 5.1 ab 5.2 ab 5.3 Abc 5.5 abc 5.3 ab 61.0trinexapac 904+452 4.2 Ab 4.5 ab 4.5 ab 4.5 Ab 4.5 ab 4.6 ab 66.2prohexadione 100+100 6.4 B 7.5 bc 7.9 b 8.0 C 9.8 cd 10.4 bc 23.5prohexadione 200+200 3.2 A 3.5 a 3.6 a 4.0 Ab 5.9 abc 7.4 b 45.6bispyribac 40+40 3.3 A 5.3 ab 6.2 ab 6.8 BC 7.6 abc 7.9 b 41.2bispyribac 60+60 3.0 a 5.2 ab 6.1 ab 6.2 Abc 7.4 bc 7.5 b 44.8Control 10.8 c 11.1 c 12.0 c 13.6 D 13.8 d 13.6 c -F Treatment 12.14* 9.04* 21.96* 21.60* 11.70* 18.38* -F Block 3.96* 6.30* 11.52* 11.71* 13.87* 9.93* -DMS 3.22 3.89 3.50 3.11 4.32 3.08 -CV (%) 29.50 31.83 26.30 22.49 27.82 21.49 -1/ DAAB = days after the second application. 2/ reduction calculated as compared to the control. NS – non-significant. * significant at 5%probability. Means followed by the same letter in the column do not differ by the Tukey’s test at 5% probability.Planta Daninha, Viçosa-MG, v. 31, n. 3, p. 695-703, 2013701Effect of plant regulators on growth and flowering of ‘Meer’ ...stem by more than 70%. The total numberof inflorescences was also significantlyreduced for most doses of plant growthregulator evaluated, with a reduction rateabove 74%. Only prohexadione-calcium at100+100 g a.i. ha-1 and sodium-bispyribac at40+40 g a.i. ha-1 were not efficient becausethe number of inflorescences was similar tothe control and reduction of emissionof theflower stems around 60%. Several studiespoint out that the application of trinexapac-ethyl may retard and/or reduce the emissionof inflorescences and prolong the visualappearance aesthetics of the turf without theneed for a new mowing (Johnson, 1990; Fry,1991; Costa et al., 2009; Mittlesteadt et al.,2009).The literature cites that type II growthinhibitors used in turfs, such as trinexapac-ethyl and prohexadione-calcium areineffective in suppressing the emission offlower stems because they interfere in thebiosynthesis of gibberellins and, thus, reducecell elongation (Johnson, 1990; Fry, 1991;Mittlesteadt, 2009). However, the largeTable 5 - Mean values of height and number of inflorescences and total dry mass of clippings (TDMC) produced by ‘Meyer’zoysiagrass at 110 days after the second application of growth regulatorsreductions in the emission of flower stemsobserved in this study probably result from thephysiological changes caused by sequentialapplications of growth regulators (Ervin &Zhang, 2007).The production of total dry mass (TDMC)of clippings of ’Meyer’ zoysiagrass wasmarkedly reduced by growth regulatorsstudied, since all the sequential applicationsproduced significantly lower amounts ofclippings than the control. The lowest amountof clippings was observed in plants wheretrinexapac-ethyl is used in a sequential doseof 904+452 g a.i. ha-1, representing a yield of99.9 g m-2 over a period of almost 124 days. Itshould be noted that reductions in TDMC wereabove 80%, regardless of the regulator used,which can represent the same rate ofreduction in the need for mowing (Table 5).Beam (2004) observed a direct correlationbetween increasing dose sequentialprohexadione-calcium (140 +140, 270 +270,410 +410, 540 +540, 670 +670 g a.i. ha-1) andpercentage reduction in dry matter clippings1/ Means transformed to √Y+1.0. Original means between brackets. 2/ Reduction calculated as compared to the control. NS – non-significant. * significant at 5% probability. Means followed by the same letter in the column do not differ by the Tukey’s test at 5%probability.MARCHI, S.R. et al.Planta Daninha, Viçosa-MG, v. 31, n. 3, p. 695-703, 2013702produced by the ’Meyer’ zoysiagrass. Thisauthor also says that mass reductions wereequivalent to sequential applications oftrinexapac-ethyl commercially recommendedfor each species.Ervin & Ok (2001) and Ervin et al. (2002)reported reductions of 35 to 75% in theamount of grass clippings produced by ‘Meyer’zoysiagrass when trinexapac-ethyl was applied.Using sequential applications of trinexapac-ethyl at 55.6+55.6 and 113+113 g a.i. ha-1,Costa et al. (2009) found reductions from 49.2to 55.6%, respectively, in the production of drymass of ’Meyer’ zoysiagrass.fa*gerness & Yelverton (2000) explainedthat a single application of trinexapac-ethyl at107 g a.i. ha-1 caused a 40% reduction in theproduction of tissues in Tifway bermudagrass.However, the researchers reported that thetriple sequential application of trinexapac-ethyl and 71 g a.i. ha -1 presents a clearadvantage in reducing the tissues produced,as compared to the double sequentialapplication of the 107 g a.i. ha-1 dose.It can be concluded that sequentialapplications of trinexapac-ethyl, prohexadione-calcium and sodium-bispyribac provedpromising as regards the retardation ofvegetative growth and inflorescence emission,thus contributing in the management of turfs,because it reduces the need for mowing for aperiod up to 110 days after the sequentialapplication of the growth regulator, and avoidsthe deleterious effect on the visual appearanceaesthetics of ’Meyer’ zoysiagrass.LITERATURA CITADAARRUDA, R. L. B.; HENRIQUES, E. Gramados. São Paulo:Europa, 1995. 63 p.BEAM, J. B. Prohexadione calcium for turfgrassmanagement and poa annua control and molecularassessment of the acetolactate synthase gene in poaannua. 2004. 85 f. Thesis (Doctor Phylosophy in PlantPathology, Physiology and Weed Science) – Faculty of theVirginia Polytechnical Institute and State University,Blacksburg, Virginia Blacksburg, Virginia, 2004.COSTA, N. V. et al. Características morfológicas de gramasem resposta a aplicação de trinexapac-ethyl.Planta Daninha, v. 27, n. 1, p. 113-122, 2009.EMPRESA BRASILEIRA DE PESQUISAAGROPECUÁRIA – EMBRAPA. Sistema brasileiro declassificação de solos. Brasília: 2006. 306 p.ERVIN, E. H.; KOSKI, A. J. Trinexapac-ethyl increasesKentucky bluegrass leaf cell density and chlorophyllconcentration. HortScience, v. 36, n. 4, p. 787-789,2001. ERVIN, E. H.; OK, C. H. Influence of plant growth regulatorson suppression and quality of ‘Meyer’ Zoysiagrass.J. Environ. 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