Produção de roseiras em vaso com aplicação de paclobutrazol no substrato

cr Ciência Rural Cienc. Rural 0103-8478 1678-4596 Universidade Federal de Santa Maria RESUMO: A aplicação de retardantes de crescimento, como o paclobutrazol, reduz a altura das plantas e tem possibilitado a comercialização de algumas espécies ornamentais de maior porte em vasos. Objetivou-se com este estudo avaliar porte, produção e qualidade da flor de duas cultivares de roseira cultivadas em vaso em função da aplicação de doses de paclobutrazol no substrato. Os tratamentos foram dispostos em esquema fatorial 2x5, com duas cultivares de roseira (Yellow Terrazza® e Shiny Terrazza®) e cinco doses de paclobutrazol (0; 0,5; 1,0; 1,5 e 2,0 mg vaso-1). O experimento foi conduzido em vasos plásticos sob ambiente protegido, em delineamento de blocos ao acaso com quatro repetições. Foram avaliados a altura das plantas; diâmetro, número de flores e folhas da haste floral; comprimento do botão floral; ciclo, área foliar; diâmetro floral e longevidade floral; teor de clorofila nas folhas e produção. A aplicação de paclobutrazol no substrato proporcionou melhoria na qualidade floral e estética de ambas cultivares de roseira. Também reduziu a produção de matéria seca foliar, altura da planta e diâmetro floral e aumentou o teor de clorofila e a longevidade floral. O paclobutrazol foi eficiente em reduzir a altura, conferindo uma relação harmoniosa entre a planta e o vaso, sem causar sintomas de toxidez e alterações morfológicas. Sugere-se a aplicação no substrato de 2mg vaso-1 de paclobutrazol para as cultivares de roseira Yellow Terrazza® e Shiny Terrazza® produzidas em vasos. INTRODUCTION: Rose is an ornamental plant, which to be marketed in pots should have small size. There are miniroses that are naturally small and are well accepted in the market; however, for medium-sized roses (30-60cm), size reduction with growth retardants is an alternative. There are various physiological and morphological responses in plants treated with growth retardants, such as: reduced height, augmented root growth, improved plant architecture, increased levels of chlorophyll, changes in leaf anatomy, longer cycle, reduced leaf area, increased antioxidant potential, increased production of alkaloids, and changes in gas exchange (JALEEL et al., 2007; MAO et al., 2014). Depending on the dose of the retardant and the plant species, phytotoxicity, chlorosis, and leaf or flowers deformation may occur (RADEMACHER, 2015). Growth retardants, such as paclobutrazol (PBZ), are important tools in floriculture that help obtain smaller plants with proper size for commercialization in pots. According to RADEMACHER (2016), these chemicals affect plant metabolism by inhibiting the production of natural gibberellins, which are responsible for cell elongation, thus controlling plant height. Paclobutrazol is a chemical compound within the group of triazoles. It is characterized by high chemical activity in almost all species of ornamental plants. It is registered in Europe and North America (GROSSI et al., 2009). Compact plants with suitable height for commercialization in pots are obtained after applying PBZ to species like cloves, zinnia, iris, lily and sunflower (PINTO et al., 2005; AL-KHASSAWNEH et al., 2006; FRANCESCANGELI et al., 2007; BARBOSA et al., 2009). The most common application methods of growth retardants are foliar sprays and media drench. Paclobutrazol shows good results for both methods (RADEMACER, 2015); however, drenches act longer and provide uniform control of plant height with lower doses (FRANÇA, et al., 2017). Efficacy of growth retardants may vary within cultivars of the same species (WHIPKER & MCCALL, 2000). Therefore, it is important to optimize their use by selecting adequate dosage, cultivars, production conditions, and the desired effect (COCHRAN & FULCHER, 2013). For that, it is important to evaluate the effect of paclobutrazol on different species, even cultivars, to check if there are any morphological changes that may impede its use and whether obtained plant size is suitable for commercialization in pots. Thus, the aim of this study was to assess the size, production and quality of flowers of two rose cultivars grown in pots on substrate amended with paclobutrazol. MATERIALS AND METHODS: The experiment was conducted in a greenhouse from October to December, 2008. During that period, the minimum and maximum daily average temperatures were 17.3°C and 33.9°C respectively, and day and night relative average humidity was 65.6% and 85.5%, respectively. The plants were kept under natural photoperiod and received the same amount of water and fertilizer. Treatments consisted of two rose cultivars ‘Yellow Terrazza®’ (YT) and ‘Shiny Terrazza®’ (ST), and five paclobutrazol doses applied to the substrate (0, 0.5, 1.0, 1.5, 2.0mg pot-1). The experimental design was randomized blocks with four replications. Each experimental block consisted of one plant. The active ingredient -paclobutrazol- was obtained from a commercial product Cultar® (25% paclobutrazol). Paclobutrazol drenches were split into two applications: first was carried out when the plants reached 1-2cm and the other 3-5cm, based on the results of the previous assay. Yellow Terrazza® has an average height of 45cm, produces up to three (or more) flowers per stem of an average diameter of 7cm with colors ranging from yellow cream to white. Shiny Terrazza® has an average height ranging from 40 to 45cm, with yellow flowers of an average diameter of 8cm. Young plants with two flower stalks were individually transplanted into plastic pots No. 12, (10cm high and 800cm-3 volume capacity) containing 0.6kg of Plantmax® substrate based on pine bark and vermiculite. Pots were spaced 25x25cm apart on benches. After transplanting and acclimatization, plants underwent pruning down to two stems. Plants were irrigated daily. Fertigation was performed twice a week, applying 100mL pot-1 of 1.4g L-1 of Peters® fertilizer (NPK+ Ca + Mg + micronutrients), providing the following nutrients and their amounts (mg L-1): N- 200; P - 29.4; K - 166, Ca - 66,6; Mg - 26.6; B - 0.2; Cu - 0.094; Fe - 1.0; Mn - 0.494; Mo - 0.094, and Zn - 0.532, according to CARVALHO-ZANÃO et al. (2017). Assessments were made using the scale proposed by CUSHMAN et al. (1994) for floral opening stages, which characterizes each stage as: (1) closed bud, (2) petals closed and sepals open, (3) early opening of petals (traditional flower bud stage), (4) several petals open, (5) fully open (6) end of vase life (wilting and/or dimming of one petal) (Figure 1). Figure 1 Scale for floral opening stages used by CUSHMAN et al. (1994): (1) closed bud, (2) petals closed and sepals open, (3) early opening of the petals (traditional flower bud stage), (4) several petals open, (5) fully open (6) end of vase life (wilting and/or dimming of one petal). The following traits were evaluated at stage 2: plant height (measured from the top edge of the pot to end of the flower bud), stem diameter, and number of leaves and flowers per flowering stem. Later, flower bud length was evaluated at stage 3 and flower diameter at stage 5. The cycle was determined by counting days between pruning and stage 2, and floral longevity by counting days between stage 2 and stage 6. After stage 6, leaf area was evaluated using the MK2 meter (AT Delta-T Devices). To determine dry matter, leaves, flowers and roots were detached from plants, washed and dried in oven with forced air circulation at 70°C until they reached constant mass. The determination of total chlorophyll content was performed using the colorimetric method described by PORRA et al. (1989), with 80% acetone as extractor. The leaves were taken from the middle third of the stem of plants with flower at stage 6. The data were submitted to analysis of variance. The effects on the cultivars were evaluated by F test at 5% probability, and PBZ doses by regression analysis, with coefficients tested up to 5% probability error by the t test. RESULTS AND DISCUSSION: Both rose cultivars did not differ in: the number of leaves and flowers per floral stem, production cycle, dry matter of flowers, and flower diameter (Table 1). Plants produced about ten leaves and two flowers with 8.2cm in diameter per stem; their cycle was around 50 days and flower dry matter 1.7g plant-1. Shiny Terrazza produced taller plants, with more leaf area and dry matter of leaves and roots relative to Yellow Terrazza. However, Yellow Terrazza produced thicker flower stems-longer floral bud, more durable flowers and higher chlorophyll content in leaves (Table 1). Table 1 Plant height; flowering stem diameters; number of leaves and flowers per flowering stem; cycle; flower bud length; flower diameter; floral longevity; leaf area; total chlorophyll content; and dry matter production of leaves, flowers and roots of two rose cultivars as a function of paclobutrazol doses applied to the growing substrate (n = 20). Production components Yellow Terrazza Shiny Terrazza CV% Plant height, cm 21.13b 23.06a 12.61 Flowering stem diameters, cm 0.27b 0.31a 9.93 Leaves per flowering stem 10.0a 9.7a 11.58 Leaf area, cm² 150.01b 246.15a 11.92 Flowers per flowering stem 2.00a 2.00a 10.97 Dry matter production of leaves, g plant-1 1.11b 2.12a 15.03 Dry matter production of flowers, g plant-1 1.70a 1.74a 6.08 Dry matter production of roots, g plant-1 1.81b 3.35a 18.45 Floral cycle, d 48.60a 50.15a 6.43 Flower bud length, cm 3.18a 2.87b 5.00 Flower diameter, cm 8.17a 8.16a 3.83 Floral longevity, d 9.45a 8.35b 10.50 Total chlorophyll content, mg L-1 4.24a 3.65b 7.23 Mean values followed by different letters in the column differ at 5% probability by F test. No interaction between the evaluated traits was observed for measured variables, which means that the effect of the retardant did not depend on the cultivar. The PBZ doses linearly reduced plant height with increasing retardant doses (Figure 2A). Application of 2mg PBZ pot-1 reduced plant height by 27% (7.3cm) relative to the control. Similar results were observed by AHMAD et al. (2014) who studied doses of the same retardant in sunflower and zinnia. Figure 2 Plant height (A); leaf area (B); flowering stem diameter (C); dry matter production of leaves (DMPL) (D), flower bud length (E), flower diameter (F); floral longevity (G) and total chlorophyll content (H) of two rose cultivars as a function of paclobutrazol doses applied to the growing substrate. ** p<0,01; * p<0,05. Height reduction of ornamental plants caused by PBZ has been observed by some authors in herbaceous plants. Doses ranging from 0.025 to 2mg pot-1 produced satisfactory results according to PINTO et al., 2005; AL-KHASSAWNEH et al., 2006; HWANG et al., 2008. According to BARROSO et al. (2012), harmony between the plant and the pot is achieved when the height of the plant is 1.5 to 2 times the height of the pot, i.e., between 15 and 20cm for plants grown in pots of 10cm, as in the present research. This ideal height was obtained in this study with 2.0mg PBZ pot-1, resulting in plants with height of 19cm. Leaf area and stem diameter decreased linearly with increasing PBZ doses (Figures 2B and 2C). Reduction of leaf area and plant height with PBZ doses has also been observed by NAVARRO et al. (2007) in Arbustus unedo, HWANG et al. (2008) in Kalanchoe blosfeldiana cv. Gold Strike, and SINGH et al. (2016) in Pelargonium x hortorum. Paclobutrazol causes growth reduction by inhibiting gibberellin biosynthesis, which expands and elongates meristematic cells in the internodes (TAIZ & ZEIGER, 2004). This fact probably explains the reduction of plant height, stem diameter, and leaf area. PBZ drench did not affect the number of leaves on the flowering stem (ŷ = 9.85 leaves). This fact was also reported by PINTO et al. (2005) and Al-KHASSAWNEH et al. (2006), who reported no effect of PBZ on the number of leaves in zinnia and iris, respectively. However, the effect of PBZ seems to depend on plant species and retardant dose, as an increase in the number of leaves in Kalanchoe (HWANG et al., 2008) and sunflower (BARBOSA et al., 2009) and reduction in Arbutus unedo (NAVARRO et al., 2007), were observed after PBZ applications. Increasing PBZ dose reduced dry matter of leaves linearly (Figure 2D). This fact is due to reduced plant height and leaf area. Similar reduction of foliar dry matter with PBZ doses was also reported in zinnia (PINTO et al., 2005) and summer tulip (PINTO et al., 2006). Dry matter production of flowers was not correlated with PBZ doses (ŷ = 1.72). But, probably there was more carbon partitioning in flowers with PBZ doses, because a reduction of dry mass of leaves without changing dry matter production of flowers was observed. According to KUMAR et al. (2012) and MABVONGWE et al. (2016), paclobutrazol can change partitioning of assimilates in favor of reproductive organs, such as flowers, in to the detriment of vegetative organs, such as leaves. Dry matter production of roots was not correlated with PBZ doses (ŷ = 2.62g plant-1). WILKINSON & RICHARDS (1987) report that the growth of the root system can be reduced if the media drench contains high paclobutrazol concentration, which did not occur in this study. Increasing PBZ doses reduced bud length and flower diameter linearly (Figures 2E and 2F, respectively). Reduction of flower diameter was subtle -0.8cm on average- compared to the control. Therefore, doses did not sabotage the commercial aspect of the flowers. YAO & FINLAYSON (2015) also observed that the use of growth regulator reduced the bud length in Arabidopsis thaliana and WANDERLEY et al. (2014) also observed reduced diameter of sunflower inflorescence and genotypic differences caused by PBZ drench applications. It is noteworthy that PBZ reduced plant size without changing the quality of flower, rendering more harmonic plants in relation to the pot. There were no deformations of buds and flowers at administered doses. Floral cycle and the number of flowers per stem were not affected by PBZ doses. On average, plants bloomed after 49.4 days and produced two flowers per stem. In ornamental plants, growth retardants often control the height without affecting flowering (BASRA, 2000). Regarding the number of flowers, it seems that this trait is affected by plant species, the retardant, and its dose. SINGH et al. (2016) obtained the highest number of flowers per plant with PBZ applied to geranium. Floral longevity increased linearly with PBZ doses (Figure 2G). The highest dose of PBZ extended flower longevity by 2.5 days relative to the control. FRANCESCANGELI & ZAGABRIA (2008) reported increased floral longevity of petunia with PBZ doses; however, SINGH et al. (2016) observed reduced floral longevity of geraniums. According to OLSEN & ANDERSEN (1995), growth retardants generally reduce flower longevity, but it depends on the dose, species, and the retardant. These authors found that PBZ did not alter floral longevity of cape marguerite (Osteospermum ecklonis cv. Calypso), but uniconazol, chloride chlormequat and flurprimidol did. Total chlorophyll content was significantly correlated with PBZ dose (Figure 2H). Increasing PBZ dose produced linear increase of total chlorophyll. This effect has already been observed by JALEEL et al. (2007), TANNIS et al. (2015) and CARVALHO et al. (2016). Chlorophyll content increased due to elevated production of endogenous cytokinin with the application of PBZ, which enhances differentiation of chloroplasts, chlorophyll synthesis and prevents its degradation (FLETCHER et al., 2000). In addition, plant cells treated with PBZ are smaller with low chlorophyll concentration and reduced intercellular space (CATHEY, 1975). According to BARBOSA et al. (2009), the contrast between the green of the leaves and the flowers, due to increased chlorophyll content after applying paclobutrazol, increases visual attractiveness of plants; and consequently, facilitates their commercialization. CONCLUSION: Paclobutrazol drench application improves floral quality and aesthetics of rose cultivars Yellow Terrazza® and Shiny Terrazza® by reducing their height and providing harmonious relationship between plant and pot without causing toxic symptoms and floral deformation. Suggested paclobutrazol on drench dose is 2mg pot-1 for Yellow Terrazza® and Shiny Terrazza® cultivars. REFERENCES: AL-KHASSAWNEH, N.M. et al. Growth and flowering of black iris (Iris nigricans Dinsm.) following treatment with plant growth regulators. Scientia Horticulturae, v.107, p.187-193, 2006. Available from: http://www.sciencedirect.com/science/article/pii/S0304423805003304>. Accessed: Nov. 2, 2016. doi: 10.1016/j.scienta.2005.10.003. AL-KHASSAWNEH N.M. Growth and flowering of black iris (Iris nigricans Dinsm.) following treatment with plant growth regulators Scientia Horticulturae 107 187 193 2006 Available from: http://www.sciencedirect.com/science/article/pii/S0304423805003304 Nov. 2, 2016 10.1016/j.scienta.2005.10.003. AHMAD, I. et al. Paclobutrazol and ancymidol lower water use of potted ornamental plants and plugs. European Journal of Horticultural Science, v.79, p.318-326, 2014. Available from: http://www.pubhort.org/ejhs/2014/4999800.htm>. Accessed: Nov. 2, 2016. AHMAD I. Paclobutrazol and ancymidol lower water use of potted ornamental plants and plugs European Journal of Horticultural Science 79 318 326 2014 Available from: http://www.pubhort.org/ejhs/2014/4999800.htm Nov. 2, 2016 BARBOSA, J.G. et al. Cultivation of ornamental sunflower (Helianthus annuus L.) in vase under diferentes paclobutrazol doses. Revista Brasileira de Horticultura Ornamental, v.14, p.205-208, 2009. Available from: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0034-737X2014000100005>. Accessed: Nov. 2, 2016. doi: 10.1590/S0034-737X2014000100005. BARBOSA J.G. Cultivation of ornamental sunflower (Helianthus annuus L.) in vase under diferentes paclobutrazol doses. Revista Brasileira de Horticultura Ornamental 14 205 208 2009 Available from: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0034-737X2014000100005 Nov. 2, 2016 10.1590/S0034-737X2014000100005. BARROSO, P.A. et al. Analysis of segregating generation for components of seedling and plant height of pepper (Capsicum annuum L.) for medicinal and ornamental purposes. Acta Horticulturae, v.953, p.269-276, 2012. Available from: https://www.actahort.org/books/953/953_37.htm>. Accessed: Jan. 19, 2018. doi: 10.17660/ActaHortic.2012.953.37. BARROSO P.A. Analysis of segregating generation for components of seedling and plant height of pepper (Capsicum annuum L.) for medicinal and ornamental purposes. Acta Horticulturae 953 269 276 2012 Available from: https://www.actahort.org/books/953/953_37.htm Jan. 19, 2018 10.17660/ActaHortic.2012.953.37. BASRA, A.S. Plant growth regulators in agriculture and horticulture: their role and commercial uses. New York: Food Products Press, 2000. 1ed. BASRA A.S. Plant growth regulators in agriculture and horticulture their role and commercial uses New York Food Products Press 2000 1 CARVALHO, M.E.A. et al. Are plant growth retardants a strategy to decrease lodging and increase yield of sunflower? Comunicata Scientiae, v.7, p.154-159, 2016. Available from: https://comunicatascientiae.com.br/comunicata/article/view/1286>. Accessed: Nov. 2, 2016. doi: 10.14295/cs.v7i1.1286. CARVALHO M.E.A. Are plant growth retardants a strategy to decrease lodging and increase yield of sunflower? Comunicata Scientiae 7 154 159 2016 Available from: https://comunicatascientiae.com.br/comunicata/article/view/1286 Nov. 2, 2016. 10.14295/cs.v7i1.1286. CARVALHO-ZANÃO, M.P. et al. Production and leaf plasticity of rose plants sprayed with paclobutrazol and daminozide. Semina: Ciências Agrárias, v.38, p.3481-3490, 2017. Available from: http://www.uel.br/revistas/uel/index.php/semagrarias/article/view/28424/22256>. Accessed: Dec. 31, 2017. doi: 10.5433/1679-0359.2017v38n6p3481. CARVALHO-ZANÃO M.P. Production and leaf plasticity of rose plants sprayed with paclobutrazol and daminozide. Semina: Ciências Agrárias 38 3481 3490 2017 Available from: http://www.uel.br/revistas/uel/index.php/semagrarias/article/view/28424/22256 Dec. 31, 2017 10.5433/1679-0359.2017v38n6p3481. CATHEY, H.M. Comparative growth retarding activities of acymidol, AMO-1618, phophon, chlormequat and SADH on ornamental plant species. HortScience, v.10, p.204-216, 1975. Available from: http://kbd.kew.org/kbd/detailedresult.do?id=47514>. Accessed: Nov. 2, 2016. CATHEY H.M Comparative growth retarding activities of acymidol, AMO-1618, phophon, chlormequat and SADH on ornamental plant species HortScience 10 204 216 1975 < Available from: http://kbd.kew.org/kbd/detailedresult.do?id=47514 Nov. 2, 2016 COCHRAN, R.C.; FULCHER, A. Type and rate of plant growth regulator influence vegetative, floral growth, and quality of little LimeTM Hydrangea. Hort Technology, v.23, p.306-311, 2013. Available from: http://horttech.ashspublications.org/content/23/3/306.full>. Accessed: Nov. 2, 2016. COCHRAN R.C. FULCHER A. Type and rate of plant growth regulator influence vegetative, floral growth, and quality of little LimeTM Hydrangea. Hort Technology 23 306 311 2013 Available from: http://horttech.ashspublications.org/content/23/3/306.full Nov. 2, 2016 CUSHMAN, L.C. et al. Cultivar, flower stage, silver thiosulfate, and BA interactions affect performance of potted miniature roses. Hort Science, v.29, p.805-808, 1994. Available from: http://hortsci.ashspublications.org/content/29/7/805.full.pdf>. Accessed: Nov. 2, 2016. CUSHMAN L.C. Cultivar, flower stage, silver thiosulfate, and BA interactions affect performance of potted miniature roses. Hort Science 29 805 808 1994 < Available from: http://hortsci.ashspublications.org/content/29/7/805.full.pdf Nov. 2, 2016. FLETCHER, R.A. et al. Triazoles as plant growth regulators and stress protectants. Horticultural Reviews, v.24, p.55-138, 2000. Available from: http://onlinelibrary.wiley.com/doi/10.1002/9780470650776.ch3/summary>. Accessed: Nov. 2, 2016. doi: 10.1002/9780470650776.ch3. FLETCHER R.A. Triazoles as plant growth regulators and stress protectants. Horticultural Reviews 24 55 138 2000 < Available from: http://onlinelibrary.wiley.com/doi/10.1002/9780470650776.ch3/summary Nov. 2, 2016 10.1002/9780470650776.ch3. FRANÇA, C.F.M. et al. Evaluation of paclobutrazol application method on quality characteristics of ornamental pepper. Ornamental Horticulture, v.23, p.307-310, 2017. Available from: https://ornamentalhorticulture.emnuvens.com.br/rbho/article/view/1074>. Accessed: Jan. 17, 2018. doi: 10.14295/oh.v23i3.1074. FRANÇA C.F.M. Evaluation of paclobutrazol application method on quality characteristics of ornamental pepper Ornamental Horticulture 23 307 310 2017 Available from: https://ornamentalhorticulture.emnuvens.com.br/rbho/article/view/1074 Jan. 17, 2018 10.14295/oh.v23i3.1074. FRANCESCANGELI, N. et al. Paclobutrazol for height control of two Lilium L.A. hybrids grown in pots. Spanish Journal of Agricultural Research, v.5, p.425-430, 2007. Available from: http://revistas.inia.es/index.php/sjar/article/view/266>. Accessed: Nov. 2, 2016. doi: 10.5424/sjar/2007053-266. FRANCESCANGELI N. Paclobutrazol for height control of two Lilium L.A. hybrids grown in pots. Spanish Journal of Agricultural Research 5 425 430 2007 Available from: http://revistas.inia.es/index.php/sjar/article/view/266 Nov. 2, 2016 10.5424/sjar/2007053-266. FRANCESCANGELI, N.; ZAGABRIA, A. Paclobutrazol for height control of petunias. Chilean Journal of Agricultural Research, v.68, p.309-314, 2008. Available from: http://www.bioline.org.br/abstract?id=cj08032>. Accessed: Nov. 2, 2016. doi: 10.4067/S0718-58392008000300012. FRANCESCANGELI N. ZAGABRIA A Paclobutrazol for height control of petunias Chilean Journal of Agricultural Research, 68 309 314 2008 < Available from: http://www.bioline.org.br/abstract?id=cj08032 > Nov. 2, 2016 10.4067/S0718-58392008000300012 GROSSI, J.A.S. et al. Retardantes de crescimento de plantas ornamentais. Informe Agropecuário, v.3, p.33-35, 2009. Available from: http://www.epamig.br/index.php?option=com_content&task=view&id=1268&Itemid=220>. Accessed: Nov. 2, 2016. GROSSI J.A.S. Retardantes de crescimento de plantas ornamentais. Informe Agropecuário 3 33 35 2009 Available from: http://www.epamig.br/index.php?option=com_content&task=view&id=1268&Itemid=220 Nov. 2, 2016 HWANG, S.J. et al. Suppression of stem growth in pot kalanchoe ‘Gold Strike’ by recycled subirrigational supply of plant growth retardants. African Journal of Biotechnology, v.7, p.1487-1493, 2008. Available from: http://www.academicjournals.org/journal/AJB/article-full-text-pdf/74706977332>. Accessed: Nov. 2, 2016. doi: 10.5897/AJB08.196. HWANG S.J. Suppression of stem growth in pot kalanchoe ‘Gold Strike’ by recycled subirrigational supply of plant growth retardants. African Journal of Biotechnology, 7 1487 1493 2008 Available from: http://www.academicjournals.org/journal/AJB/article-full-text-pdf/74706977332 Nov. 2, 2016. 10.5897/AJB08.196. JALEEL, C.A. et al. Paclobutrazol enhances photosynthesis and ajmalicine production in Catharanthus roseus. Process Biochemistry, v.42, p.1566-1570, 2007. Available from: http://fulltext.study/preview/pdf/35723.pdf>. Accessed: Nov. 2, 2016. doi: 10.1016/j.procbio.2007.08.006. JALEEL C.A. Paclobutrazol enhances photosynthesis and ajmalicine production in Catharanthus roseus Process Biochemistry, 42 1566 1570 2007 Available from: http://fulltext.study/preview/pdf/35723.pdf Nov. 2, 2016 10.1016/j.procbio.2007.08.006. KUMAR, S. et al. Paclobutrazol treatment as a potential strategy for higher seed and oil yield in field-grown camelina sativa L. Crantz, BMC Research Notes, v. 137, p. 1-13, 2012. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3320555/>. Accessed: Jan. 18, 2018. doi: 10.1186/1756-0500-5-137. KUMAR S. Paclobutrazol treatment as a potential strategy for higher seed and oil yield in field-grown camelina sativa L. Crantz, BMC Research Notes 137 1 13 2012 Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3320555/ Jan. 18, 2018 10.1186/1756-0500-5-137. MABVONGWE, O. et al. The effect of paclobutrazol application time and variety on growth, yield, and quality of potato (Solanum tuberosum L.), Advances in Agriculture, Article ID 1585463, 5 pages, 2016. Available from: https://www.hindawi.com/journals/aag/2016/1585463/>. Accessed: Jan. 18, 2018. doi:10.1155/2016/1585463. MABVONGWE O. The effect of paclobutrazol application time and variety on growth, yield, and quality of potato (Solanum tuberosum L.), Advances in Agriculture Article ID 1585463 5 5 2016 Available from: https://www.hindawi.com/journals/aag/2016/1585463/ Jan. 18, 2018 10.1155/2016/1585463 MAO, L. et al. Crop growth, light utilization and yield of relay intercropped cotton as affected by plant density and a plant growth regulator. Field Crops Research, v.155, p.67-76, 2014. Available from: http://www.sciencedirect.com/science/article/pii/S0378429013003274>. Accessed: Jan. 17, 2018. doi: 10.1016/j.fcr.2013.09.021. MAO L. Crop growth, light utilization and yield of relay intercropped cotton as affected by plant density and a plant growth regulator Field Crops Research, 155 67 76 2014 Available from: http://www.sciencedirect.com/science/article/pii/S0378429013003274 Jan. 17, 2018. 10.1016/j.fcr.2013.09.021. NAVARRO, A. et al. Influence of paclobutrazol on water consumption and plant performance of Arbutus unedo seedlings. Scientia Horticulturae , v.111, p.133-139, 2007. Available from: http://digital.csic.es/handle/10261/16920?mode=full&locale=en>. Accessed: Nov. 2, 2016. doi: 10.1016/j.scienta.2006.10.014. NAVARRO A. Influence of paclobutrazol on water consumption and plant performance of Arbutus unedo seedlings. Scientia Horticulturae 111 133 139 2007 Available from: http://digital.csic.es/handle/10261/16920?mode=full&locale=en Nov. 2, 2016 10.1016/j.scienta.2006.10.014. OLSEN, W.W.; ANDERSEN, A.S. The influence of five growth retardants on growth and postproduction qualities of Osteospermum ecklonis cv. “Calypso’. Scientia Horticulturae , v.62, p.263-270, 1995. Available from: http://www.worldpapercat.com/1758/Article2965464.htm>. Accessed: Nov. 2, 2016. doi: 10.1016/0304-4238(95)00769-P. OLSEN W.W. ANDERSEN A.S. The influence of five growth retardants on growth and postproduction qualities of Osteospermum ecklonis cv. “Calypso’. Scientia Horticulturae 62 263 270 1995 Available from: http://www.worldpapercat.com/1758/Article2965464.htm Nov. 2, 2016 10.1016/0304-4238(95)00769-P. PINTO, A.C.R. et al. Growth retardants on development and ornamental quality of potted Lilliput’ Zinnia elegans Jacq. Scientia Agricola, v.62, p.337-345, 2005. Available from: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-90162005000400006>. Accessed: Nov. 2, 2016. doi: 10.1590/S0103-90162005000400006. PINTO A.C.R. Growth retardants on development and ornamental quality of potted Lilliput’ Zinnia elegans Jacq Scientia Agricola 62 337 345 2005 Available from: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-90162005000400006 Nov. 2, 2016 10.1590/S0103-90162005000400006. PINTO, A.C.R. et al. Growth retardants on production of flowering potted thai tulip. Bragantia, v.65, p.369-380, 2006. Available from: http://repositorio.unesp.br/handle/11449/1459>. Accessed: Nov. 2, 2016. doi: 10.1590/S0006-87052006000300002. PINTO A.C.R. Growth retardants on production of flowering potted thai tulip. Bragantia 65 369 380 2006 Available from: http://repositorio.unesp.br/handle/11449/1459 Nov. 2, 2016 10.1590/S0006-87052006000300002. PORRA, R.J. et al. Determination of accurate extinction coefficients and simultaneous equation for assaying chlorophylls a and b extracted with four different solvents: verification of the concentration of chlorophylls standards by atomic absorption spectroscopy. Biochimica et Biophysica Acta, v.975, p.384-394, 1989. Available from: http://www.chem.ucla.edu/dept/Faculty/merchant/pdf/Porra_1989.pdf>. Accessed: Nov. 2, 2016. doi: 10.1016/S0005-2728(89)80347-0. PORRA R.J. Determination of accurate extinction coefficients and simultaneous equation for assaying chlorophylls a and b extracted with four different solvents: verification of the concentration of chlorophylls standards by atomic absorption spectroscopy. Biochimica et Biophysica Acta 975 384 394 1989 Available from: http://www.chem.ucla.edu/dept/Faculty/merchant/pdf/Porra_1989.pdf Nov. 2, 2016 10.1016/S0005-2728(89)80347-0. RADEMACHER, W. Plant Growth regulators: backgrounds and uses in plant production. Journal of Plant Growth Regulation, v.34, p.845-872, 2015. Available from: https://link.springer.com/article/10.1007/s00344-015-9541-6>. Accessed: Jan. 17, 2018. doi: 10.1007/s00344-015-9541-6. RADEMACHER W. Plant Growth regulators: backgrounds and uses in plant production Journal of Plant Growth Regulation 34 845 872 2015 Available from: https://link.springer.com/article/10.1007/s00344-015-9541-6 Jan. 17, 2018 10.1007/s00344-015-9541-6. RADEMACHER W. Chemical regulators of gibberellin status and their application in plant production. In: HEDDEN, P (ed) Annual plant reviews, vol 49, The Gibberellins. Hoboken: Wiley-Blackwell, 2016. Cap. 12, p.359-404. RADEMACHER W. Chemical regulators of gibberellin status and their application in plant production HEDDEN P Annual plant reviews 49 The Gibberellins Hoboken Wiley-Blackwell 2016 Cap. 12 359 404 SINGH, B.S.D. et al. Effect of growing media and paclobutrazol on growth, flowering and pot presentability of geranium, Pelargonium x hortorum LH Bailey. International Journal of Farm Sciences, v.6, p.128-136, 2016. Available from: http://www.inflibnet.ac.in/ojs/index.php/IJFS/article/view/4005>. Accessed: Nov. 2, 2016. SINGH B.S.D. Effect of growing media and paclobutrazol on growth, flowering and pot presentability of geranium, Pelargonium x hortorum LH Bailey International Journal of Farm Sciences 6 128 136 2016 Available from: http://www.inflibnet.ac.in/ojs/index.php/IJFS/article/view/4005 Nov. 2, 2016 TAIZ, L.; ZEIGER, E. Fisiologia vegetal. Porto Alegre: Artmed, 2004. 3.ed. TAIZ L. ZEIGER E. Fisiologia vegetal Porto Alegre Artmed 2004 3 TANNIS, S.R. et al. Effects of paclobutrazol and fertilizer and the physiology, growth and biomass allocation on three Frazins species. Urban Forestry and Urban Greening, v.14, p.590-598, 2015. Available from: http://www.sciencedirect.com/science/article/pii/S1618866715000813>. Accessed: Nov. 2, 2016. doi: 10.1016/j.ufug.2015.05.011. TANNIS S.R. Effects of paclobutrazol and fertilizer and the physiology, growth and biomass allocation on three Frazins species. Urban Forestry and Urban Greening, 14 590 598 2015 Available from: http://www.sciencedirect.com/science/article/pii/S1618866715000813 Nov. 2, 2016 10.1016/j.ufug.2015.05.011. WANDERLEY, C.S. et al. Growth of potted sunflower in response to paclobutrazol. Revista Ceres, v.61, p.035-041, 2014. Available from: http://search.proquest.com/openview/95288010f0886d00adb63aa4aa149964/1?pq-origsite=gscholar>. Accessed: Nov. 2, 2016. doi: 10.1590/S1413-70542007000600011. WANDERLEY C.S. Growth of potted sunflower in response to paclobutrazol. Revista Ceres 61 035 041 2014 Available from: http://search.proquest.com/openview/95288010f0886d00adb63aa4aa149964/1?pq-origsite=gscholar Nov. 2, 2016 10.1590/S1413-70542007000600011. WHIPKER, B.E.; MCCALL, I. Response of potted sunflower cultivars to daminozide foliar sprays and paclobutrazol drenches. Hort Technology , v.10, p.209-211, 2000. Available from: http://horttech.ashspublications.org/content/10/1/209.abstract>. Accessed: Nov. 2, 2016. WHIPKER B.E. MCCALL I. Response of potted sunflower cultivars to daminozide foliar sprays and paclobutrazol drenches Hort Technology 10 209 211 2000 Available from: http://horttech.ashspublications.org/content/10/1/209.abstract Nov. 2, 2016 WILKINSON, R.I.; RICHARDS, D. Effects of paclobutrazol on growth and flowering of Bouvardia humboldtii. Hort Science , v.22, p.444-445, 1987. Available from: http://www.pakbs.org/pjbot/PDFs/41(5)/PJB41(5)2323.pdf>. Accessed: Nov. 2, 2016. WILKINSON R.I. RICHARDS D Effects of paclobutrazol on growth and flowering of Bouvardia humboldtii. Hort Science 22 444 445 1987 Available from: http://www.pakbs.org/pjbot/PDFs/41(5)/PJB41(5)2323.pdf Nov. 2, 2016 YAO, C.; FINLAYSON, S.A. Abscisic acid is a general negative regulator of Arabidopsis axillary bud growth. Plant Physiology, v.169, p.611-626, 2015. Available from: http://www.plantphysiol.org/content/plantphysiol/169/1/611.full.pdf>. Accessed: Jan. 19, 2018. doi: 10.1104/pp.15.00682. YAO C. FINLAYSON S.A Abscisic acid is a general negative regulator of Arabidopsis axillary bud growth. Plant Physiology 169 611 626 2015 Available from: http://www.plantphysiol.org/content/plantphysiol/169/1/611.full.pdf Jan. 19, 2018 10.1104/pp.15.00682. 0 CR-2016-1002.R2