Paclobutrazol or Ancymidol Effects on Postharvest Performance of Potted Ornamental Plants and Plugs

Abstract

<jats:p>Effects of paclobutrazol and ancymidol on postharvest performance and growth control of potted sunflower (<jats:italic>Helianthus annuus</jats:italic> L.), zinnia (<jats:italic>Zinnia elegans</jats:italic> Jacq.) and marigold (<jats:italic>Tagetes erecta</jats:italic> L.), petunia (<jats:italic>Petunia ×hybrida</jats:italic> Vilm.) plugs, respectively, were studied. Paclobutrazol was applied as a drench at 0, 1.0, 2.0, or 4.0 mg of a.i. per 15.2-cm pot for sunflower and 0, 0.5, 1.0, or 2.0 mg per 12.5-cm pot for zinnia, while ancymidol was applied at 0, 40, 80, and 160 mg·L<jats:sup>−1</jats:sup> with a volume of 0.21 L·m<jats:sup>−2</jats:sup> as a foliar spray for marigolds or petunia plug crops. With an increase in paclobutrazol dose or ancymidol concentration, plant growth (plant height and diameter, shoot fresh or dry weight) was controlled for all species tested. Use of 1.0–2.0 mg paclobutrazol per pot produced 21% to 28% shorter plants with 12% to 15% smaller plant diameter, 13% to 19% less shoot fresh weight, 15% to 21% less dry weight, and darker green foliage color for potted sunflower than nontreated plants. Treatment with 1.0–4.0 mg paclobutrazol per pot delayed first wilting by 0.7–1.4 days compared with nontreated plants. For zinnia, 0.5–1.0 mg paclobutrazol controlled plant growth, produced dark green foliage, and extended shelf life by delaying first wilting by 2.6–3.9 days and second wilting by 1.4–2.0 days than nontreated plants. For marigold and petunia plugs, 40–80 mg·L<jats:sup>−1</jats:sup> ancymidol provided ample growth control with darker green foliage; however, postharvest longevity was extended only when plugs were sprayed with 160 mg·L<jats:sup>−1</jats:sup> ancymidol. During simulated storage and shipping, plant growth retardants maintained darker green foliage for potted sunflower, zinnia, and marigold plugs and prevented postharvest stem elongation of petunia plugs. In summary, use of plant growth retardants effectively controlled excessive plant growth and extended shelf life of potted plants and plugs.</jats:p>

Substrate Drench Applications of Flurprimidol and Paclobutrazol Influence Growth of Swamp Sunflower

“…1 were higher than the control. These results are consistent with those of Ahmad et al (2015) who observed darker green foliage for 'Pacino Gold' potted sunflower treated with 2 to 4 mg/pot paclobutrazol substrate drenches and for Barbosa et al (2008) who reported increased chlorophyll meter measurements with increased paclobutrazol substrate drench rates, peaking between 4 to 6 mg/pot for 'Golden' potted sunflower. Increased foliar chlorophyll content with increasing paclobutrazol rate has been reported in additional plant genera to sunflowers [Helianthus sp.…”

“…2, plants treated with paclobutrazol at 4.0 mg/pot had 27% and 36% reductions in height growth, respectively, compared with the control. Similar results with a substrate drench application of 4 mg/pot paclobutrazol were observed as 26% to 36% shorter plants than the control by Dasoju et al (1998), Whipker and McCall (2000), and Ahmad et al (2015) for potted annual sunflower. Although previous studies observed 20% to 27% shorter plants with a 2 mg/pot drench of paclobutrazol on potted sunflower (Ahmad et al, 2015;Dasoju et al, 1998;Whipker and McCall, 2000;Whipker et al, 2004), the same application method and concentration in this study on swamp sunflower was not different from the control.…”

“…The most widely used PGR in the United States to control excessive growth in greenhouse-grown floricultural crops is the plant growth retardant paclobutrazol (Rademacher, 2000;Whipker, 2013). Restrictions in height of annual sunflower (Helianthus annuus) in response to paclobutrazol and other PGRs have been demonstrated (Ahmad et al, 2015;Barbosa et al, 2008; 1998; Koutroubas et al, 2014;Vernieri et al, 2003;Whipker and Latimer, 2016;Whipker and McCall, 2000). The rate of paclobutrazol has been evaluated on potted sunflower in previous studies, for example, with Dasoju et al (1998) finding paclobutrazol at 2 mg/pot as a substrate drench on potted sunflower 'Pacino' reduced height by 17% to 25%.…”

“…Similar responses from a similar application of paclobutrazol were obtained by Whipker and McCall (2000) on five cultivars of annual sunflower. Whipker and McCall (2000) and Ahmad et al (2015) determined that 4 mg/pot effectively reduced growth of 'Pacino Gold'. Barbosa et al (2008) observed reduced plant height with increased paclobutrazol concentration and recommended 6 mg/pot for the annual sunflower 'Golden'.…”

Average Daily Temperature Effects on Paclobutrazol Efficacy of Four Floriculture Crops

“…These smaller, sturdier plants allow growers to use bench space more efficiently and help plants to endure shipping and retail handling. In addition, there are other potential benefits of PGRs including improved plant water-use efficiency (Ahmad et al, 2014;Jungklang and Saengnil, 2012) and disease suppression (Hill and Latimer, 2004).…”