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Michael Kantar, Kevin Betts, Brent S. Hulke, Robert M. Stupar and Donald Wyse

a resource for disease and insect resistance in Helianthus annuus L. breeding programs ( Charlet and Brewer, 1995 ; Hulke and Wyse, 2008 ; Miller and Gulya, 1987 ). Cultivated H. annuus is the world’s second largest hybrid crop in acreage and

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Sophia Kamenidou and Todd Cavins

Silicon (Si) is a beneficial element to many agricultural crops. We found improved horticultural traits in our preliminary Si supplementation research on floricultural greenhouse crops produced in soilless substrates. The objective of this study was to establish optimum Si rates based on previous results and investigate the relationship of Si tissue and substrate content. Potassium silicate (KSiO3) weekly drenches (0, 50, 100, 150 mg·L-1 SiO2), media-incorporated KSiO3 flakes (0, 280, 400, 520 g·m-3 SiO2), and ashed rice hulls (0, 200, 270, 360 g·m-3 SiO2) were provided to Helianthusannuus`Ring of Fire'. Leaf, stem, and flower tissues as well as soilless substrate samples were collected for Si analysis. Several Si treatments resulted in plants with increased flower and stem diameter compared to untreated controls (P ≤ 0.05). Weekly drenches with KSiO3 (150 mg·L-1 SiO2), KSiO3 flakes (280 g·m-3 SiO2), and ashed rice hulls (360 g·m-3 SiO2) were the most efficient treatments based on the increased quality characteristics. Leaf tissue had the highest Si content, followed by flower, then stem tissue. Correlation analysis indicated that leaf and flower Si content was positively correlated with saturated media extract substrate samples (correlation coefficients r= 0.75 and 0.63, respectively).

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Rodney B. Jones, Margrethe Serek and Michael S. Reid

The vase life of cut sunflowers given a simulated transport period (3 days dry storage at 8C) was significantly enhanced by a l-hour pulse with 0.01% Triton X-100 administered before storage. The Triton pulse increased solution uptake during the l-hour pulse, decreased fresh weight loss during dry storage, and significantly improved water uptake thereafter, resulting in greater leaf turgidity and longer vase life. Leaf stomata] conductance measurements indicated that Triton X-100 maintained stomatal opening at a higher level during the pulse and after storage, but had no effect during dry storage. Chemical name used: octylphenoxypolyethoxyethanol (Triton X-100).

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Hans C. Wien

. van den Berg, D. 2002 Possibilities for using photoperiodism to program flowering of sunflowers ( Helianthus annuus ) in the greenhouse and in the open Acta Hort. 580 101 109 Dyer, J.H. Skok, J. Scully, N.J. 1959 Photoperiod behavior of sunflower Bot

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Andrea R. Garfinkel and Karen L. Panter

. Straver, N. van den Berg, D. 2002 Possibilities for using photoperiodism to program flowering of sunflowers ( Helianthus annuus ) in the greenhouse and in the open Acta Hort. 580 101 109 Criley, R.A. 2007 Year-round production of cut sunflower in Hawaii

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Jennifer K. Boldt, James C. Locke and James E. Altland

Pink’) grown in an 85 sphagnum peat: 15 perlite soilless substrate amended with 0% or 20% rice hulls (by volume). Table 3. Plant growth and tissue silicon (Si) of sunflower ( Helianthus annuus ‘Pacino Gold’) grown in an 85 sphagnum peat: 15 perlite

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Karen L. Panter, Timmothy M. Gergeni, Casey P. Seals and Andrea R. Garfinkel

. 2019. < > Blacquière, T. Straver, N. van den Berg, D. 2002 Possibilities for using photoperiodism to program flowering of sunflowers ( Helianthus annuus ) in the greenhouse and in the open Acta Hort

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Norman B. Best, Xingang Wang, Scottie Brittsan, Eric Dean, Seth J. Helfers, Ryan Homburg, Mariah L. Mobley, Tiffeny L. Spindler, Bofan Xie, Menglu Zhang, Paul M. Hasegawa, Robert J. Joly, David Rhodes and Brian P. Dilkes

Gibberellins (GAs) are phytohormones that regulate plant height and flowering time in plants. Plants with reduced GA or disrupted in GA signaling exhibit a dwarf phenotype. DELLA proteins are transcriptional repressors that attenuate GA-mediated promotion of plant growth. Alleles in which the eponymous DELLA motif in these proteins is disrupted result in constitutive repression of GA signaling and a dominantly inherited dwarf phenotype. We found that the dwarf Helianthus annuus (sunflower) cultivar Sunspot is hyposensitive to GA3 as compared with the tall cultivar Mammoth Grey. Sequencing of the HaDella1 gene indicates that ‘Sunspot’ has a single nucleotide polymorphism resulting in a missense mutation in the DELLA motif as compared with ‘Mammoth Grey’ and the reference sequence. Helianthus annuus has five genes encoding DELLA proteins, including HaDella1. We propose that the DELLA motif alteration in the HaDella1 gene results in a dominant mutation in ‘Sunspot’ and is the cause of its dwarf phenotype.

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Hans C. Wien

Most sunflower cultivars (Helianthus annuus) grown as cut flowers produce single stems and do not form branches. If pinched (i.e., apical meristem removed) in the seedling stage, plants form branches from basal nodes. In four experiments conducted under field conditions, pinching seedlings increased the number of marketable sunflower stems per plant 2.6 to 4.6 times, but the flowers formed were reduced in diameter by 43%, and flowering was delayed by 1 week to 10 days. Leaving six instead of four basal nodes after pinching only increased stem yield slightly in 2005 but not in 2006. Increasing the space available per plant from 9 × 9 to 12 × 12 inches increased flower diameter of pinched and control plants from 7 to 7.9 cm, but the resulting lower yield per unit area reduced overall value. In three out of four experiments, ‘Procut Orange’ produced more stems after pinching than ‘Sunrich Orange’. Pinching nonbranching sunflowers is a promising technique, increasing yield by a factor of three, and the value of the harvested flowers by 82%.

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Iftikhar Ahmad, Brian E. Whipker and John M. Dole

Effects of paclobutrazol and ancymidol on postharvest performance and growth control of potted sunflower (Helianthus annuus L.), zinnia (Zinnia elegans Jacq.) and marigold (Tagetes erecta L.), petunia (Petunia ×hybrida 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−1 with a volume of 0.21 L·m−2 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−1 ancymidol provided ample growth control with darker green foliage; however, postharvest longevity was extended only when plugs were sprayed with 160 mg·L−1 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.