Coreopsis Grandiflora Research Articles

Latent and active aurone synthase from petals of C. grandiflora: a polyphenol oxidase with unique characteristics.

Main conclusion Aurone synthase belongs to the novel group 2 polyphenol oxidases and the presented kinetic characterization suggests a differing aurone biosynthesis in Asteraceae species compared to snapdragon. Aurone synthases (AUS) are polyphenol oxidases (PPO) physiologically involved in the formation of yellow aurone pigments in petals of various Asteraceae species. They catalyze the oxidative conversion of chalcones into aurones. Latent (58.9 kDa) and active (41.6 kDa) aurone synthase from petals of C. grandiflora was purified by a quantitative removal of pigments using aqueous two-phase separation and several subsequent chromatographic steps. The purified enzymes were identified as cgAUS1 (A0A075DN54) and sequence analysis revealed that cgAUS1 is a member of a new group of plant PPOs. Mass determination experiments of intact cgAUS1 gave evidence that the C-terminal domain, usually shielding the active site of latent polyphenol oxidases, is linked to the main core by a disulfide bond. This is a novel and unique structural feature of plant PPOs. Proteolytic activation in vivo leads to active aurone synthase possessing a residual peptide of the C-terminal domain. Kinetic characterization of purified cgAUS1 strongly suggests a specific involvement in 4-deoxyaurone biosynthesis in Coreopsis grandiflora (Asteraceae) that differs in various aspects compared to the 4-hydroxyaurone formation in Antirrhinum majus (Plantaginaceae): cgAUS1 is predicted to be localized in the thylakoid lumen, it possesses exclusively diphenolase activity and the results suggest that aurone formation occurs at the level of chalcone aglycones. The latent enzyme exhibits allosteric activation which changes at a specific product concentration to a constant reaction rate. The presented novel structural and functional properties of aurone synthase provide further insights in the diversity and role of plant PPOs.Electronic supplementary materialThe online version of this article (doi:10.1007/s00425-015-2261-0) contains supplementary material, which is available to authorized users.

Site-directed mutagenesis around the CuA site of a polyphenol oxidase from Coreopsis grandiflora (cgAUS1)

Aurone synthase from Coreopsis grandiflora (cgAUS1), catalyzing conversion of butein to sulfuretin in a type-3 copper center, is a rare example of a polyphenol oxidase involved in anabolism. Site-directed mutagenesis around the CuA site of AUS1 was performed, and recombinant enzymes were analyzed by mass spectrometry. Replacement of the coordinating CuA histidines with alanine resulted in the presence of a single copper and loss of diphenolase activity. The thioether bridge-building cysteine and a phenylalanine over the CuA site, exchanged to alanine, have no influence on copper content but appear to play an important role in substrate binding.

Cloning and functional expression in E. coli of a polyphenol oxidase transcript from Coreopsis grandiflora involved in aurone formation

Polyphenol oxidases are involved in aurone biosynthesis but the gene responsible for 4-deoxyaurone formation in Asteraceae was so far unknown. Three novel full-length cDNA sequences were isolated from Coreopsis grandiflora with sizes of 1.80kb (cgAUS1) and 1.85kb (cgAUS2a, 2b), encoding for proteins of 68–69kDa, respectively. cgAUS1 is preferably expressed in young petals indicating a specific role in pigment formation. The 58.9kDa AUS1 holoproenzyme, was recombinantly expressed in E. coli and purified to homogeneity. The enzyme shows only diphenolase activity, catalyzing the conversion of chalcones to aurones and was characterized by SDS–PAGE and shot-gun type nanoUHPLC–ESI-MS/MS.

Do protocols for the intensive production of Coreopsis grandiflora affect its garden performance?

Scheduled production of ornamentals has facilitated the development of novel crop lines that can be sold in flower over an extended period, thereby maximising sales potential. Research activities have aided the development of protocols for these ‘forced’ crops, but little attention has been given to knowledge of how such protocols affect subsequent garden performance. The aim of this study therefore, was to investigate the influence of different production factors (cutting size, temperature, photoperiod and time of propagation) on flower induction both with respect to the main marketing stage, but also in terms of ‘after-sales’ performance. The short-lived herbaceous perennial Coreopsis grandiflora cv. Flying Saucers was used as a model subject. When exposed to five diurnal temperatures (14, 20, 24, 27 and 31°C) and grown at four photoperiods (8, 11, 14 and 17h), time to first open flower was optimal at 27°C (42 days). Speed of flowering was aided by longer photoperiod (approximately 5 days earlier at 17h than at 14h). Greatest numbers of flowers produced overall though was associated with the 14°C/14h regime. Comparisons based on original cutting size demonstrated that large cuttings, rooted under long-day photoperiods produced plants with greater flower numbers than other cutting treatments. Once planted out, however, plants from all treatment combinations had similar floral performance (mean of 160 flowers per plant). Time of propagation/planting-out also had no overall effect on the numbers of flowers produced within the lifespan of the plant. It was concluded that conditions during production and planting time did not influence garden performance over the longer term.

Importance of population size for offspring fitness at conservation of the gene pool of cultivars

Effective population size for conservation of cultivated plants was studied in Coreopsis grandiflora on populations in variants of 1, 5, 10, 30, 50 and 100 individuals. In five consecutive years these traits were studied on seeds originating from parental populations: seed number and weight per infructescence, thousand seed weight and germination. Plant height and flower size were investigated in a field trial. The influence of population size was expressed mainly in traits of early life-history stages. Inbreeding depression influenced germination already in the first year and was similar for the five years while seed weight was influenced from the second year. In the fifth year there were significant differences among variants of 30 individuals and less and variant of 50 individuals in all evaluated traits. The results document that mostly cross-pollinated cultivars of a population smaller than 50 individuals are exposed to impairment. The population of 10 individuals and less is at risk of extinction. This result will be influenced by the level of cross-pollination and degree of selection.  

Response of Herbaceous Perennials to Growth Retardants Applied at Different Developmental Stages when Grown Under Night-Interrupted Lighting Outdoors in the Southern United States

A study was conducted in 2004 and 2005 to determine how ‘Early Sunrise’ coreopsis (Coreopsis grandiflora Hogg ex Sweet. ‘Early Sunrise’), ‘Moonbeam’ coreopsis (Coreopsis verticillata L. ‘Moonbeam’) and ‘Goldsturm’ rudbeckia (Rudbeckia fulgida Aiton ‘Goldsturm’) responded to two plant growth retardants applied at three stages of plant development (SOD) when plants were exposed to night-interrupted lighting (NIL) while grown outdoors under nursery conditions in the southern United States. With few exceptions, height of all species was suppressed by 2 weeks after first treatment (WAT) compared to NIL only, regardless of whether 5000 ppm B-Nine or 20 ppm Sumagic was applied at the beginning of a period of rapid shoot elongation (SOD 2) or 2 weeks prior to (SOD 1) or following this stage (SOD 3), and continued throughout the plants’ vegetative phase, although the level of suppression varied with SOD and PGR. Applying either PGR at SOD 2, when rapid shoot elongation first began, was most effective in suppressing vegetative height of ‘Early Sunrise’ coreopsis and ‘Goldsturm’ rudbeckia, whereas vegetative height suppression of ‘Moonbeam’ coreopsis was not affected by SOD when Sumagic was applied, but suppression was greatest when B-Nine was applied at SOD 1, two weeks before rapid shoot elongation began. ‘Early Sunrise’ coreopsis and ‘Goldsturm’ rudbeckia were shortest at first flower when PGRs were applied at SOD 2 and SOD 3, respectively, but plant height of ‘Moonbeam’ coreopsis at first flower was not affected by SOD. Where differences in height suppression occurred at first flower, B-Nine was more effective than Sumagic. Plant SOD when PGRs were applied had no effect on flowering or plant quality of ‘Moonbeam’ coreopsis and minimal effect on ‘Early Sunrise’ coreopsis or ‘Goldsturm’ rudbeckia.

End-of-Day Lighting Effects on Herbaceous Perennials Grown Under Night Interrupted Lighting Outdoors in the Southern United States

A study was conducted in 2004 to determine if end-of-day lighting (EOD) alone or in combination with night-interrupted lighting (NIL) could be used to suppress stem elongation of ‘Goldsturm’ coneflower (Rudbeckia fulgida Aiton ‘Goldsturm’), ‘Moonbeam’ coreopsis (Coreopsis verticillata L. ‘Moonbeam’) and ‘Early Sunrise’ coreopsis (Coreopsis grandiflora Hogg ex Sweet. ‘Early Sunrise’) when grown outdoors under nursery conditions in the southern U.S. without negating the benefits of earlier flowering from NIL. End-of-day lighting, NIL, and the combination of the two treatments accelerated time to flowering of all three cultivars compared to that of plants under a natural photoperiod (NP); however, rudbeckia flowered quicker when exposed to NIL or NIL + EOD than when grown under EOD only. Height of rudbeckia grown under EOD or NIL was greater than that of plants grown under NP, whereas ‘Moonbeam’ coreopsis exposed to EOD, NIL or EOD + NIL were similar in height and taller than plants grown under NP. Height of ‘Early Sunrise’ coreopsis was minimally affected by treatments, except that plants under EOD were shorter than those under EOD + NIL. Growth index, flower number, shoot length and quality rating were similar in almost all cases for plants of the three cultivars when grown under EOD lighting, NIL, or EOD + NIL. These results indicate EOD was ineffective in suppressing height growth and provided no benefit, either alone or in combination with NIL, over NIL alone in the accelerated production of these cultivars outdoors under nursery conditions.

The Biotic Resistance of Soil Biota on the Invasive Weed Coreopsis grandiflora Varies with Irradiance Levels

A greenhouse experiment was carried out to study the effects of the sterilization of the soil on the invasive weed Coreopsis grandiflora Hogg. at two irradiance levels. The sterilization was done by benomyl which is a fungicide used worldwide to sterilize the fungal pathogens. The study found that the effects of the sterilization on C. grandiflora varied with the light intensity in terms of the leaf biomass, total biomass and the root-shoot ratio. At high irradiance (60%) the sterilization significantly increased the leaf biomass, total biomass and the ability of photosynthesis of C. grandiflora, suggesting there are soil pathogenic fungi which contribute to biotic resistance against the invasive plants. In contrast, at low irradiance, the sterilization did not have significant effects on the biomass of the plant although the Fv/Fm was significantly increased, suggesting that the light was the key factor and the biotic resistance of soil biota have some minor effects on the plant invasion of C. grandiflora in low light habitat such as forest canopy. The biotic resistance of soil biota on C. grandiflora varies with irradiance levels, suggesting the limiting factors of invasive plants are complex and vary with microhabitats.

Replacing incandescent lamps with compact fluorescent lamps may delay flowering

The natural photoperiod is often modified in the commercial production of floriculture crops to promote or inhibit flowering. In addition, low-intensity lighting is sometimes provided in growth chambers to influence flowering of photoperiodic plants. Incandescent (INC) lamps have been commonly used to provide photoperiodic lighting, but they are being phased out of production because of their energy inefficiency. Here, we compared flowering and morphological responses of two short-day chrysanthemum (Chrysanthemum×grandiflorum) potted varieties and four long-day (LD) plants grown in a controlled environment greenhouse at 20°C with a truncated 9-h day and a 2- or 4-h night interruption (NI) or 6-h day extension (DE) lighting with INC lamps, compact fluorescent lamps (CFLs), or a combination of the two (INC+CFLs). Bulb type had no effect on flowering percentage of campanula (Campanula carpatica ‘Pearl Deep Blue’), coreopsis (Coreopsis grandiflora ‘Early Sunrise’), petunia (Petunia×hybrida ‘Wave Purple Classic’), and rudbeckia (Rudbeckia hirta ‘Becky Cinnamon Bicolor’). Within bulb type, the LD lighting regimen had no effect on flowering percentage, with the exception of chrysanthemum ‘Bianca’, in which the 4-h NI inhibited flowering more than the 2-h NI or 6-h DE treatments. However, petunia that received a 4-h NI or 6-h DE from CFLs flowered 2–3 weeks later than when the lighting treatments were provided by INC lamps. Therefore, complete replacement of INCs with CFLs can delay flowering in some crops such as petunia, whereas a hybrid approach (INC+CFL) or use of lamps that emit far-red light can alleviate this potential problem.

Development status of Arbuscular mycorrhizal fungi associated with invasive plant Coreopsis grandiflora Hogg.

According to the distribution of Coreopsis grandiflora Hogg., samples were collected from two natural invasion sites; Jufeng and Beijiushui and cultivated site to research AM fungal arbuscule structure of C. grandiflora Hogg., colonization status in different sample plotsand altitudes, and the correlation between colonization status and soil factors in the rhizosphere of C. grandiflora. The result showed that C. grandiflora could form heavyParis-type arbuscule structure, Beijiushui mycorrhizal colonization percentage and numbers of entry points was highest and significant differences with Jufeng and campus.C. grandiflora Hogg. mycorrhizal colonization percentage was on the rise with rising altitudes. In addition to altitudes, soil factors as well as to influence AM fungal colonizationstatus, there were very positive correlation (r=0.792) and positive correlation (r=0.725) between mycorrhizal colonization percentage and the content of organic carbon, availablepotassium in soil, respectively; there were very positive correlation (r=0.854) and very negative correlation (r=-0.966) between numbers of vesicles P-type arbuscule) and the content of available potassium, pH in soil; there were negative correlation (r=-0.782) between numbers of entry points and the content of available phosphorus. High infection rate and the formation of typical arbuscular form of C. grandiflora Hogg. at Laoshan should have an important role on the process from the invasion to becoming constructive species. Key words: Coreopsis grandiflora, Arbuscular mycorrhiza fungi (AM fungi), mycorhizae structure, soil factors.

Identification of drought-tolerant plants for roadside greening—An evaluation of chlorophyll fluorescence as an indicator to screen for drought tolerance

Drought is a major limitation to plant growth and development so the identification of suitable screening techniques and quantifiable traits associated with drought tolerance can potentially help reduce the impact of water deficit on plant replacement needs and allow for remedial action where necessary to be undertaken. Twelve species of flowering plants ( Excocecaria cochinensis Lour., Russelia equisetiformis Schlecht. & Cham., Lantana montevedensis (Spreng.) Briq., Phyllanthus cochinchinensis (Lour.) Spreng., Evolvulus pilosus Syne., Talinum triangulare (Jacq.) Willd., Coreopsis grandiflora Hogg ex Sweet, Chlorophytum cosmosum (Thunb.) Jacques., Elephantopus scaber L., Periscaria hydropiper (L.) Spach., Stenotaphrum secundatum (Walter.) Kuntze. and Tradescantia pendula (Schnizl.) Hunt.) commonly planted along streets and roads for aesthetic purposes were examined here using the chlorophyll fluorescence ratio ( F v/ F m – a measure of photochemical efficiency) and digital image analysis of green foliage coverage. Both have been confirmed to be reliable indicators in the identification of drought tolerant and susceptible species. Plants were initially allowed to establish for 60 days under adequate irrigation following containerization (establishment phase). This was followed by another 60 days of drought (drought phase). For the last 60 days of the experiment, plants were re-watered and allowed to recover (recovery phase). Based on fluctuations in photochemical efficiency over the different phases, five species were identified as susceptible to drought whilst another five were considered to have the ability to resist water stress and two were identified as drought intermediate species – exhibiting reduced sensitivity to drought conditions where a decline in values of F v/ F m were only observed in the recovery phase. One of the drought intermediate species ( T. triangulare) exhibited little to no relationship between chlorophyll fluorescence and soil moisture content. Plants were deemed drought tolerant through stable F v/ F m values and lower leaf senescence as recorded by a greater extent of green foliage at the end of the drought and recovery phase. The identification of drought tolerant and susceptible species was further confirmed through regression analysis of F v/ F m and soil moisture content where linear relationships were observed between leaf chlorophyll fluorescence and soil moisture for most of the plants examined in this study. Results of this study strongly suggest that evaluation of whole shrubs using chlorophyll fluorescence is capable of providing a means to identifying the susceptibility of plants to water stress.

Intermittent Light from a Rotating High-pressure Sodium Lamp Promotes Flowering of Long-day Plants

A technology for long-day (LD) lighting was evaluated for commercial production of ornamentals using a stationary high-pressure sodium (HPS) lamp with an oscillating aluminum parabolic reflector (rotating HPS lamp). We performed an experiment with four LD species (Campanula carpatica Jacq., Coreopsis grandiflora Hogg ex Sweet, Petunia ×hybrida Vilm.-Andr., and Rudbeckia hirta L.) to compare the efficacy of a rotating HPS lamp in promoting flowering with night-interruption (NI) lighting using incandescent (INC) lamps. Seedlings were grown under natural short-day (SD) photoperiods (12 h or less) and NI treatments were delivered from a 600-W rotating HPS lamp mounted at one gable end of the greenhouse or from INC lamps that were illuminated continuously for 4 h or cyclically for 6 min every 30 min for 4 h. Plants were grown at lateral distances of 1, 4, 7, 10, or 13 m from the rotating HPS lamp, which provided a maximum photosynthetic photon flux of 25.4 μmol·m−2·s−1 (at 1 m) to 0.3 μmol·m−2·s−1 (at 13 m). Control plants were grown under an uninterrupted 15-h skotoperiod. Within 16 weeks, 80% or greater of the plants within each species that received NI lighting had a macroscopic visible flower bud or inflorescence, whereas all species but Petunia ×hybrida remained vegetative under the SD. Flowering of all species grown at 13 m from the rotating HPS lamp was delayed by 14 to 31 d compared with those under continuous INC. The weekly operational costs to provide NI lighting to a 139-m2 greenhouse with one 600-W rotating HPS lamp or a standard cyclic INC lamp installation was estimated to be 80% to 83% lower compared with INC lighting for the entire 4-h NI. These results indicate that a rotating HPS lamp can be used to efficiently deliver LD lighting, but flowering time was delayed and flower number reduced in some species when the maximum NI light intensity was less than 2.4 μmol·m−2·s−1.

The effect of growth retardants on annual and perennial pot plants.

There are more chemicals in circulation that have a dwarf-growth influence for the plants (Basra, 2000; Korting, 2010; Reiners, 2007; Richter, 2006; Ueber, 2007). Among these substrates we took into the trial five chemicals: CCC, Caramba, Cultar, Regalis and Toprex. These substrates were accommodated in concentration by the reference of the producer. Examined species were: In this preliminary experiment the reaction of the species was observed. We measured the height of the plants, the number of lateral branches, the diameter of the plant bush and the size of leaves. The unfavourable effects (necrosis) were also detected. The trial was started on 19. April, 2010. The seeds were sown into seedflats, and were put into a greenhouse in Matrafured. The seeds sprouted within 14-16 days. When the plants reached the 2 leaf stage they were transplanted into pots on 5. May 2010. At first, 6 groups of plants were composed, 5 chemicals in the trial and a control group. By Matthiola incana, Coreopsis grandiflora and Scabiosa atropurpurea 25 pots consisted of a group, while by Godetia grandiflora 15 pots, as germinating of Godetia was just about 60%. Treating data were: 11th May 2010, 27th May 2010, 17th June 2010. All the chemicals showed adequate results except Caramba. By this substrate we found burned leafs. So a new concentration of Caramba was made.

Natural monoacetylenes studied by quantum-chemical chemistry

This study is a part of the project focused on the vibrational analysis of natural mono- and polyacetylenes by using Raman spectroscopy and theoretical calculations. Their vibrational spectra show strong and polarized –C≡C– bands in the region of about 2200 cm–1. Mono- as well as polyacetylenes are supposed to be active in plants yet not available in an isolated form, so theoretical simulation of their vibrational spectra and comparison with the registered ones seems to be an excellent way to confirm or exclude the presence of these compounds in the investigated plants. Such an approach was applied here to analyze polyacetylenes in roots of Coreopsis grandiflora. According to literature, this plant should contain a monoacetylene substituted by a thiophene ring. Theoretical calculations allowed to confirm this assumption.

Limited Inductive Photoperiod Affects Herbaceous Perennials Grown Under Nursery Conditions in the Southern United States

Abstract A study was conducted to determine if limited inductive photoperiod (LIP) initiated in late winter could be used to control stem elongation in ‘Goldsturm’ coneflower (Rudbeckia fulgida ‘Goldsturm’), ‘Moonbeam’ coreopsis (Coreopsis verticillata ‘Moonbeam’), or ‘Early Sunrise’ coreopsis (Coreopsis grandiflora ‘Early Sunrise’), grown outdoors under nursery conditions in the southern United States, without negating the benefits of earlier flowering from night-interrupted lighting (NIL). Treatments were NIL beginning on February 1 and ending on February 15, March 1, March 15, or April 1,2002, plus a natural photoperiod (NP) treatment. The experiment was repeated in 2003 with the inclusion of an additional NIL treatment ending on April 15. LIPs of at least 15 to 30 days, 30 to 45 days, and 30 to 45 days promoted earlier flowering of ‘Early Sunrise’ coreopsis, ‘Moonbeam’ coreopsis, and ‘Goldsturm’ coneflower, respectively. Flower counts and quality ratings of the three cultivars that received LIPs were similar to or higher than those of plants under a NP, except for a reduction in flowering and quality ratings of ‘Goldsturm’ coneflower exposed to LIPs ending on March 1 and March 15, 2002, and on March 1, 2003, and later. LIP effects on plant height were mixed, although there was at least one duration of LIP that resulted in earlier flowering of the three cultivars and plants similar to or shorter than plants under a NP.

Genetic diversity of the invasive plant Coreopsis grandiflora at different altitudes in Laoshan Mountain, China

In order to understand the relationship between genetic diversity and the invasiveness of exotic plants, genetic diversity was studied in the invasive plant Coreopsis grandiflora Hogg. at different altitudes in Laoshan Mountain, Northern China. Coreopsis grandiflora has produced a great deal of damage in Laoshan Mountain. Its genetic diversity was examined using 16 random amplified polymorphic DNA (RAPD) primers, and 125 bands were collected from all individuals. The mean percentage of polymorphic loci (P%) was 39.54%, and the total percentage of polymorphic loci (P%) was 86.40%. The mean Shannon's Information index (H0) was 0.2326 and the mean Nei's genetic diversity (H) was 0.1596. These results indicated a comparatively high genetic diversity in C. grandiflora in Laoshan Mountain. The genetic differentiation among populations (GST) was 0.3948, indicating that most genetic diversity occurs within populations. On the whole, the abundance and the genetic diversity of C. grandiflora decreased with increasing altitude. The high genetic diversity may be related to the invasion of C. grandiflora in Laoshan Mountain. Key words: Biological invasions, Coreopsis grandiflora Hogg., genetic distance, genetic diversity, random amplified polymorphic DNA (RAPD), sexual reproduction, Shannon’s information index

(43) Salinity Tolerance in Herbaceous Perennials

In this preliminary study, we evaluated the salinity tolerance of selected herbaceous perennials. Liners of Rudbeckia hirta `Becky Orange', Phlox paniculata `John Fanick', Coreopsis grandiflora `Early Sunrise', Lantana ×hybrida `New Gold' and Cuphea hyssopifolia `Allyson' were transplanted to 4-gal plastic containers filled with peat moss: pine bark: sand (3:1:1) medium amended with dolomite, Micromax and Osmocote 18-6-12 (at 2, 0.6, and 6 kg·m3, respectively). The plants were irrigated for 14 weeks with tap water containing 0, 1.5, 3, 6, 12, and 24 mM of NaCl: CaCl2 salt mixture (2:1 molar ratio). Increasing salt stress had differential effects on plant growth and quality, with Rudbeckia and Phlox being the most adversely affected even by the lowest salt treatment of 1.5 mM, with dry weight reductions of ∼25% compared to the controls. Conversely, Lantana and Cuphea tolerated extremely well salinity up to 12 mM, where dry weight reductions were less than 10% of the nonsalinized controls. The Lantana and Cuphea plants also presented the lowest leaf Cl accumulation with increasing salinity, whereas Coreopsis showed the highest Cl accumulations at any salinity level. Plots of leaf Cl concentration against dry weights showed steeply declining relationships for Rudbeckia and Phlox plants, confirming our observations and assessment that these species are to be considered salt-sensitive. Leaf Na accumulation is currently being analyzed.

Night-Interrupted Lighting Accelerates Flowering of Herbaceous Perennials Under Nursery Conditions in the Southern United States

Abstract Night-interrupted lighting (NIL) outdoors in a southern nursery setting was evaluated as a system for accelerated production of herbaceous perennials requiring long days to flower. Treatments were NIL beginning February 1, February 15, March 1, or March 15, and a natural photoperiod control. Compared to plants under the natural photoperiod and depending upon initiation of NIL treatment and year, NIL accelerated and increased flowering of ‘Moonbeam’ coreopsis (Coreopsis verticillata L. ‘Moonbeam’) 7 to 36 days and 20 to 244%, ‘Early Sunrise’ coreopsis (Coreopsis grandiflora Hogg ex Sweet. ‘Early Sunrise’) 3 to 20 days and 26 to 64%, ‘Sunray’ coreopsis (Coreopsis grandiflora Hogg ex Sweet. ‘Sunray’) 6 to 13 days and 21 to 44%, ‘Autumn Joy’ stonecrop (Sedum x ‘Autumn Joy’) 26 to 57 days and 200 to 300%, and ‘Blue Queen’ salvia (Salvia x superba Stapf ‘Blue Queen’) 7 to 12 days and 56 to 83%. Flowering of ‘Red Beauty’ obedient plant (Physostegia virginiana (L.) Benth. ‘Red Beauty) was accelerated 20 to 54 days; however, inflorescence counts decreased 38 to 46% in one year and was not affected by treatments in the second year. Plants of all cultivars, except ‘Autumn Joy’ sedum and ‘Red Beauty’ obedient plant, were taller when exposed to NIL than when grown under the natural photoperiod, however plant quality rating of all cultivars was as high or higher under NIL.

Coreopsis grandiflora `Sunray' Flowers in Response to Short Days or Vernalization

Coreopsis grandiflora `Sunray' has been reported to flower under long days (LD) following vernalization or short days (SD). The objectives of this study were to characterize the effective duration of vernalization and SD and to determine if photoperiod during vernalization influences flowering. Vegetative cuttings taken from stockplants developed from one seedling were rooted for 2 weeks and grown for 5 weeks. Plants were provided with a 9-hour photoperiod for 2, 4, 6, or 8 weeks or were vernalized at 5 °C under a 16-hour photoperiod for 2, 4, 6 or 8 weeks or under a 9-hour photoperiod for 2 or 8 weeks. Following treatments, plants were grown in a greenhouse at 20 °C under a 16-hour photoperiod. Control plants were grown under constant 9- or 16-hour photoperiod. Leaf development, days to first visible bud (DVB), days to first open flower (DFLW), and height and total number of flower buds at FLW were recorded. No plants flowered under continuous SD. Under continuous LD, two plants flowered on axillary shoots but only after 95 days. All vernalized and SD-treated plants flowered on both terminal and axillary shoots. Photoperiod during vernalization did not affect subsequent flowering. DFLW decreased from 56 to 42 and from 50 to 42 after 2 to 8 weeks of vernalization and SD treatments, respectively. Following 2, 4, 6, and 8 weeks of vernalization, plants had 116, 116, 132, and 204 flower buds, respectively. Plant height at FLW of all SD-treated and vernalized plants was similar. Thus, 2 weeks of 9-hour SD or vernalization at 5 °C followed by LD was sufficient for flowering of our clone of C.`Sunray', although longer durations hastened flowering and increased flower bud number.

HEIGHT CONTROL OF HERBACEOUS PERENNIALS FORCED USING NIGHT-INTERRUPTED LIGHTING UNDER NURSERY CONDITIONS

In previous studies, night-interrupted lighting (NIL) promoted earlier flowering of summer-blooming herbaceous perennials grown under outdoor nursery conditions in the southeastern U.S. However, NIL promoted excessive plant height, thus reducing product quality. Our objective was to control plant height of Coreopsis grandiflora `Early Sunrise' (ES) and Rudbeckia fulgida `Goldsturm' (RG) grown under NIL with plant growth retardants (PGR) without offsetting earlier flowering promoted by NIL. Treatments under NIL were three rates of daminozide, daminozide plus chloromequat, flurprimidol, uniconazole, and NIL and natural controls. Plant height was reduced 3% to 38% in ES and 8% to 31% in RG and time to visible bud was unchanged by all PGR treatments compared to the NIL control. Time to visible bud was unchanged in RG by all PGR treatments and flurprimidol in ES, but the remaining PGR treatments increased time to visible bud compared to the NIL control in ES. Only ES plants treated with daminozide and daminozide plus chloromequat at the two highest rates and all rates of uniconazole were similar in height to the natural control. RG plant heights with the two highest rates of flurprimidol and uniconazole and the highest rate of daminozide plus chloromequat were less than the natural control; heights of plants in the remaining PGR treatments were similar to the natural control. Quality rating was unchanged in RG but was increased in ES by all PGR treatments compared to the NIL control.