Impatiens Hawkeri Research Articles

Cocopeat Perlite Mixture as an Alternative for Rooted Cuttings Growth Medium of Impatiens hawkeri x platypetala in Indonesia

<p><em>Impatiens hawkeri x platypetala </em>rooted cuttings are typically cultivated using rice husks as a substrate. However, due to the poor water-holding capacity of this medium, <em>Impatiens</em> grows slowly in this environment. A viable alternative is the cocopeat perlite mixture which has a better water-holding capacity compared to the rice husk. Currently, there is no sufficient information available regarding the best growth medium to improve the quality of <em>I. hawkeri x platypetala</em> rooted cuttings in Indonesia. Therefore, this study aimed to obtain the best medium for quality rooted cuttings <em>I. hawkeri x platypetala</em>. The method employed was a randomized complete block design with two factors. The first factor was the <em>Impatiens</em> varieties consisting of Impala Agrihorti, Imadata Agrihorti, and Lavender, while the second was the growth medium, comprised of four levels namely rice husk (control), as well as a mixture of cocopeat with 3%, 5% and 8% perlite. The result showed that there was no interaction between varieties and growth medium. The mixture of 3% perlite in cocopeat exhibited better outcomes compared to other treatments. This medium increased the number and length of roots, stem diameter, plant height, leaves thickness, leaves number and survival rate. Therefore, the addition of 3% perlite in cocopeat could replace the rice husk as a rooted cutting growth medium for <em>I. hawkeri x platypetala</em>.</p>

Establishment of a highly efficient in vitro plant regeneration system for Impatiens hawkeri W. Bull cv. ‘Pink’ and its background resistance to kanamycin

Establishment of a highly efficient in vitro plant regeneration system for Impatiens hawkeri W. Bull cv. ‘Pink’ and its background resistance to kanamycin

First Report of New Guinea Impatiens (Impatiens hawkeri) Leaf Spot Caused by Alternaria burnsii - A. tomato species complex in Taiwan.

New Guinea impatiens (Impatiens hawkeri) is a common ornamental crop usually planted in pots and planters, flower beds, home gardens, or parks in Taiwan. In June 2021, leaf spots on 87.1% (27/31) of potted I. hawkeri plants on National Chung Hsing University (NCHU) campus were observed. Initially, tiny chlorotic leaf spots were found, which aged into brown to grayish white necrotic spots with reddish-purple margins. The necrotic spots enlarged, coalesced, and formed concentric rings. To isolate the pathogen, diseased leaves were surface-disinfected with 70% ethanol for 15 seconds and blotted dry with a paper towel. Small pieces (~2×6 mm2) of tissues were excised from the junction of the lesions and healthy areas, placed onto 2% water agar, and incubated at 25°C with 12-h photoperiod for three days. Individual hyphal tips growing out of diseased tissues were transferred onto potato dextrose agar (PDA). Three isolates, OM10, OM43, and OM45, were obtained and grown on half-strength PDA at 28°C in the dark for at least two weeks. Conidia of each isolate produced on the half-strength PDA were washed off in sterile water with 0.01% of Tween 20. Pathogenicity tests were performed by spraying leaves of 2- to 3-month-old potted healthy I. hawkeri plants with 5 ml of conidial suspension (1 × 105 conidia/ml) of the three isolates, respectively. Control plants were sprayed with sterile water. There were four plants per treatment and the experiments were conducted twice. Inoculated plants were covered with plastic bags for two days and incubated in a greenhouse with a temperature range of 19 to 31°C. Leaf spots similar to those observed in the field were observed at 7 to 14 days after inoculation in both trials. The same fungus was isolated from inoculated plants, whereas control plants showed no symptoms. Thereafter, the three isolates were subjected to morphological and molecular identification. Colonies were brown to gray in the center and white in the border with abundant aerial mycelia. Conidia were brown, obclavate to ovoid, produced in single or branched chains, one to seven transverse and zero to three longitudinal septa. Conidial size of the three isolates ranged between 11.2 to 43.1 × 6.0 to 12.7 μm (n = 50 for each isolate). Conidiophores of the three isolates were dark-brown, septate, branched or unbranched, and measured 27.0 to 147.65 × 2.71 to 4.54 μm (n = 50 for each isolate). Based on the morphological characteristics, the three isolates were identified as Alternaria spp. (Simmons 2007). For molecular identification, the internal transcribed spacer (ITS) region, RNA polymerase II second largest subunit (RPB2), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and major allergen Alt-a-1 gene (Alt-a-1) were amplified using primer pairs ITS1/ITS4 (White et al. 1990), RPB2-5F2/RPB2-7cR (Sung et al. 2007), gpd1/gpd2 (Berbee et al. 1999), and Alt-for/Alt-rev (Hong et al. 2005), respectively. Sequence analyses of isolates OM10 (ITS: GenBank Accession no. OP358436; RPB2: OP377483; GAPDH: OP377468; Alt-a-1: OP377471), OM43 (ITS: OP358437; RPB2: OP377484; GAPDH: OP377469; Alt-a-1: OP377472), and OM45 (ITS: OP358438; RPB2: OP377485; GAPDH: OP377470; Alt-a-1: OP377473) showed 100%, 99.61 to 100%, 99.65%, and 100% identities with a reference strain CBS 107.38 of A. burnsii for ITS (KP124420), RPB2 (KP124889), GAPDH (JQ646305), and Alt-a-1 (KP123967), respectively. They also showed 100%, 99.61 to 100%, 99.65%, and 99.58% identities with an A. tomato strain CBS 103.30 for ITS (KP124445), RPB2 (KP124915), GAPDH (KP124294), and Alt-a-1 (KP123991), respectively. Based on the morphological and sequence characteristics, the pathogen causing New Guinea impatiens leaf spot was identified as a member of the Alternaria burnsii - A. tomato species complex. The diseased plants on NCHU campus were destroyed. There have been no reports of the disease in other landscape areas or nurseries. To our knowledge, this is the first report of A. burnsii - A. tomato species complex causing New Guinea impatiens leaf spot in Taiwan. Since the pathogens in the species complex have been documented causing diseases on several important economic crops and the New Guinea impatiens is widely planted in nurseries and landscapes, the host range and the significance of the pathogen in agro-ecosystem may warrant further investigations.

Pengaruh Berbagai Konsentrasi Eco Enzyme dan Pinching Terhadap Pertumbuhan dan Pembungaan Tanaman Pacar Air (Impatiens hawkeri Bull) Pada Vertical Pipe

New Guinea Impatiens (Impatiens hawkeri Bull) is a plant with beautiful crown with a lot varieties of colors that has potentially used as an ornamental plant. Production is influenced by many factors such as knowledge about technologies in cultivation techniques. The cultivation techniques are being implementation a vertical system using paralon pipes and application of eco enzyme and pinching treatment. The aim of this research is to learn the interaction between application of various concentrations of eco enzyme and pinching methods on the growth and flowering of New Guinea Impatiens. The research was conducted from December 2021 to April 2022 at greenhouse on the experimental area of the Faculty of Agriculture, Brawijaya University, Jatimulyo Village, Lowokwaru District, Malang City, East Java. This research used a Randomized Complete Block Design (RCBD) with two factors and 3 repetition. The first factor is concentration of eco enzyme and the second factor is pinching treatment. Observations were made on plant growth and flower production. The data which is obtained from the observations were analyzed using ANOVA with the rate of 5%, if there is a significant effect, a further test using the Honest Significant Difference (HSD) with the rate of 5%. The results showed that there is significant interaction occurred in the application of eco enzyme and pinching treatment in all observation variables. The highest result of New Guinea Impatiens’s growth and flower production was obtained in the eco enzyme treatment with concentration of 10 ml.l-1 and double pinching. Number of flowers of New Guinea Impatiens in that treatment increased 2.95 times compared to without eco enzyme and without pinching. The time of flower appear of Impatiens hawkeri Bull showed a significant interaction with the application of eco enzyme with concentration of 5 ml.l-1 and double pinching treatment because the average time of flowers appear is 9.44 days slower than the treatment without eco enzyme and without pinching.

Air temperature during cutting propagation of cold-intermediate and -sensitive crops can be reduced if root-zone heating is provided

Asexual propagation of herbaceous ornamentals occurs from late winter to early spring coincides with seasonally low daily light integrals (DLIs) and average daily temperatures (ADT) outdoors. Supplemental lighting and air and root-zone heating (RZH) can be used to promote rapid callus induction and rooting of cuttings. Due to the range of greenhouse crop base temperatures (cold-tolerant, cold-intermediate, and cold-sensitive), one strategy is to reduce the air ADT of certain crops while using RZH as a potential energy saving strategy. Therefore, the objective of this study was to quantify how reduced air ADT and increased RZH temperatures influence root initiation and development of cold-intermediate and-sensitive herbaceous annual and perennial crops propagated by shoot-tip cuttings. Unrooted vegetative cuttings of angelonia ‘Archangel Raspberry’ (Angelonia angustifolia), lantana ‘Landmark Sunrise Rose Improved’ (Lantana camara), New Guinea impatiens ‘Clockwork White Improved’ (Impatiens hawkeri), scaevola ‘Scalora Brilliant’ (Scaevola aemula), thunbergia ‘Sunny Lemon Star’ (Thunbergia alata), verbena ‘Cadet Upright Red’ (Verbena × hybrida), geranium ‘Moxie! Deep Rose’ (Pelargonium interspecific), Kwik Kombos ‘Pink Lemonade Mix’ [petunia ‘Dekko Star Rose’ (Petunia × hybrida), lobelia ‘Techno Heat Light Blue Improved’ (Lobelia erinus), and calibrachoa ‘Callie Yellow Improved’ (Calibrachoa × hybrida)] and portulaca ‘Cupcake Carrot’ and ‘Colorblast Lemon Twist’ (Portulaca grandiflora) were inserted into a soilless medium and placed in a greenhouse with an air ADT of 21°C and RZH set point of 24°C to callus. After 6 d, trays of cuttings were placed between two greenhouses with an air ADT of 16 or 21°C and among 3 benches which provided RZH set points of 21, 24, or 27°C. After 14 or 16 d post-callus, measurements were collected for all genera and geranium and portulaca ‘Colorblast Lemon Twist’ were transplanted into a common environment. The air ADT and RZH individually influenced stem length of angelonia, lantana, kwik kombos, portulaca, thunbergia, and verbena, and interacted to influence angelonia and lantana. Under an air ADT of 21°C, angelonia was 30%-45% taller than an air ADT of 16°C. Stem length of geranium, New Guinea impatiens, and scaevola were not influenced by air ADT or RZH. With an RZH set point of 21°C, the root dry mass of thunbergia was 72% greater under an air ADT of 21 than 16°C. Lantana shoot dry mass was 23% smaller under an air ADT of 16°C and RZH of 21°C compared to an RZH of 24°C. Finished plants of geranium and portulaca were not influenced by air ADT or RZH and were comparable in size and date of marketability between treatments. Due to little to no differences in crop timing or quality, the majority of the crops studied can be propagated with an air ADT and RZH of 16 and 24°C, respectively, without negative effects during or after propagation.

Efficient plant regeneration system for New Guinea Impatiens (Impatiens hawkeri W. Bull) CV. ‘Violet’ and ‘Scarlet Bronze Leaf’

New Guinea Impatiens (Impatiens hawkeri W. Bull) is an eye-popping landscaping plant of bright and colorful blooms. A highly efficient in vitro plant regeneration system via direct shoot organogenesis was established for the first time from hypocotyl with partial cotyledons of New Guinea Impatiens. Our results showed that the explant sterilization method, basic medium type, AgNO3, sucrose and plant growth regulators have significantly influenced in vitro morphogenesis. The regeneration rate in regeneration media that MS supplemented with 0.5 mg·L−1TDZ and 0.1 mg·L−1NAA was acceptable, the induction rate of ‘Violet’ was 86.67%, and its proliferation coefficient was 5.27, while the induction rate of 'Scarlet Bronze Leaf' was 83.33%, and its proliferation coefficient 5.13. PIC could not induce clumped sprouts; however, it had a better effect on callus induction. We also included a shoot multiplication stage using regeneration New Guinea Impatiens medium that MS supplemented with 0.8 mg·L−16-BA, 0.5 mg·L−1TDZ and 0.05 mg·L−1NAA. Reducing sucrose concentration to 20 g·L−1 or adding 1 mg·L−1AgNO3 could alleviate the hyperhydricity phenomenon in the process of tufted bud proliferation. The optimal root culture medium for the regenerated seedlings of ‘Violet’ and 'scarlet bronze leaf' of New Guinea Impatiens was MS supplemented with 0.05 mg·L−1IBA, the rooting rate reached 100%.The study examined the micropropagation responses of New Guinea Impatiens in the presence of various growth regulators, which provide a simple and more suitable protocol adapted for the mass propagation of clones.

Gibberellin and polyamines effects in growth and flowering of New Guinea impatiens

Abstract To meet the high demand of the consumer market for ornamental plants, various techniques are used to increase production and flowers quality, through growth regulators. Despite all the benefits arising from the use of regulators, it is essential to establish concentrations that meet the purpose of their use. The aim of the study was to evaluate the growing and flowering characteristics of Impatiens hawkeri, after the exogenous application of different dosages of spermine, spermidine and gibberellic acid. Two pulverizations were made separated by 15 days, with polyamines (500/2,000 and 1,000 μM), or gibberellic acid (50 and 100 μM), and for the control, water was used. The evaluated parameters were the number of leaves, plant height, number of flower buds, dry and fresh weights of the root system and the aerial parts, and also volume of the root system and the chlorophyll content (SPAD). The treatments with gibberellin caused higher averages in all measurements, except for SPAD. Based on the results obtained, the use of gibberellin with the dosage of 100 µM as a regulator is the most appropriate to meet the needs of the Impatiens hawkeri market with more vigorous plants and with a greater number of flowers.

First report of powdery mildew caused by Podosphaera xanthii on New Guinea impatiens in Korea

From August to November 2020, a previously unseen powdery mildew disease was encountered repeatedly on New Guinea impatiens (Impatiens hawkeri, syn. Impatiens ‘New Guinea’ hybrid) in Uijeongbu, Korea. It occurred on plants growing in partial shade along high buildings or walls, but not on those planted in sunny gardens. Symptoms included white, effuse, amphigenous mycelial patches on leaves and stems, reducing the aesthetic value of plants (Fig. 1). Microscopic examination of freshly collected leaves revealed the following morphological characteristics: upright conidiophores (110–210 × 10–12 μm) producing 2 to 5 catenescent conidia, and ellipsoid to doliiform conidia (26–38 × 16–22 μm) containing conspicuous fibrosin bodies. In autumn, scattered chasmothecia were found on leaves, mainly on the lower surface (Figs. 2–3). These measured 80–100 μm in diameter, had mycelioid appendages, and contained a single ascus with 8 ellipsoid to ovoid ascospores (16–20 × 12–16 μm) (Fig. 4). These characteristics were consistent with the description of Podosphaera xanthii in Braun & Cook (2012). To confirm the morphology-based determination, genomic DNA was extracted from a representative specimen (KUS-F32140, Korea University herbarium, Seoul, Korea). PCR products were amplified using the primer sets ITS1F/PM6 for the internal transcribed spacer (ITS) and PM3/TW14 for the large subunit (LSU) of rDNA (Takamatsu & Kano, 2001). The sequences obtained in this study (GenBank Accession Nos. MW750225 (ITS) and MW750226 (LSU)) were compared with other sequences in GenBank using BLASTn. The analysis showed 100% identity with other P. xanthii sequences (e.g., AB462799, AB462803 for ITS, and MT919354, LC371331 for LSU) and neighbour-joining analysis of ITS sequences placed the Korean isolate in a well-supported clade with the reference sequences of P. xanthii (Fig. 5). Podosphaera (previously Sphaerotheca) powdery mildews on Impatiens spp. have been previously assigned to P. balsaminae (Braun & Cook, 2012; Farr & Rossman, 2021). However, P. balsaminae was shown to be limited to the Asian materials of Podosphaera on I. noli-tangere (Ito & Takamatsu, 2010). The remainder of Podosphaera powdery mildews on Impatiens spp. were proved to belong to or were tentatively assigned to the P. xanthii complex (Braun & Cook, 2012). Podosphaera powdery mildews on New Guinea impatiens seem to be uncommon considering the world-wide cultivation of the host as a potted and garden plant. Previously, Wolcan (2004) recorded P. balsaminae on I. hawkeri from Argentina, and Garibaldi et al. (2012) recorded Podospahera sp. on I. hawkeri from Italy. We prove here that the earlier collection from Italy also represents P. xanthii (Figure 5). To our knowledge, this is the first confirmed report of powdery mildew caused by P. xanthii on New Guinea impatiens. This finding could be useful for the breeding programme of Impatiens spp. and future plantings of New Guinea impatiens in gardens. This work was supported by Korea IPET through Crop Viruses and Pests Response Industry Technology Development Program, funded by MAFRA.

Complete Genome Sequence Resource for the Necrotrophic Plant-Pathogenic Bacterium Dickeya dianthicola 67-19 Isolated From New Guinea Impatiens.

New Guinea impatiens (NGI, Impatiens hawkeri) are popular bedding plants that can be affected by a number of pathogens. Using 16S rDNA sequencing and genus-specific PCR, we identified the first Dickeya dianthicola strain isolated from NGI presented with blackleg symptoms, herein designated as D. dianthicola 67-19. Here, we report a high-quality complete and annotated genome sequence of D. dianthicola 67-19. The 4,851,809 bp genome was assembled with Nanopore reads and polished with Illumina reads, yielding 422× and 105× coverage, respectively. This closed genome provides a resource for future research on comparative genomics and biology of D. dianthicola, which could translate to improved detection and disease management.

A protocol for fast in vitro propagation of Impatiens hawkeri cv. Sweeties Blue Star, an important ornamental-cover species

Abstract Impatiens hawkeri is among the three important bedding plants in the world. There is no efficient protocol for fast micropropagation of Impatiens hawkeri cv. Sweeties Blue Star. Single nodes were germinated on Murashige and Skoog (MS) medium supplemented with 1-naphthaleneacetic acid (NAA; 0.00, 0.10 and 0.50 mg l-1), 6-benzyladenine (BA; 0.00, 0.10, 0.50 and 1.00 mg l-1) and kinetin (KIN; 0.00, 0.10, 0.50 and 1.00 mg l-1). The shoot length was highest in medium containing 0.10 mg l-1 NAA and control. The largest number of shoots (14.06 and 14.00 per explant) was produced in media supplemented with 1.00 mg l-1 BA, 0.50 mg l-1 NAA and 1.00 mg l-1 BA, 0.10 mg l-1 NAA, respectively. The 0.10 mg l-1 NAA along with 1.00 mg l-1 BA was found to be superior for production of leaf (57.13). Maximum root length (33.80 mm) and root number (29.13) were obtained on medium supplemented with 0.10 mg l-1 NAA without BA and KIN. Plantlets were transplanted to pots filled with perlite and peat moss (in ratio of 1:1) and transferred to the greenhouse for acclimatization. Regenerated plantlets were morphologically identical with mother plants. Upon ex vitro transfer, 100% of plants survived.

First Report of Dickeya dianthicola causing blackleg on New Guinea Impatiens (Impatiens hawkeri) in New York State, USA.

First Report of Dickeya dianthicola causing blackleg on New Guinea Impatiens (Impatiens hawkeri) in New York State, USA.

Acceptability of Bedding Plants by the Leatherleaf Slug, Leidyula floridana (Mollusca: Gastropoda: Veronicellidae)

Leidyula floridana (Leidy) (Gastropoda: Veronicellidae) has long been known to be a plant pest in the Caribbean region and southern Florida, though its range has expanded to include northern Florida, other Gulf Coast states, and Mexico. It is nocturnal, and often overlooked as a source of plant damage. Although polyphagous, it does not feed on all plants, and it is desirable to know what bedding plants will likely be damaged by this common herbivorous slug. To identify readily accepted bedding plants, I conducted a series of comparative trials of 7 d duration to assess the acceptance of 30 commonly grown bedding plants relative to French marigold, a plant that is commonly fed upon by slugs and snails. Several commonly grown bedding plants were shown to be very susceptible to feeding injury. In a second set of 7-d trials, I compared 14 plants from among those that were not readily accepted in the first set of trials to determine if they would remain poorly accepted when not provided with favored food. In the second set of trials, the levels of herbivory shown in the first trials were maintained, demonstrating that some bedding plants are not acceptable to L. floridana even when the slugs do not have access to acceptable food. Thus, a list of readily available bedding plants that resist herbivory by this slug has been determined, providing gardeners with slug-resistant choices. The most unacceptable species (damage rating = 1.00) were: lantana (Lantana camara L.; Verbenaceae), tickseed (Coreopsis spp.; Asteraceae), torenia (Torenia fournieri Linden ex E. Fourn.; Linderiaceae), angelonia (Angelonia angustifolia Benth.; Plantaginaceae), and snapdragon (Antirrhinum majus L.; Plantaginaceae). Additional plant species that were not very acceptable (damage rating of between 1.00 and 1.50) were blue daze (Evolvulus glomeratus Choisy; Convolvulaceae), dusty miller (Centaurea cineraria [L.] Jacq. ex Nym.; Asteraceae), viola (Viola hybrid; Violaceae), celosia (Celosia argentea L.; Amaranthaceae), and geranium (Geranium spp.; Geraniaceae). In contrast, plant species that seem to be at considerable risk of damage (damage rating 3 to 5) by L. floridana were: French marigold (Tagetes patula L.; Asteraceae), Madagascar periwinkle (Catharanthus roseus [L.] G. Don; Apocyanaceae), coleus (Plectranthus scutellarioides [L.] R. Br.; Laminaceae), petchoa (Petunia × Calibrachoa; Solanaceae), zinnia (Zinnia elegans Jacq.; Asteraceae), polka dot plant (Hypoestes phyllostachya Baker; Acanthaceae), chrysanthemum (Chrysanthemum morifolium Ramat; Solanaceae), petunia (Petunia spp.; Solanaceae), Stokes' aster (Stokesia laevis [Hill] Greene; Asteraceae), scarlet sage (Salvia splendens Sellow ex Nees; Lamiaceae), butter daisy (Melampodium paludosum Kunth; Asteraceae) and verbena (Verbena spp.; Geraniaceae). A few species were intermediate in susceptibility, namely: impatiens (Impatiens hawkeri W. Bull; Balsamaniaceae), wax begonia (Begonia × Semperflorens × Cultorum; Begoniaceae), sweet potato vine (Ipomoea spp.; Convolvulaceae), firecracker flower (Crossandra infundibuliformis [L.] Nees; Acanthceae), sweet William (Dianthus barbatus L.; Caryophyllaceae), pansy (Viola × Wittrochinana; Violaceae), purslane (Portulaca oleraceae L.; Portulacaceae), and alyssum (Lobularia maritima [L.] Desv.; Brasscaeae).

Impatiens ‘New Guinea’ (Impatiens hawkeri Bull) Hormonal Effects during the Post-transplant Biomass Accumulation

Pot ornamental plant productivity is related to the environmental growth facilities but negatively affected by the pot root restriction syndrome so during nursery as the post-transplant stage. The physiological mechanism involved included both the synthesis and translocation of auxins and cytokinins. However, clear sink-source and dose-response relationships of exogenous plant regulators such as indole acetic acid (AIA) and benzyl amino purine (BAP) and environment on biomass accumulation in most ornamental foliage plants, including New Guinea Impatiens (Impatiens hawkeri) are lacking. The aim of this work was to analyze the effects of an exogenously shoot-applied auxin and a cytokinin, separately or successively, on the post-transplant biomass accumulation of I. hawkeri through the anatomical, morphological and physiological changes observed. Two experiments were performed. The first experiment included the response to only BAP-sprayed plants (0, 5, 50, or 100 mg L-1). For the second experiment, rooting cuttings of I. hawkeri were sprayed with different concentrations of IAA (0, 5, 50, or 100 mg L-1) followed by different BAP concentrations (0, 5, 50, or 100 mg L-1) one week later to run-off at sunset. Results showed that (a) a single BAP or AIA dose increased increase post-transplant biomass accumulation through a higher leaf area expansion and photo assimilate production, (b) as a result of both AIA and BAP spray, the higher NAR the higher post-transplant biomass accumulation, (c) leaf anatomical changes (leaf thickness, intercellular spaces) let a higher carbon dioxide diffusion and fixation with a correlative increase in photo assimilates, (d) a higher root system would be related to a higher cytokinin synthesis. In summary, similarities between responses to either hormone, together with the lack of any IAA - BAP interaction, provide two independent routes for commercial growers to increase the productivity of I. hawkeri ornamental plants by using early foliar sprays.

Phosphorus Restriction as an Alternative to Chemical Plant Growth Retardants in Angelonia and New Guinea Impatiens

Chemical plant growth retardants (PGRs) are commonly used to produce compact bedding plants. Few PGRs are labeled for sensitive species because of the concern of excessive restriction of stem elongation or phytotoxicity. Growers are therefore presented with a dilemma: produce untreated plants that may be too tall or risk applying a PGR that can potentially lead to irreversible aesthetic damage to the plant. Nutrient restriction, specifically of phosphorus (P), may be used to control plant height. This study was conducted to determine if restricting P fertilization yielded comparable growth control to plants produced with PGRs. Two cultivars each of new guinea impatiens (Impatiens hawkeri) and angelonia (Angelonia angustifolia) were grown using five fertilizers that varied by P concentration (0, 2.5, 5, 10, and 20 ppm). Half of the plants from each P fertilizer concentration were treated with paclobutrazol at 4 and 5 weeks after transplant for angelonia and new guinea impatiens, respectively. On termination of the experiment, data were collected for height, diameter, and dry weight, which were used to determine a growth index (GI). Angelonia GI values were maximized with 7–9 ppm P, whereas new guinea impatiens GI was maximized with 8–11 ppm P. Concentrations of 3–5 ppm P provided similar height control to plants grown with nonlimiting P and a paclobutrazol application. Concentrations of ≤2.5 ppm P resulted in low-quality plants with visual symptoms of P deficiency. These results indicate that a narrow range of P concentrations may be used to control stem elongation and keep plants compact.

Aesthetic Quality and Strength of Bioplastic Biocontainers at Different Substrate Volumetric Water Contents

Various types of emerging bioplastic containers present a range of physical and chemical properties and can perform differently from one another in production environments. Container performance may be affected by substrate moisture content. We quantified the effects of bioplastic container type and substrate volumetric water content (VWC) on the aesthetic and mechanical strength properties of bioplastic containers and on plant growth. Seedlings of ‘Divine Cherry Red’ new guinea impatiens (Impatiens hawkeri W. Bull) and ‘Pinot Premium Deep Red’ zonal geranium (Pelargonium ×hortorum L.H. Bailey) were transplanted into five types of 11.4-cm–diameter containers, four types made from bioplastics and one type made from petroleum-based plastic and used as a control. Plants were watered to container capacity at transplant, allowed to dry down to VWC thresholds of 0.20 or 0.40 m3·m−3, and subsequently maintained at desired set points by using a precision irrigation system controlled by soil moisture sensors. Total volume of water applied per plant to new guinea impatiens was affected by VWC and not container type, whereas irrigation volume was affected by both for geranium. Growth index and shoot dry mass (SDM) of new guinea impatiens and geranium were affected by VWC. Container type affected growth index and SDM of geranium only. Water use efficiency (WUE) of both species was similar regardless of container type and VWC. Aesthetic quality varied based on VWC for only one container type, which was made from a blend that included soy-based bioplastic. Containers manufactured with polyhydroxyalkanoates (PHA) and dried distiller’s grains and solubles (DDGS) or polylactic acid (PLA), soy polymer with adipic anhydride (SP.A), and a proprietary bio-based filler (BR) derived from modified DDGS were stronger when maintained at a lower VWC, 0.20 m3·m−3. Our findings indicate that restricting irrigation to the minimum needed to achieve the desired crop growth is a viable strategy for sustaining aesthetic quality and strength of bioplastic containers manufactured with plant protein–based fillers such as SP.A and BR. Other bioplastic containers, such as those made of PLA–lignin biocomposite, show durability equal to that of petroleum-based plastic containers and maintain pristine appearance regardless of substrate VWC during production.

Propagation success of cuttings as influenced by stage of propagation, 1-MCP and ethylene exposure and storage: part 1Impatiens

The propagation success of cuttings can be influenced by the stage of development at which they are shipped and stored, storage duration and exposure to ethylene inhibitors and/or ethylene. The objective of this study was to determine the effect of the propagation stage and ethylene inhibitor 1-MCP on the sensitivity of Impatiens hawkeri 'Super Sonic White' and 'Super Sonic Red' to ethylene and simulated shipment. Nine combinations of the propagation stage (1 = unrooted; 2 = callused; 3 = rooted), 1-MCP treatment (0 or 700 nL L-1) followed by ethylene treatment (0 or 1 µL L-1), and storage duration (0 or 2 days) were administered. Impatiens cuttings that were stored after being propagated to Stage 3 had the most yellow/necrotic leaves, while overall, 'Super Sonic White' had more than 'Super Sonic Red'. In both cultivars, cuttings propagated until Stage 3, before any gas treatment or storage, took the most propagation days to reach Stage 3 and had the lowest root fresh and dry weights. Stage 1 cuttings stored for 2 days reached Stage 3 in fewer days than unstored cuttings, such that if the 2-day storage was counted towards propagation days, the difference between unstored and stored cuttings was negligible. Cuttings treated with ethylene, and stored for 2 days at Stage 2, reached Stage 3 in the least number of propagation days. Most postharvest parameters were not significantly affected by 1-MCP. Cuttings treated with 1-MCP prior to ethylene took slightly longer to root than cuttings just treated with ethylene, but differences were ≤0.6 days. In summary, root development continued on cuttings in storage indicated that short term storage may be beneficial.

Low Substrate pH–Induced Iron/Manganese Toxicity of New Guinea Impatiens: A Diagnostic Guide

New Guinea impatiens (Impatiens hawkeri) are popular bedding plants, but the knowledge of diagnosing abiotic disorders during greenhouse production is evolving. Symptomology of nutrient deficiencies and excessive fertilization have been extensively documented. Exact symptomology of low substrate pH (<5.5) and toxic iron (Fe) and/or manganese (Mn) leaf tissue levels are not defined or photographed, thereby aiding in diagnosis. Therefore, the objective of the diagnostic guide was to photograph symptomology and document the tissue levels in New Guinea impatiens to provide a definitive guide of low substrate pH–induced Fe and/or Mn toxicity.

Growth Response of Herbaceous Ornamentals to Phosphorus Fertilization

A series of experiments investigated the effects of increasing phosphate–phosphorus (P) concentrations on the growth and development of four horticultural species. In experiment 1, petunia [Petunia atkinsiana (Sweet) D. Don ex W.H. Baxter] plants were grown using eight P concentrations, and we found that the upper bound for plant growth was at 8.72–9.08 mg·L−1 P, whereas concentrations ≤2.5 mg·L−1 P caused P deficiency symptoms. Experiment 2 investigated P growth response in two cultivars each of New Guinea impatiens (Impatiens hawkeri W. Bull) and vinca [Catharanthus roseus (L.) G. Don]. Growth for these plants was maximized with 6.43–12.42 mg·L−1 P. In experiment 3, ornamental peppers (Capsicum annuum L. ‘Tango Red’) were given an initial concentration of P for 6 weeks and then switched to 0 mg·L−1 P to observe whether plants could be supplied with sufficient levels of P, and finished without P to keep them compact. Plants switched to restricted P began developing P deficiency symptoms within 3 weeks; however, restricting P successfully limited plant growth. These experiments indicated that current P fertilization regimens exceed the P requirements of these bedding plants, and depending on species, concentrations of 5–15 mg·L−1 P maximize growth.

Identifying the Optimal Application Rate of Three Fertilizers Used to Grow New Guinea Impatiens

This manuscript describes the effect of controlled-release, and water-soluble fertilizers on the growth and quality of New Guinea impatiens (NGI) (Impatiens hawkeri Bull.). Three different fertilizers were applied at three rates each in order to investigate their effect on growth and quality of ‘Paradise New Red.’ NGI. Fertilizer treatments included 1) a 20-4.4-16.6 water-soluble fertilizer (WSF), 2) a 10-1.8-2.5 soybean-based fertilizer (SBF), and 3) a 15-4-10, three-to four-month longevity controlled-release fertilizer (CRF). CRF was applied as a pre-plant at 1×, 0.75×, and 0.5× the label rate. WSF and SBF fertigation rates of 75, 150, and 250 mg·L−1 N (75, 150, and 250 ppm N), respectively, were used based on a common range of fertigation rates in a greenhouse setting from what is considered relatively low, moderate, and high for NGI production. Plants were irrigated or fertigated by hand every 1 to 5 days as needed, based on environmental conditions and plant size, with either approximately 300 mL (10.4 oz) of either tap water or a fertilizer solution. SPAD readings, above ground plant weight, consumer preference ratings, and cumulative flower number were measured and used to calculate a quality index (QI). Optimal fertilizer rates as determined by the QI were found to be 1) CRF at 7.11 kg·m−3 (11.8 lb·yd−3), 2) SBF at 150 mg·L−1 (150 ppm) N, and 3) WSF at 75 mg·L−1 (75 ppm) N. With the application method used in this work, the WSF was more efficient than the SBF because it produced high quality plants with less fertilizer applied. While for the most part overall consumer preference ratings coincided with plant dry weight, there were some exceptions, indicating that consumers can prefer plants that are not necessary the largest as indicated by their dry weights. Consumer preferences may not coincide with typical plant parameters of plant growth all the time. Consumer preferences should be always considered in an industry that sell its products based mainly on their appearance.

Evaluation of Antitranspirants for Enhancing Temporary Water Stress Tolerance in Bedding Plants

Water stress during shipping and retailing reduces the postproduction quality and marketability of bedding plants. Antitranspirants can temporarily prevent plants from wilting by either physically blocking stomata or physiologically inducing stomatal closure, limiting transpirational water loss from leaves. The goal of this research was to evaluate the efficacy of commercially available antitranspirants on enhancing temporary water stress tolerance in bedding plants. Two physical antitranspirants [β-pinene polymer (βP) and vinyl-acrylic polymer (VP)], and three physiological antitranspirants [two sugar alcohol-based compounds (SACs) and a biologically active form of abscisic acid (s-ABA)] were applied to begonia (Begonia semperflorens-cultorum), new guinea impatiens (Impatiens hawkeri), impatiens (Impatiens walleriana), petunia (Petunia ×hybrida), african marigold (Tagetes erecta), and french marigold (Tagetes patula). Physical antitranspirants were sprayed on foliage and physiological antitranspirants were drenched to the media. All antitranspirants were applied at half (0.5×), equal to (1×), or twice (2×) the manufacturer’s recommended rate. Extended shelf life was observed when βP or s-ABA was applied. Treatment with βP increased the shelf life of impatiens and african marigold by 1 and 1.3 days compared with control plants, respectively. The application of βP at 2× was more effective at delaying visual wilting than at lower rates (0.5× and 1×) in african marigold. Applications of s-ABA delayed wilting by 1.3 to 3.7 days in all tested cultivars. The shelf lives of impatiens and petunia treated with s-ABA at 2× were extended the most by 3.7 and 3.0 days compared with control plants, respectively. A rapid reduction of stomatal conductance (gS) was observed within 4 hours of βP or s-ABA application in plants showing delayed wilting symptoms. s-ABA treatment appeared to cause marginal leaf chlorosis in impatiens, whereas application of βP damaged the opened flowers in all tested cultivars. The application of VP or SACs did not extend shelf life in any treated plants. These results suggest that foliar application of βP on selected species and treatment with s-ABA on most of species would allow bedding plants to withstand water deficit during shipping and/or retailing.