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Free access

Christopher J. Currey and Roberto G. Lopez

Our objectives were to quantify the effects of controlled-release fertilizer (CRF) on the growth, morphology, and tissue nutrient concentration of annual bedding plants during propagation. Unrooted cuttings of Angelonia angustifolia ‘AngelFace White’ and ‘Sundancer Pink’, Impatiens hawkeri ‘Celebrette Apricot’ and ‘Celebrette Rose Hot’, Nemesia fruticans ‘Bluebird’ and ‘Raspberry Sachet’, Pelargonium ×hortorum ‘Savannah Red’, and Petunia ×hybrida ‘Cascadia Marshmallow Pink’ and ‘Suncatcher Yellow’ were received from a commercial propagator. Cuttings were immediately stuck individually in cells containing soilless substrate supplemented with 0, 3, 6, 12, or 24 g·L−1 CRF (Osmocote Plus 15–3.9–10 3–4 month) and placed under clear mist water or cuttings were stuck in substrate containing no CRF and fertilized with water-soluble fertilizer beginning immediately after placing cuttings into propagation. Shoot dry mass of cuttings grown in substrates containing up to 12 or 24 g·L−1 CRF increased by up to 150% for some taxa compared with unfertilized cuttings. Incorporating CRFs into propagation substrates increased the concentration of nitrogen (N), phosphorus (P), and potassium (K) in tissues by up to 103%, 42%, and 137%, respectively, compared with unfertilized cuttings. Additionally, tissue nutrient concentrations for cuttings fertilized with 6 g·L−1 CRF or greater were similar to cuttings receiving water-soluble fertilizer (WSF). When the impact of CRF on growth and nutrient concentrations are taken together, our results indicate that CRF is a fertilization application technology that holds promise for use during propagation of herbaceous stem-tip cuttings.

Open access

Annika E. Kohler and Roberto G. Lopez

Domestic production of culinary herbs continues to increase in the United States. Culinary herbs are primarily propagated by seed; however, some herbs have poor germination rates and slow growth. Thus, there are advantages of propagating herbs by vegetative stem-tip cuttings as they lead to true-to-type plants and a shortened production time. Previous research of ornamental young plants and finished culinary herbs have shown a reduction in rooting time and increases in plant quality with increases in the photosynthetic daily light integral (DLI). To our knowledge, little to no research has addressed how the DLI influences culinary herb liner quality. Therefore, the objectives of this study were to quantify morphological traits of five economically important culinary herbs when grown under DLIs ranging from 2.8 to 16.4 mol·m−2·d−1. Stem-tip cuttings of Greek oregano (Origanum vulgare var. hirtum), rosemary ‘Arp’ (Rosmarinus officinalis), sage ‘Extrakta’ (Salvia officinalis), spearmint ‘Spanish’ (Mentha spicata), and thyme ‘German Winter’ (Thymus vulgaris) were excised from stock plants and rooted under no shade or aluminum shading of 36%, 56%, or 76% to create a range of DLI treatments. After 9 days (spearmint) or 16 days (all other genera) of DLI treatments, the root, shoot, and total dry mass of all culinary herb liners generally increased by 105% to 449%, 52% to 142%, and 82% to 170%, respectively, as the DLI increased from 2.8 to 16.4 mol·m−2·d−1 or genus-specific DLI optimums. Stem length of oregano, spearmint, and thyme decreased by 37%, 28%, and 27%, respectively, as the DLI increased from 2.8 to 16.4 mol·m−2·d−1. However, stem length of rosemary and sage were unaffected by the DLI. The quality index of all genera was greatest at DLIs from 10.4 to 16.4 mol·m−2·d−1. Furthermore, all culinary herbs grown under a DLI of ≤6 mol·m−2·d−1 had low root and shoot dry mass accumulation; and oregano, spearmint, and thyme were generally taller. Therefore, DLIs between 10 to 12 mol·m−2·d−1 should be maintained during culinary herb propagation, because a DLI ≥16 mol·m−2·d−1 may be deleterious and energy inefficient if supplemental lighting use is increased.

Free access

Wesley C. Randall and Roberto G. Lopez

To produce uniform, compact, and high-quality annual bedding plant seedlings in late winter through early spring, growers in northern latitudes must use supplemental lighting (SL) to achieve a photosynthetic daily light integral (DLI) of 10 to 12 mol·m−2·d−1. Alternatively, new lighting technologies may be used for sole-source photosynthetic lighting (SSL) to grow seedlings in an indoor high-density multilayer controlled environment. The objective of this study was to compare seedlings grown under low greenhouse ambient light (AL) to those grown under SL or SSL with a similar DLI. On hypocotyl emergence, seedlings of vinca (Catharanthus roseus), impatiens (Impatiens walleriana), geranium (Pelargonium ×hortorum), petunia (Petunia ×hybrida), and French marigold (Tagetes patula) were placed in a greenhouse under AL or AL plus SL delivering a photosynthetic photon flux (PPF) of 70 µmol·m−2·s–1 for 16 hours, or under multilayer SSL delivering a PPF of 185 µmol·m−2·s–1 for 16 hours in a walk-in growth chamber. Supplemental lighting consisted of high-pressure sodium (HPS) lamps or high-intensity light-emitting diode (LED) arrays with a red:blue light ratio (400–700 nm; %) of 87:13, and SSL consisted of LED arrays providing a red:blue light ratio (%) of 87:13 or 70:30. Root and shoot dry mass, stem diameter, relative chlorophyll content, and the quality index (a quantitative measurement of quality) of most species were generally greater under SSL and SL than under AL. In addition, height of geranium, petunia, and marigold was 5% to 26%, 62% to 79%, and 7% to 19% shorter, respectively, for seedlings grown under SSL compared with those under AL and SL. With the exception of impatiens, time to flower was similar or hastened for all species grown under SL or SSL compared with AL. Seedlings grown under SSL were of similar or greater quality compared with those under SL; indicating that LED SSL could be used as an alternative to traditional greenhouse seedling production.

Free access

W. Garrett Owen and Roberto G. Lopez

Under low-light greenhouse conditions, such as those found in northern latitudes, foliage of red leaf lettuce (Lactuca sativa L.) varieties is often green and not visually appealing to consumers. Our objective was to quantify the effect of end-of-production (EOP; prior to harvest) supplemental lighting (SL) of different sources and intensities on foliage color of four red leaf lettuce varieties, ‘Cherokee’, ‘Magenta’, ‘Ruby Sky’, and ‘Vulcan’. Plants were finished under greenhouse ambient solar light and provided with 16-hours of day-extension lighting from low intensity light-emitting diode (LED) lamps [7:11:33:49 blue:green:red:far red (control)] delivering 4.5 μmol·m−2·s−1, or 16-hours of EOP SL from high-pressure sodium (HPS) lamps delivering 70 μmol·m−2·s−1, or LED arrays [100:0, 0:100, or 50:50 (%) red:blue] delivering 100 μmol·m−2·s−1, or 0:100 blue LEDs delivering 25 or 50 μmol·m−2·s−1. Relative chlorophyll content (RCC) and foliage L* (lightness), and chromametric a* (change from green to red) and b* (change from yellow to blue) values were significantly influenced by EOP SL and days of exposure. Generally, RCC of all varieties increased from day 3 to 14 when provided with EOP SL from the HPS lamps and LEDs delivering 100 μmol·m−2·s−1. End-of-production SL providing 100 μmol·m−2·s−1 of 100:0, 0:100, or 50:50 red:blue light for ≥5 days resulted in increasing a* (red) and decreasing L* (darker foliage), b* (blue), and h° (hue angle; a measure of tone) for all varieties. Our data suggests that a minimum of 5 days of EOP SL providing 100 μmol·m−2·s−1 of 100:0, 0:100, or 50:50 red:blue light enhanced red pigmentation of ‘Cherokee’, ‘Magenta’, ‘Ruby Sky’, and ‘Vulcan’ leaves when plants are grown under a low greenhouse daily light integrals (DLIs) <10 mol·m−2·d−1.

Full access

Christopher J. Currey and Roberto G. Lopez

The influence of pre-plant bulb dips in paclobutrazol solutions on final plant height, days to flower, and flower bud number were evaluated for easter lily (Lilium longiflorum). ‘Nellie White’ easter lily bulbs were placed in solutions of paclobutrazol containing 0, 30, 60, or 120 mg·L−1 for 15 min preceding planting. Days to flower and flower bud number were unaffected by paclobutrazol. Plant height at flowering for bulbs dipped in paclobutrazol solutions was 15% to 26% shorter compared with untreated bulbs. Additionally, dipping bulbs in 120 mg·L−1 paclobutrazol resulted in plants that met target height specifications for commercially grown easter lily. Based on these results, dipping easter lily bulbs in paclobutrazol solutions can be an effective strategy for reducing stem elongation without negatively impacting days to flower or flower bud number for commercially grown easter lily.

Free access

Roberto G. Lopez and Erik S. Runkle

Miltoniopsis orchids have appealing potted-plant characteristics, including large, fragrant, and showy pansylike flowers that range from white and yellow to shades of red and purple. Scheduling orchid hybrids to flower on specific dates requires knowledge of how light and temperature regulate the flowering process. We performed experiments to determine whether a 9- or 16-h photoperiod [short day (SD) or long day (LD)] before vernalization and vernalization temperatures of 8, 11, 14, 17, 20, or 23 °C under SD or LD regulate flowering of potted Miltoniopsis orchids. Flowering of Miltoniopsis Augres `Trinity' was promoted most when plants were exposed to SD and then vernalized at 11 or 14 °C. Additional experiments were performed to determine how durations of prevernalization SD and vernalization at 14 °C influenced flowering of Miltoniopsis Augres `Trinity' and Eastern Bay `Russian'. Plants were placed under SD or LD at 20 °C for 0, 4, 8, 12, or 16 weeks and then transferred to 14 °C under SD for 8 weeks. Another set of plants was placed under SD or LD at 20 °C for 8 weeks and then transferred to 14 °C with SD for 0, 3, 6, 9, or 12 weeks. After treatments, plants were grown in a common environment at 20 °C with LD. Flowering of Miltoniopsis Augres `Trinity' was most complete and uniform (≥90%) when plants were exposed to SD for 4 or 8 weeks before 8 weeks of vernalization at 14 °C. Flowering percentage of Miltoniopsis Eastern Bay `Russian' was ≥80 regardless of prevernalization photoperiod or duration. This information could be used by greenhouse growers and orchid hobbyists to more reliably induce flowering of potted Miltoniopsis orchids.

Full access

Christopher J. Currey, Roberto G. Lopez, and Neil S. Mattson

Energy accounts for one of the largest costs in commercial greenhouse (GH) production of annual bedding plants. Therefore, many bedding plant producers are searching for energy efficient production methods. Our objectives were to quantify the impact of growing annual bedding plants in an unheated high tunnel (HT) compared with a traditional heated GH environment at two northern latitudes. Ten popular bedding plants [angelonia (Angelonia angustifolia), vinca (Catharanthus roseus), celosia (Celosia argentea), dianthus (Dianthus chinensis), geranium (Pelargonium ×hortorum), petunia (Petunia ×hybrida), french marigold (Tagetes patula), viola (Viola ×cornuta), snapdragon (Antirrhinum majus), and osteospermum (Osteospermum ecklonis)] were grown both in an unheated HT and a glass-glazed GH with an 18 °C temperature set point beginning on 1 Apr. 2011 at both Cornell University (Ithaca, NY) and Purdue University (West Lafayette, IN). Although seven of the species exhibited a delay in flowering in the HT as compared with the heated GH, there were no differences in days to flower (DTF) for geranium, osteospermum, and viola grown at Cornell and viola at Purdue. The remaining species exhibited delays in flowering in the HT environment, which varied based on species. At Purdue, several species were lost because of a cold temperature event necessitating a second planting. For the second planting, osteospermum was the only species grown that flowered significantly later in the HT; 7 days later than the GH-grown plants. Production of cold-tolerant annuals in unheated or minimally heated HTs appears to be a viable alternative for commercial producers aiming to reduce energy costs.

Free access

César Guzmán-Loza, J. Farías-Larios, and J.G. López-Aguirre

Use of arbuscular mycorrhizal fungi (MA) on horticultural plant production has great potential as a biotechnological alternative; however, information on its effects on the early growth phase of honeydew melon is lacking. Nevertheless, it would seem that inoculation at the time of sowing would decrease the stress of transplant, improve root vigor, make plants grow faster, improve drought resistance, and lessen the effect of roots diseases. In this study, we evaluated the effects of inoculating honeydew melon seedlings with two commercial formulations of MA fungi at different study times in an effort to select for higher resistance and infective capacity. `Moonshine' hybrid melon seeds were sown in trials with 200 cavities containing specific doses of inoculate: 0, 100, 200, 250, 500, and 1000 cc/trial of BuRIZE, Mycorrhiza NES. A factorial design was used (formulations and study times) with a randomized distribution and four replications. Four destructive samples were taken at 10, 15, 20, and 25 days after inoculations. Number of leaves, shoot fresh weight, dry weight, root fresh weight, foliar area, and mycorrhizal colonization were recorded. Results obtained showed a highly significant effect between commercial formulations and study times and an interaction of both factors to studied variables. Mycorrhizal colonization percentages were too low (0.3% to 1.7%). At 20 days after inoculations, it was possible to see all the components of functional arbuscular mycorrhizal symbiosis on melon plants roots. Using commercial formulations of mycorrhizal fungi decreased applications of fertilizers in melon plants.

Free access

S. Guzman, H. Alejandro, J. Farias, A. Michel, and G. Lopez

Watermelon (Citrullus vulgaris Schrad.) is a widely grown crop throughout the tropics and subtropics. In Mexico, it is an economically important crop. In vitro adventitious shoot regeneration of watermelon has been reported from shoot tip culture, leaf, hypocotyl, and cotyledons. Hence, the objective of this study was to evaluate in vitro plant regeneration from axillary buds of triploid watermelon. Axillary buds explants were prepared from shoot of commercial cultivar in field of 60 old day plants. Explants of 2 to 3 mm were incubated 2 weeks on Murashige and Skoog (MS) shoot regeneration medium containing 2.5 mg/L kinetin (KT) or indole-3-butyric acid (IBA), or gibberellic acid (GA3), followed by 3 weeks on shoot elongation medium supplemented with different combinations of the same phytohormones. The percentage of explants (83% to 90%) that produced shoots, expansion in size of explant (0.81–1 cm) and shoot length (6 mm) were highest in MS medium containing KT or IBA. In the shoot elongation step, shoot length (0.9–1 cm) and leaves number (6–7) were highest in MS medium supplemented with 2.5 mg/L of KT or GA3 and 0.2 mg/L IBA, but the better induction of roots in elongated shoot occurred on MS medium with 2.5 mg/L KT and 0.2 mg/L IBA. The results show that axillary buds from watermelon is an alternative for the micropropagation of this crop.

Free access

Francisco Lopez-Gutierrez, Harrison G. Hughes, and Nicholas C. Carpita

After 6 months of growth in 200,400, and 500 mm NaCl, cultured cells of Distichlis spicata showed a decreased cell volume (size) despite maintenance of turgor pressure sometimes 2-fold higher than that of the control. Tensile strength, as measured by a nitrogen gas decompression technique, showed empirically that the walls of NaCl-stressed cells were weaker than those of nonstressed cells. Breaking pressures of the walls of control cells were ≈68 ± 4 bars, while that of the walls of cells grown in 500 mm NaCl (-25 bars) were 14 ± 2 bars. The relative amount of cellulose per cell remained about constant despite salt stress. However, glucuronoarabinoxylans were more readily extractable, presumably because of a decrease in cross-linkage with phenol substances. Therefore, we suggest that cellulose microfibrils are not the only determinants that confer tensile strength to the primary cell wall, but rather subtle changes in the matrix polysaccharides are likely responsible for this event.