The effects of cooling temperature [constant (10, 13, 15, or 18 °C, or 15, 18, or 21 °C)] and duration (2, 3, 4, 5, or 6 weeks, or 3, 4, 5, 6, or 7 weeks) at two separate locations (College Station and Weslaco, TX) on growth and flowering of Dendrobium Sea Mary ‘Snow King’, a Dendrobium nobile Lindl. hybrid, were investigated and the cooling requirement for flowering was quantified. Interactions between temperature and cooling duration were significant on time required to reach anthesis from either the beginning or completion of cooling, average flower number per flowering node, and percentage of nodes with aborted buds. Increasing cooling duration from 2 to 6 or 3 to 7 weeks resulted in less time to reach anthesis after the completion of cooling. However, the increased cooling durations extended the time needed for producing a flowering crop. Plants cooled at a relatively higher temperature among 10, 13, and 15 °C required less time to reach anthesis after the completion of cooling. Plants had more flowering nodes and total flowers when cooled at 10, 13, or 15 °C than at 18 °C in College Station or at 15 or 18 °C than at 21 °C in Weslaco. The results suggest that 3 weeks at 13 °C has saturated the cooling requirement, and 3 weeks at 13 or 15 °C is a recommended cooling treatment that saves production cost without retarding flower development.
Christine Yung-Ting Yen, Terri W. Starman, Yin-Tung Wang, and Genhua Niu
Xi Wang, Genhua Niu, Mengmeng Gu, Paul A. Baumann, and Joseph Masabni
Mustard Seed Meals (MSMs) are by-products of biodiesel and an alternative to conventional herbicides for organic farming. However, MSMs might also suppress the emergence of vegetable seedlings. The objective of this study was to determine the response of vegetable seedling emergence to different MSM types and rates applied as an alternative herbicide. Six types of vegetable seeds, onion (Allium cepa), two cultivars of lettuce (Lactuca sativa ‘Black Seeded Simpson’ and ‘Buttercrunch’), mustard (Brassica juncea), kale (Brassica oleracea), and Mizuna (Brassica rapa var. japonica), were sowed in petri dishes containing germination mix. MSMs (Sinapis alba ‘IdaGold’ and B. juncea ‘Pacific Gold’) were incorporated into the germination mix at 0, 88, 176, or 265 g·m−2. Petri dishes were sealed for 1, 3, 5, or 7 days after sowing. For onion, ‘Pacific Gold’ had a greater suppressive effect on seedling emergence than ‘IdaGold’. For kale and mustard, ‘IdaGold’ and ‘Pacific Gold’ had similar suppressive effects on seedling emergence, but ‘Pacific Gold’ delayed emergence of kale at 88 g·m−2 when sealed for 3, 5, and 7 days. For Mizuna, ‘IdaGold’ had more suppressive effects than ‘Pacific Gold’ on seedling emergence, while sealing delayed but did not decrease emergence percentage (EP) at the lower rate (88 g·m−2) compared with the control treatment. For ‘Buttercrunch’ lettuce, there were no differences in the suppressive effects between the two MSMs. For ‘Black Seeded Simpson’ lettuce, ‘Pacific Gold’ had more suppressive effects on seedling emergence than ‘IdaGold’ when sealed at the lower rate (88 g·m−2) for longer durations (7 days) or at higher rates (176 and 265 g·m−2) for shorter durations (1 and 3 days). These results suggest that MSMs might suppress vegetable seedling emergence when applied at high rates (176 and 265 g·m−2), and sealing for more than 7 days after sowing may strengthen the suppressive effect. Extending sealing duration at the medium rates could achieve similar weed control results to high rates without sealing.
James E. Faust, Jeffrey W. Adelberg, Kelly P. Lewis, and Genhua Niu
The effects of storage temperature and shoot preparation of elephant ears (Colocasia antiquorum `Illustris') were examined to determine how to successfully store plants prior to greenhouse forcing. A series of experiments were conducted that provided storage temperatures of 4, 7, 10, 13, or 16 °C (39.2, 44.6, 50.0, 55.4, or 60.8 °F), and plants were placed into storage with the shoots uncut or cut to 3.0 cm (1.18 inches) above the surface of the growing medium. The storage duration ranged from 40 to 49 days. All plants stored at 4 or 7 °C died. Plant survival was 89% to 100% at 10 °C, while plant survival was 100% at 13 or 16 °C. Shoot emergence and plant growth was faster following storage at 13 and 16 °C, than storage at 10 °C. Storage at 16 °C resulted in leaf growth occurring during storage, which was undesirable. Removing shoots prior to storage had no effect on plant survival and performance during forcing. A fungicide drench with iprodione immediately prior to storage did not improve plant survival. This study suggests that 13 °C is near the base temperature for leaf development of elephant ears, thus the plants survive at this temperature with no growth occurring. Shoot removal prior to storage is recommended in order to optimize storage room space.
Huan Xiong, He Sun, Feng Zou, Xiaoming Fan, Genhua Niu, and Deyi Yuan
Castanea henryi is an important woody grain tree species native to China. The objective of the current study was to find the suitable plant growth regulators (PGRs) and the optimal concentrations for direct organogenesis by using axillary shoots and cotyledonary nodes. Seeds were collected from the field, sterilized, and germinated in vitro. Axillary shoots and cotyledonary nodes of 3-week-old seedlings were used as explants. To find the suitable PGR for adventitious shoot induction, 0.5 mg·L–1 6-benzylaminopurine (6-BA), 0.1 mg·L–1 indole-3-acetic acid (IAA), 0.1 mg·L–1 2,4-dichlorophenoxyacetic acid (2,4-D), or 0.1 mg·L–1 1-naphthaleneacetic acid (NAA) was supplemented to Murashige and Skoog (MS) medium containing 0.65% agar and 3% sucrose. A high induction percentage of adventitious shoots (85.67%) was obtained from cotyledonary nodes supplemented with 0.1 mg·L–1 2,4-D. The type of explant influenced shoot proliferation rates and quality. Apical explants produced more and longer shoots than nodal segments. For shoot multiplication, 1 mg·L–1 6-BA + 0.05 mg·L–1 indole-3-butyric acid (IBA) supplemented with MS medium produced 12.33 and 6.25 shoots per explant, respectively, from apical and nodal explants. For shoot elongation and strengthening, 2 mg·L–1 6-BA + 0.05 mg·L–1 IBA supplemented with MS medium was the best combination, producing shoots with a mean length of 3.50 cm, a diameter of 0.46 cm, and about eight leaves per shoot. The greatest rooting of 76.70% and 11.33 roots per shoot was achieved when cultured in MS medium supplemented with 3.5% perlite + 1.5 mg·L–1 IBA. For acclimatization of the rooted plantlets in the greenhouse, a survival rate of 80% was achieved. This protocol—from multiplication to acclimation—is helpful to realize mass propagation of high-quality trees of chinquapin for increasing production and nut quality.
Qiang Liu, Youping Sun, Genhua Niu, James Altland, Lifei Chen, and Lijuan Jiang
Because of limited supply of high-quality water, alternative water sources have been used for irrigation in water-scarce regions. However, alternative waters usually contain high salt levels, which can cause salt damage on salt-sensitive plants. A greenhouse study was conducted to evaluate the relative salt tolerance of 10 common ornamental taxa to saline water irrigation. The 10 taxa studied were Chaenomeles speciosa ‘Orange Storm’ and ‘Pink Storm’ (Chaenomeles Double Take™); Diervilla rivularis ‘G2X885411’, ‘G2X88544’ (Diervilla Kodiak®, Black, Orange, and Red, respectively), and ‘Smndrsf’; Forsythia ×intermedia ‘Mindor’ (Forsythia Show Off®); Hibiscus syriacus ‘ILVOPS’ (Hibiscus Purple Satin®); Hydrangea macrophylla ‘Smhmtau’ and ‘Smnhmsigma’ (Hydrangea Let’s Dance® Blue Jangles® and Rave, respectively); and Parthenocissus quinquefolia ‘Troki’ (Parthenociss quinquefolia Red Wall®). Plants were irrigated with a nutrient solution at an electrical conductivity (EC) of 1.2 dS·m−1 (control) or saline solutions at EC of 5.0 or 10.0 dS·m−1 (EC 5 or EC 10) eight times on a weekly basis. The results indicated that the 10 ornamental taxa had different morphological and physiological responses to salinity. The C. speciosa and D. rivularis plants in EC 5 had severe salt foliar damage, whereas those in EC 10 were dead. Hibiscus syriacus ‘ILVOPS’ performed well in EC 5 treatment with a shoot dry weight (DW) reduction of 26%, but those in EC 10 had severe foliar salt damage. Hydrangea macrophylla, F. ×intermedia ‘Mindor’ and P. quinquefolia ‘Troki’ were the most salt tolerant with minor foliar salt damage. The two H. macrophylla cultivars had the highest shoot sodium (Na) and chlorine (Cl) concentrations with a visual quality of 3 (scale 0 to 5 with 0 for dead plants and 5 for excellent performance), indicating that H. macrophylla plants adapted to elevated salinity by tolerating high Na and Cl concentrations in leaf tissue. Forsythia ×intermedia ‘Mindor’ and P. quinquefolia ‘Troki’ had relatively low leaf Na and Cl concentration, indicating that both taxa are capable of excluding Na and Cl. Chaenomeles speciosa and D. rivularis were sensitive to salinity with great growth reduction, severe foliar salt damage, and high Na and Cl accumulation in leaf tissue.
Genhua Niu, Raul I. Cabrera, Terri W. Starman, and Charles R. Hall
Susmitha Nambuthiri, Amy Fulcher, Andrew K. Koeser, Robert Geneve, and Genhua Niu
Market researchers have found that nursery and greenhouse production practices that reduce plastic use can increase consumer interest. However, there are broader crop performance, production efficiency, and environmental factors that must be considered before adopting containers made with alternative materials. This review highlights current commercially available alternative containers and parent materials. In addition, findings from recent and ongoing nursery, greenhouse, and landscape trials are synthesized, identifying common themes, inconsistencies, research gaps, and future research needs.
Youping Sun, Genhua Niu, Christina Perez, H. Brent Pemberton, and James Altland
Marigolds (Tagetes sp.) are ornamental plants with fine-textured, dark green foliage, and yellow, orange, or bicolored flowers. The relative salt tolerance of eight marigolds [‘Discovery Orange’, ‘Discovery Yellow’, ‘Taishan Gold’, ‘Taishan Orange’, and ‘Taishan Yellow’ african marigold (Tagetes erecta); ‘Hot Pak Gold’, ‘Hot Pak Orange’, and ‘Hot Pak Yellow’ french marigold (Tagetes patula)] was evaluated in a greenhouse experiment. Plants were irrigated weekly with nutrient solution at an electrical conductivity (EC) of 1.2 dS·m−1 (control) or saline solutions at an EC of 3.0 or 6.0 dS·m−1 (EC 3 or EC 6). Marigold plants began to show foliar salt damage (leaf burn and necrosis) at 6 weeks after the initiation of treatment. At harvest (9 weeks after the initiation of treatment), ‘Discovery Orange’, ‘Discovery Yellow’, ‘Taishan Gold’, and ‘Taishan Yellow’ plants exhibited severe foliar salt damage with visual scores less than 2 (on a scale of 0 to 5, with 0 = dead and 5 = excellent with no foliar salt damage) in EC 6. In the same treatment, ‘Hot Pak Gold’ and ‘Taishan Orange’ plants all died and only one of nine ‘Hot Pak Orange’ and ‘Hot Pak Yellow’ plants survived. In EC 3, all cultivars had slight or minimal foliar salt damage with visual scores ≈4 with the exception of Taishan Gold and Taishan Orange plants that showed moderate foliar damage with a visual score of 2.3 and 2.1, respectively. Treatment EC 3 reduced the flower number of ‘Discovery Orange’, ‘Discovery Yellow’, ‘Hot Pak Gold’, and ‘Hot Pak Yellow’ by 52%, 28%, 50%, and 30%, respectively, whereas EC 6 decreased the flower number of ‘Discovery Orange’ and ‘Discovery Yellow’ by 48% and 52%, respectively. In addition, both EC 3 and EC 6 did not reduce total dry weight (DW) of any cultivars, except Hot Pak Yellow and Taishan Yellow. In conclusion, all marigold cultivars are moderately sensitive to salt. ‘Discovery Orange’, ‘Taishan Yellow’, ‘Discovery Yellow’, and ‘Taishan Gold’ were more tolerant than ‘Hot Pak Gold’, ‘Hot Pak Orange’, ‘Hot Pak Yellow’, and ‘Taishan Orange’.
Genhua Niu, Royal D. Heins, Arthur C. Cameron, and William H. Carlson
Pansy [Viola ×wittrockiana Gams. `Delta Yellow Blotch' (Yellow) and `Delta Primrose Blotch' (Primrose)] plants were grown in a greenhouse under two CO2 concentrations [ambient (≈400 μmol·mol-1) and enriched (≈600 μmol·mol-1)], three daily light integrals (DLI; 4.1, 10.6, and 15.6 mol·m-2·d-1), and nine combinations of day and night temperatures created by moving plants every 12 h among three temperatures (15, 20, and 25 °C). Time to flower decreased and rate of flower development increased as plant average daily temperature (ADT) increased at all DLIs for Yellow or at high and medium DLIs for Primrose. Increasing the DLI from 4.1 to 10.6 mol·m-2·d-1 also decreased time to flower by 4 and 12 days for Yellow and Primrose, respectively. Both cultivars' flower size and Yellow's dry weight [(DW); shoot, flower bud, and total] decreased linearly as plant ADT increased at high and medium DLIs, regardless of how temperature was delivered during day and night. DW in Yellow increased 50% to 100% when DLI increased from 4.1 to 10.6 mol·m-2·d-1 under both CO2 concentrations. Flower size in Yellow and Primrose increased 25% under both CO2 conditions as DLI increased from 4.1 to 10.6 mol·m-2·d-1, but there was no increase between 10.6 and 15.6 mol·m-2·d-1, regardless of CO2 concentration. Plant height and flower peduncle length in Yellow increased linearly as the difference between day and night temperatures (DIF) increased; the increase was larger under lower than higher DLIs. The ratio of leaf length to width (LL/LW) and petiole length in Yellow increased as DIF increased at medium and low DLIs. Carbon dioxide enrichment increased flower size by 4% to 10% and DW by 10% to 30% except for that of the shoot at medium DLI, but did not affect flower developmental rate or morphology. DW of vegetative and reproductive parts of the plant was correlated closely with photothermal ratio, a parameter that describes the combined effect of temperature and light.
Yuxiang Wang, Youping Sun, Genhua Niu, Chaoyi Deng, Yi Wang, and Jorge Gardea-Torresdey
Ornamental grasses are commonly used in urban landscapes in Utah and the Intermountain West of the United States. The relative salt tolerance of Eragrostis spectabilis (Pursh) Steud. (purple love grass), Miscanthus sinensis Andersson ‘Gracillimus’ (maiden grass), Panicum virgatum L. ‘Northwind’ (switchgrass), and Schizachyrium scoparium (Michx.) Nash (little bluestem) were evaluated in a greenhouse. Plants were irrigated with a nutrient solution at an electrical conductivity (EC) of 1.2 dS·m–1 (control), or saline solution at an EC of 5.0 or 10.0 dS·m–1. At harvest (65 days after the initiation of treatment), P. virgatum and S. scoparium exhibited no foliar salt damage, and E. spectabilis and M. sinensis had minimal foliar salt damage when irrigated with saline solution at an EC of 5.0 dS·m–1. At an EC of 10.0 dS·m–1, P. virgatum and S. scoparium still had no foliar salt damage, but E. spectabilis and M. sinensis displayed slight foliar salt damage, with visual scores greater than 3 (0 = dead; 5 = excellent). Compared with the control, saline solution at an EC of 5.0 and 10.0 dS·m–1 reduced the shoot dry weight of all ornamental grasses by 25% and 46%, respectively. The leaf sodium (Na+) concentration of E. spectabilis, M. sinensis, P. virgatum, and S. scoparium irrigated with saline solution at an EC of 10.0 dS·m–1 increased 14.3, 52.6, 5.3, and 1.7 times, respectively, and the chloride (Cl–) concentration increased by 9.4, 11.1, 2.8, and 2.7 times, respectively. As a result of the salt-induced water deficit, plant height, leaf area, number of inflorescences and tillers, net photosynthesis rate (Pn), stomatal conductance (g S), and transpiration rate of four tested ornamental grasses decreased to some extent. Although high Na+ and Cl– accumulated in the leaf tissue, all ornamental grass species still had a good visual quality, with average visual scores greater than 3. In conclusion, all ornamental grasses showed a very strong tolerance to the salinity levels used in this research.