The morphological anatomy of leaf and rhizome was studied at different developmental stages in Zingiber officinale Roscoe using both light and electron microscopy, with an emphasis on characterizing secretory structures. The results show that the leaf comprises epidermal cells, mesophyll cells, and vascular bundles. Oil and crystal cells are scattered throughout the parenchyma, and some are within or in close contact to the vascular bundle sheath. The rhizome consists of epidermis, cortex, and stele. The pericycle of the rhizome remains meristematic and produces tissues centripetally, whereas the endodermis has no meristematic activity. Starch grains vary in shape from round to oval and vary in size from small to large throughout rhizome development. Oil cells and cavities are scattered and cavities are of lysigenous origin. When mature, the starch grains decrease in abundance while an increasing number of oil cells and cavities are formed. This anatomic characterization provides a theory foundation for medicinal exploitation and utilization of Z. officinale Roscoe.
Huanfang Liu, Chelsea D. Specht, Tong Zhao and Jingping Liao
Qiang Liu, Youping Sun, James Altland and Genhua Niu
Tatarian dogwood (Cornus alba) is an ornamental shrub with white fruits, creamy-white flowers, and red stems in fall through late winter and is widely used in residential landscape, public parks, and botanical gardens. Two greenhouse experiments were conducted to characterize the survival, morphological, aesthetic, and physiological responses of tatarian dogwood seedlings to salinity and drought stresses. In Expt. 1, tatarian dogwood seedlings grown in three soilless growing substrates (Metro-Mix 360, 560, and 902) were irrigated with a nutrient solution at an electrical conductivity (EC) of 1.2 dS·m−1 (control) or saline solution (by adding calculated amount of sodium chloride and calcium chloride) at an EC of 5.0 or 10.0 dS·m−1 once per week for 8 weeks. Results showed that substrate did not influence the growth of tatarian dogwood seedling. All plants irrigated with saline solutions at an EC of 10.0 dS·m−1 died, whereas those irrigated with saline solutions at an EC of 5.0 dS·m−1 exhibited severe foliar salt damage with an average visual score of 1.0 (on a scale of 0 to 5, with 0 = dead and 5 = excellent without foliar salt damage). Compared with the control, saline solutions at an EC of 5.0 dS·m−1 reduced plant height and shoot dry weight (DW) by 50.8% and 55.2%, respectively. Relative chlorophyll content [soil plant analysis development (SPAD) reading], chlorophyll fluorescence (Fv/Fm), and net photosynthesis rate (Pn) also decreased when plants were irrigated with saline solutions at an EC of 5.0 and 10.0 dS·m−1. Leaf sodium (Na+) concentration of tatarian dogwood seedlings irrigated with saline solutions at an EC of 5.0 and 10.0 dS·m−1 increased 11 and 40 times, respectively, compared with the control, whereas chloride (Cl-) concentration increased 25 and 33 times, respectively. In Expt. 2, tatarian dogwood seedlings were irrigated at a substrate volumetric water contents (volume of water/volume of substrate, VWC) of 15%, 20%, 25%, 30%, 35%, 40%, or 45% using a sensor-based automated irrigation system for 60 days. Results showed that drought stress decreased plant growth of tatarian dogwood seedlings with a reduction of 71%, 85%, and 87% in plant height, leaf area, and shoot DW, respectively, when VWC decreased from 45% to 15%, but all plants survived at all VWC treatments. Significant reductions of photosynthesis (Pn), stomatal conductance (g S), transpiration rate (E), and water potential were also found in plants at a VWC of 15%, compared with other VWCs. However, SPAD readings and Fv/Fm of tatarian dogwood seedlings were similar among the VWCs. In conclusion, tatarian dogwood seedlings were sensitive to the salinity levels tested in this study but could survive at all tested substrate volumetric water contents and exhibited resistance to drought conditions.
John E. Montoya Jr., Michael A. Arnold, Juliana Rangel, Larry R. Stein and Marco A. Palma
Cucumber (Cucumis sativus L.) and habanero pepper (Capsicum chinense Jacq.) growers have observed increased crop yield by placing bees in close proximity to these vegetable crops. However, adding managed bees typically may not be feasible for small-scale farmers or homeowners. Limited studies have demonstrated the potential of pollinator-attracting plants to be used as a lure to enhance the visitation of pollinators to adjacent food crops. This study evaluated the potential of adding pollinator-attracting plants in close proximity to cucumber and habanero plants to improve yields by either establishing permanent perennial companion plantings adjacent to the crops or interplanting annual companion plants within the row anew with each crop. The perennial treatment group consisted of Phyla nodiflora (L.) Greene, Borrichia frutescens (L.) DC., Salvia farinacea Benth. ‘Henry Duelberg’, and Eysenhardtia texana Scheele. The annual treatment group consisted of Cosmos bipinnatus Cav., Zinnia ×marylandica D.M. Spooner, Stimart, & T. Boyle, Borago officinalis L., and Ocimum basilicum L. Multiple cropping cycles were initiated using both spring and fall seasons, and yield was assessed for three successive cropping cycles. Fruit quality was unaffected by pollinator-attracting companion plantings; however total and marketable yields were impacted. Cucumber yields were significantly (P < 0.05) greater during fall harvests with annual companion plantings and with the second fall harvest in perennial companion plant plots. Perennial companion plots initially yielded less than control plots or annual companion plots due to the space allocated to the companion plantings and the fewer pollinators initially attracted to the plots compared with the annual companion plantings. When the perennial plots became more established, they resulted in similar yields as the annual companion planting plots. Although habanero yields were increased by annual companion plantings in spring and fall, cucumbers were unaffected by companion plantings in spring. This suggests a potential seasonality for the efficacy of some pollinator-attracting companion plantings for a given crop that could offer an opportunity to tailor companion plantings to attract specific pollinators at different times of the year.
Mokhles A. Elsysy, Andrew Hubbard and Todd C. Einhorn
Metamitron is a relatively new postbloom thinning compound for pome fruits that inhibits the photosystem II (PS II) pathway of photosynthesis. Reduced assimilation of carbohydrate by metamitron action may lead to a carbohydrate deficit that promotes fruit abscission. We have evaluated the thinning efficacy of metamitron rate and, to a limited extent, application timing for ‘Bartlett’ pear in five separate trials over 3 years (2015–17) in northern Oregon. Comparisons were made to a nontreated control and, depending on the trial, a commercial standard thinning compound [benzyladenine (6-BA) or abscisic acid (ABA)]. Application timings ranged between 7- and 16-mm fruit diameter depending on the trial. Metamitron markedly inhibited photosynthesis (PN), typically for a duration of 2 to 3 weeks, although longer persistence was observed in two trials. Generally, PN was reduced linearly with increasing metamitron rate, but the effect varied by rate and year and may have been enhanced by high temperatures. Metamitron effectively thinned in four of five trials whereby pear fruit set was negatively and linearly related to rate. Rates of 200 to 300 ppm were efficacious and produced target crop loads. In only one trial, increasing concentrations (600 ppm) led to greater thinning. Metamitron significantly thinned ‘Bartlett’ pears when applied between 10 and 13 mm. In contrast, early application timing (≈7 mm) had little effect on fruit abscission. Fruit size increased with decreasing crop load and thus was significantly improved by metamitron. Interaction between biological and environmental factors likely contributed to year-to-year variability in efficacy.
Masahiro Toyoda, Yuko Yokota, Marni Barnes and Midori Kaneko
In modern society, stress reduction in the workplace is a pressing issue. Although many studies have been done on the psychological and physiological effects of indoor plants, the majority of them have been conducted in laboratory or quasi-office settings. The objective of this study was to verify the stress reduction effects of the presence of small indoor plants on employees in a real office setting. We investigated the changes in psychological and physiological stress before and after placing a plant on a worker’s desk. Sixty-three office workers at an electric company in Japan were the participants of this study. The participants were directed to take a 3-minute rest while sitting at their desk when they felt fatigue. There were two phases of the study: a control period without plants and an intervention period when the participants were able to see and care for a small plant. We measured psychological stress in the participants using the State-Trait Anxiety Inventory (STAI). As an index of physiological stress, the participants measured their own pulse rate throughout the study. STAI scores decreased significantly after the intervention period (P < 0.05). The ratio of the participants whose pulse rate lowered significantly after a 3-minute rest increased significantly during the intervention period (P < 0.05). Our study indicates that having opportunities to gaze intentionally at nearby plants on a daily basis in the work environment can reduce the psychological and physiological stress of office workers.
Bryan J. Peterson, Gregory J.R. Melcher, Ailish K. Scott, Rebecca A. Tkacs and Andrew J. Chase
Sweetgale (Myrica gale), rhodora (Rhododendron canadense), and catberry (Ilex mucronata) are shrubs of eastern North America that may have potential for broader use in horticultural landscapes. Because information on their vegetative propagation is scarce, we conducted experiments over 2 years to evaluate the effects of cutting collection date, wounding, substrate composition, and the concentration of applied potassium salt of indole-3-butyric acid (K-IBA) on rooting of each species. In 2015, we collected cuttings of each species on three dates to obtain both softwood and semihardwood cuttings. Cuttings were unwounded or wounded with a razor blade, and treated by dipping into water containing K-IBA at concentrations ranging from 0 to 15,000 mg·L−1, after which they were inserted into a substrate of 3:1 perlite:peat (by volume) and placed under intermittent mist. In 2016, semihardwood cuttings of each species were all wounded, treated with K-IBA from 0 to 15,000 mg·L−1, and inserted into substrates of 100%, 75%, or 50% perlite, with the remaining volume occupied by peat. In both years, the greatest percentage of sweetgale cuttings rooted when no K-IBA was applied. K-IBA application also reduced root ratings, root dry weights, and root lengths of sweetgale. For rhodora and catberry, maximal responses for all measures of rooting occurred when 5000 to 15,000 mg·L−1 K-IBA was applied. We recommend that growers use no exogenous auxin to propagate sweetgale, and 5000 to 10,000 mg·L−1 K-IBA to propagate rhodora and catberry. Cuttings of all three species can be collected from softwood or semihardwood shoots. Finally, sweetgale can be rooted in perlite alone, whereas rhodora and catberry required the addition of peatmoss for satisfactory root development.
Katherine Bennett, Jared Jent, Uttara C. Samarakoon, Guido Schnabel and James E. Faust
Botrytis blight on petunia flowers causes significant losses in the postharvest environment. Infection occurs during greenhouse production, and symptoms are expressed during transport. This phenomenon is termed petunia flower meltdown because of the rapid collapse of flower petal tissue as the plants are transported from the production greenhouse to the retail store. The objective of this study was to determine the effect of calcium (Ca) spray applications on botrytis blight severity in petunia flowers. For the first experiment, petunia ‘Pretty Grand Red’ plants were sprayed twice per week for 2 weeks with calcium chloride (CaCl2) at rates of 0, 400, 800, and 1200 mg·L−1 Ca. A fungicide (cyprodinil, 37.5%; fludioxonil, 25%) was used as an additional control treatment. Twenty-four hours after the last treatment, freshly opened flowers were harvested, placed into a humidity chamber with 99% relative humidity, and inoculated with a Botrytis cinerea spore suspension (1 × 104 conidia/mL). Disease progression was recorded every 12 hours for 72 hours. The results showed a 96% reduction in botrytis blight severity as Ca concentration increased from 0 to 1200 mg·L−1 Ca. The Ca treatments provided better disease control than the fungicide treatment because of the fungicide resistance of the isolate used in the study. A second experiment was performed to determine whether the beneficial response to CaCl2 application was influenced by chlorine (Cl) or the electrical conductivity (EC) of the spray solutions, and no significant responses were observed. These studies prove Ca is the sole source of the reduction in botrytis blight severity following treatment with CaCl2 sprays, and demonstrate the benefit of using Ca as a tool for the management of botrytis blight on petunia flowers.
Ruying Wang, James W. Hempfling, Bruce B. Clarke and James A. Murphy
Sand size can affect the ability to incorporate topdressing into the turf canopy and thatch on golf course putting greens; unincorporated sand interferes with mowing and play. This 3-year field trial was initiated to determine the effects of sand size on sand incorporation, surface wetness, and anthracnose (caused by Colletotrichum cereale Manns sensu lato Crouch, Clarke, and Hillman) of annual bluegrass [Poa annua L. f. reptans (Hausskn) T. Koyama] maintained as a putting green. The experimental design was a randomized complete block with four replications; treatments included a non-topdressed control and three topdressing sands (medium-coarse, medium, or medium-fine) applied every 2 weeks at 0.15 L·m−2 during the summer. Topdressing with medium-coarse sand was more difficult to incorporate than the medium and medium-fine sands, resulting in a greater quantity of sand collected with mower clippings. Analyzing the particle distribution of sand removed by mowing confirmed that coarser sand particles were more likely to be removed in mower clippings. Surface wetness measured as volumetric water content (VWC) at the 0- to 38-mm depth zone was greater in non-topdressed plots than topdressed plots on 35% of observations. Few differences in VWC were found among sand size treatments. Turf responses to topdressing were not immediate; however, as sand accumulated in the turf canopy, topdressed plots typically had lower anthracnose severity than non-topdressed turf after the first year. Additionally, topdressing with medium and medium-fine sands produced similar or occasionally lower disease severity than topdressing with medium-coarse sand. The lack of negative effects of medium and medium-fine sands combined with better incorporation after topdressing and less disruption to the putting surface should allow golf course superintendents to apply topdressing at frequencies and/or quantities needed during the summer to maintain high-quality turf and playing conditions.
Roland Ebel, Esmaeil Fallahi, John L. Griffis Jr., Dilip Nandwani, Donielle Nolan, Ross H. Penhallegon and Mary Rogers
Urban horticulture describes economically viable horticultural production activities conducted in a city or suburb. It is a growing segment of horticulture in the United States as well as in developing countries, where the enormous growth of megalopolis is not backed by a simultaneous increase of farmland or agricultural productivity. Today, urban horticulture includes food sovereignty in underprivileged neighborhoods, increased availability of vegetables and fruits in big cities, healthy and diverse diets, improved food safety, low transportation costs, efficient resource use, and the mitigation of environmental impacts of horticultural production such as the emission of greenhouse gases. The workshop “Urban horticulture: From local initiatives to global success stories,” held at the 2018 American Society for Horticultural Science (ASHS) conference in Washington, DC, featured present and historical success stories of urban horticulture from Asia, Africa, Latin America, and the United States.
Gerardo H. Nunez
Hands-on activities enhance learning and increase student satisfaction in horticulture courses. Nevertheless, hands-on activities can have widely different impacts on student learning. To achieve and maintain educational quality, instructors need to evaluate and improve activities. This research used text mining and sentiment analysis to gauge student sentiments about hands-on activities in a protected agriculture course. Students participated in five hands-on activities and submitted short reflective essays about them. Essay texts were separated into single-word (unigram) or three-word (trigram) objects. Unigrams were compared with general-use emotion lexica to extract student sentiments from the texts. Trigrams were used to assess essay content. All activities elicited positive sentiments among students. Trust, anticipation, and joy were the most prominent emotions identified. The activity focused on freeze protection was preferred over the other activities. Although other activities were also well received, they should be refined for future offerings. The presented method could be used to assess hands-on activities, leading to continuous improvement and successful implementation of experiential learning in horticulture courses.