The Ebony series of crepe myrtle (Lagerstroemia indica) cultivars includes several (Ebony Embers, Ebony Fire, Ebony Flame, Ebony Glow, and Ebony and Ivory), marketed today under the Black Diamond® brand. These are relatively new crepe myrtle cultivars unique for their dark foliage, but with little information concerning their performance in north-central Texas, especially in low-input landscapes. The study was conducted from 2014 to 2017 at three locations in north-central Texas with three soil types, an acidic fine sandy loam, a neutral pH silt loam, and an alkaline heavy clay. Although soils and environmental conditions caused variations between sites, overall performance among cultivars was consistent across all study sites, with Centennial Spirit having better landscape performance than any of the Ebony cultivars tested. ‘Ebony and Ivory’ and ‘Ebony Blush’ had the overall lowest landscape performance. Ebony cultivars grew more slowly, had fewer blooms, and were more susceptible to powdery mildew than Centennial Spirit. While the trees may perform better in more intensively managed landscapes, the Ebony cultivars did not perform as well as Centennial Spirit in low-input landscapes in north-central Texas.
Derald Harp, Kevin Chretien, Mariah Brown, Curtis Jones, and Jose Lopez-Serrano
Seon-Ok Kim, Ji-Eun Jeong, Yun-Ah Oh, Ha-Ram Kim, and Sin-Ae Park
This study aimed to compare the brain activity and emotional states of elementary school students during horticultural and nonhorticultural activities. A total of 30 participants with a mean age of 11.4 ± 1.3 years were included. This experiment was conducted at Konkuk University campus in Korea. Participants performed horticultural activities such as harvesting, planting, sowing seeds, and mixing soil. Nonhorticultural activities included playing with a ball, solving math problems, watching animation videos, folding paper, and reading a book. The study had a crossover experimental design. Brain activity of the prefrontal lobes was measured by electroencephalography during each activity for 3 minutes. On completion of each activity, participants answered a subjective emotion questionnaire using the semantic differential method (SDM). Results showed that relative theta (RT) power spectrum was significantly lower in both prefrontal lobes of participants when engaged in harvesting and reading a book. The relative mid beta (RMB) power spectrum was significantly higher in both prefrontal lobes when participants engaged in harvesting and playing with a ball. The ratio of the RMB power spectrum to the RT power spectrum reflects concentration. This ratio increased during harvesting activity, indicating that children’s concentration also increased. The sensorimotor rhythm (SMR) from mid beta to theta (RSMT), another indicator of concentration, was significantly higher in the right prefrontal lobe during harvesting than during other activities. Furthermore, SDM results showed that the participants felt more natural and relaxed when performing horticultural activities than nonhorticultural activities. Horticultural activities may improve brain activity and psychological relaxation in children. Harvesting activity was most effective for improving children’s concentration compared with nonhorticultural activities.
Renjuan Qian, S. Brooks Parrish, Sandra B. Wilson, Gary W. Knox, and Zhanao Deng
Porterweed (Stachytarpheta spp.), a member of the verbena family, is frequently used in pollinator gardens to attract butterflies. This study was conducted to assess the morphological features, pollen stainability and morphology, nuclear DNA content, and chromosome number of five porterweed selections. Coral porterweed (S. mutabilis), ‘Naples Lilac’ porterweed (S. cayennensis × S. mutabilis ‘Violacea’), and nettleleaf porterweed (S. cayennensis) had the largest plant heights. Flower number was significantly higher in nettleleaf porterweed, jamaican porterweed (S. jamaicensis), and U*J3-2 porterweed (S. cayennensis × S. jamaicensis), with an average of 65–72 flowers per inflorescence. Internode length and flower width of jamaican porterweed had much lower values than the other selections. Coral porterweed recorded the lowest pollen stainability with only 10.6% stainability, but it had the largest relative pollen production. ‘Naples Lilac’ porterweed had the highest DNA content with an average of 3.79 pg/2C, like jamaican porterweed with 3.73 pg/2C. Ploidy levels varied between selections, and the basic chromosome number was x = 28. Coral, jamaican, and ‘Naples Lilac’ porterweed had 2n = 6x = 168 chromosomes, first reported in this genus. These results provide a guide and a new tool to distinguish native and non-native porterweed and may aid future breeding toward the production of noninvasive cultivars.
Paweł Petelewicz, Paweł M. Orliński, and James H. Baird
Decreased stand uniformity together with reduced aesthetics and playability caused by annual bluegrass (Poa annua) intrusion in creeping bentgrass (Agrostis stolonifera) putting greens is one of the major problems that golf course superintendents face with managing newer playing surfaces. Few herbicides are registered for selective control of annual bluegrass in creeping bentgrass greens, and the risk of herbicide resistance remains an issue, thus use of plant growth regulators (PGRs) is still the primary method of annual bluegrass suppression. This study was conducted to evaluate eight PGR treatments, employed as a series of 15 consecutive, biweekly applications to suppress annual bluegrass encroachment in ‘Pure Distinction’ creeping bentgrass maintained as a golf course putting green in Los Angeles, CA. Best annual bluegrass suppression was observed with products containing flurprimidol (FP) at 0.256 lb/acre, paclobutrazol (PB) at 0.119 lb/acre, or three-way mixture of FP, trinexapac-ethyl (TE), and PB (FP+PB+TE) at 0.055, 0.014, and 0.055 lb/acre, respectively. Although all treatments caused some significant creeping bentgrass injury, which increased over time, PB at 0.119 lb/acre and FP+PB+TE at 0.055, 0.014, and 0.055 lb/acre, respectively, appeared to be safest among effective treatments. Additionally, those treatments caused significantly darker green turf, which may be desirable on putting greens. This research confirms the potential of PGR use to limit annual bluegrass infestation on creeping bentgrass greens in a Mediterranean climate and reveals the most effective treatments that could be used in a putting green maintenance program.
Mark K. Ehlenfeldt and James L. Luteyn
Vaccinium meridionale (section Pyxothamnus), a tetraploid species native to higher altitude locations in Jamaica, Colombia, and Venezuela, is of considerable interest to blueberry breeders for its profuse, concentrated flowering and monopodial plant structure, both of which may be useful in breeding for mechanical harvest. In this study, tetraploid V. meridionale was successfully hybridized as a male with 4x V. corymbosum (section Cyanococcus, highbush blueberry). The first-generation hybrids with highbush blueberry selections were intermediate in morphology and notably vigorous. The 4x F1 hybrids displayed variable branching structure, dormancy, prolificacy, fruit wax, etc.; however, most appear to be deciduous to semi-evergreen, with small, dark-colored fruit. The F1 hybrids displayed good fertility as females in backcrosses to 4x highbush and these crosses have produced numerous offspring morphologically indistinguishable from 4x highbush at the seedling stage. Evaluations of male fertility found variation for pollen production and quality but, significantly, found some clones with very good shed, high stainability, and almost complete tetrad production. The fertility suggests that these hybrids, despite being derived from intersectional crosses, might be conventionally used without significant difficulty. These hybrids also have potential value for the nascent V. meridionale breeding efforts occurring in Colombia, South America.
Jennifer K. Boldt and James E. Altland
Silicon (Si) is a plant-beneficial element that can alleviate the effects of abiotic and biotic stress. Plants are typically classified as Si accumulators based on foliar Si concentrations (≥1% Si on a dry weight basis for accumulators). By this definition, most greenhouse-grown ornamentals are low Si accumulators. However, plants that accumulate low foliar Si concentrations may still accumulate high Si concentrations elsewhere in the plant. Additionally, screening cultivars for variability in Si uptake has not been investigated for low Si accumulator species. Therefore, the objective of this study was to assess cultivar variability in Si accumulation and distribution in petunia (Petunia ×hybrida). Eight cultivars (Supertunia Black Cherry, Supertunia Limoncello, Supertunia Priscilla, Supertunia Raspberry Blast, Supertunia Royal Velvet, Supertunia Sangria Charm, Supertunia Vista Silverberry, and Supertunia White Improved) were grown in a commercial peat-based soilless substrate under typical greenhouse conditions. They were supplemented with either 2 mm potassium silicate (+Si) or potassium sulfate (-Si) at every irrigation. Silicon supplementation increased leaf dry mass (4.5%) but did not affect total dry mass. In plants not receiving Si supplementation, leaf Si ranged from 243 to 1295 mg·kg−1, stem Si ranged from 48 to 380 mg·kg−1, flower Si ranged from 97 to 437 mg·kg−1, and root Si ranged from 103 to 653 mg·kg−1. Silicon supplementation increased Si throughout the plant, but most predominantly in the roots. Leaf Si in the 2 mm Si treatment ranged from 1248 to 3541 mg·kg−1 (173% to 534% increase), stem Si ranged from 195 to 654 mg·kg−1 (72% to 376% increase), flower Si ranged from 253 to 1383 mg·kg−1 (74% to 1082% increase), and root Si ranged from 4018 to 10,457 mg·kg−1 (593% to 9161% increase). The large increase in root Si following supplementation shifted Si distribution within plants. In nonsupplemented plants, it ranged from 51.2% to 76.8% in leaves, 8.2% to 40.2% in stems, 2.8% to 23.8% in flowers, and 1.2% to 13.8% in roots. In Si-supplemented plants, it ranged from 63.5% to 67.7% in leaves, 10.5% to 22.6% in roots, 9.4% to 17.7% in stems, and 1.6% to 9.6% in flowers. This study indicates that petunia, a low foliar Si accumulator, can accumulate appreciable quantities of Si in roots when provided supplemental Si.
Kevin Laskowski and Emily Merewitz
Annual bluegrass (Poa annua var. reptans), when grown as a putting green species, is sensitive to winter injury such as ice cover. Inhibiting plant ethylene production could be a way to improve annual bluegrass tolerance of ice encasement. The goals of this study were to determine how winter conditions and ethylene regulatory treatments affect the antioxidant system, fatty acid composition, and apoplastic proteins of annual bluegrass plant tissues. Ethylene-promotive (1-aminocyclopropane-1-carboxylic acid or ethephon) and ethylene inhibition treatments [aminoethoxyvinylglycine (AVG)] were applied to plants in the field during acclimation. Plant plugs were taken and subjected to low temperature (−4 °C) and ice-encasement treatments in growth chamber conditions. Antioxidant activities of ascorbate peroxidase (APX), peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD) were measured along with malondialdehyde content (MDA) and apoplastic protein content in leaf and crown tissue. Saturated and unsaturated fatty acid contents were measured in leaf, crown, and root tissue. Higher unsaturated fatty acids are often associated with greater low-temperature tolerance. Compared with the untreated controls, ethephon-treated annual bluegrass had greater MDA contents, lower POD and SOD activity, and greater saturated and decreased unsaturated fatty acids. Ethylene inhibition treatments caused annual bluegrass to have less saturated fatty acid content and greater unsaturated fatty acid content, a greater content of apoplast proteins, and higher CAT activity when compared with the untreated controls. The activity of APX was greater in AVG-treated annual bluegrass than in controls. Ethylene may reduce physiological health overwinter, and inhibitory treatments may promote winter tolerance by promoting antioxidant activity, apoplast proteins, and the content of unsaturated fatty acids in plant tissues.
Qiannan Hu, Fei Ding, Mingna Li, Xiaxiang Zhang, Shuoxin Zhang, and Bingru Huang
Accelerated or premature leaf senescence induced by dark conditions could be associated with chlorophyll degradation and regulated by hormones. To study the effects of strigolactone (SL) on dark-induced leaf senescence and to examine the interaction effects of SL and ethylene on regulating dark-induced leaf senescence, plants of perennial ryegrass (Lolium perenne) exposed to darkness for 8 days were treated with a synthetic SL analogue (GR24), aminoethoxyvinyl glycine [AVG (an ethylene biosynthesis inhibitor)], or SL and AVG by foliar spray. Chlorophyll content, photochemical efficiency, electrolyte leakage, and ethylene production were measured. Expressions of genes associated with leaf senescence, SL biosynthesis and signaling, ethylene biosynthesis and signaling, and chlorophyll biosynthesis and degradation were determined. Foliar application of GR24 promoted leaf senescence in perennial ryegrass grown in darkness, and the intensity of action increased with the GR24 concentration. SL-accelerated leaf senescence was associated with the downregulation of four chlorophyll biosynthesis-associated genes and upregulation of four chlorophyll degradation-associated genes. AVG had functions counteractive to SL, suppressing dark-induced leaf senescence by downregulating chlorophyll degradation genes and SL synthesis genes. Our results suggested that SL and ethylene interactively regulated leaf senescence, mainly by controlling chlorophyll degradation induced by darkness in perennial ryegrass.
Qiang Zhang, Minji Li, Beibei Zhou, Junke Zhang, and Qinping Wei
This study aimed to understand the effects of meteorological factors on the ‘Fuji’ apple quality in the Circum-Bohai and Loess Plateau apple production regions of China and to guide apple production based on local climate. Fruit samples of the ‘Fuji’ apple and meteorological data were investigated from 132 commercial ‘Fuji’ apple orchards covering 44 counties in the two aforementioned production regions (22 counties per region). The partial least-squares regression (PLSR) method was first used to screen major meteorological factors that greatly affected fruit quality; these were subsequently used to establish the regression equation of fruit quality attributes and major meteorological factors. Linear programming was used to estimate optimum meteorological factors for good apple quality. The results showed that in the Circum-Bohai production region, many meteorological factors (total annual precipitation, total precipitation from April to October, lowest temperature from April to October, sunshine percentage from April to October) were significantly higher than those in the Loess Plateau production region; however, the temperature difference between day and night from April to October was significantly smaller than that in the Loess Plateau production region. The soluble solids content and skin color area of apples from the Loess Plateau production region were significantly greater than those from the Circum-Bohai production region. The same fruit quality factor of ‘Fuji’ apple was affected by different meteorological factors in the two production regions. The monthly mean temperature and monthly highest temperature from April to October of the Circum-Bohai production region had relatively larger positive effect weights on fruit quality, whereas the total annual precipitation, monthly mean relative humidity from April to October, and total precipitation from April to October of the Loess Plateau production region had relatively larger positive effect weights on fruit quality. The major influencing meteorological factors of the fruit soluble solids content were total precipitation from April to October (X 7), mean annual temperature (X 1), and the monthly highest temperature from April to October (X 5) in the Circum-Bohai production region; however, it included the monthly mean temperature difference between day and night from April to October (X 6), total annual precipitation (X 2), and total precipitation from April to October (X 7) in the Loess Plateau production region. In the Circum-Bohai production region, the optimum meteorological factors for ‘Fuji’ fruit quality of vigorous apple orchards were the mean annual temperature (13.4 °C), total annual precipitation (981 mm), monthly mean temperature (16.8 to 22.4 °C), lowest temperature (11.9 °C), highest temperature (19.5 to 26.8 °C), temperature difference between day and night (12.3 °C), total precipitation (336–793 mm), relative humidity (55.7% to 70.7%), and sunshine percentage (42.3% to 46.1%) during the growing period (April–October). In the Loess Plateau production region, the optimum meteorological factors for ‘Fuji’ fruit quality of vigorous apple orchards were the mean annual temperature (5.5 to 11.6 °C), total annual precipitation (714 mm), monthly mean temperature (13.3 to 19.9 °C), lowest temperature (7.9 to 9.3 °C), highest temperature (19.6 to 27.3 °C), temperature difference between day and night (7.1 to 12.4 °C), total precipitation (338–511 mm), relative humidity (56.1% to 82.4%), and sunshine percentage (37.3% to 55.9%) during the growing period (April–October). The restrictive factors for high-quality ‘Fuji’ apples of the Circum-Bohai production region were the smaller monthly mean temperature difference between day and night, higher monthly mean lowest temperature, and larger monthly mean relative humidity during the growing period; however, those of the Loess Plateau production region were drought or less precipitation from November to March, lower monthly mean temperature, and higher monthly mean highest temperature during the growing period.
David Campbell, Ali Sarkhosh, Jeffrey K. Brecht, Jennifer L. Gillett-Kaufman, Oscar Liburd, Juan Carlos Melgar, and Danielle Treadwell
Fruit bagging is an acceptable cultural practice for organic production that provides a physical barrier to protect fruit. It can reduce pest and pathogen injury for a variety of fruit crops, but quality attributes have been inconsistent for peach [Prunus persica (L.) Batsch] and other bagged fruit. A 2-year experiment on a U.S. Department of Agriculture (USDA) organic-certified peach orchard in central Florida was conducted to analyze the effects of a commercially available paper bag designed for fruit protection and cardinal quadrant (north, south, east, and west sides) of the tree canopy on low-chill peach ‘TropicBeauty’ fruit quality. Protective bags appeared to delay fruit maturity. Flesh firmness and chlorophyll concentration of bagged fruit were 31% and 27% greater than unbagged fruit, respectively. Bagged fruit were protected as demonstrated with a reduction in mechanical injury by 95%, fruit fly injury by 450%, and scab-like lesions by 810%. Bagging reduced fruit brown rot (Monilinia fructicola) at harvest and 7 days after harvest; unbagged fruit were 2 and 3.5 times more likely to have rot at harvest and 7 days after harvest, respectively. Fruit bags did not affect yield, fruit size, total soluble solids, titratable acidity, pH, peel lightness, peel hue angle, or flesh color. Overall, canopy cardinal quadrant location had minimal effect on fruit quality or fruit injury. These results demonstrate that bagging peach fruit protects against various pests and diseases but has minimal effects on fruit quality. Broad adoption of this technology is highly dependent on available labor, market demands, and profitability but may be suitable for producers using direct-to-consumer market channels.