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  • Author or Editor: Mengmeng Gu x
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Four birch taxa, Betulaalleghaniensis, B. davurica, B. nigra `Heritage', and B. papyrifera, were grown in a greenhouse and exposed to water deficit stress for 35 days. Daily water was withheld from the plants until the combined weight of each container and the plant was reduced to 40% of the control. Supplemental water was supplied to each container to maintain 40% of the initial combined weight. Predawn water potential, gas exchange, and abscised leaf area were measured daily during the first week and at 3-day intervals after the first week. Predawn water potential dropped to lowest value before the containers were rehydrated and remained low throughout the treatment period. Net CO2 assimilation (A), stomatal conductance (gs) and evapotranspiration (Et) of all taxa decreased significantly during the first week of water deficits. Changes in A and Et varied among taxa after the first week of water deficits. Water use efficiency (WUE = A/Et) of four birch taxa decreased to significant lower values than control in the first week that water was withheld, and then increased to significantly higher values than control. Gas exchange data were fit into 2- or 3-segmented linear model. The type and shape of the models, and the joint of each segment gave an indication of how the gas exchange responded to the long-term water deficit stress. At the end of the water deficit treatment, B. papyrifera had abscised most of its leaves and maintained a high A, while B. alleghaniensis maintained more leaves on the tree, but had a relatively low A.

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An online survey was conducted to gain information about nursery management and production (NMP) course content and enrollment, attitudes regarding the use of multimedia resources in the classroom, and opinions about the use of virtual field trips to supplement or replace traditional field trips. Results reflected current organizational and curriculum changes within colleges of agriculture that have impacted traditional horticulture courses such as NMP and in many cases have resulted in the merging of NMP courses with other courses such as greenhouse or garden center management. The number of departments with “horticulture” in the department name was similar to the number of departments with “plant science” in the department name (and not “horticulture”). The five topics covered most frequently included container production, container substrates, fertility, field production, and pot-in-pot production. Most of the respondents indicated that the NMP course in their department included at least one field trip. The top criteria used for selecting field trip locations included type of nursery, distance, innovation, reputation, and the number of aspects that could be viewed. Accessibility and distance to nurseries were listed as primary limitations for providing comprehensive field trips. Most respondents currently use multimedia resources in courses other than NMP, and a majority of respondents indicated that multimedia resources such as DVDs or web-based videos would be valuable for supplementing instruction in NMP, particularly for aspects not observed during field trips.

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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.

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Consumption of basil (Ocimum basilicum) has been increasing worldwide in recent years because of its unique aromatic flavor and relatively high concentration of phenolics. To achieve a stable and reliable supply of basil, more growers are turning to indoor controlled-environment production with artificial lighting due to its high environmental controllability and sustainability. However, electricity cost for lighting is a major limiting factor to the commercial application of indoor vertical farming, and little information is available on the minimum light requirement to produce uniform and high-quality sweet basil. To determine the optimal daily light integral (DLI) for sweet basil production in indoor vertical farming, this study investigated the effects of five DLIs, namely, 9.3, 11.5, 12.9, 16.5, and 17.8 mol·m−2·d−1 on basil growth and quality. ‘Improved Genovese Compact’ sweet basil was treated with five DLIs provided by white fluorescent lamps (FLs) for 21 d after germination, and gas exchange rate, growth, yield, and nutritional quality of basil plants were measured to evaluate the effects of the different DLIs on basil growth and quality. Results indicated that basil plants grown under higher DLIs of 12.9, 16.5, or 17.8 mol·m−2·d−1 had higher net photosynthesis, transpiration, and stomatal conductance (g S), compared with those under lower DLIs of 9.3 and 11.5 mol·m−2·d−1. High DLIs resulted in lower chlorophyll (Chl) a+b concentration per leaf fresh weight (FW), higher Chl a/b ratios, and larger and thicker leaves of basil plants. The shoot FW under DLIs of 12.9, 16.5, and 17.8 mol·m−2·d−1 was 54.2%, 78.6%, and 77.9%, respectively, higher than that at a DLI of 9.3 mol·m−2·d−1. In addition, higher DLIs led to higher soluble sugar percent and dry matter percent than lower DLIs. The amounts of total anthocyanin, phenolics, and flavonoids per plant of sweet basil were also positively correlated to DLIs, and antioxidant capacity at a DLI of 17.8 mol·m−2·d−1 was 73% higher than that at a DLI of 9.3 mol·m−2·d−1. Combining the results of growth, yield, and nutritional quality of sweet basil, we suggest a DLI of 12.9 mol·m−2·d−1 for sweet basil commercial production in indoor vertical farming to minimize the energy cost while maintaining a high yield and nutritional quality.

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One-year-old paper birch (Betula papyrifera Marsh.) seedlings were exposed to water deficit, ethylene, or inhibitors of ethylene action under greenhouse conditions to investigate ethylene's role in water-deficit stress-induced leaf abscission. Exposing well-watered and water-stressed paper birch to 20 ppm ethylene resulted in more than 50% leaf abscission after 96 h regardless of plant water status. However, application of a physiological level (1 ppm) of ethylene did not cause leaf abscission in either well-watered or water-stressed paper birch. Inhibitors of ethylene action (1ppm 1-methylcyclopropene or 0.1 mm silver thiosulfate) did not affect predawn water potential, gas exchange, or chlorophyll fluorescence. A significant increase in ethylene production was not detected in water-stressed paper birch before the onset of significant leaf abscission. Based on these observations, ethylene would appear to play a minor role in water-deficit stress-induced leaf abscission in paper birch.

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The genus Betula consists of approximately 50 deciduous species throughout northern hemisphere. Net CO2 assimilation ([A]) of four birch taxa (Betula alleghaniensis Britton, B. davurica Pall., B. nigra L. `Heritage', and B. papyrifera Marsh.) was measured with a portable gas exchange system, CIRAS-I. Light was increased from 0 to 2000 μmol· m-2·s-1 at increments of 25, 50, 100, 250, 500, 750, 1000, 1250, 1500, 1750, 2000 μmol·m–2·s–1 to create an [A] light-response curve. CO2 concentration was gradually increased to 1100 ppm in increments 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100 ppm to create an [A]-Ca (ambient CO2) curve. B. davurica had significantly higher potential A capacity than the other taxa under high CO2 conditions. Betula nigra `Heritage' had the highest carboxylation efficiency among four taxa. B. davurica and B. nigra `Heritage', had higher [A] when ambient CO2 is 0ppm. Betula davurica and B. nigra `Heritage', had higher light-saturated rate of gross [A] than B. alleghaniensis and B. papyrifera.

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Crapemyrtle bark scale [CMBS (Acanthococcus lagerstroemiae)], a newly emerged pest in the United States, has spread to 16 U.S. states and unexpectedly spread on a native species american beautyberry (Callicarpa americana) in Texas and Louisiana in 2016 since it was initially reported on crapemyrtles (Lagerstroemia sp.) in Texas in 2004. The infestation of CMBS negatively impacted the flowering of crapemyrtles. We observed the infestation on the two most commercially available edible fig (Ficus carica) cultivars Beer’s Black and Chicago Hardy in a preliminary trial in 2018. To help estimate CMBS potential in aggravating risks to the ecosystem stability and the green industry, we conducted a host range and suitability test using ‘Bok Tower’ american beautyberry as a positive control with other eight beautyberry (Callicarpa) species [mexican beautyberry (C. acuminata), ‘Profusion’ bodinieri beautyberry (C. bodinieri), ‘Issai’ purple beautyberry (C. dichotoma), japanese beautyberry (C. japonica var. luxurians), ‘Alba’ white-fruited asian beautyberry (C. longissima), taiwan beautyberry (C. pilosissima), luanta beautyberry (C. randaiensis), and willow-leaf beautyberry (C. salicifolia)] and three fig (Ficus) species [creeping fig (F. pumila), roxburgh fig (F. auriculata), and waipahu fig (F. tikoua)] over 25 weeks. All the tested beautyberry species and waipahu fig sustainably supported the development and reproduction of nymphal CMBS and were confirmed as CMBS hosts. Furthermore, comparing with the control, mexican beautyberry, ‘Profusion’ bodinieri beautyberry, taiwan beautyberry, and willow-leaf beautyberry were significantly less suitable, while ‘Issai’ purple beautyberry, japanese beautyberry, ‘Alba’ white-fruited asian beautyberry, and luanta beautyberry were as suitable as ‘Bok Tower’ american beautyberry. Thus, when using beautyberries in landscapes, their different potential to host CMBS should be considered to minimize spreading CMBS through the native ecosystems.

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Net CO2 assimilation (A) of four birch genotypes (Betula nigra L. ‘Cully’, B. papyrifera Marsh., B. alleghaniensis Britton, and B. davurica Pall.) was studied under varied photosynthetic photon flux density (PPFD) and CO2 concentrations (CO2) as indicators to study their shade tolerance and potential for growth enhancement using CO2 enrichment. Effect of water-deficit stress on assimilation under varied PPFD and (CO2) was also investigated for B. papyrifera. The light saturation point at 350 ppm (CO2) for the four genotypes varied from 743 to 1576 μmol·m−2·s−1 photon, and the CO2 saturation point at 1300 μmol·m−2·s−1 photon varied from 767 to 1251 ppm. Light-saturated assimilation ranged from 10.4 μmol·m−2·s−1 in B. alleghaniensis to 13.1 μmol·m−2·s−1 in B. davurica. CO2-saturated A ranged from 18.8 μmol·m−2·s−1 in B. nigra ‘Cully’ to 33.3 μmol·m−2·s−1 in B. davurica. Water-deficit stress significantly reduced the light saturation point to 366 μmol photon m−2·s−1 but increased the CO2 saturation point in B. papyrifera. Carboxylation efficiency was reduced 46% and quantum efficiency was reduced 30% by water-deficit stress in B. papyrifera.

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The Coastal Roots School Seedling Nursery Program for Habitat Restoration was initiated by Louisiana State University in 2000 in cooperation with Louisiana Sea Grant. The program enhances learning areas such as plant growth, wetland issues, conservation, and hands-on habitat restoration, and includes the installation of a small container nursery for the production of coastal plants in schoolyards. The program was adopted by Mississippi State University's Coastal Research and Extension Center in 2008. The aim of this article is to provide an overview of the program as well as Mississippi's plans to adapt the Louisiana model to demonstrate teaching by example through hands-on demonstration that will supply students with real-world conservation and stewardship experience.

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Water was withheld from 2-year-old seedlings or rooted cuttings of four birch genotypes (Betula alleghaniensis Britton, B. davurica Pall., B. nigra L. ‘Cully’, and B. papyrifera Marsh.) until the combined weight of the container and plant decreased below 40% of its original value to induce plant predawn water potential between −1.5 MPa and −2.1 MPa, after which plants were supplied with a requisite amount of water to reach 40% of its original value for 5 weeks under controlled conditions to investigate changes in gas exchange, osmotic solutes, leaf abscission, and growth compared with well-watered (WW) plants. Observations indicated that three of the four genotypes (except B. papyrifera) expressed three stages of photosynthetic response during water deficit: 1) a stress stage, 2) an acclimation stage, and 3) an adapted (or tolerance) stage. The stages were characterized by decreasing, increasing, and stabilized Pnws/ww (net photosynthesis presented as a ratio of water-deficit stressed (WS) plants to WW plants), respectively. A strong relationship between Pn and g S observed in the WS plants of the four genotypes, suggested inhibition of Pn by stomatal closure. After exposure to water deficit for 5 weeks, Pnws/ww recovered to 70% of the initial value for B. alleghaniensis and B. nigra ‘Cully’ and 98% for B. davurica and B. papyrifera. WS plants had higher foliar concentrations of chlorophyll a and b (nmol/g) and potassium (%) than the WW plants. Increased levels of polyols (mg/g) were detected only in the WS plants of B. allegahaniensis. Increased levels of carbohydrates or organic acid under water deficit were not detected. A significant increase in leaf abscission in the WS plants of B. papyrifera compared with the other genotypes could be a morphological adaptation to water deficit conditions and facilitate recovery of Pnws/ww during the acclimation stage.

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