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  • Author or Editor: R. Wagner x
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Robinia L. (locust) species are among the most widely planted tree species in the world because they are ornamentally attractive, drought tolerant, fast growing, fix nitrogen, have very hard durable wood, and are adaptable to many sites and climates. Recent taxonomic analysis indicates there are four species, black locust (R. pseudoacacia L.); bristly locust (R. hispida L.); clammy locust (R. viscosa Vent.); and new mexican locust (R. neomexicana A. Gray). All four species originate in the southern United States and northern Mexico. Many horticultural cultivars are available. Locusts are tolerant of a wide range of soil types so long as there is good drainage, adequate moisture, and it is not very clayey. The environmental tolerance of locust makes it an excellent candidate for horticultural uses and for future breeding and selection to enhance its many desirable traits. It is easy to propagate via seed, root cuttings, soft- or hardwood cuttings, budding/grafting, or tissue culture. Locust has indeterminate growth. Spacing of plants in plantations is critical for the production of multiple products including high value timber. Locust is known for its ability to withstand drought conditions however at the cost of leaf shedding. Black locust contributes high levels of nitrogen to the soil from nitrogen fixing bacterial symbiosis. The major drawback to large-scale production of black locust in its native range is the damage that occurs from the locust borer (Megacyllene robiniae Forster). When planted outside the range of the locust borer it can be grown successfully as landscape specimen trees and as trees large enough for lumber production when varieties with straight trunks are grown. Damage from locust leaf miner (Odontata dorsalis Thunberg) can greatly detract from the trees ornamental qualities. Its most common use is as a site reclamation species. The tree is also used in honey production. The wood is highly decay resistant and is greatly valued for poles and posts. The wood is extremely hard and easy to work making it highly desirable for many construction uses.

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Gomphrena globosa L. `Gnome Pink' and Salvia farinacea Benth. `Victoria Blue' were grown under different photoperiod treatments with day and night temperatures ranging from 15 to 30°C ± 1°C air temperature for 14 weeks after germination or until anthesis. Days to anthesis and leaf number were lowest when plants were grown under 9 hr of daylight and daylight plus 4-hr day extension from 1700–2100 HR (100 μmol·m–2·s–1 from high-pressure sodium lamps) for Gomphrena and Salvia, respectively. Days to anthesis decreased as temperature increased from 15 to 25°C with Gomphrena. Further increasing night temperature from 25 to 30°C delayed flowering and increased leaf number below the first flower of Gomphrena, but hastened flowering of Salvia. Plant height and internode elongation were greatest and least in the night interruption (2 μmol·m–2·s–1 from incandescent lamps from 2200–0200 HR) and continuous light (daylight plus 100 μmol·m–2·s–1 from high-pressure sodium lamps) treatments, respectively. Implications of these data with respect to classification of Gomphrena and Salvia flower induction are discussed and revised production schedules are presented.

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Field studies were conducted for 4 years on putting green turf to determine the influence of cultivation practices on the transition from overseeded perennial ryegrass (Lolium perenne L. ‘Yorktown II’) turf to hybrid burmudagrass [Cynodon dactylon (L.)Pers. × C. transvaalensis Burtt-Davies] in the spring. The cultivation practices of core aeration, vertical mowing, and topdressing were shown to have no positive influence of increasing the rate of bermudagrass coverage during the spring on bermudagrass greens overseeded with perennial ryegrass. The verticut treatment resulted in decreased bermudagrass coverage as well as a reduction in turf quality. All cultivation practices resulted in some quality loss at various times during the spring transition period compared to the control.

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The effect of bottom heat, wounding, and duration of stem basal IBA dip on macropropagation of Milicia excelsa was investigated. Bottom heat enhanced root dry mass and accelerated root initiation. Percentage rooting and root dry mass were not affected by wounding and duration of stem basal treatment. However, wounding interacted with bottom heat to affect dry mass (P < 0.05). Root biomass was 60% higher from wounded cuttings than from nonwounded cuttings under the nonheated condition. Chemical names used: 1H-indole-3-butyric acid (IBA).

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Small conifers often must coexist with the components of early plant succession for prolonged periods of time in forest regeneration. Forest regeneration and the management of perennial horticultural crops are similar in this respect, since individual “crop” plants in both instances usually occur in close proximity to each other or associated species. Association of the crop with its neighbors may be detrimental in both situations (10, 15), but other interactions also are possible (8). Thus it is necessary for forest managers and horticulturists to recognize the physical, physiological, and environmental components that influence the outcome of plant-to-plant associations. It also is necessary for land managers (foresters, horticulturists, etc), to understand the consequences of their actions, since short-term impacts on vegetation can have long-term influences on environmental resource availability, subsequent vegetation, and the populations of other organisms. Long-term impacts of management are not exclusive to forest regeneration, but the need for prediction may be most obvious there because of the relative longevity of forest communities in comparison to most of those in agriculture.

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Petunia × hybrida Vilm. cvs. `Purple Wave', `Celebrity Burgundy', `Fantasy Pink Morn', and `Dreams Red' were treated with temperature and photoperiod treatments for different lengths of time at different stages of development during the first 6 weeks after germination. Plants were grown with ambient light (≈8–9 hr) at 16°C before and after treatments. Flowering was earliest and leaf number below the first flower was lowest when plants were grown under daylight plus 100 μmol·m–2·s–1 continuous light (high-pressure sodium lamps). Flowering did not occur when plants were grown under short-day treatment (8-hr daylight). Plants grown with night interruption lighting from 2200–0200 HR (2 μmol·m–2·s–1 from incandescent lamps) flowered earlier, and with a reduced leaf number compared to plants grown with daylight + a 3-hr day extension from 1700–2000 HR (100 μmol·m–2·s–1 using high-pressure sodium lamps). Plant height and internode elongation were greatest and least in night interruption and continuous light treatments, respectively. `Fantasy Pink Morn' and `Purple Wave' were the earliest and latest cultivars to flower, respectively. Flowering was hastened as temperature increased from 12 to 20°C, but not as temperature was further increased from 20 to 24°C. Branching increased as temperature decreased from 24 to 12°C. Implications of data with respect to classification of petunia flower induction and pre-fi nishing seedlings are discussed.

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Viola × wittrockiana Gams. cvs `Delta Pure Rose' and `Sorbet Yellow Frost' were grown under different photoperiod and temperature treatments (12–24 ± 2°C) for different lengths of time at different stages of development during the first 6 weeks after germination. Plants were grown with ambient light (≈9 hr) at 16°C before and after treatments. Days to anthesis and leaf number were lowest when plants were grown under night interruption from 2200–0200 hr (2 μmol·m–2·s–1 from incandescent lamps) and daylight plus continuous light (100 μmol·m–2·s–1 from high-pressure sodium lamps) for `Sorbet Yellow Frost' and `Delta Pure Rose', respectively. Days to anthesis decreased as temperature increased from 12 to 24°C. Plant height and internode elongation were greatest and least in the night interruption and continuous light treatments, respectively. Branching decreased as temperature increased from 12 to 24°C. Implications of these data with respect to classification of Viola × wittrockiana flower induction and development of prefinished seedlings is discussed.

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Abstract

Extensive losses in N applied to container-grown woody ornamental plants prompted this investigation to determine a) leaching of N from urea (U) and isobutylidene diurea (IBDU); b) influence of nitrapyrin (NI), a nitrification inhibitor, on N leaching losses from U; and c) to evaluate influences of these materials on growth, quality, and N uptake by Rhododendron obtusum Lindl. cv. Hinodegiri. In root medium composed of 60 pine bark : 30 sand : 10 soil (by volume), 48.8% of applied N from U was leached after 87 days, whereas leachate losses of N from IBDU and U + NI were 42.3% and 37.2%, respectively. All plants attained marketable quality by the end of the study. Azaleas fertilized with IBDU were of significantly higher quality on days 70 and 77 than those treated with U + NI and higher quality on days 77, 84, and 87 than those treated with U. No differences were found in shoot dry weight or N content in shoot tissues.

Open Access

Abstract

Mineralization of nitrogen fertilizers was determined in an organic medium composed of 6 pine bark : 3 sand : 1 soil (by volume). Nitrification was evident by day 7 following treatment with urea and isobutylidene diurea (IBDU) and increased rapidly after day 14. Nitrification was not evident until day 56 in medium treated with urea + nitrapyrin (NI). Medium treated with urea or IBDU were depleted of NH4 + within 1 month, which corresponded to a peak in NO2 + NO3 accumulation. Only a small amount of NH4 + was not accounted for by nitrification and was assumed to be adsorbed by bark particles. Chemical names used: 2-chloro-6-(trichloromethyl)pyridine (nitrapyrin), 1,1-diureido isobutane (IBDU).

Open Access