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  • Author or Editor: A.M. Wagner x
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Dormancy level is an important factor in rooting stem cuttings of conifers. Eldarica pine, a Mediterranean species, is a multiple flushing pine that does not appear to express endodormancy in southern New Mexico. Photoperiod manipulations can alter the dormancy level of some conifer species; however, effects on eldarica pine are unknown. Half-sib stock plants were randomly assigned to one of three photoperiods: natural daylength (>12 hours, control), long-term (7 months) exposure to 9-hour daylength (LTSD), and 2-week exposure to 9-hour daylength (STSD). Of the cuttings from LTSD stock plants, 78% rooted; however, only 67% of the cuttings from the other two treatments rooted. Differences in rooting also were related to shoot type of the cuttings. Cuttings from expanded short shoots without a bud rooted more frequently than cuttings from branch shoots with or without a bud present. Applications of these results are discussed.

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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

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

Pollination effectiveness was evaluated for pollen (pollinia) from two Dendrobium hybrids, ‘Sena Red’ and ‘Mini WRL’, submitted to cryopreservation using a vitrification protocol. Parameters evaluated included pollinia exposure to a previtrification solution (PVS2) under ice (0 °C) or room (27 ± 2 °C) temperatures from 1 to 4 hours before cryopreservation (LN). On removal from cryopreservation, pollinia were used to pollinate flowers of the same hybrids to verify viability and germination. All pollinia showed high percentages of germination (greater than 80%) after crosses were performed, except for pollinia from Dendrobium ‘Sena Red’ submitted to 3 hours of precooling (0 °C) in PVS2 followed by LN (60%) and for pollinia submitted to PVS2 for 3 hours at room temperature with no precooling (70%). Capsules were formed for both hybrids and seeds were successfully produced. The seed viability test revealed high viability (90% to 95%) for all treatments for both hybrids. Seeds observed under a microscope contained well-formed embryos and no abnormalities were identified. Seeds from all treatments germinated. Germinating seeds developed into healthy seedlings with well-formed leaves and roots. Cryopreservation of pollinia was successfully accomplished either by direct storage in liquid nitrogen without cryoprotection treatments or by using a PVS2 vitrification protocol.

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Historically, calendar date has been used to determine when cuttings are collected for rooting. However, year-to-year variations in climate limits the usefulness of using calendar date. More recently, rooting of stem cuttings has been associated with chilling accumulation. In the winter, daily temperatures in northern New Mexico can fluctuate from below freezing to well above freezing. Eight chilling accumulation models and calendar date were tested to determine the best predictor of rooting of white fir. The chilling accumulation models ranged from those based on number of hours at low temperatures to weighted models that calculated chilling unit accumulation and loss. In addition, temperature data based on 3-, 6-, 12-, and 24-hour averages were used. Most of the models were better than calendar date in predicting rooting. The best model was a weighted model that accumulated chilling from -5 to 10C with loss of chilling >15C and less than -10C. Other models that performed well included models that accumulated chilling from 0 to 7.2C, 0 to 15C, or -3.5 to 10C. On the average, the data based on 12-hour means was the best for modeling chilling accumulation to predict rooting.

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Worldwide, there remains a reliance on repeated chemical applications as a control strategy for the coconut mite, but these are impractical, not economical, and environmentally hazardous. In this study, the damage severity of Aceria guerreronis on coconut fruits was studied under different conditions to investigate the effects of bunch management on the amount of damage to newly produced bunches. The damage was evaluated using a diagrammatic scale under four different conditions: 1) plants with bunches removed; 2) bunches with the distal portion of the spikelet removed; 3) bunches sprayed monthly with abamectin (9 g a.i./ha); and 4) control plants. For each treatment, two fruits from bunches 1 to 6 (counted from the last open inflorescence) from 10 plants were randomly collected every month for 4 months. The removal of the distal portion of the spikelets had no effect on the damage level of new bunches but delayed the damage severity by ≈1 month. After the removal of all of the bunches, the damage severity was restored within 2 months to the newly produced bunches, whereas the chemical control with abamectin kept the A. guerreronis damage intensity at a low level. Thus, the removal of bunches or the distal portion of spikelets is not an effective practice for the control of A. guerreronis in areas with high levels of infestation.

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The term Ethnobotany describes the study of people's relationships to plants as foods, fibers, medicines, dyes, and tools throughout the ages. Using the student active technique of experiential learning, undergraduate students enrolled in landscape design and implementation classes at Clemson University planned and installed an Ethnobotany garden in partnership with the South Carolina Botanical Garden (SCBG) staff, volunteers, and Sprouting Wings children. Sprouting Wings is an after-school gardening and nature exploration program for under-served elementary school students. College students and faculty working on this service-learning project contributed over 1,000 hours to their community while learning more about both the art and the science of landscape design and implementation. Students enrolled in the landscape Implementation class were surveyed to evaluate their perceptions on a variety of possible learning outcomes for this class. Students indicated that their service learning experience with the Ethnobotany project allowed them to acquire and practice new skills, broadened their understanding of the surrounding community, increased their ability to work in real world situations, introduced new career possibilities, gave students a better understanding of their course work, increased their ability to work on a team, increased their knowledge of environmental sustainability, and allowed them to discover or develop leadership capabilities. In a survey question regarding preference for service learning rather than traditional classes, the majority of students prefer the service learning pedagogy. In addition, most students reported a high degree of initiative for this project in their reflections.

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