As universities are required to “right-size,” faculty resources of time and expertise are strained as the institution must cater to undergraduate students while providing a complete graduate curriculum. Thus, many institutions are offering more team taught courses. For a new upper-level undergraduate and lower-level graduate course offering in Plant Nutrition and Nutrient Management, the team consists of faculty from two institutions who each bring different expertise into the classroom. The course utilized weekly chat room discussions to bring students into contact with experts from around the United States and the world. Two-way compressed video was used to allow for synchronous lecture delivery and discussion across sites. A Web site was created to facilitate student interaction and provide chat room access. Multiple student evaluations were conducted to separate learning objectives with the effectiveness of using technology. A flow-chart will be presented which details the steps and problems/accomplishments encountered in successfully delivering this course via distance technologies, including: funding procurement, determining technological compatibility across institutions, delineation of course content, Web page development, and course evaluations.
Kim Williams, Ellen T. Paparozzi and Jerry Maranville
Li-Chun Huang and Ellen T. Paparozzi
previous studies indicate that there is a significant relationship between the levels of nitrogen and sulfur applied and the growth of floricultural crops. Poinsettia and roses grew well in experiments involving hydroponic solutions that contained reduced nitrogen and some sulfur.
Cuttings of Dendranthema grandiflora cv Dark Yellow Fuji Mefo, were grown in hydroponics with either 64, 127, or 254 ppm N in combination with either 0, 1, 2, 4, 8, 16, 32, 64 ppm S. Plants were grown unpinched and short day treatment started at the end of week 3. Data recorded included symptoms of S deficiency, date of flower initiation, stem length, flower diameter and visual observation of root growth. Color difference of leaves was measured with a chromameter. New leaves and flower heads were taken for sulfur analysis; mature leaves were used for N analysis.
Plants receiving no S showed depressed initiation and development of branch roots, delayed flower initiation, reddened lower leaves and reduced plant growth. Plants receiving some S in combination with any level of N showed good color and acceptable flower diameter and stem length.
M. Elizabeth Conley and Ellen T. Paparozzi
In order to understand the effects of reduced nitrogen and sulfur on overall poinsettia plant growth and development, experiments were run to determine the relationship, if any, between nitrogen and sulfur applied and other macroand micronutrients. Cuttings of `Freedom Red' (Euphorbia pulcherrima Willd. ex Klotzsch) were grown vegetatively in a peat:perlite:vermiculite mix during the fall and spring. Three levels of sulfur (0, 12.5, 25 ppm) were applied in combination with four levels of nitrogen (50, 100, 200, 275 ppm). The experimental design was a randomized complete block. Leaf samples were analyzed using LECO for nitrogen and ICP-ES for sulfur. X-ray fluorescence was used to determine trends in the nutrient concentration of other macronutrients and micronutrients. Nutrient analyses indicated that all nutrients were present in sufficient quantities. Leaf concentrations of nitrogen, sulfur, potassium, and copper were distinctly higher in spring and fall, while phosphorus, calcium, magnesium, and iron concentrations were higher in fall. The typically subtle effects of sulfur were most obvious in magnesium and calcium leaf concentrations. Phosphorus and calcium concentrations increased at lower levels of applied nitrogen. Concentrations of boron, copper, and manganese also increased strikingly at lower levels of applied nitrogen. Apparently when levels of nitrogen less than 200 ppm are applied, micronutrient uptake increases, suggesting the potential of either luxury consumption or possible toxic effects if too little nitrogen is supplied.
Stacy A. Adams and Ellen T. Paparozzi
Nitrogen and sulfur are macronutrients required by plants to form amino acids used in protein synthesis and other metabolic processes. Commercial poinsettia nutrient recommendations suggest N levels of 350-400 ppm later reduced to 200-250 ppm N. Previous hydroponic research determined that N may be reduced by half if supplied S levels are adequate. The purpose of this study was to look at multiple N and S levels and gauge the effects these combinations had on plant quality.
Poinsettia cv. `Dark Red Hegg' plants, grown in a soilless mix, were fertilized with 56 N and S combinations. N was supplied from 100-275 ppm and S from 0-75 ppm. Plants were evaluated quantitatively by chroma meter readings every three weeks and qualitatively by marketability evaluations from commercial producers, retailers, and consumers.
Results indicate 0 ppm S plant color was more yellow-green than all others. Plants were greener as N increased from 100-150 ppm with no difference above 175 ppm. Evaluators identified plants receiving 0 ppm S and 100 or 125 ppm N as unmarketable. N may be reduced to 175 ppm with no effect on plant quality if adequate S is applied.
Matthew H. Kramer, Ellen T. Paparozzi and Walter W. Stroup
We examined all articles in volume 139 and the first issue of volume 140 of the Journal of the American Society for Horticultural Science (JASHS) for statistical problems. Slightly fewer than half appeared to have problems. This is consistent with what has been found for other biological journals. Problems ranged from inappropriate analyses and statistical procedures to insufficient (or complete lack of) information on how the analyses were performed. A common problem arose from taking many measurements from the same plant, which leads to correlated test results, ignored when declaring significance at P = 0.05 for each test. In this case, experiment-wise error control is lacking. We believe that many of these problems could and should have been caught in the writing or review process; i.e., identifying them did not require an extensive statistics background. This suggests that authors and reviewers have not absorbed nor kept current with many of the statistical basics needed for understanding their own data, for conducting proper statistical analyses, and for communicating their results. For a variety of reasons, graduate training in statistics for horticulture majors appears inadequate; we suggest that researchers in this field actively seek out opportunities to improve and update their statistical knowledge throughout their careers and engage a statistician as a collaborator early when unfamiliar methods are needed to design or analyze a research study. In addition, the ASHS, which publishes three journals, should assist authors, reviewers, and editors by recognizing and supporting the need for continuing education in quantitative literacy.
Stacy A. Adams, Ellen T. Paparozzi and W.W. Stroup
`Dark Red Annette Hegg' poinsettias (Euphorbia pulcherrima Willd. ex Klotzsch) were grown in a 1 peat : 1 perlite : 1 vermiculite medium using a pinched production schedule with varying N and S fertilizer application rates. Fifty-six treatments consisting of eight N levels (100 to 275 mg·L−1 in 25-mg·L−1 increments) and seven S levels (0 to 75 mg·L−1 in 12.5-mg·L−1 increments) were supplied. Other required nutrients were supplied at commercial recommendations for all treatments. Foliage of each plant was evaluated quantitatively by chromometer readings every 3 weeks. Marketability was determined by sensory evaluations from commercial producers, retailers, and consumers. Results indicated distinct color differences (hue, chroma, value) between S levels of 0 and 12.5 mg·L−1 and a slight difference between S at 12.5 and 25 mg·L−1. The foliage of plants receiving 0 S was lighter, more vivid, and more yellow-green in color. As N levels increased, there was a linear response; foliage became more green, darker, and more dull. Commerical and consumer evaluators rated plants that received S at 0 or 12.5 mg·L−1 at all N levels and plants receiving N at 100 mg L−1 as unmarketable. This research indicates that `Annette Hegg' poinsettia requires S at a minimum of 25 mg·L−1 and N at a minimum of 125 mg·L−1 for commercial acceptance, and commercial N application rates may be greatly reduced when adequate S is supplied.
Mary E. Dale, Ellen T. Paparozzi and James D. Carr
Cuttings of Euphorbia pulcherrima Willd. ex Klotzsch `Dark Red Annette Hegg' were grown hydroponically in minus S Hoagland's solution modified to supply 0, 1, 2, 4, or 8 mg S/liter for 8 weeks. Nutrient solution changes; visual observations, sampling of tissue, and measurement of electrical conductivity and pH were done every 2 weeks. Deficiency symptoms appeared after 4 weeks of growth in treatments supplying 0 or 1 mg S/liter and occasionally in treatments supplying 2 mg S/liter. Symptoms included reddening of the petiole and main vein of new leaves followed by yellowing of these leaves. Leaf tissue S levels ranged from 700 to 3600 mg S/kg of plant. Deficient levels were identified as <2200 mg S/kg of plant. Suggested critical tissue levels of S would be 2300 to 3000 mg S/kg of plant leaf tissue.
Ellen T. Paparozzi, M. Elizabeth Conley and Walter W. Stroup
Three cultivars of poinsettia, Freedom Red, Lilo and Red Sails, were grown in a peat:perlite:vermiculite mix according to a commercial production schedule. Twelve selected nitrogen–sulfur fertilizer combinations were applied (125, 150, 175 ppm N with either 12.5, 25, or 37.5 ppm S, 225 and 275 ppm N with either 37.5 or 75 ppm S). The experimental design was a split plot with cultivars as the whole plot and fertilizer levels as the split-plot factor. Mix samples were taken initially, at production week 7 and at the end of the experiment. Nitrate-nitrogen, sulfate-sulfur and total nitrogen were determined. Data were analyzed using SAS PROC MIXED. Visually all cultivars responded similarly to all treatments and were salable. Thus, levels of N as low as 125 or 150 with 12.5 ppm S produced quality plants. Sulfate-S tended to accumulate in the mix while nitrate-N and total N did not. Both nitrate-N and sulfate-S concentrations were affected by an interaction between the cultivar and the amount of S applied with `Freedom' better able to utilize available sulfur. `Lilo' removed more nitrate-N and total N from the mix than `Freedom' which removed more than `Red Sails', but only at specific levels of sulfur. There was no cultivar by nitrogen interaction for any variable measured.
Ellen T. Paparozzi, Joshua R. Widhalm and M. Elizabeth Conley
Common swedish ivy plants when exposed to nitrogen (N) stress display typical nitrogen deficiency symptoms such as reddening of stems and petioles and yellowing of leaves. When N levels are restored, leaves of swedish ivy plants will re-green without leaf loss. An experiment was conducted to determine how proteins change when leaves were re-greened after N deficiency. Cuttings of Plectranthus australis were rooted under mist and allowed to yellow. Plants were then potted up and fertilized with one of two treatments: complete nutrients with N at 150 ppm or complete nutrients with 0.8 ppm N. The experimental design was a randomized complete-block design with six blocks. Each block had the two N treatments and six plants per treatment. After 3–4 weeks, all plants in the 150-ppm N treatment had re-greened and leaf samples for protein analysis were taken. Plants in four of the six blocks were then switched to the other treatment. After leaves had re-greened once again, leaf samples were taken and the experiment was terminated. Two-dimensional polyacrylamide gel electrophoresis was used to compare the treatments. No obvious differences in protein absence or presence were noted. However, Rubisco appeared to be differentially expressed between the two treatments. 2-D gel analysis with subsequent Western blots showed that for most of the leaf samples, the large subunit of Rubisco (56kD) was quantitatively about 1.3 times more concentrated in the N-deficient plants and possibly modified. The small subunit (12kD) was not reliably detectable. Additional protein results for repeated leaf re-greening and the role Rubsico may play in leaf re-greening will be discussed.
Melinda McVey McCluskey, Ellen T. Paparozzi and Susan L. Cuppett
Previous research on leaf lettuce has shown that altering the N:S ratio has an effect on plant color and N and S content. It appears that nitrogen rates can be decreased if known rates of sulfur are applied. The next step was to determine what effect altering the N:S ratio in lettuce had on consumer acceptance of the product.
`Grand Rapids' lettuce was grown hydroponically at six rates of S (0, 7.5, 15, 30, 60, 120 ppm) and four rates of N (30, 60, 120, 240 ppm). Sensory evaluation was performed on 20 of 24 treatments. The sensory panel was composed of 12 panelists who used the nonstructured hedonic scale to evaluate each lettuce treatment on appearance, color, texture, flavor, bitter flavor, and overall acceptability.
Results from the sensory evaluation indicate that differences in color, appearance, and bitter flavor were detected between treatments by the panel. Lettuce plants that received higher amounts of N in relation to S were considered less bitter in flavor and, over all, more acceptable than plants which received higher amounts of S in relation to N. These results indicate that altering the N:S ratio will affect consumer acceptance of leaf lettuce.