Ellen T. Paparozzi

Stability of leaf anatomy and light response curves of field grown maize as a function of age and nitrogen status

Summary Little information exists linking leaf anatomical characteristics, gas exchange rates and the effects of irrigation and nitrogen applications in field grown maize. The objectives of this study were: (i) to characterize the light response curves of leaves 13 and 17; (ii) to characterize leaf anatomical features (leaf thickness; bundle sheath diameter; separation between bundle sheaths; number of mesophyll cells between bundle sheaths; number of mesophyll cells separating the bundle sheaths from the epidermis; bundle sheath area ratio) over the season as a function of leaf position (leaves 13 and 17, counting from stem base), and (iii) to relate these anatomical features to the net assimilation rate at a PPFD of 2000 µmol m –2 s –1 (Amax) and to the convexity parameter of a light response curve of field grown maize in response to extremes in irrigation and nitrogen. Experiments were conducted in 1995 and 1996 with the maize hybrid Pioneer 3394. A randomized complete block with split-plot treatment design with two replications was used. Irrigation/no irrigation was the main plot and nitrogen (120 kg nitrogen ha –1 or no nitrogen) was the split plot treatment. Leaves from tagged plants were measured and then fixed for anatomical measurements. Environmental conditions during each year were markedly different providing a wide range of responses. Leaf thickness as well as other anatomical features were influenced by water stress and nitrogen in a coordinated fashion such that environmental conditions had little or no effect on the ratio of mesophyll and bundle sheath tissue. Amax increased with leaf thickness but the correlation was weak. The convexity parameter and Amax decreased with leaf age, with no correlation to the anatomical features described here.

EFFECT OF NITROGEN AND SULFUR APPLICATIONS ON POT CHRYSANTHEMUM PRODUCTION AND POSTHARVEST PERFORMANCE. I. LEAF NITROGEN AND SULFUR CONCENTRATIONS

Chrysanthemums are one of the most important flowering plants produced internationally year round. The objectives of this research were to evaluate the effects of reducing nitrogen (N) applications by adding sulfur (S) and to determine if N* S interactions occur during the production and postharvest longevity of pot chrysanthemums. Pot chrysanthemum ‘White Diamond’ was grown in a peat-based medium following a typical production schedule except for fertilization. Plants received N at 50, 100, 150, or 200 mg L−1 in combination with S at 0, 5, 10, 20, or 80 mg L−1. Variablesevaluated were leaf N and S concentrations, plant height, leaf area, days to bud set, and first flower color and inflorescence anthesis as well as size and longevity under simulated interior conditions. In this article, leaf N and S concentrations are the variables discussed. In general, N* S interactions were significant for leaf S, but not leaf N concentration. Applications of 50 mg N L−1 resulted in poor leaf N and S concentration and plants of questionable quality. Nitrogen applied at 100, 150, or 200 mg L−1 in combination with at least 10 mg S L−1 had acceptable leaf N concentrations and produced plants of commercial quality. Thus, N applications can be reduced by half when S is applied during commercial production.

An Investigation of Reflective Mulches for Use Over Capillary Mat Systems for Winter-time Greenhouse Strawberry Production

Photosynthethically active radiation (PAR) is a principle environmental variable used by horticultural specialists, agronomists, and ecosystem modelers to characterize the quantity and quality of light conducive to plant growth and development. Spatial distribution of PAR in a greenhouse can be quite variable and diffuse throughout the daytime photoperiod, especially at low sun angles in northern regions of the United States. Four colors of reflective plastic mulches (white, red, olive, and black) were evaluated for winter-time strawberry (Fragaria × ananassa Duch.) production based on their reflectance and transmittance properties in a double-polyethylene, plastic-glazed Quonset greenhouse in Nebraska. The spectral properties of the plastic film mulches were investigated in the laboratory using a spectral radiometer and integrating sphere. For greenhouse spectral studies, a modified field of view set of LiCOR PAR sensors and infrared thermocouple sensors (IRT/c) were mounted over the greenhouse gravel floor and the strips of plastic films of four different colors. Both incident and reflected PAR and plastic mulch temperatures were recorded during the day using a wireless, LabVIEW-based data logger system. The red mulch reflected less than half the amount of PAR than that from the white mulch and the olive and black mulches reflected even less. The white 6-mil reflective mulch was then selected to cover a capillary mat (CapMatII) irrigation system in a greenhouse strawberry production study. A three-month production study using the white reflective mulch under 312 strawberry pots resulted in the production of over 1700 saleable berries with a mass of over 19 kg. Plastic mulches could enhance the PAR environment of greenhouses and thus translate to more consistent plant production during winter months.

Glycerol and microwave preservation of annual statice (Limonium sinuatum Mill.)

Abstract Stems of annual statice ( Limonium sinuatum Mill.) were harvested from the field in 1982 and soaked in varying concentrations of glycerol:water solutions for 24 and 48 h and then microwaved for 0, 1, 3 or 5 min. Half of the branch stems were measured for flexibility, with the remainder being assessed 1 year later. Stems harvested in 1983 were wet- and dry-stored at 3°C for varying lengths of time and then preserved. Preservation was best when statice was preserved immediately. Cold storage decreased preserved statice flexibility, but was better than air-drying. Fresh cut statice stems, up to 34 cm long, should be preserved by soaking in a 1:2 or 1:3 glycerol:water solution for 48 h followed by microwaving for 1 min at medium-high (34°C).

Nitrogen sulfur interaction in poinsettia 1

Abstract Poinsettia cuttings of Euphorbia pulcherrima Willd. ex Klotzsch ‘Dark Red Annette Hegg’ were grown hydroponically at varying levels of nitrogen (N) (0, 127, or 254 mg N/L) and sulfur (S) (0, 32, or 64 mg S/L) in a 3x3 factorial arrangement. Young and lower, fully expanded leaves were sampled and analyzed for S and N content every two weeks. Plants supplied with no nitrogen showed little growth, and without nitrogen, sulfur had little effect on plant growth. Roots appeared healthy in all treatments where S and N were supplied. Roots were usually branchless when no S was supplied and were thinner and shorter when N was absent. Plants supplied S and 127 mg N/L showed better or comparable N and S content and root and shoot growth as plants supplied S and 254 mg N/L.

Effect of nitrogen and sulfur applications on pot chrysanthemum production and postharvest performance. II. Plant growth responses

Chrysanthemums are one of the most important flowering plants produced internationally year round. The objectives of this research were to evaluate the effects of reducing nitrogen (N) applications by adding sulfur (S) and to determine if N * S interactions occur during the production and postharvest longevity of pot chrysanthemums. Pot chrysanthemum ‘White Diamond’ was grown in a peat-based medium following a typical production schedule except for fertilization. Plants received N at 50, 100, 150, or 200 mg L−1 in combination with S at 0, 5, 10, 20, or 80 mg L−1. Variables evaluated were leaf N and S concentrations, plant height, leaf area, days to bud set, and first flower color and inflorescence anthesis as well as size and longevity under simulated interior conditions. N * S interactions were significant for significantfor all plant growth response variables. Applications of 50 mg N L−1 resulted inpoor leaf N and S concentration and plants of questionable quality, yet maximal postharvest longevity. Nitrogen applied at 100, 150, or 200 mg L−1 in combination with at least 10 mg L−1 S had acceptable leaf N and S concentrations and produced plants of commercial quality with adequate postharvest longevity. Thus, N applied at 100 mg L−1 was the minimum acceptable fertilizer rate. Thus, N applications can be reduced by half when S is applied during commercial production without compromising postharvest longevity.

Evaluation of Alternative Methods of Applying Sulfur Fertilizers to Chrysanthemums

ABSTRACT Previous research has shown that supplying adequate sulfur (S) continuously in combination with reduced amounts of nitrogen (N) will produce a quality plant. However, not all commercially available fertilizers use the same source of S, contain the same or optimal concentration of it, or contain any S at all. Additionally, nutrient incompatibility can occur if all the macronutrients are combined in one solution or one dry fertilizer. Thus, the objective of this research was to determine the effect of different methods of application and different types of S fertilizers on chrysanthemum growth. Two experiments were conducted in which three S sources (H2SO4, MgSO4, and K2SO4) were applied in combination with three N concentrations (50, 100, and 150 mg L−1) as fertilizer treatments. Sulfur was applied at 10 mg L−1, either continuously—by slightly acidulating the fertilizer solution with H2SO4—or in one, two, or three single, discrete applications as either K2SO4 or MgSO4. Leaf N concentration was greatest when 100 or 150 mg N L−1 was applied. As expected, S applied continuously by slightly acidulating the fertilizer solution with sulfuric acid resulted in higher leaf S concentration and larger flower diameter than under any of the other treatments. Together, plants fertilized with S continuously at 10 mg S L−1 and N at 100 mg L−1 were the largest, had the largest flower diameter, and contained the greatest leaf N and S concentrations. Sulfur concentration in the mix was highest and N concentration lowest when S was supplied continuously. Thus, if growers need to supply S and acidulate their water, sulfuric acid would be the best choice. If there are concerns about possible S contamination in landfills or in mix recycling, either potassium or magnesium S, applied multiple times as single applications in combination with 100 or 150 mg N L−1, may be a better choice.

Time of Day Effect on Foliar Nutrient Concentrations in Corn and Soybean

Foliar nutrient concentrations vary during the day. Field research was conducted to quantify and better understand this variation in corn (Zea mays L.) and soybean (Glycine max L. Merr.) with foliar sampling during the vegetative and reproductive stages. Time of day effects occurred inconsistently across nutrients. Nitrogen (N), manganese (Mn), iron (Fe), and zinc (Zn) foliar concentrations were generally high early in the day. Phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S) foliar concentrations varied inconsistently with time of day, while concentrations of boron (B) in both crops and copper (Cu) in corn were not affected. Limiting foliar sampling to after 10:00 AM reduced the variation for soybean but not for corn. Interpretation by Diagnosis and Recommendation Integrated System (DRIS) did not reduce the time of day effect. The variation caused by time of day, along with other causes, affects confidence in interpretation of foliar results suggesting use of the information with either additional foliar sampling or soil testing in making nutrient management decisions.

Effect of chelates vs. ionic salts of microelements and nitrogen form on hydroponic solution pH

Abstract Microelements are supplied at low concentrations, yet have a profound effect on plant growth. These experiments explore the role of their chemical form and that of nitrogen on plant uptake. Chrysanthemum × morifolium cv. Bright Golden Anne, which is sensitive to ammonium, was the test plant. There were four hydroponic treatments with nitrogen supplied at 200 ppm as either 100% nitrate or 25:75 ammonium to nitrate. Micronutrients were supplied either in the chelate or ionic salt form. All other macro cations and anions were the same concentration. All solutions were allowed to stand for 24 h and then adjusted to pH 5.9–6.0. Once the plants were set into the solution they were allowed to adjust for 1 h before the pH was measured hourly for 24 h and then measured 4 times per day for 14 days. As expected both solutions of 100% showed an increase in pH from 6.2 and 7.1 within 5 h. As expected, the pH of the 25:75 ammonium:nitrate, with micronutrients as ionic salts decreased from 5.8 to 5.2, while the chelate solution was stable between 5.8 and 6.3. During the entire time course there was a daily oscillation within each pH range for the nitrate-based solutions.

Stolon Development and Cultural Production Practices of Winter-Grown Strawberries

ABSTRACT The four experiments described here are part of a 5-year program focused on determining whether day-neutral and short-day strawberries would be suitable for commercial off-season/winter (temperate climate) production in greenhouses. All research was performed using container-grown plants fertigated through a capillary mat production system with heat supplied under the benches. The first experiment focused on stolon development. The second experiment investigated the influence of stolon removal on berry production and included the removal of flowers for the first three weeks. The third and fourth experiments were conducted as a comparison of university research (experiment 3) versus a commercial operation (experiment 4). In experiment one, of 13 cultivars, ‘AC Wendy’ plants produced significantly more stolons than the other cultivars. In experiment two, stolon production peaked at weeks 12 and 13, with ‘Chandler’ plants producing significantly more stolons (starting at week 9) than the other cultivars. At week 13, ‘Seascape’ plants produced more total berry weight than the other cultivars. The influence of stolon removal on total berry weight varied, with ‘Evie-2+’ plants (large crowns) producing higher total berry weight with the stolons on as compared to ‘Evie-2’ plants, which produced higher total berry weight with the stolons removed. In experiment 2, fruit production was low and was probably a result of deflowering for three weeks. Consequently, it may not be advisable to deflower during the ‘off-season’ for greenhouse-grown strawberries. In the final two experiments, which involved a commercial cooperator as well as the university greenhouse, it was found that of the five cultivars trialed, the same cultivars at both sites produced the maximum total berry weight. Stolon production differed at the two locations, but the optimal time for stolon removal was similar. Thus, it is recommended that for winter greenhouse production, stolons be removed initially at week 8 and then at weeks 11–12 of the production cycle.