Ornamental Plants

Annual Reports and Research Reviews

Abstracts

Seasonal Patterns of Nitrogen Use in Three Woody Ornamentals

Barbara Biernacka,
Mary Ann Rose

Department of Horticulture and Crop Science, The Ohio State University. 1996. HortScience 31(4):673.

Seasonal patterns of N uptake and allocation in Buxus microphylla, Acer x freemanii, and Fothergilla gardenii were investigated for improving fertilization strategies. Rooted cuttings were planted in 3.5 liter containers May 25, 1995. Plants were drip-irrigated on an as-needed basis with 50, 100, or 200 mg^.N^.l^-1 solutions. Leaves, stems, and roots were destructively harvested every six weeks, starting June 24. Net changes in dry weight and N uptake were determined for each of six periods throughout the first growing season and twice in the second season after growth began.

Dry weights of Acer increased with N rate in the first year, but in the second year, there was no difference on the new flush of growth (dry weight) between the 100 and 100 mg^.N^.l^-1 treatments, for any species. The 200 mg^.N^.l^-1 rate caused severe injury to Fothergilla.

N uptake of the deciduous species increased in the first three periods, with greatest N uptake between September and October. Greatest N uptake in Buxus occurred between July and September. Increasing the N fertilization rate increased tissue N concentration in all species. Total N content in Buxus increased between October and December with a large proportion of N appearing to shift from leaf to stem tissue. In the other species, leaf abscission caused a net reduction in whole-plant N contents in the 100 and 200 mg^.N^.l^-1 rates between October and December, although stem and root N contents increased. Increasing the N fertilization rate in Acer delayed fall coloration but hastened leaf abscission.

End-of-experiment N recovery (nitrogen taken up / N applied) was extremely low, and decreased with increasing rate of N. Acer in June 1996 recovered 3.0%, 2.7%, and 1.1% of total N applied for low, medium, and high fertilizer rates. Buxus recovery was even lower (2.6%, 1.0%, 1.0%, for 50, 100 and 200 mg^.N^.l^-1 respectively).

Why Do Roses Die: How Can We Make Them Last Longer?

Michael Knee

Department of Horticulture and Crop Science, The Ohio State University

Roses are among the most attractive and the most short-lived cut flowers. We have all been disappointed by the fading and shriveling of petals after a few days. At this point the flower is losing more water than it takes up through the stem, but why should this occur? Among the simpler possibilities are:

• The permeability to water increases in cell membranes in the petals.
• The rose uses up its food reserves; when the sugar runs out it has no more energy to maintain cellular organization.
• The rate of production or sensitivity to ethylene increases and this triggers cellular changes.
• Bacteria accumulate in the vase solution and these block the xylem so that water uptake becomes impossible.

An undergraduate class in postharvest physiology was asked to test these hypotheses through a number of experiments. They also reviewed the extensive literature on roses as cut flowers. One can question whether it is necessary to know why roses die in order to improve their vase-life. As in many other areas of applied plant science, practical improvements have been achieved by a purely empirical approach. Plant physiologists then try to explain why these treatments are effective. Floral preservatives have been developed by screening formulations of sugar and inhibitors of microbial growth. The students ran all of their experiments with roses in water and in a commercial preservative to see whether they could relate the effects of preservative to any of the hypotheses. Further experiments have involved a number of commercially available preservatives.

Data obtained by the students indicated that shriveling of the petals and development of "bent-neck" were associated with physiological changes in the flower itself, rather than blockage of the stem by bacteria. Ethylene treatment promoted these changes, and the changes could be delayed by treatment with inhibitors of ethylene synthesis or action.

Additional information can be found on the World Wide Web at http://hortwww-2.ag.ohio-state.edu/hvp/rose/rose1.htm.

Development of a National On-Line Interactive Database of Internship Opportunities for Students of Horticultural Science

Robert E. Lyons

Department of Horticulture, Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Tim Rhodus

Department of Horticulture and Crop Science, The Ohio State University. 1996. HortScience 31(4):589.

Internships are becoming an increasingly used mechanism of providing undergraduates with experience in their chosen profession before job placement, and potential employers view internships favorably in making hiring decisions. Many horticulture programs require internships as part of their curricula, while others are considering the option.

Because internship opportunities in horticulture have been compiled in a wide variety of discipline-specific resources with no central, inclusive "clearinghouse," students often overlook potential opportunities, particularly those outside of their home state, leaving some industry members without interns.

The internet-based database of internships developed jointly by Virginia Tech and Ohio State will be discussed within the context of being a resource for all horticulture programs. Other schools will be shown how to contribute to and to use the database so its national scope can be fully used and expanded.

Copper Sulfate Filters Influence Photoperiodic Response But Not Post-Production Longevity of Chrysanthemum "Spears"

Margaret J. McMahon

Department of Horticulture and Crop Science, The Ohio State University

John W. Kelly

Department of Horticulture, Clemson University

"Spears" of chrysanthemums grown under solar filters filled with CuSO₄ solution or water were exposed to natural and artificial long and short days. Plants that flowered were evaluated for postharvest performance. Internode length and/or plant height was reduced under CuSO₄ filters compared to controls, regardless of photoperiod.

Plants grown under control filters and receiving natural long days flowered 10 days after plants grown in the same photoperiod under CuSO₄ filters, and 17 days after plants grown under control or CuSO₄ filters that received artificial short days. Although plants grown under CuSO₄ filters and receiving long days flowered seven days after control- or CuSO₄-filter grown plants receiving short days, the number of nodes was the same for all treatments indicating flower induction occurred simultaneously. Plants under both filters flowered at the same time during natural short days. A fluorescent light night break prevented or delayed flowering of plants grown under control and CuSO₄ filters during natural short days.

Leaf chlorophyl increased when plants were grown under CuSO₄ filters and were subjected to natural long days, natural short days, or artificial short days compared to plants grown under clear filters and subjected to respective photo-periods. Plants grown under CuSO₄ filters and subjected to a night break did not exhibit increased chlorophyll levels compared to plants that were grown under clear filters and received a night break. Postproduction quality was not affected by filter.

Influence of Spectral Filters on Growth of Euphorbia pulcherrima 'Glory'

Margaret J. McMahon

Department of Horticulture and Crop Science, The Ohio State University

John W. Kelly

Department of Horticulture, Clemson University

Plants of poinsettia (Euphorbia pulcherrima) 'Glory' were grown in chambers fitted with double-walled polycarbonate panels filled with light-filtering solutions of a blue dye, 6% (w:v), CuSO4, or water (control) that altered the ratio of R to FR to 1.00, 3.30, and 1.16, respectively. Plants grown under CuSO₄-filters were shorter (32%) with shorter internodes (48%) than control plants. Leaf chlorophyll was 56% greater in CuSO4-grown plants compared to control.

Plants from all treatments flowered at the same time when placed in the chambers during photoperiods inductive for flowering (short day) (year one). Plants flowered two weeks earlier under CuSO4 filters compared to controls when placed in the chambers during non-inductive photoperiods (year two). Informal postproduction evaluations of plants showed no differences in the rate of senescence of plants from any treatment.

Publishing Newsletters on the World Wide Web Using Database Software

Tim Rhodus

Department of Horticulture and Crop Science, The Ohio State University. 1996. HortScience 31(4):588.

Preparing newsletters for distribution over the World Wide Web generally requires one to learn HTML (hypertext markup language), purchase an HTML editor, or convert existing word-processing documents through a utility program.

As an alternative, an input form was developed for county agents that facilitates the direct publishing of their weekly Buckeye Yard and Garden On-line newsletter over the Internet. Using FileMaker Pro 3.0 for Macintosh and the ROFM acgi script for WebSTAR, agents cut and paste text from their word processing file into specific input boxes on the screen and then submit it to the server located in Columbus. Their newsletter articles are then made available to anyone on the Web through a searchable database that allows for searching by date or title.

Preparation of the input form and corresponding search form creates two distinct advantages: county agents do not have to spend time learning about HTML coding, and all their newsletters are indexed in a searchable database with no additional effort by the site manager. Modification of this procedure has been done to facilitate the creation of online term projects for students and a directory for horticultural internships.

Red Thread Management Study - Kentucky Bluegrass

Joseph W. Rimelspach

Department of Plant Pathology, The Ohio State University

Methods

A red thread (Laetisaria fuciformis) study was initiated on May 29, 1996 at the TruGreen- ChemLawn Research and Development Center, Delaware, Ohio, on a four-year-old stand of Kentucky bluegrass (Poa pratensis) consisting of 'Julia,' 'Merit,' 'Schamrock,' and 'Touchdown' at 25% each. The soil is Blount silt loam, with a pH of 6.2. The turfgrass was maintained at two-inch cutting height, with clippings returned, and irrigated as needed to avoid water stress. The condition of the stand was fair with good color and medium density.

Liquid treatments were made with a CO₂ small plot sprayer with nozzle tips 8004 operating at 40 psi (2.5 gallons/1,000 sq. ft.). Dry treatments were made by hand. The plots measured 6 x 10 ft. and were replicated three times in a randomized complete block design. Spring conditions in Delaware were unusually wet and cool. Red thread was very active. A single application was made of the treatments.

Results

Readings of the number of patches of red thread were taken at approximately two and three weeks after application. Outstanding control was achieved with Heritage and ProStar. Sentinel shows excellent results over time; however, initial control was slow. Chipco 26019 WDG and 2F both demonstrate good management of this disease. Daconil demonstrated good short-term reduction of the disease, but since this material is a contact fungicide, repeat applications would be needed. The fertilizer applications that were done were not adquate this year to manage the disease.

Red Thread Management Study - Perennial Ryegrass

Joseph W. Rimelspach

Department of Plant Pathology, The Ohio State University

Methods

A red thread (Laetisaria fuciformis) study was initiated on May 18, 1996, at The Ohio State University Turfgrass Research Center, Columbus, Ohio. The turfgrass was an established stand of perennial ryegrass (Lolium perenne), cultivar unknown, maintained at 2.5 inches with clippings removed. The soil was a clay with a pH of 7.3. The area received minimal maintenance with no fertilization or irrigation during the past year. The condition of the stand was fair with poor color and rather low density. No thatch was present. Liquid treatments were made with a CO₂ small plot sprayer with nozzle tips 8004 operating at 40 psi (2.5 gallons/1,000 sq. ft.). Dry treatments were made by hand. The plots measured 6 x 10 ft. and were replicated three times in a randomized complete block design. At the time of application, the disease was active, and 30­40% of the surface of each plot was diseased. Spring conditions in Columbus were unusually wet and cool. Red thread was active at the time of applications.

Discussion

Initial reduction in red thread was most evident with Heritage and Prostar. Other materials that showed an initial reduction included Lynx, Chipco 26019 WDG, Sentinel, and the chlorothalonil products. Primo treatments initially had no effect on red thread activity. However, by the end of the study, considerable disease was present in the Primo plots. The likely reason was the reduction in turfgrass growth from the application of Primo (a plant growth regulator).

Nutrient Uptake Patterns in Forsythia

Hao Wang,
Mary Ann Rose

Department of Horticulture and Crop Science, The Ohio State University. 1996. HortScience 31(4):674.

Nutrient uptake and allocation patterns of Forsythia ovata x Europaea 'Meadowlark' grown in a recirculating hydroponic system were observed for five months in the greenhouse. Dormant rooted cuttings were placed in the system on May 8, 1995. The nutrient solution supplied, in mg.l-1, 100 N, 48 P, 210 K, 30 Mg, 70 Ca, 117 SO4, 3 Fe, 0.5 Mn, 0.15 Zn, 0.15 Cu, 0.5 B, 0.1 Mo. Solutions were completely replaced every two weeks. Leaves, stems, and roots were harvested for dry weight and nutrient analysis at monthly intervals.

Nitrogen uptake and dry weight accumulation in the roots increased throughout the experiment, reaching a maximum in the fifth month (September). Nitrogen uptake and dry weight accumulation of leaves and stems increased rapidly throughout the first three months, then leveled off.

Whole-plant N recovery (N taken up/N in hydroponics system) reached a maximum (58%) between July 6 and August 3. N recovery in the hydroponics system was about 10 times greater than what was observed in related experiments with woody plants in typical production environments, suggesting that there is potential for manipulating fertilization and cultural practices to increase fertilization efficiency in woody ornamentals.