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- Author or Editor: Margaret McMahon x
Two chrysanthemum [Dendranthema ×grandiflorum (Ramat) Kitamura] cultivars, `Spears' and `Bright Golden Anne', were grown under artificial short or natural long photoperiod in benchtop chambers covered with clear double-walled acrylic panels (control) or under similar panels filled with CuSO4 (CuSO4 *5H2O in solution at 6% w:v) that removed far-red (FR) (700 to 800 nm) light. Three times per week, a tip from one lateral branch from each of three plants per chamber was harvested and the stage of meristem development recorded. The experiment was conducted April through May and repeated May through June. For `Spears' all short photoperiod treatments developed floral primordia at the same time and the rate of development did not differ. All plants in natural photoperiod treatments initiated flower primordia simultaneously with plants in short photoperiod treatments, but development was delayed ≈3 d in the first experiment compared to plants receiving short photoperiods. During the longer photoperiods of the second experiment, plants under FR-absorbing filters and receiving natural photoperiods initiated and developed flowers ≈2 d after plants in short photoperiod treatments initiation and development. Plants under control filters and natural photoperiods had initiation delayed by ≈4 d and development was delayed by ≈11 d. Bud development was normal for all treatments. For `Bright Golden Anne' only short photoperiod treatments developed normal floral primordia. Plants under FR-absorbing filters and exposed to natural photoperiods eventually initiated floral primordia but development was abnormal. No floral primordia developed under natural photoperiod and control filter conditions. The results indicate that if FR-absorbing filters are used to regulate height of chrysanthemum and possibly other photoperiodic plants, the time of flowering may be affected. However, if artificial short photoperiods are imposed with the use of blackout cloth, FR-absorbing filters do not affect flowering response.
Student-centered learning means having students actively engaged in many aspects of a course to promote learning. Allowing students to participate in syllabus development is a method that involves students in the course and, in the process, assume responsibility for much of their learning. Students can help set course objectives, decide what is the evaluation criteria and who evaluates, determine and deliver some of the course content, and approve the code of conduct for the class. By helping with the aforementioned areas, students can see the relevance of the course to their needs and interests. They tend to take a greater interest in the course and participate more actively in the class. The process of student involvement in syllabus development requires several steps and utilizes techniques that are presented in the following paper.
There is significant interest in using non-chemical methods to control seedling height in vegetable transplant production. One method being evaluated is the use of greenhouse films that filter signifcant amounts of far-red light from ambient light, resulting in shorter tranplants. This study was undertaken to evaluate fruit yield and quality of field-grown tomatoes produced from seedlings grown under light-filtering plastics. Tomato seedlings were grown under clear polyethylene tents or light-filtering laminate tents in a polyethylene-covered Quonset greenhouse in northern Ohio. Standard 288 deep plug trays, filled with MetroMix 360, were used. Seedlings were placed under the tents at the cotyledon stage and transplanted 28 days later. Once in the field, they were grown as staked plants under open conditions using locally accepted horticultural practices. Differences in seedling height were detected within a few days after being placed under the tents. Compared to those grown under clear polyethylene tents, seedlings grown under the light-filtering plastic increased in height more slowly and were shorter at transplanting. At harvest, within each of the three cultivars tested, no significant differences in fruit number, yield, or mean fruit size were found between treatments. It is inferred that this non-chemical method for reducing vegetable transplant height may be a viable production option in the future.
Using spectral filters to reduce the amount of far-red (FR) light perceived by plants has been shown to effectively reduce internode elongation of many floriculture crops. It is theorized that gibberellin (GA) function is inhibited in some way by the increase in the red: far-red light ratio. Sex expression of flowers are effected by exogenous applications of gibberellin and cause a shift in flower sex expression towards maleness. The use of growth regulators (GA inhibitors) have demonstrated a shift towards femaleness. Flowering of spinach, a dioecious species, and cucumber (staminate and pistillate lines), a monoecious species, were surveyed for shifts in flower sex expression, indicating a suppression of GA. Male: female flower ratio decreased from 7.6:1 to 4.06:1 when comparing the controls and –FR for the staminate cucumber line and 1:13 to 1:40 for the gynecious cucumber line. The decrease in male flowers on plants grown in a –FR environment are an indication that the function of GA is inhibited. There was no significant effect on the male: female flower ratios of the spinach.
It is theorized that photomorphogenic reductions in stem elongation are similar to thermomorphogenic plant response, i.e. increased red:far-red light response is similar to –DIF (day temperature < night temperature). The long hypocotyl (hy) mutants of Arabidopsis thaliana Landsberg are phytochrome mutants that are less responsive to light quality than wild type. These include mutants of phytochrome chromophore biosynthesis (hy 1, hy2, hy6), phytochrome B (hy3), blue-light receptor (hy4), and signal transduction (hy5). These mutants were grown in growth chambers with temperatures of 18C day/24C night (–DIF) and 24°C day/18°C night with a 14-h photoperiod. Lighting consisted of both incandescent and fluorescent lamps. Growth measurements of five of the mutants were consistent with reported effects of DIF. The height of these plants were significantly greater in the +DIF regime when compared to –DIF. The hy5 mutant showed little difference in the height measurements of plants grown in either -DIF or +DIF. This mutant has a phytochrome signal transduction deficiency. This result indicates that a functional photoreceptor is required, even in reduced quantities as in the phytochrome chromophore biosynthesis mutants, to signal perception of DIF temperature conditions.
`Spears' chrysanthemums were grown in chambers fitted with double-walled exolite filled with spectral filtering solutions: a blue textile dye that absorbed red light, CuSO4·5H2O that absorbed far-red light, and H2O that was spectrally non-selective (control).
Leaves of `Spears' grown under CuSO4-filters had increased chlorophyll a (23%), chlorophyll b (26%), xanthophyll (22%), and β-carotene (24%) compared to plants grown under H2O or blue-dye filters. Ratios of total carotenoid: chlorophyll and chlorophyll a: chlorophyll b were not affected by filter.
Individual leaf area was reduced 25% under CuSO4 filters compared to other filters. Stomates per unit area were not affected by filters, however stomates per leaf were reduced 25% under CuSO4 filters because of leaf size reduction. Stomate length and width were not affected by filter. Leaves from plants grown under CuSO4-filters had an internal structure resembling that of sun-type leaves. Other filters induced a shade-type leaf.
`Celebrity White' hybrid petunia plants (Petunia ×hybrida Hort. Vilm-Andr.) were grown either in chambers constructed of CuSO4-filled panels acting as spectral filters removing the far-red light (-FR) or in environmental control chambers under temperature treatments of 24 °C day/18 °C night (+DIF) or 18 °C day/24 °C night (-DIF). Growth responses for plants grown under CuSO4 filter (-FR) or -DIF temperatures were similar in that both treatments resulted in decreased internode length, increased stem diameter, and decreased cell length and cell diameter in epidermal, cortical, and pith tissues. Reduced cortical cell length contributed the largest percentage to internode length reductions compared to epidermal and pith tissue for the -FR treatment while reductions in cell length of all three tissues contributed to internode reduction of -DIF-treated plants. Chlorophyll a increased for plants grown under -FR, but decreased for plants grown in -DIF when compared to the appropriate controls.
Latin America is targeted as one of the most rapidly growing areas for expansion for McDonald's International. For example, McDonald's opened its first store in Mexico in 1985 and now has over 50 stores in that country. McDonald's is projecting to have over 100 stores in Mexico by the year 2000. Producing vegetable crops in the same country as a store is desirable to reduce shipping problems and to enhance vegetable production within the country. Problems with lettuce in Latin America include field production (poor growth and yields) and postharvest processing and handling (short shelf life). Beginning in 1992, field studies in cooperation with McDonald's International and Asgrow Seed Company were established in three field sites in Mexico and one site in Panama to determine seasonal uses of varieties (Mexico and Panama) and sites (Mexico) in order to provide quality year round production of lettuce for processing. Results suggest that varieties acceptable for trade in fresh market may not have desirable characteristics during processing (color and cut) and storage (shelf life and odor). In addition, the introduction of new varieties may be needed for year-round production.
This decision case concerns production and marketing problems that many ornamental growers incur. At the retail level, popular ornamental crops are often used as loss leaders to draw the public into stores to make other purchases. As a result, retail buyers are concerned not with quality but with price and volume. To meet the needs of price-conscious buyers, growers may attempt to reduce their production costs by reducing the level of production inputs, with some sacrifice in product quality. The owners of Two Sisters Greenhouses must decide whether they are going to produce lower-quality plants, change marketing strategies, or grow alternative crops to retain their current profit margins. This case study was intended for use in greenhouse management, nursery management, and floriculture courses where students assume the role of a decisionmaker in poinsettia production and marketing.
The growth of Rosa × hybrida and Exacum affine under different spectral filters was evaluated. Three filters that altered light quality were developed. One, a red textile dye, filtered out much of the blue/green portion of the light spectrum but did not change far-red to red (FR/R) light ratio. Another, a blue textile dye, raised FR/R by filtering out a portion of red light. The third, a salt (copper sulfate) lowered FR/R by filtering out a greater portion of far-red than red light. Two controls were used that did not alter light quality. The filters were installed in specally built growth chambers. Photosynthetic Photon Flux Density (PPFD) was adjusted to equal values in each chamber.
Plants of both species were significantly shorter and had higher leaf chlorophyll, when grown under the low FR/R filter.