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  • Author or Editor: Dennis R. Decoteau* x
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Abstract

Demonstrations and evaluations of plastic mulch, trickle irrigation, and row cover effects on vegetable crops are primarily conducted in the field (1, 2). However, field evaluations of these procedures during the summer months are often not available for observation by grower groups that traditionally meet during the winter and spring months, or by students in plant production courses taught during the spring or fall semester. This report describes a plant bed system in a greenhouse that could be used for demonstrating plastic mulch, trickle irrigation, and row cover effects on selected vegetable crops regardless of season.

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The influence of leaf removal and decapitation (removal of apical bud and top two nodes) of determinate tomato (Lycopersicon esculentum Mill cv. Mountain Pride) plants on canopy development was investigated. Leaf removal and decapitation influenced subsequent leaf development and distribution, and early fruiting of greenhouse-grown tomato plants. `Removal of young axillary leaves increased the size of main (true) leaves in the middle and upper nodes, increased the number of nodes, and increased the number of early fruit produced. Removal of main leaves reduced axillary leaf development at nodes 5 and 9. Decapitation increased axillary leaf development in the middle and upper nodes and delayed early fruit production. These results suggest that cultural practices of tomatoes that remove leaves or apical buds to influence fruiting also affect canopy leaf development and distribution.

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The Teaching Portfolio is a factual description of a professor's strengths and accomplishments. It includes documents and materials that collectively suggest the scope and quality of a professor's teaching performance. The Teaching Portfolio is a living, breathing document that changes over time. Items in a Teaching Portfolio include a statement of teaching responsibilities, description of steps to improve teaching, instructional innovations, student and teaching evaluations, awards and honors, and a record of students who have succeeded. I will discuss the steps taken at Clemson University to use the Teaching Portfolio.

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A one-credit course, Writing in Horticulture, was developed and taught to graduate students in the Dept. of Horticulture at Clemson Univ. The course focused on discussion and explanation of the philosophies and methods of writing in the horticulture field. Discussions included a review of writing mechanics, types of writing and audiences, examples of exemplary writings, editing and reviewing, and examples and methods of professional correspondence. Real-life writing experiences were emphasized. Hands-on activities included writing and reviewing peer manuscripts and grant proposals. Three original written works were completed by the end of the semester: 1) a popular press article, 2) a grant proposal (maximum three pages long), and 3) an abstract for a manuscript published previously in a scientific journal.

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The influence of polyethylene (plastic) mulch surface color (white versus black) on leaf area distribution of tomato (Lycopersicon esculentum) was investigated in simulated planting beds at two sampling periods: an early sampling with relatively young plants that had been in the mulch treatment for 22 days and a late sampling with relatively mature plants that had been in the mulch treatments for 50 days. At the early sampling period, tomato plants grown with white mulch had more axillary leaves than plants in the black mulch, resulting in a greater axillary:main leaf area ratio for the plants with white mulch. Leaf area for total leaves (main + axillary) and plant biomass was unaffected by mulch surface color at the early sampling period. Tomato plants grown in black mulch at the early sampling period had significantly more area of main leaves partitioned to node 3, whereas plants grown in white mulch had more area of main leaves in nodes 8 and 9. Plants grown in the white mulch treatment had significantly more axillary leaf area at nodes 1, 2, and 3, whereas plants in black mulch had more axillary leaf area at node 6. At the later sampling period, most of the leaf area from both mulch treatments was recorded in the axillary leaves and there was no effect of mulch surface color on the amount of total leaf area partitioned to main, axillary, or total leaves; to the amount of biomass of the measured top growth; or to the nodal distribution of leaf area among main leaves or axillary leaves. Tomato plants in white mulch had significantly more fruit on plants at the later sampling period than plants in the black mulch. Mulch surface color also affected the plant light environment and soil temperatures. These results suggest that the polyethylene mulch surface color can induce changes in the plant microclimate and affect leaf area distribution of young tomato plants (as recorded at the early sampling) and fruiting of relatively more mature plants (as recorded at the later sampling).

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The influence of end-of-day (EOD) light treatments of tomato (Lycopersicon esculentum Mill. cv. Mountain Pride) transplants on growth and subsequent fruit production was investigated. In the first experiment, transplants were treated with EOD red (R) and far-red (FR) light for 2 weeks in a controlled environment and then placed in the greenhouse under ambient light conditions from November to March. Before transplanting to the greenhouse, transplants treated with EOD R light were shorter and had less total leaf length than plants that were not treated with EOD light (controls). EOD R light increased the number of flowers on the plants before first harvest but had no effect on subsequent fruit production (as compared to plants treated with EOD FR light or control plants). In the second experiment, cool-white fluorescent lights (a light source high in red wavebands) were used to supplement solar light that transplants received in a nonshaded glasshouse for 1 hour before the end of the natural photoperiod. The fluorescent light reduced transplant height and total leaf length as compared to plants not treated with supplemental light. Supplemental fluorescent light for transplants had no effect on subsequent fruit production in the field. These results suggest that EOD light treatments that affect tomato transplant growth do not affect subsequent fruit production.

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The influence of N and K rates in Hoagland's nutrient solution on Jalapeño pepper (Capsicum annuum L.) plant growth and pod production was determined on greenhouse-grown plants in sand culture. Varying the rates of N (1 to 30 mm) and K (1 to 12 mm) in Hoagland's solution identified optimum concentrations for Jalapeño plant growth and pod production. Two experiments were conducted to determine Jalapeño pepper sensitivity to differential fertilization. In the experiment seeded in April, nutrient treatments began at transplanting, and in the one seeded in May, treatments began after all plants had flower buds and half had flowered. Biomass and pod production per plant responded curvilinearly to N rate in both experiments. Optimum N rate for pod yield was 15 mm. Nitrogen rate affected pungency of pods only in the first experiment, with 1 mm N reducing capsaicin levels in fruit compared to other N rates. Biomass, fruit count, and fruit weight per plant increased linearly with increasing K rate in the first experiment and curvilinearly with K rate in the second experiment. The optimum K rate for pod yield was 6 mm. Potassium rates did not affect pod pungency. Jalapeño peppers grown in sand culture required 15 mm N and at least 3 mm K for optimum pod production.

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Similarities exist between the effects of phytochrome and cytokinins on plant growth and development (e.g., chloroplast development, amaranthin synthesis, seed germination). It is unclear, however, if and how these two systems interact. The coaction between phytochrome and cytokinins was investigated by using Nicotiana plumbaginifolia plants transformed with the isopentenyl transferase (ipt) cytokinin gene and treated with end-of-day (EOD) red (R) and far-red (FR) light. The ipt gene was under control of either a constitutive cauliflower mosaic virus promoter (35S-plants) or an inducible, heat shock promoter (HS-plants). When treated with EOD FR light, whole plants were characterized by decreased chlorophyll concentrations and increased fresh weights. When treated with EOD R light, 35S-plants contained high concentrations of zeatin riboside (ZR) compared to plants treated with EOD FR light. When treated with EOD FR light, HS-plants contained high concentrations of ZR compared to plants treated with EOD R light. Both cytokinin responses were photoreversible. The reasons for the differences between the 35S- and HS-plant responses are not known. Results appear to implicate interactions between phytochrome and cytokinins in plant growth and development.

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Similarities exist between the effects of phytochrome and cytokinins on plant growth and development (e.g., chloroplast development. amaranthin synthesis, seed germination, photomorphogenesis). It is unclear. however, if and how these two systems interact.

To determine the effects of phytochrome activity on cytokinin synthesis and ultracellular plant development, we utilized tobacco transformed with the Agrobacterium tumefaciens isopentenyl transferase (ipt) gene. This gene encodes for isopentenyl transferase (iptase) which is an enzyme active in cytokinin biosysthesis.

Ipt-transgenic tobacco cultures were treated with end-of-day red or far-red light for 15 minutes. After 15-30 days of treatment, the plant tissue was harvested and ipt expression was verified by SDS-PAGE and western blot analysis. Polyclonal antibodies specific to iptase were used as a primary antibody. Colloidal gold conjugated to goat. anti-rabbit antiserum served as an electron dense, secondary antibody and a probe to light-influenced iptase synthesis and distribution within the cell.

A Hitachi 600AB transmission electron microscope was used to determine the influence of phytochrome/light treatments on the ultrastructure of ipr-transgenic cells.

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