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  • Author or Editor: Kent D. Kobayashi* x
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Controlling plant height is an important practice in the ornamental plant industry. With high cost of growth regulators and concern about their environmental aspects and health of workers, alternative ways of controlling growth may be advantageous. Objective was to determine effect of photoselective shadecloth and plastic film on growth of `Barbara', `Shasta', and `Chesapeake' mums under supplemental lighting. In experiment 1, `Barbara' plants (two and four weeks old) were placed under either wide spectrum fluorescent lamps and incandescent light bulbs (control) or lights covered with photoselective shadecloth. In experiment 2, 3-week-old `Shasta' and `Chesapeake' plants were placed under lights or lights covered with photoselective plastic film. Effect of shadecloth differed with age of `Barbara' plants. For 1-month-old plants placed under lights, stem diameter, stem dry weight, and root dry weight were reduced under shadecloth compared to control. No differences were observed for plant height, pot height, leaf number, leaf area/plant, and leaf dry weight. For 2-week-old plants, leaf number, leaf area/plant, leaf dry weight, and stem dry weight were less under shadecloth than control. No effects on plant height, pot height, stem diameter, and root dry weight were observed. Plastic film reduced plant height and pot height for `Shasta' and `Chesapeake' plants and reduced stem dry weight and total plant dry weight for `Shasta'. No differences were seen for other growth measurements. This study indicated photoselective shadecloth did not control height of `Barbara' and its effect on growth was influenced by plant age. Photoselective plastic film controlled height of `Shasta' and `Chesapeake' and offers an alternative method for growth control of mum plants.

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The simulation programs Stella® (High Performance Systems) and Extend™ (Imagine That!) were used on Apple® Macintosh® computers in a graduate course on crop modeling to develop crop simulation models. Students developed models as part of their homework and laboratory assignments and their semester project Stella offered the advantage of building models using a relational diagram displaying state, rate, driving, and auxiliary variables. Arrows connecting the variables showed the relationships among the variables as information or material flows. Stella automatically kept track of differential equations and integration. No complicated programming was required of the students. Extend used the idea of blocks representing the different parts of a system. Lines connected the inputs and outputs to and from the different blocks. Extend was more flexible than Stella by giving the students the opportunity to do their own programming in a language similar to C. Also, with its dialog boxes, Extend more easily allowed the students to run multiple simulations answering “What if” questions. Both programs quickly enabled students to develop crop simulation models without the hindrance of extensive learning of a programming language or delving deeply into the mathematics of modeling.

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Controlling plant height is an important practice in the ornamental plant industry. Though commonly used, growth regulators are expensive, and there are concerns about environmental consequences and safety of workers. Alternative ways of controlling growth may be advantageous. The objective of this study was to determine the effects of photoselective shadecloths on the growth and flowering of `Arezzo' chrysanthemum. One-month-old potted `Arezzo' chrysanthemum plants were grown in a saranhouse in chambers built with PVC (polyvinyl chloride) pipe covered with 30% shadecloths—red, blue, gray, and black (control). The blue shadecloth was more effective in reducing plant height, with no differences among the other shadecloths. Plant canopy dimensions—greatest canopy width and average canopy width—did not show any differences among the shadecloths. The red shadecloth was more effective in hastening flowering, followed by the blue shadecloth. This was evident by flowering first occurring with the red shadecloth and initially the greatest number of buds showing color. Additionally, the red shadecloth had the highest proportion of the number of flowers to the combined number of flowers and buds showing color. Specifically, the total number of flowers was similar to the total number of buds showing color. In contrast with the other shadecloths, there was a greater number of buds showing color than the number of flowers. The most buds showing color occurred with the gray shadecloth. The three shadecloths resulted in a greater number of the combined buds showing color and flowers than the black shadecloth. In conclusion, photoselective shadecloths may provide an alternative to controlling plant height and altering the flowering pattern of potted chrysanthemums.

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How do we enhance the learning experience of graduate students in scientific writing, an essential skill in their professional development? A graduate course TPSS 711 “Scientific Writing for Graduate Students” was developed to address this need. Its objectives were to help students write, analyze, and revise parts of a scientific paper; critically evaluate their own writing and the writings of others; and become familiar with types of publications. The diverse topics included purpose of scientific writing; organizing your writing; parts of a scientific paper; data analysis and growth analysis; writing the content of a poster or oral presentation; newspaper articles and popular works; extension publications; technical writing for the general public; thesis/dissertation writing; a journal editor's perspective; and reviewing a manuscript. TPSS 711 had an enrollment of 11 TPSS master's students. Students were in their second through fifth semesters of their graduate program. A student survey showed no student had submitted a manuscript to a peer-reviewed journal, had a peer-reviewed article published, or had a newspaper, trade magazine, or popular work published. Only 9% of the students had a paper published in a conference proceedings or presented a scientific paper outside Hawaii, with only 18% having presented a paper in Hawaii. Writing assignments, in-class activities, and evaluations of the writings of others helped students gain intensive hands-on experience in scientific writing. As a course requirement, students submitted an abstract and presented a paper at our college's annual scientific symposium. Course evaluations indicated this course was important and valuable in helping enhance the students' learning experience.

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How do we enhance students' learning experience and help them be aware of current and emerging technology used in horticulture? An undergraduate course on “Computer Applications, High Technology, and Robotics in Agriculture” was developed to address these needs. Its objectives were to familiarize students with the ways computers, high technology, and robotics are used in agriculture and to teach students how to design, build, and run a robot. The diverse topics included computer models and simulation, biosensors and instrumentation, graphical tracking and computer scheduling, new methods in plant ecology, automation and robotics, Web-based distance diagnostic and recommendation system, GIS and geospatial analysis, and greenhouse environmental control. An individual speaker presented one topic each week with students also visiting some speaker's labs. The students did active, hands on learning through assignments on computer simulations (STELLA simulation language) and graphical tracking (UNH FloraTrack software). They also built, programmed, and ran robots using Lego Mindstorms robotic kits. The course was evaluated using the Univ.'s CAFE system. There were also open-ended questions for student input. On a scale of 1 (strongly disagree) to 5 (strongly agree), mean scores of the 20 CAFE questions ranged from 3.71 to 4.75 with an overall mean of 4.22. When comparisons to other TPSS courses were possible, this course had a higher mean score for four out of seven questions. Course evaluations indicated this special topics course was important and valuable in helping enhance the students' learning experience.

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A simulation model consists of equations that represent the important relationships between components in a system, e.g., a plant or plant part. One of the purposes of simulation models is to simulate plant growth or plant growth processes to help further our understanding of plant growth and development. Simulation models are mechanistic or process based models that account for the physiological processes occurring in the system.

Model development involves several steps. We define the problem and defuse the system, its entities, their attributes, and important relationships. A conceptual model is often expressed visually in a relational diagram showing the components and their relationships. This diagram is formally expressed as a simulation model through the use of equations repenting the relationships in the system. We often make assumptions regarding the components and their relationships to simply the model or because of a lack of knowledge. Simulation models are generally written using a simulation language such as CSMP or STELLA® or with a programming language such as FORTRAN or BASIC. The model is verified through checking the appropriateness of the relationships and the integrity of the computer program. The model is then validated through seeing bow well it simulates the behavior of the system. Simulation models provide additional insights by enabling us to ask “What if” questions by changing of the conditions of the model and seeing the resulting changes in plant growth.

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Crop modeling encompasses the use of mathematics, statistics, and equations to describe quantitatively crop growth and development. It can be useful tool to describe, quantify, and predict crop growth, development, and phenology. Crop models fall into two general classes—statistical (empirical) or mechanistic (physiological)—or they may be a combination of the two. The model type depends upon several factors including the objectives of the modeler, understanding of underlying physiological processes, and availability of data. Model development proceeds from a preliminary conceptual model through formalization into a mathematical model. Models are later verified, and validated, if possible. Model development is an iterative process with continual refinement as more data becomes available and understanding increases. Simulations are dynamic models that follow the growth and development of crops over time. They are more mechanistic in nature and involve changes in measurable quantities of the crop as affected by changes in rates of physiological processes.

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Abstract

The objective of this symposium was to present current information on the physiological and hormonal mechanisms of dormancy and rest in buds and seeds of temperate plants. Papers in the symposium provide current information on new terminology on dormancy; rest-breaking effects of chilling on seeds and buds; hypotheses of apical dominance, auxin transport, and apical dominance; effect of environmental factors on dormancy development; mechanisms of dormancy breaking agents; and role of abscisic acid in bud dormancy.

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A shade experiment for pruned coffee trees was conducted on Maui, Hawaii, in 1996. Nine-year-old `Guadalupe' trees were stumped at 70 cm above the ground, and three main verticals were allowed to remain on the main trunk. Each stumped tree was randomly selected and covered with shade cloth. The shade cloths were 30%, 50%, and 70% shade, and each shade structure had a length × width × height of 1.5 × 1.5 × 2.5 m. Data were collected in 1997. In general, the basal diameters of the verticals were similar in all treatments, as were the lengths of the verticals. The total number of laterals in the full-light treatment was slightly more than that of the other treatments. The numbers of flowering laterals were similar in all treatments. The numbers of fruit per tree in the full light, 30%, 50%, and 70% shade treatments were 1876, 3434, 2399, and 403, respectively. Fruit per flowering node was the best index relating to yield. Fruit per node was highest under 30% shade, followed by full light and 70% shade. At the beginning, fruit ripened faster in the full light treatment than in the other treatments, but at the end of September, fruit in 70% shade ripened slower than the other treatments. Therefore, after stumping, coffee trees grew best under 30% shade. For coffee, pruning under the field condition, stumping every other row of trees may be a satisfactory way to obtain the best yield in the future.

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It is difficult to estimate the total leaf area of coffee plants with accuracy due to the large number of leaves and the high leaf density of the plant canopy. In 1996, on Maui, Hawaii, 98 leaves of various sizes were randomly collected for each of five cultivars of Coffea arabica L. The cultivars used were `Guadalupe', `Guatemalan', `Mokka', `Red Catuai', and `Yellow Caturra'. Leaf length, width, and area were measured. Seventy-five leaves were used to develop leaf area models, and the remaining leaves were used to test the accuracy of the models using a 1:1 line. We then developed leaf area devices (LADs), which were made of sheet plastic and shaped to resemble coffee leaves. There were three groups of areas in the leaf area devices, based on leaf sizes. Total leaf area (TLA) contained three components. Each component related to the mean leaf area (k) and the number of leaves (n) in that group. The model for the total leaf area was: TLA = k1n1 + k2n2 + k3n3, where k is a constant in each group. The estimation errors for the different cultivars ranged from 5.6% to 12.3% for 1-year-old plants (four cultivars) and from 1.9% to 7.8% for mature plants (five cultivars). By using the LADs and counting the number of leaves, we can obtain the total leaf area for coffee plants in the field.

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