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Rebecca G. Bichsel, Terri W. Starman and Yin-Tung Wang

Experiments were conducted to determine how nitrogen (N), phosphorus (P), and potassium (K) rate and fertilizer termination time affect the growth and flowering of a Dendrobium nobile Lindl. hybrid, Dendrobium cv Red Emperor ‘Prince’. Nitrogen, P, and K were tested in separate experiments as a factorial combination of five rates and three termination dates (1 Sept., 1 Oct., and 1 Nov. 2005). Nitrogen and K rates were 0, 50, 100, 200, and 400 mg·L−1. Phosphorus rates were 0, 25, 50, 100, and 200 mg·L−1. Levels of the nutrients not being tested were held constant. For all nutrients, ending fertilization on 1 Sept. resulted in greater or similar pseudobulb thickness compared with ending fertilization on 1 Oct. or 1 Nov. Pseudobulbs grew taller as the N rate increased, peaking at 100 and 200 mg·L−1. There were interactions between the N rate and fertilizer termination time on all reproductive characteristics. For all fertilizer termination times, flower number increased once N was applied. When ended on 1 Nov., 200 and 400 mg·L−1 N caused a delay to reach anthesis. All P rates resulted in taller plants with equally more nodes when compared with 0 mg·L−1. As the K rate increased from 0 to 100 mg·L−1, plant height increased, with no further increase at higher rates. The number of leaves remaining increased as N and K rates increased up to 200 mg·L−1. Total flower number and flowering node number increased as the K rate increased to 100 mg·L−1 (terminated on 1 Sept.) or 50 mg·L−1 (terminated on 1 Oct. or 1 Nov.). In the fourth experiment, only N was ended at four termination times, whereas all other nutrients continued to be supplied until flowering. Control plants received all fertilizer elements until flowering. The duration of N application did not affect vegetative or flowering characteristics. No aerial shoots were observed as a result of prolonged application of N at all rates. In summary, 100 mg·L−1 N, 25 mg·L−1 P, and 100 mg·L−1 K are recommended for optimal vegetative growth and reproductive development of Dendrobium cv Red Emperor ‘Prince’.

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Michael Raviv, J. Heinrich Lieth, David W. Burger and Rony Wallach

Physical characteristics of two media were studied concerning water availability to roots, as reflected in specific transpiration rate, stomatal conductance, and specific growth rate of very young leaflets of `Kardinal' rose (Rosa ×hybrida L.), grafted on Rosa canina L. `Natal Brier'. Plants were grown in UC mix [42% composted fir bark, 33% peat, and 25% sand (by volume)] or in coconut coir. Water release curves of the media were developed and hydraulic conductivities were calculated. Irrigation pulses were actuated according to predetermined media moisture tensions. Transpiration rate of plants was measured gravimetrically using load cells. Specific transpiration rate (STR) was calculated from these data and leaf area. STR and stomatal conductance were also determined using a steady-state porometer. Specific growth rate (RSG) of young leaflets was calculated from the difference between metabolic heat rate and respiration rate, which served as an indicator for growth potential. Low STR values found at tensions between 0 and 1.5 kPa in UC mix suggest this medium has insufficient free air space for proper root activity within this range. Above 2.3 kPa, unsaturated hydraulic conductivity of UC mix was lower than that of coir, possibly lowering STR values of UC mix-grown plants. As a result of these two factors, STR of plants grown in coir was 20% to 30% higher than that of plants grown in UC mix. STR of coir-grown plants started to decline only at tensions around 4.5 kPa. Yield (number of flowers produced) by coir-grown plants was 19% higher than UC mix-grown plants. This study demonstrated the crucial role of reaching sufficient air-filled porosity in the medium shortly after irrigation. It also suggests that hydraulic conductivity is a more representative measure of water availability than tension.

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Elisabet Claveria, Jordi Garcia-Mas and Ramon Dolcet-Sanjuan

Homozygous doubled haploid lines (DHLs) from new cucumber (Cucumis sativus L.) accessions could be useful to accelerate breeding for resistant varieties. DHLs have been generated by in vitro rescue of in vivo induced parthenogenic embryos. The protocol developed involves the following: 1) induction of parthenogenic embryos by pollinating with pollen irradiated with a Co60 γ-ray source at 500 Gy; 2) in vitro rescue of putative parthenogenic embryos identified by their morphology and localized using a dissecting scope or X-ray radiography; 3) discrimination of undesirable zygotic individuals from the homozygous plants using cucumber and melon SSR markers; 4) determination of ploidy level from homozygous plants by flow cytometry; 5) in vitro chromosome doubling of haploids; and 6) acclimation and selfing of selected lines. Codominant markers and flow cytometry confirmed the gametophytic origin of plants regenerated by parthenogenesis, since all homozygous lines were haploids. No spontaneous doubled haploid plants were rescued. Chromosome doubling of haploid plants was accomplished by an in vitro treatment with 500 μm colchicine. Rescue of diploid or chimeric plants was shown by flow cytometry, prior to their acclimation and planting in the greenhouse. Selfing of colchicine-treated haploid plants allowed for the perpetuation by seed of homozygous lines. The high rate of seed set, 90% of the lines produced seed, facilitated the recovery of inbred lines. Despite some limiting factors, parthenogenesis is routinely used in a cucumber-breeding program to achieve complete homozygosity in one generation. Breeding for new commercial hybrid cultivars will be accelerated. DHLs are ideal resources for genomic analyses.

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Chieri Kubota* and Mark Kroggel

Increasing numbers of vegetable growers purchase their transplants from specialized transplant producers. Possible deterioration of transplants during transportation limits the market size as well as the potential sources of high quality transplants. To determine best conditions for transportation of seedlings, tomato (Lycopersicon esculentum; `Durinta') seedlings with visible flower buds were placed for 4 days under varied air temperature (6, 12, or the conventional transportation temperature of 18 °C) and light intensity 0 (conventional darkness) or dim light at 12 μmol·m-2·s-1 PAR). Plants were evaluated for visual quality, photosynthetic capacity, growth and ultimately fruit yield. Lower temperatures and illumination significantly maintained visual quality of the seedlings. Lower temperature maintained high photosynthetic capacity of the seedlings during transportation. Growth and development of the seedlings were significantly affected by higher temperature resulting in significantly delayed growth and development. Number of fruits set on the first truss was significantly reduced when seedlings were at 18 °C during transportation. Overall, simulated transport at 6 °C under light showed the best transportability without experiencing negative impact for the 4-day simulated transportation. Seedlings at 6 °C in darkness and at 12 °C under light and in darkness also showed satisfactory transportability. Seedlings at 18 °C exhibited serious quality deterioration of seedlings, delay in early growth and development, loss of flower buds on the first truss and yield reduction, which agrees with the fact that conventional transportation is currently able to be no longer than 3 days in duration.

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Jeffrey W. Burcaw, Bruce W. Wood and Michael W. Poole

A decision support system (DSS) is described that quantitatively analyzes certain important light climate characteristics of crops planted in discrete canopy, hedgerow, or trellis cropping systems. The DSS facilitates rapid and efficient calculation of the theoretical maximum shading (or, conversely, the theoretical minimum level of insolation) for use in determining the planting pattern that minimizes canopy shading during user-specified temporal intervals. It addresses canopy shading in field plantings within a wide variety of geometric patterns, interplant spacings, canopy sizes and forms, global latitudes, pattern orientations, site reliefs and aspects. Calculations describe insolation characteristics during any hour(s) of the day or day(s) of the year within the range of planting parameters. The DSS functions as a systems tool, or module, for design of the spatial subsystem component of a particular cropping strategy where horticulturally important traits are regulated by the light climate.

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Patrick H. Brown

34 WORKSHOP 2 (Abstr. 672-673) Nutrient Balances in Horticultural Ecosystems: Optimizing Fertilization and Maximizing Environmental Protection Monday, 24 July, 10:00 a.m.-12:00 noon

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K.R. Goldman and C.A. Mitchell

Mineral resources will be recycled in a controlled ecological life-support system (CELSS) deployed in space. N typically is supplied to crops as \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document} or \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}+\mathrm{NO}_{3}^{-}\) \end{document} mixtures. In a CELSS, \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document} will be abundant, but nitrification will require energetically costly chemical or biological \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document} oxidization. Rice is tolerant of \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document} and preferentially absorbs \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document} if provided a 1 \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document}: 1 \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document} ratio in hydroponics. Hybrid rice absorbs more N as \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document} than does inbred rice. To determine how much and in what proportion to \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document} rice will tolerate \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document} and how varying N sources will affect grain yield, semi-dwarf hybrid rice cultivar `Ai-Nan-Tsao' was grown hydroponically in a growth chamber. Nutrient solutions supplied 5 mm N as 40%, 60%, or 80% \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document}, the remainder as \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document}. Periodic analysis of solutions tracked mineral uptake, and solutions were modified to maintain proper concentrations. Treatment stands were harvested 84 to 86 DAP. Across all treatments, yield characteristics were similar but were highest for the border plants, presumably due to greater light absorption. Yield-efficiency rate (YER: grams of grain·per cubed meter per day·[grams inedible shoot biomass]) was 0.09 for all treatments (border) and ranged from 0.03 to 0.05 (interior), Harvest index ranged from 0.28 to 0.30 (border) and 0.26 to 0.39 (interior). Edible yield rate (EYR: grams of grain per cubed meter per day) ranged from 20.97 to 26.45 (border) and 8.52 to 14.96 (interior). The sector provided with 80% \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document} had the highest YER, HI (interior), and EYR (interior), indicating that rice productivity was not limited by high percentages of N supplied as \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document}. Supported by NASA grant NAGW-2329.

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Clinton C. Shock and Feng-Xin Wang

irrigation ( Tjosvold and Schulbach, 1991 ). The nutrients lost in the excess irrigation water have the potential to contaminate groundwater and surface water. Careful irrigation scheduling by SWT provides the grower with techniques to simultaneously optimize

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Joey H. Norikane

of biomass would have the value of $1 million. But, there are significant embedded costs, in terms of time and money, for hybrid vector development and optimization, expression screening of multiple constructs, purification scale-up and process

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Martin M. Williams II

significant interaction between hybrid and plant density ( P ≥ 0.870). Ear yield was optimized at 5.5 plants/m 2 and gross profit margin was optimized at 6.1 plants/m 2 ( Fig. 2 ). If data from growers’ fields reflect actual plant densities that white