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Ronald W. Moore, K.M. Eskridge, P.E. Read, and T.P. Riordan

The concept that greater callus mass will induce competence was investigated. The second most immature nodal segments were removed from heavily fertigatcd greenhouse grown plants. Shoots initiated from those nodes were only cut back to one-third their total length. They were subjected to the following treatments: (1) dicamba from 1μM to 5μM in increments of 1.0; (2) B5 medium salt concentrations from 1/3x to 5/3x in increments of 1/3; (3) sucrose levels from 2% to 10% in increments of 2; (4) casein hydrolysate from 0 to 200mg/l in increments of 50. The experiment consisted of twenty-five different treatment combinations in a central composite rotatable second order design. Explants were placed in continuous cool white fluorescent light at 26°C.

Dicamba, B5 salts, and sucrose had significant effects on callus mass (p<.12), while casein hydrolysate had no notable effects on callus mass (p ≥ .57). It was determined that optimum response occurred at 5/3x concentration of B5 salts, 10% sucrose, and 5.0μM dicamba. White, compact calli were observed in treatment combinations that yielded callus fresh weights of two-hundred milligrams or higher.

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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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Abdoulaye Traore, Zizhuo Xing, Amy Bonser, and John Carlson

A successful tissue culture initiation step often begins with effective explant sterilization. To improve douglas fir bud culture initiation, five sterilization treatments (20% bleach, 100% bleach, 3 second flaming, 5 second flaming, and self-extinguishing flaming) were evaluated for their effectiveness on winter and spring bud sterilization. The 20% and 100% bleach treatments resulted in the highest percentage of healthy bud cultures (>90% for winter buds). Spring buds showed a higher level of contamination with 20% bleach sterilization (36%) than did winter buds (1%). Successful sterilization was also achieved by flaming, but bud injury was observed. Increased flaming time caused a decrease in the percentage of healthy actively growing buds. The percentage of healthy bud cultures after 3 second flaming, 5 second flaming and self-extinguishing-flaming (9 to 14 s) were 66%, 59%, and 10% respectively. In addition, sterilization by either approach required subsequent bud dissection to remove the outer scales; otherwise most buds were lost to contamination. When sterilization was followed by bud dissection, contamination rates for winter buds were <2% for all treatments. After successful sterilization and culture initiation, bud expansion was the highest (50% to 98%) in the presence of low concentrations of BA (0 to 0.045 μmol·L–1), while high concentrations of BA (0.448 to 4.527 μmol·L–1) reduced bud expansion (0% to 60%), but promoted bud multiplication.

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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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Raymond P. Chée, Daniel I. Leskovar, and Daniel J. Cantliffe

Embryogenic callus growth of sweetpotato [Ipomoea batatas (L.) Lam.] was selectively enhanced by subculture on basal callus proliferation medium modified to contain 15 mm NH4NO3. Embryogenic callus production was doubled on basal callus proliferation medium modified to contain 60 mm K+, while nonembryogenic callus production was reduced 40%. Additions of up to 40 mm NaCl to basal callus proliferation medium did not affect callus proliferation. The development of embryos from calli subculture to embryo production basal medium was unaffected by the KCl or NaCl treatments of the callus proliferation phase. However, embryo production was increased by subculturing callus from callus proliferation medium containing 20 mm NH4 + to embryo production medium containing 10 mm NH4 + Our results demonstrate that changes in mineral nutrition, in addition to growth regulator differences between callus proliferation and embryo production media, are important factors in sweetpotato somatic embryogenesis.

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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