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Terence L. Robinson

`Empire'/M.26 apple trees which were planted in 1978 and trained to a Y-trellis were pruned differentially from 1989-1993. Trees were dormant pruned by removing from 1-4 scaffold limbs. The annual increase in trunk cross-sectional area (TCA), and the number and length of shoots removed during summer pruning increased linearly as the severity of pruning increased. The number of shoots removed during summer pruning from the most severe pruning treatment was more than double that of the least severe treatment Cumulative fruit number and yield were reduced linearly with increasing severity of pruning while average fruit size was increased only slightly by severity of pruning. Light interception was reduced with increasing severity of pruning. Tree efficiency of converting light energy into fruit (g fruit/MJ PAR intercepted) was linearly reduced with increasing pruning severity. Most of the reduction in conversion efficiency appeared to be due to reduced partitioning of resources into fruit since partitioning index (g fruit/unit increase in TCA) was more highly correlated to pruning severity than to conversion efficiency. Conversion efficiency and partitioning index accounted for a greater portion of the yield variation than did light interception indicating that the influence of pruning on yield was more a function of changing internal physiology than reduced light interception.

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Jonathan M. Frantz and Cary A. Mitchell

A major source of power consumption in controlled-environment crop production is plant-growth lighting. Methods developed to minimize this source of power consumption will reduce the negative environmental impact of crop production through more-efficient management of non-renewable resources. One such method uses “intracanopy lighting,” in which the plants are allowed to grow through multiple levels of low-intensity lamps to irradiate the understory that normally is shaded when traditional overhead lighting is used. Early results with cowpea (Vigna unguiculata L. Walp `IT87D-941-1') indicate a significant reduction in net power consumption within a given growth area or volume while enhancing the harvest index (HI = percent edible biomass). Incorporation of mylar reflectors and manipulation of lamp geometries for more-efficient use of available photosynthetically active radiation, while maintaining low power consumption are the focus of present experiments. Photosynthetic rates by leaves of different ages and positions within the canopy are measured as a way of determining lighting efficiency. The productivity parameters HI, edible yield rate (EYR = gDW × m–2 × day–1), yield efficiency rate (YER = gDW edible × m–2 × day–1 [gDW non-edible]-1), energy conversion efficiency (ECE = EYR × [kW·h]–1), and energy partition efficiency (EPE = YER × [kW·h]–1) express the costs of edible biomass production in terms of the spatial, temporal, energetic, and non-edible biomass penalties. [Research supported in part by NASA grant NAGW-2329.]

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R.J. Bula, R.C. Morrow, T.W. Tibbitts, D.J. Barta, R.W. Ignatius, and T.S. Martin

Development of a more effective radiation source for use in plant-growing facilities would be of significant benefit for both research and commercial crop production applications. An array of light-emitting diodes (LEDs) that produce red radiation, supplemented with a photosynthetic photon flux (PPF) of 30 μmol·s-1·m-2 in the 400- to 500-nm spectral range from blue fluorescent lamps, was used effectively as a radiation source for growing plants. Growth of lettuce (Lactuca sativa L. `Grand Rapids') plants maintained under the LED irradiation system at a total PPF of 325 μmol·s-1·m-2 for 21 days was equivalent to that reported in the literature for plants grown for the same time under cool-white fluorescent and incandescent radiation sources. Characteristics of the plants, such as leaf shape, color, and texture, were not different from those found with plants grown under cool-white fluorescent lamps. Estimations of the electrical energy conversion efficiency of a LED system for plant irradiation suggest that it may be as much as twice that published for fluorescent systems.

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Michael P. Dzakovich, Celina Gómez, and Cary A. Mitchell

producing large amounts of radiant waste heat. Some of the most efficient HPS lamps have an energy conversion efficiency of 1.70 µmol·J −1 , which is commensurate with some of the most efficient LED arrays (1.66 µmol·J −1 ) presently available ( Nelson and

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Bandara Gajanayake, K. Raja Reddy, Mark W. Shankle, and Ramon A. Arancibia

. Belehu et al. (2004) also observed that slips produce adventitious roots and some of those roots develop into storage roots. To date, there are no studies on conversion efficiency of storage roots from the total roots produced under different

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Haiyan Zhao, Haiying Liang, Yibing Chu, Congcong Sun, Ning Wei, Mengnan Yang, and Caixia Zheng

maximum light energy conversion efficiency of PSII after adaptation to darkness, indicating that photoinhibition reflects the efficiency of light energy conversion in the active center of PSII ( Lichtenthaler and Burkart, 1999 ). Φ PSII reflects the

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Jeffrey Adelberg, Maria Delgado, and Jeffrey Tomkins

.4 g·L −1 in tissue DW. Therefore, Hemerocallis spp. in liquid medium fixed 74% of the sucrose mass as dry matter, with the remainder exhausted as CO 2 and water, or remaining otherwise uncounted. Plant cells have roughly 50% conversion efficiency

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M. Carmen González-Mas, M. José Llosa, Antonio Quijano, and M. Angeles Forner-Giner

a reduction in energy conversion efficiency of PSII (Φ PSII ) for Carrizo citrange during fluorescence kinetics, because its yield was significantly lower compared with the other rootstocks 2 min into the kinetics study ( Fig. 1A ). Moreover, the

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Brad Geary, Corey Ransom, Brad Brown, Dennis Atkinson, and Saad Hafez

conversion efficiency from metam sodium to methyl isothiocyanate ( Draper and Wakeham, 1993 ; Geddes et al., 1995 ). The difference in the amount of a.i. applied per acre of biofumigant plants and metam sodium is large and is likely the contributing factor

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Sanjeev K. Bangarwa, Jason K. Norsworthy, and Edward E. Gbur

species of the mustard family. Moreover, the amount of glucosinolate production and glucosinolate to isothiocyanates conversion efficiency, which are highly dependent on soil and environmental conditions and management practices, governs the release of