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Luca Corelli-Grappadelli, Gianfranco Ravaglia, and Eugenio Magnanini

Training system efficiency may be defined as the ratio of fruit produced to the amount of light intercepted by the canopy. In apple, a positive, linear relationship between yield and light intercepted is generally found, but in peach similar data are hard to come by. This paper reports data from an ongoing training systems trial now in the 7th year, with trees trained as Y, palmette, and delayed vase. During the life of the orchard, light interception has been measured for the different tree shapes, the yields have been recorded, and, in some years, whole-canopy gas exchanges of cropping trees have been measured. In general, the trees have been intercepting light in amounts proportional to canopy shape and tree density, with the Y (planted at higher density) intercepting more light than the other two systems, which appear more comparable to each other, despite the fact that they intercept light during the day in different ways, with the delayed vase exposing more or less the same leaves to incoming light during most of the day. Cropping has followed the amounts of light intercepted, with higher yields for the Y, without appreciable differences in fruit quality traits. The data accumulated so far indicate furthermore that the palmette and the delayed vase, despite slightly different light interception potentials (lower for the palmette), have similar yields. This might depend in part on the fact that these two systems intercept light according to different patterns during the day, with the palmette—which distributes the light intercepted in a more even fashion between the two sides—perhaps at an advantage over the vase in terms of managing the stress of excessive light (heat) loads during the central hours of the day. Whole canopy Carbon exchange data have been found to be in agreement with the patterns of light interception.

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Terence L. Robinson and Alan N. Lakso

Bases of orchard productivity were evaluated in four 10-year-old apple orchard systems (`Empire' and `Redchief Delicious' Malus domestics Borkh. on slender spindle/M.9, Y-trellis/M.26, central leader/M.9/MM.111, and central leader/M.7a). Trunk cross-sectional areas (TCA), canopy dimension and volume, and light interception were measured. Canopy dimension and canopy volume were found to be relatively poor estimators of orchard light interception or yield, especially for the restricted canopy of the Y-trellis. TCA was correlated to both percentage of photosynthetically active radiation (PAR) intercepted and yields. Total light interception during the 7th to the 10th years showed the best correlation with yields of the different systems and explained most of the yield variations among systems. Average light interception was highest with the Y-trellis/M.26 system of both cultivars and approached 70% of available PAR with `Empire'. The higher light interception of this system was the result of canopy architecture that allowed the tree canopy to grow over the tractor alleys. The central leader/M.7a had the lowest light interception with both cultivars. The efficiency of converting light energy into fruit (conversion efficiency = fruit yield/light intercepted) was significantly higher for the Y-trellis/M.26 system than for the slender spindle/M.9 or central leader/M.9/MM.111 systems. The central leader/M.7a system bad the lowest conversion efficiency. An index of partitioning was calculated as the kilograms of fruit per square centimeter increase in TCA. The slender spindle/M.9 system had significantly higher partitioning index than the Y-trellis/M.26 or central leader/M.9/MM.111. The central leader/M.7a system had the lowest partitioning index. The higher conversion efficiency of the Y/M.26 system was not due to increased partitioning to the fruit; however, the basis for the greater efficiency is unknown. The poor conversion efficiency of the central leader/M.7a was mostly due to low partitioning to the fruit. The Y-trellis/M.26 system was found to be the most efficient in both intercepting PAR and converting that energy into fruit.

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Marc W. van Iersel and Lynne Seymour

Respiration is important in the overall carbon balance of plants, and can be separated into growth (Rg) and maintenance respiration (Rm). Estimation of Rg and Rm throughout plant development is difficult with traditional approaches. Here, we describe a new method to determine ontogenic changes in Rg and Rm. The CO2 exchange rate of groups of 28 `Cooler Peppermint' vinca plants [Catharanthus roseus (L.) G. Don.] was measured at 20 min intervals for 2 weeks. These data were used to calculate daily carbon gain (DCG, a measure of growth rate) and cumulative carbon gain (CCG, a measure of plant size). Growth and maintenance respiration were estimated based on the assumption that they are functions of DCG and CCG, respectively. Results suggested a linear relationship between DCG and Rg. Initially, Rm was three times larger than Rg, but they were similar at the end of the experiment. The decrease in the fraction of total available carbohydrates that was used for Rm resulted in an increase in carbon use efficiency from 0.51 to 0.67 mol·mol-1 during the 2-week period. The glucose requirement of the plants was determined from Rg, DCG, and the carbon fraction of the plant material and estimated to be 1.39 g·g-1, while the maintenance coefficient was estimated to be 0.031 g·g-1·d-1 at the end of the experiment. These results are similar to values reported previously for other species. This suggests that the use of semicontinuous CO2 exchange measurements for estimating Rg and Rm yields reasonable results.

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Yan-Ling Zheng and Huan-Cheng Ma

incubation. Seedling growth components were calculated as outlined by Soltani et al. (2006) . The weight of used (mobilized) seed reserve was calculated as the dry weight of the original seed minus the dry weight of the seed remnant. Conversion efficiency of

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Arend-Jan Both, Bruce Bugbee, Chieri Kubota, Roberto G. Lopez, Cary Mitchell, Erik S. Runkle, and Claude Wallace

conversion efficiency is included on the label. The PAR conversion efficiency was calculated as the ratio of the radiant energy output (watts) across the PAR wave band divided by the total electric energy consumption of the lamp (watts). Using the PAR

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Geoffrey Weaver and Marc W. van Iersel

driver still consumed some power. The estimated increase in dry weight per Joule used for supplemental lighting (conversion efficiency) was determined by first subtracting the mean dry weight of the controls for each experiment, averaged over all five

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Celina Gómez, Robert C. Morrow, C. Michael Bourget, Gioia D. Massa, and Cary A. Mitchell

than the average 31 kWh per day consumed for the LED-ICL treatment (2 reps × 4 towers). Results for kilowatthours per gram of fruit FW indicated that the electrical conversion efficiency of LED-ICL into fruit biomass was 75% higher than that for HPS

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María José Gómez-Bellot, Pedro Antonio Nortes, María Fernanda Ortuño, María Jesús Sánchez-Blanco, Karoline Santos Gonçalves, and Sebastián Bañón

equipped with a fluorometer (6400-40; LI-COR Inc., Lincoln, NE). The energy conversion efficiency in photosystem II (F′ v /F′ m ) was determined during the day in the same plants in which gas exchange was measured. The maximal photochemical efficiency of

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Joshua R. Gerovac, Joshua K. Craver, Jennifer K. Boldt, and Roberto G. Lopez

light sources, including high photoelectric conversion efficiencies, narrowband spectral distribution, low thermal output, and adjustable LIs ( Yeh and Chung, 2009 ). These advantages may become even more prevalent and defined as technology and research

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Natalie R. Bumgarner, Mark A. Bennett, Peter P. Ling, Robert W. Mullen, and Matthew D. Kleinhenz

. Lettuce shoot fresh weight and aerial and subsurface growing degree days [GDD; 5 °C (41.0 °F) base] conversion efficiency measured ≈4 weeks after sowing in field and high-tunnel setting raised beds containing red romaine leaf lettuce in Wooster, OH, in