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D.C. Ferree, S.J. McArtney, and D.M. Scurlock

Vines of container grown `DeChaunac', `Vidal blanc', `Seyval blanc' and `Chambourcin' grapes were subjected to 5 days of 80% shade at prebloom, bloom or 2 and 4 weeks after bloom. Fruit set, cluster weight, berries per cluster and juice components [soluble solids concentration (SSC), pH and titratable acidity] of `DeChaunac' and `Vidal blanc' were not affected by a short period of intensive shade. `Chambourcin' was sensitive to a shade period near the time of bloom for most of the aforementioned factors, while `Seyval blanc' was intermediate in sensitivity. Shot (green, hard, and undersized) berries of `Chambourcin' and `Seyval blanc' were increased by a 5-day period of shade 2 or 4 weeks after bloom. In a second study, container-grown `Chambourcin' on 3309C (V. riparia × V. rupestris) with one or two clusters and `Vidal blanc' with one cluster were subjected to the following light regimes beginning at bloom for 5 weeks: supplemental light, ambient greenhouse light and 30%, 50% or 80% shade. Yield, fruit set, specific leaf weight (leaf dry weight/leaf area), saturation index, and total leaf chlorophyll increased linearly with increasing irradiance. `Chambourcin' juice pH, SSC, leaf chlorophyll a/b ratio, cluster color development and hue angle decreased as irradiance increased, likely related to crop reduction. Responses in `Vidal blanc' followed similar trends, but differences were not as great. Results demonstrate that light is an important determining factor in fruit set of French-American hybrid grapes and fruit set of some cultivars are sensitive to short periods of intense shade.

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(DLI) on several growth parameters measured for tomato seedlings propagated in a glass-glazed greenhouse in West Lafayette, IN, under different lighting treatments. The treatments evaluated were natural solar light only (control); natural + supplemental

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Dominique-André Demers, Serge Yelle, and André Gosselin

Exposure of tomato and pepper plants to long photoperiods (20 hours or more for tomato; 24 hours for pepper) results in leaf chlorosis (tomato), leaf deformities (pepper), and decreased growth and productivity (both species). Some researchers have suggested that excessive starch accumulation in the leaves could be the cause of the negative effects. We observed that tomato and pepper plants do accumulate more starch in their leaves when grown under a long photoperiod (24 hours) compared to a shorter one (16 hours). However, our results indicated that these accumulations were not caused by a limited sink strength but by an alteration of the carbon metabolism at the leaf level. In our last experiment, we studied the activity of enzymes [sucrose phosphate synthase (SPS), sucrose synthase (SS), invertase] of leaf carbon metabolism in tomato and pepper plants grown under different photoperiods (natural, natural + supplemental light of 100 μmol·m-2·s-1 during 16 and 24 hours). We observed a 10% to 15% decrease in leaf SPS activity in tomato (not in pepper) plants grown under a 24-hour photoperiod. In both species, invertase and SS activities were not affected by photoperiod treatments. In tomato plants grown under a 24-hour photoperiod, the decrease in SPS activity corresponded to the appearance of leaf chlorosis (6 to 7 weeks after the beginning of treatments). Therefore, it appears that leaf carbon metabolism could be involved in the development of negative effects of long photoperiod in tomato plants, but not in pepper plants. The fact that photoperiod had no apparent effect on leaf carbon metabolism of pepper may explain why this species can tolerate longer photoperiods than tomato plants.

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Claudine Menard, Blanche Dansereau, and Yves Desiardins

The general objective of this project is to study the impact of pre-harvest growth conditions (supplementary lighting; HPS, MH: fertilization on the biochemistry and post-harvest quality of greenhouse roses. On January 25, 1991, 288 plants (Rosa × hybrida: `Royalty', `After Glow' and `Obsession') 3X caliber were planted in pots. A split-split plot experimental design made up of four blocks was used. Light treatments (3) were in main plot while fertilization (2) and cultivars (3 cultivars; 4 plants per cultivar) were in sub-plots and sub-sub-plots respectively. The two fertilization regimes used had respectively a nitrogen potassium ratio of 150N:300K ppm (F1) and 300N:300K ppm (F2). Three light treatments (ambient light conditions (control), and ambient light conditions + PPF of 100 μmolm-2 s-1 supplied by 400 W HPS and MH lamps) were compared. Since the beginning of this experiment 14 431 flowering stems have been harvested. Only the results obtained with `Royalty' and `After Glow' will be presented for the following harvest periods; (1) October 6 to December 6, 1991; (2) January 30 to April 22, 1992. Yields were significantly affected by light and/or fertilization regardless of cultivar. Preliminary results indicate that stems harvested from HPS and MH light treatments combined to fertilization regime F1 had a longer vase life than those grown with F2. Preliminary results indicate that HPS lamps significantly increased vase life compared to MH. The level of ABA was higher under MH then under HPS lamps at to and this was similar for all cultivars. Furthermore, when supplemental light was combined to the F1 fertilization a lower level of ABA was obtained. Low levels of ABA are correlated to longer vase life expectancy.

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Geoffrey Weaver and Marc W. van Iersel

dimmability have the potential to reduce the electricity costs associated with providing supplemental light, and to increase the efficiency with which supplemental light is used for promoting plant growth. These adaptive, or dynamic, supplemental LED lighting

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Qinglu Ying, Yun Kong, and Youbin Zheng

. (1969) found that low-intensity supplemental light is efficient for carbon assimilation and plant growth, and ≈13 μmol·m −2 ·s −1 supplemental light is five-times more efficiently used during nighttime compared with daytime in terms of CO 2 fixation

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Kim D. Bowman and Ute Albrecht

through research, such as using clean stock ( Vidalakis et al., 2010 ) and nutritional management ( Bernardi et al., 2015 ; Maust and Williamson, 1994 ). Supplemental light to increase daylength and accelerate plant production is one component of the

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Alexander Miller, Petrus Langenhoven, and Krishna Nemali

, respectively. An average photoperiod was 10.5 h in the NSL treatment and 24 h in the PSL and WSL treatments. Fig. 1. Spectral composition of supplemental light provided to plants at nighttime in the study (PSL = sunlight with narrow-spectrum supplemental light

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Ricardo Hernández and Chieri Kubota

., Helsinki, Finland) installed in the middle of the experimental area. All sensors were connected to a CR-1000 data logger with a multiplexer (Campbell Scientific, Logan, UT) scanned every minute to record averages at 10-min intervals. Supplemental light

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Christopher J. Currey and John E. Erwin

daily light integral (DLI) on dry weight gain on six kalanchoe species. Discussion Our results are in agreement with the previous reports on the effect of DLI or supplemental light on other potted and bedding plants ( Carvalho et al., 2006 ; Erwin and