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Leonardo Lombardini, Hermann Restrepo-Diaz, and Astrid Volder

. Photosynthetic light response curves. Light response curves were performed on three leaves per leaf type and cultivar using a portable IR gas analyzer (LI-6400; LI-COR, Lincoln, NE) equipped with a standard LI-6400, 2 × 3-cm leaf chamber and a red/blue light

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Sydney Lykins, Katlynn Scammon, Brian T. Lawrence, and Juan Carlos Melgar

parameters, and light response curves. The photosynthetic light responses of the four cultivars were determined between the months of May and July during three sampling periods: 1) BH, 2) during PH, and 3) when nearly all or all fruit had naturally fallen

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Richard J. Campbell, Richard P. Marini, and Jeffrey B. Birch

Light response curves for gas exchange characteristics were developed for spur leaves of `Stayman' and `Delicious' apple (Malus domestica Borkh.) from interior, intermediate, and exterior canopy positions throughout the season. At full bloom (FB), before full leaf expansion, exterior leaves had higher maximum rates of net photosynthesis (Pn), and a statistically different Pn light response curve than the interior leaves. Intermediate leaves had intermediate Pn rates and light response curves. Pn light response curves for all three `Delicious' canopy positions differed from each other from FB + 6 weeks until the end of the season. Interior leaves had maximum Pn rates of only 50% to 60% of those for the exterior leaves from FB + 10 weeks until the end of the season. Light saturation levels were higher for the exterior leaves than for interior or intermediate leaves. Exterior leaves had a tendency throughout the season for higher quantum efficiency of Pn at subsaturating light levels than interior or intermediate leaves. Stomatal conductance was higher for the exterior than the interior or intermediate leaves of `Delicious' on all dates. Water-use efficiency was equivalent among all leaves. Exterior leaves had higher specific leaf weight, dark respiration rates, and incident light levels on all dates than interior or intermediate leaves.

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Jeffrey T. Baker, Marvin L. Baker, D. Ron Earhart, Leonard M. Pike, Kil S. Yoo, and Roger Horns

Eight individual potatoes, exhibiting a wide range of quality characteristics, were cloned at the Texas A&M Vegetable Improvement Center, College Station, Tex., in order to produce a large number of slips for field trials. Leaf photosynthetic light response for six of these clonal selections was determined during a greenhouse experiment conducted at the Texas A&M Univ. Agricultural Research and Extension Center at Overton, Tex. Photosynthesis data were fit to a rectangular hyperbola in order to estimate light saturated leaf photosynthetic rate (Amax), quantum efficiency (QE), and dark respiration rate (Rd). Significant differences (P ≥ 0.05) were detected in all three of these parameter estimates among the six clonal selections. Parameter estimates ranged from 23.4 to 28.8 μmol (CO2) m-2·s-1, 0.056 to 0.071 mol (CO2)/mol (photons), and –0.9 to –2.0 μmol (CO2) m-2·s-1 for Amax, QE, and Rd, respectively. However, these differences were not clearly related to quality characteristics determined for these clones in field trials.

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Peter R. Hicklenton, Julia Y. Reekie, Robert J. Gordon, and David C. Percival

Seasonal patterns of CO2 assimilation (ACO2), leaf water potential (ψ1) and stomatal conductance (g1) were studied in three clones (`Augusta', `Brunswick', and `Chignecto') of lowbush blueberry (Vaccinium angustifolium Ait.) over two growing seasons. Plants were managed in a 2-year cycle of fruiting (year 1) and burn-prune (year 2). In the fruiting year, ACO2 was lowest in mid-June and early September. Rates peaked between 10 and 31 July and declined after fruit removal in late August. Compared with the fruiting year, ACO2 in the prune year was between 50% and 130% higher in the early season, and between 80% and 300% higher in mid-September. In both years, however, mid-season maximum ACO2 for each clone was between 9 and 10 μmol·m–2·s–1CO2. Assimilation of CO2 increased with increasing photosynthetic photon flux (PPF) to between 500 and 600 μmol·s–1·m–2 in `Augusta' and `Brunswick', and to between 700 and 800 μmol·s–1·m–2 in `Chignecto'. Midday ψ1 was generally lower in the prune year than in the fruiting year, reflecting year-to-year differences in soil water content. Stomatal conductance (g1), however, was generally higher in the prune year than in the fruiting year over similar vapor pressure deficit (VPD) ranges, especially in June and September when prune year g1 was often twice that observed in the fruiting year. In the fruiting year, g1 declined through the day in response to increasing VPD in June, but was quite constant in mid-season. It tended to be higher in `Augusta' than in the other two clones. Stomatal closure imposes limitations on ACO2 in lowbush blueberries, but not all seasonal change in C-assimilative capacity can be explained by changes in g1.

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Toshio Shibuya, Ryosuke Endo, Yuki Kitamura, Yoshiaki Kitaya, and Nobuaki Hayashi

light with high R:FR light on the potential photosynthetic advantage of transplants, we investigated the photosynthetic light responses of cucumber ( Cucumis sativus L.) seedlings grown under fluorescent lamps with high R:FR light and compared them with

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Lingyan Chen, Jinli Lai, Tianyou He, Jundong Rong, Muhammad Waqqas Khan Tarin, and Yushan Zheng

pigments, chloroplast structure, and photosynthesis light-response curve in different phenotypes of variegated temple bamboo to understand the differences in leaf color and to explore the relationship among photosynthetic pigments, chloroplast structure

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Geoffrey Weaver and Marc W. van Iersel

). Thus, chlorophyll fluorescence measurements provide a convenient, rapid, accurate, and robust means of evaluating photochemical responses to PPFD . Light response curves collected using chlorophyll fluorescence measurements are typically performed over

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Min Wu and Chieri Kubota

stage. The overall difference in g l between treatments was smaller during the reproductive growth stage than that during the vegetative growth stage. Photosynthetic light response. The photosynthetic light response curves during the vegetative growth

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Rebecca M. Harbut, J. Alan Sullivan, John T.A. Proctor, and Harry J. Swartz

system with an integrated light source to maintain constant light, temperature, and CO 2 during measurements. Light response curves were generated using light levels between 100 and 2000 μmol·m −2 ·s −1 at 100-μmol·m −2 ·s −1 intervals. Single leaflet