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Steven J. McArtney, John D. Obermiller, and Consuelo Arellano

·L −1 metamitron. The maximum potential quantum efficiency of photosystem II (PSII) (Fv/Fm), quantum photosynthetic yield of PSII (ΦPSII), and estimated relative electron transport rate (ETR) were measured on four leaves on each tree. Lower case letters

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Geoffrey Weaver and Marc W. van Iersel

solar noon; open symbols represent measurements taken after solar noon. The regression line represents the equation Φ PSII = 0.171 + 0.643e –0.00178 PPFD , with R 2 = 0.89 and P < 0.0001 (top). Electron transport rate (ETR) of ‘Green Towers’ lettuce

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Marc W. van Iersel, Geoffrey Weaver, Michael T. Martin, Rhuanito S. Ferrarezi, Erico Mattos, and Mark Haidekker

estimate electron transport rate through PSII ( Baker and Rosenqvist, 2004 ; Genty et al., 1989 ). Because chlorophyll fluorescence is relatively easy to measure and provides detailed physiological information, such measurements can be a valuable tool to

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Meijun Zhang, Duanduan Zhao, Zengqiang Ma, Xuedong Li, and Yulan Xiao

were the same as the first experiment for the PM and PA treatments, respectively. The experiment was conducted once. Chlorophyll content, the ratio of variable to maximum chlorophyll fluorescence (F v /F m ), and electron transport rate (ETR) were not

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Shuyang Zhen and Marc W. van Iersel

, and are thus unable to use the absorbed light for photochemistry ( Baker, 2008 ; Maxwell and Johnson, 2000 ). Fig. 2. Light response curves of quantum yield of photosystem II (Φ PSII ) ( A – C ), linear electron transport rate (ETR) ( D – F ), and non

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Chenping Xu and Beiquan Mou

: soil amended with 5% or 10% (v/v) vermicompost. Fig. 6. Effect of vermicompost on spinach leaf photochemical efficiency (F v /F m ; A ), photochemical yield [Y(II); B ], and electron transport rate (ETR; C ) 35 d after transplanting. The values are

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Francesco Loreto, Domenico Tricoli, Mauro Centritto, Arturo Alvino, and Sebastiano Delfine

Short-term fumigation with 1% methanol in air was carried out to investigate effects on the photosynthetic apparatus of horticultural species characterized by leaves with different stomatal distribution. Methanol decreased the photosynthetic capacity of all species. The hypostomatous cherry (Prunus avium L.) was the most sensitive species. Between the two amphistomatous species, the effect was smaller in pepper (Capsicum annuum L. var. annuum) than in melon (Cucumis melo L.). A 4-minute fumigation caused a stronger inhibition of photosynthesis than a 90-second fumigation. The time course of the inhibition of the photosynthetic electron transport following a methanol fumigation of cherry leaves suggests that methanol starts inhibiting photosynthesis and photorespiration after ≈60 seconds and that the effect is complete after 180 seconds. This inhibition is not permanent, however, since gas-exchange properties recovered within 24 hours. Methanol vapor effects were greatest when leaves were fumigated on the surfaces with stomata. However, fumigation with methanol does not affect stomatal conductance. Therefore, inhibition of photosynthesis following methanol fumigation can be attributed to a temporary inhibition of biochemical reactions.

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Chenping Xu and Beiquan Mou

; Konica Minolta Sensing, Tokyo, Japan). Leaf maximum photochemical efficiency (F v /F m ), photochemical yield [Y(II)] and electron transport rate (ETR) were measured with a fluorometer (MINI-PAM-II; Heinz Walz, Effeltrich, Germany) on the four largest

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Hector Valenzuela, Stacy Riede, and Harry Yamamoto

Portable chlorophyll fluorometers have made it possible to evaluate the photosynthetic efficiency of photosystem 11 for vegetable crops under ambient conditions. A sampling protocol was first established to eliminate variability due to positioning of the fiber optics in relation to the leaf, leaf selection, and natural environmental variability. Fluorescence parameters of the quantum yield of noncyclic electron transport (DF/Fm') and electron transport rate (ETR) were taken from several economically important vegetables under ambient conditions between 11 and 14 h. The objective of the second part of the study was to conduct in situ chlorophyll fluorescence and biomass determinations as affected by salt stress and N deficiency. DF/Fm' and ETR were studied in rhizobium inoculated, noninoculated and inorganic N-fed soybean and differences in fluorescence were related to yield. The influence that salt stress, and several N rates have on fluorescence photochemical quenching (qP) and nonphotochemical quenching (qN), NPQ ([Fm-Fm']/Fm'), DF/Fm' and ETR for hydroponically grown lettuce will also be presented.

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Joo Hyun Lee, Yong-Beom Lee, and Kyu Sook Lee

Wasabi japonica plantlets were acclimatized in a hydroponic system to determine effective procedures. The plantlets were cultured on solid Murashige-Skoog medium with 3% sucrose. Shoots that formed roots were transplanted into hydroponic systems: 1) acclimatization in ebb-and-flow (EBB) for subirrigation (medium: granulated rockwool and coir); and 2) acclimatization in deep flow technique (DFT). The plantlets were acclimatized for 5 weeks under two irradiance treatments, 50 and 300 mmol·m-2·s-1. Photosynthetic capacity in high PPF was higher than that in low PPF during acclimatization. Electron transport rate from PS II (ETR) and biomass production increased significantly with increased light availability. The fresh weight, dry weight, and leaf area of plantlets in high PPF were higher than those in low PPF. In particular, the dry weight and ETR of the plantlets grown in high PPF increased more than twice as much as those in low PPF. At 50 mmol·m-2·s-1 PPF, growth indexes, such as number of leaves, leaf length, leaf width, leaf area, fresh weight, and dry weight, were higher in EBB (granulated rockwool) > EBB (coir culture) > DFT. At 300 mmol·m-2·s-1 PPF, those indexes were higher in DFT > EBB (granulated rockwool) > EBB (coir). The Wasabi japonica plantlets acclimatized in a hydroponic system also had a superior performance when they were transferred to the field.