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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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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.

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Shuang Han, Jiafu Jiang, Huiyun Li, Aiping Song, Sumei Chen and Fadi Chen

The response to reduced light intensity of two contrasting cultivars Puma Sunny (shade intolerant) and Gongzi (shade tolerant) was characterized in terms of plant height, the root/shoot ratio, photosynthetic capacity, and the morphology and ultrastructure of their chloroplasts and phloem companion cells. The initial response to shading of cultivar Puma Sunny plants was to extend their stems, and while the equivalent response of cultivar Gongzi was less marked. Shading depressed the maximum relative electron transport rate (rETR) in both cultivars, and while the efficiency of light capture in cultivar Puma Sunny was compromised by shading, this was not the case for cultivar Gongzi. Low levels of incident light inhibited the formation of starch grains in the chloroplast and increased the volume of interspace between the grana lamellae. In cultivar Puma Sunny, but less so in cultivar Gongzi, the chloroplasts became more slender and the stroma lamellae more swollen. Adjusting chloroplast morphology by developing extra layers of grana lamellae and maintaining the integrity of the phloem companion cells are both adaptations which help make ‘Gongzi’ a more shade-tolerant cultivar.