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Jia-yi Wang, Jian-shuang Shen, Mengmeng Gu, Jia Wang, Tang-ren Cheng, Hui-tang Pan, and Qi-xiang Zhang

photosynthetic system, which then results in yellow leaves with lower photosynthetic capacity and weak growth in Brassica napus and Ulmus pumila ‘Jinye’ ( Xiao et al., 2013 ; Zhu et al., 2014 ). Forsythia koreana ‘Suwon Gold’ is a beautiful cultivar with

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Guoting Liang, Junhui Liu, Jingmin Zhang, and Jing Guo

available for actual photochemical reactions in the PSII reaction center ( Stefanov and Terashima, 2008 ). Maximum F V / F M is reflective of potential maximum photosynthetic capacity of plant leaves under nonstressful conditions after a sufficient dark

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Fan Li, Shenchong Li, and Qinli Shan

response of photosynthesis in transgenic rice showed that photosynthetic rate was predominantly limited by Rubisco capacity from 15 to 20 °C ( Makino and Sage, 2007 ). Consistent with this, several studies reported that Rubisco played a main role in the

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Li-Song Chen, Brandon R. Smith, and Lailiang Cheng

Own-rooted 1-year-old `Concord' grapevines (Vitis labruscana Bailey) were fertigated twice weekly for 11 weeks with 1, 10, 20, 50, or 100 μm iron (Fe) from ferric ethylenediamine di (o-hydroxyphenylacetic) acid (Fe-EDDHA) in a complete nutrient solution. As Fe supply increased, leaf total Fe content did not show a significant change, whereas active Fe (extracted by 2,2′-dipyridyl) content increased curvilinearly. Chlorophyll (Chl) content increased as Fe supply increased, with a greater response at the lower Fe rates. Chl a: b ratio remained relatively constant over the range of Fe supply, except for a slight increase at the lowest Fe treatment. Both CO2 assimilation and stomatal conductance increased curvilinearly with increasing leaf active Fe, whereas intercellular CO2 concentrations decreased linearly. Activities of key enzymes in the Calvin cycle, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), NADP-glyceraldehyde-3-phosphate dehydrogenase (GAPDH), phosphoribulokinase (PRK), stromal fructose-1,6-bisphosphatase (FBPase), and a key enzyme in sucrose synthesis, cytosolic FBPase, all increased linearly with increasing leaf active Fe. No significant difference was found in the activities of ADP-glucose pyrophosphorylase (AGPase) and sucrose phosphate synthase (SPS) of leaves between the lowest and the highest Fe treatments, whereas slightly lower activities of AGPase and SPS were observed in the other three Fe treatments. Content of 3-phosphoglycerate (PGA) increased curvilinearly with increasing leaf active Fe, whereas glucose-6-phosphate (G6P), fructose-6-phosphate (F6P), and the ratio of G6P: F6P remained unchanged over the range of Fe supply. Concentrations of glucose, fructose, sucrose, starch, and total nonstructural carbohydrates (TNC) at both dusk and predawn increased with increasing leaf active Fe. Concentrations of starch and TNC at any given leaf active Fe content were higher at dusk than at predawn, but both glucose and fructose showed the opposite trend. No difference in sucrose concentration was found at dusk or predawn. The export of carbon from starch breakdown during the night, calculated as the difference between dusk and predawn measurements, increased as leaf active Fe content increased. The ratio of starch to sucrose at both dusk and predawn also increased with increasing leaf active Fe. In conclusion, Fe limitation reduces the activities of Rubisco and other photosynthetic enzymes, and hence CO2 assimilation capacity. Fe-deficient grapevines have lower concentrations of nonstructural carbohydrates in source leaves and, therefore, are source limited.

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Hui-lian Xu, Laurent Gauthier, and André Gosselin

`Capello' tomato plants (Lycopersicon esculentum Mill.) were grown in a greenhouse in peat-based substrate (70% sphagnum peat and 309'. perlite, by volume) and supplied with nutrient solutions of high (4.5 mS·cm-1) or low (2.3 mS·cm-1) electrical conductivity (EC) under high (95% ± 5%) or low (55% ± 8% of capillary capacity) soil water conditions. Three weeks after treatments started, stomatal transpiration (TRst) and cuticular transpiration (TRcu) rates were measured by three methods: 1) analyzing TRst and TRcu from a water retention curve obtained by drying excised leaves in air under a photosynthetic photon flux (PPF) of 400 μmol·m-1·s-1, 2) analyzing TRst and TRcu from a transpiration decline curve obtained by measuring transpiration rates after cutting the leaf from the stem of the dehydrated plant in the gas-exchange system, and 3) measuring transpiration rates under light and in dark respectively using the gas-exchange method. TRst and TRcu were decreased by high EC and/or low soil water content. For method 1, the transpiration decline curve shows two distinct phases: the initial steep slope that indicates TRst and the gently sloped section that indicates TRcu. Both slopes were lower for high EC and/or water-stressed plants compared to the control (low EC and high soil water content). The tangent lines of these two phases of the curve intersect at one point (t, w). The value oft that indicates the time for stomatal closure was longer and the value of w that indicates the critical tissue water level for stomatal closure was lower for high EC and/or water-stressed plants. In method 2, the initial rate of total transpiration was higher in high EC and/or water-stressed plants. Leaf wax content increased, especially under high EC stress. This suggests that increased deposition of wax prevents water loss from the cuticle. A delay in complete stomatal closure, complete closure at lower RWC, and reduced TRcu or an increase in wax deposit were adaptations to water and salinity stresses in tomato plants under our controlled environmental conditions.

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Donavon Sonnenberg, Patrick A. Ndakidemi, Ambrose Okem, and Charles Laubscher

( Chartzoulakis and Drosos, 1995 ; Sedibe, 2003 ). Drip irrigation is a localized technology that supplies water and dissolved nutrients directly to the roots of crops. This improves photosynthetic capacity of plants, maximizing yield, minimizing water usage, and

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Jyotsna Joshi, Geng Zhang, Shanqi Shen, Kanyaratt Supaibulwatana, Chihiro K.A. Watanabe, and Wataru Yamori

fully expanded leaves (inner leaves; sixth layer) of control plants were measured to assess the leaf photosynthetic capacity under different levels of supplemental upward lighting (0, 30, 60, or 90 µmol·m −2 ·s −1 PPFD; Fig. 5 ). The maximum

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Alexandra García-Castro, Astrid Volder, Hermann Restrepo-Diaz, Terri W. Starman, and Leonardo Lombardini

assimilation rate [photosynthetic rate (P n )] of Passiflora incarnata plants subjected to two irrigation treatments, well-watered [irrigation at container capacity (CT)] and reduced irrigation (RI). CT plants were irrigated daily to replenish 100

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Ming Ding, Beibei Bie, Wu Jiang, Qingqing Duan, Hongmei Du, and Danfeng Huang

photosynthetic capacity as a result of their higher root absorption capacity. More photosynthate accumulated in the form of starch was found in the leaves of grafted watermelon seedling compared with non-grafted ones before storage (0 d) ( Fig. 1A ). However

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Vahid Rahimi Eichi, Stephen D. Tyerman, and Michelle G. Wirthensohn

maximum A is highly dependent on the capacity of the leaf hydraulic system to supply water for mesophyll photosynthetic cells ( Sack and Frole, 2006 ). Therefore, it can be concluded that hydraulic conductance ( k leaf ) is highly correlated with