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Jieshan Cheng, Peige Fan, Zhenchang Liang, Yanqiu Wang, Ning Niu, Weidong Li, and Shaohua Li

constitute the main sink for photoassimilates during the fruit growth period. Removing or retaining fruit has often been used in studies of plant source-sink relationships ( Syvertsen et al., 2003 ; Vaast et al., 2005 ). Reduced photosynthetic rates under

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Chieri Kubota and Toyoki Kozai

Growth and net photosynthetic rate of potato (Solanum tuberosum L.) `Benimaru' plantlet in vitro were studied under a conventional photomixotrophic condition [with 20 g sucrose/liter in the medium and under 70 μmol·m-2·s-1 photosynthetic photon flux (PPF)] with minimal ventilation (MV) and under photoautotrophic conditions (without sugar in the medium and under 190 μmol·m-2·s-l PPF) with enhanced natural ventilation using an air diffusive filter (DV) or with forced ventilation (FV). Fresh weight of the plantlets cultured in the FV and DV treatments was 2.4 times that of the plantlets cultured in the MV treatment. Net photosynthetic rate and dry weight per plantlet were the highest in FV followed by DV. For photoautotrophic micropropagation, FV was superior to DV.

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Cheryl R. Hampson, Anita N. Azarenko, and John R. Potter

In hazelnut (Corylus avellana L.), vigorous vegetative growth and traditional orchard practices that include little or no pruning combine to produce a dense, shady canopy. A study designed to quantify the effect of shade on reproduction and photosynthetic rate in this shade-tolerant species was undertaken to assess whether some degree of pruning might improve productivity. Shade cloth was used to exclude 30%, 47%, 63%, 73%, or 92% of ambient sunlight from whole `Ennis' and `Barcelona' trees from mid-May until harvest. Photosynthetic light response curves were obtained for leaves that had developed in full sunlight, deep inside the canopy of unshaded trees, or in 92% shade. Light-saturated net photosynthetic rates were 12.0, 6.1, and 9.3 μmol·m-2·s-1 of CO2 and dark respiration rates were 2.0, 1.1, and 0.7 μmol·m-2·s-1 of CO2, respectively, for the three light regimes. Light-saturated photosynthetic rates of leaves from 30% or 63% shade differed little from the control (0% shade). Area per leaf increased by 49% and chlorophyll concentration (dry weight basis) by 157% as shading increased from 0% to 92%. Shading to 92% reduced specific leaf weight (68%), stomatal density (30%), light compensation point (69%), and dark respiration rate (63%) compared to controls. Female inflorescence density declined by about one-third and male inflorescence density by 64% to 74% in the most heavily shaded trees of both cultivars compared to controls. Shade was more detrimental to yield than flowering: yield per tree dropped by >80%, from 2.9 to 3.4 kg in full sun to 0.6 to 0.9 kg in 92% shade. Shade reduced yield primarily by decreasing nut number and secondarily by decreasing nut size. The incidence of several kernel defects increased as shade increased. Therefore, hazelnut leaves showed considerable capacity to adapt structurally and functionally to shade, but improving light penetration into the canopy would probably increase orchard productivity.

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Chieri Kubota, Natsuko Kakizaki, Toyoki Kozai, Koichi Kasahara, and Jun Nemoto

Nodal explants of tomato (Lycopersicon esculentum Mill.) were cultured in vitro to evaluate the effects of sugar concentration, photosynthetic photon flux (PPF), CO2 concentration, ventilation rate of the vessel, and leaf removal on growth and photosynthesis. After 20 days of culture, the dry weights of plantlets derived from explants with leaves and cultured photoautotrophically (without sugar in the medium) under high PPF, high CO2 concentration, and high ventilation rate were more than twice as great as those of plantlets derived conventionally from explants without leaves and cultured photomixotrophically (with sugar in the medium) under low PPF, low CO2 concentration, and low ventilation rate (107 and 45 mg per plantlet, respectively). Under photomixotrophic micropropagation conditions, the dry weights of plantlets from explants with leaves increased more than did those of plantlets from explants without leaves. High PPF, high CO2 concentration, and high ventilation rate increased net photosynthetic rate and promoted growth of the plantlets under photomixotrophic micropropagation conditions. Photomixotrophic conditions produced the greatest dry weight and the longest shoots, but photoautotrophic conditions produced the highest net photosynthetic rate. The number of leaves did not differ significantly between photoautotrophically and photomixotrophically cultured plantlets. Thus, photoautotrophic micropropagation is applicable to the production of high quality tomato transplants.

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Jeffrey Adelberg, Kazuhiro Fujiwara, Chalermpol Kirdmanee, and Toyoki Kozai

Growth and net photosynthetic rates of shoots of a triploid melon clone, `(L-14 × B) × L-14', were observed over 21 days following transfer from a multiplication MS medium containing 3% sucrose and 10 μM BA to a shoot development medium containing 1 μM BA at varying levels of sucrose in the medium (0%, 1%, and 3%), and light (50, 100, and 150 PPF) and CO2 (500, 1000, and 1500 ppm) in the headspace. Largest numbers of shoot buds were observed in media with 3% sucrose. Increased light and CO2 had a positive interactive effect. Fresh and dry weights were greatest at highest levels of sucrose, light, and CO2. Although there was less growth in the absence of sucrose, fresh or dry weight of shoot buds grown without sucrose in the media still doubled over the 21 days of culture. Net photosynthetic rates of buds were negative 4 days after initiation of culture and approximately zero after 20 days of treatment. When transferring buds to fresh, sugar-free media, net photosynthetic rates became highly positive. Buds that had been cultured in the absence of sucrose and at highest light levels had the highest net photosynthesis rates upon transfer to fresh, sugar-free media.

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How-Chiun Wu and Chun-Chih Lin

in photosynthesis ( Kubota et al., 2001 ; Xiao and Kozai, 2006 ), whereas increases in chlorophyll content are also reported. Findings by Xiao et al. (2005) showed that the net photosynthetic rate and chlorophyll concentration of Gerbera jamesonii

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

by improving the photosynthetic efficiency of plants. Plant biomass production is directly dependent on the net photosynthetic rate ( Sing et al., 2013 ). Photosynthesis is the process by which photosynthetically active radiation (within the

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Tadahisa Higashide and Ep Heuvelink

from the 1930s and that this increase was related to increases in harvest index, photosynthetic rate, and stomatal conductance and a decrease in leaf area index (LAI). These reports show that an increase in yield in these crops by breeding is primarily

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

, Fv/Fm (ratio of variable to the maximal chlorophyll fluorescence) using a pulse-modulated fluorometer (Model OS1-FL; Opti-Sciences, Hudson, NH) after 30 min dark adaptation. Net photosynthetic rate and g S of watermelon seedlings after transplanting

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Amir M. González-Delgado, Manoj K. Shukla, and Brian Schutte

availability, and tolerance capacity of species. Deb et al. (2012) reported that the stem water potential of pecan trees decreased with decreasing soil moisture content and increasing air temperature. Similarly, lower photosynthetic rate was observed in blue