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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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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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Genhua Niu, Makio Hayashi and Toyoki Kozai

Potato (Solanum tuberosum L. cv. Benimaru) plantlets were cultured under four lighting cycles (photoperiod/dark period: 16 h/8 h, 4 h/2 h, 1 h/0.5 h, and 0.25 h/0.125 h) photoautotrophically (without sugar in the medium), and photomixotrophically (with sugar in the medium) in vitro for 28 days. Simulations of time courses of CO2 concentration in the vessel (Ci) and dry weight accumulation of the plantlets cultured photoautotrophically were conducted using a previously developed model (Niu and Kozai, 1997). While underestimation and overestimation of time courses of Ci in some treatments were observed, the simulated results of Ci and dry weight accumulation of the plantlets generally agreed with the measured ones. The difference of net photosynthetic rate response to Ci throughout the culture period was examined between the plantlets cultured photoautotrophically and photomixotrophically. Quantitative relationship between daily net photosynthetic rate (daily net production) and vessel ventilation rate per plantlet was simulated under various CO2 levels outside the vessel for given sizes of potato plantlets cultured photoautotrophically in vitro to aid appropriate CO2 enrichment and vessel design in commercial micropropagation.

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Adriane Cannon*, Dennis Deyton, Carl Sams and William Klingeman

Two experiments were conducted in a greenhouse to evaluate soy-bean oil (SO) formulations for effects on powdery mildew (PM) and photosynthesis of dogwood trees. In the first experiment, one-year-old potted trees were sprayed with different formulations of 2% SO one day before exposure to PM. The formulations were emulsified with: teric/termul, lauriciden, lecithin, lecithin/MD 1, lecithin/MD 2, or Latron B-1956. A commercial formulation of Golden Natur'l was also used. The trees were arranged in a completely randomized design with six replications and eight treatments. In the second experiment, trees were sprayed 4 days after initial exposure to PM with the same treatments and arranged in a similar experimental design. The severity of PM infection was rated using the scale: 1 = 0%, 2 = 1% to 3%, 3 = 4% to 6%, 4 = 7% to 12%, 5 = 13% to 25%, 6 = 26% to 50%, 7 = 51% to 87%, and 8 = 88% to 100% of leaves visually displaying PM. The net photosynthetic (Pn) rates were measured using an infrared gas analyzer. In the first experiment, trees sprayed pre-inoculation with Golden Natur'l, lecithin, lecithin/MD 1, or Latron B-1956 formulation had less PM than control trees at 19 and 24 days after spraying (DAS). Pn of leaves sprayed with lecithin or Latron B-1956 formulations had 68% and 40% lower Pn rates, respectively, of the control leaves at one DAS. However, by 11 DAS, none of the SO formulations significantly affected Pn rates. Leaves of plants (expt. 2) sprayed with teric/termul, lauriciden, lecithin, and lecithin/MD 2 formulations had less PM than control trees at 28 DAS. All formulations reduced Pn rates at 6 DAS, with only Golden Natur'l treated leaves recovering to rates similar to control leaves by 15 DAS.

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Ze Li, Kai Shi, Fanhang Zhang, Lin Zhang, Hongxu Long, Yanling Zeng, Zhiming Liu, Genhua Niu and Xiaofeng Tan

yield (AQY), maximum net photosynthetic rate ( A max ), light saturation point (LSP), light compensation point (LCP), and dark respiration rate ( R d ) of tung tree seedlings grown under different light treatments. In July, g S increased slowly until a

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Gang-Yi Wu, Jun-Ai Hui, Zai-Hua Wang, Jie Li and Qing-Sheng Ye

, these four species were C3 rather than CAM plants. Fig. 3. Diurnal variation of net photosynthetic rate (P n ) ( A ), stomatal conductance ( g S ) ( B ), transpiration rate (T r ) ( C ), and environmental photosynthetically active radiation (PAR) ( D

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Joseph Masabni, Youping Sun, Genhua Niu and Priscilla Del Valle

control early in the summer. Fig. 3. Net photosynthetic rates in response to light intensity (light response curves) of tomato and chili pepper plants grown at 50% shadecloth, 70% shadecloth, and full sun [photosynthetically active radiation ( PAR

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Genhua Niu, Toyoki Kozai and Chieri Kubota

A system was designed for measuring the CO2 exchange rates [net photosynthetic rate (Pn) and dark respiration rate] of in vitro plantlets in situ (in the vessel with natural ventilation). The system, excluding gas cylinders, was placed in a growth chamber so that the desired photosynthetic photon flux (PPF) and temperature could be maintained during the measurement. The CO2 concentration inside the culture vessel (Ci) was indirectly controlled by controlling the CO2 concentration outside the vessel (Co). The Pn of the plantlets was estimated based on the measured Ci and Co at steady state using a gas chromatograph according to the method described by Fujiwara et al. (1987). The performance of the system was demonstrated by measuring the in situ Pn of sweetpotato [Ipomoea batatas (L.) Lam., cv. Beniazuma] and tomato (Lycopersicon esculentum Mill., cv. Hana Queen) plantlets in vitro under a range of CO2 concentrations and PPF. The photosynthetic parameters of the Pn model (Niu and Kozai, 1997) for the plantlets were then estimated based on the measured Pn. The preliminary measurements demonstrated the potential application of the system.