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Wook Oh*, In Hye Cheon, and Ki Sun Kim

This research was conducted to investigate the growth and flowering responses of Cyclamen persicum Mill. `Piccolo' to temperature and photosynthetic photon fluxes (PPF), and to obtain fundamental data for production of good quality pot plant. Cyclamen plants with 10 fully unfolded leaves were grown in growth chambers maintained at three day/night temperatures [20/10 (LT), 25/15 (MT), and 30/20 °C (HT)] combined with three PPF [250 (LF), 350 (MF), and 650 (HF) μmol·m-2·s-1] under 14 h-photoperiod. After 3 months, the higher the temperature was, the greater plant width was. It was the greatest under MT/MF and HT/MF. The number of leaves was greater with increasing temperature and PPF. Petiole length, leaf size, and fresh weight were higher with increase in temperature but decrease in PPF. Days to flowering were lower in MT/MF and MT/HF, but higher under LT regardless of PPF. The number of flowers was the highest under MT/MF and MT/HF, and higher under MF in each temperature treatment. Flowering period was longer in LT and MT compared with HT. Most leaves of plants grown under HT curled upward because of boron deficiency induced by higher temperature and lower humidity. Chlorophyll content was higher in medium and low temperature, except LT/HF. The lower side of leaf in low temperature was more reddish compared to that in higher temperature due to some pigments considered as anthocyanin. Photosynthesis was the highest in MT/MF, but low in MT/HF and LT/HF in accordance with the chlorophyll fluorescence (Fv/Fm) which was lower under the same environment. These results indicate that 25/15°C and 350 μmol·m-2·s-1 yielded the best pot cyclamen in this study.

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Xuan-Chun Piao, Debasis Chakrabarty, Eun-Joo Hahn, and Kee-Yoeup Paek

In vitro nodal cuttings of potato (Solanum tuberosum L.) `Atlantic' and `Russet Burbank' from bioreactor culture were hydroponically cultured for 28 days using a deep flow technique (DFT) system. The response of plant growth and photosynthesis to different levels of solution electrical conductivity (EC; 0.08, 0.15, 0.22 and 0.36 S·cm-1) and pH (3, 4, 5, 6 and 7) were studied. The best growth, characters of shoot length, total shoot and root fresh and dry weight, were obtained in nutrient solution of pH 6.0 and EC 0.15 S·cm-1 for `Atlantic', while pH 7.0 and EC 0.15 S·cm-1 were found to be best for `Russet Burbank'. Plantlet growth was reduced by low solution pH (3.0) and high EC level (0.36 S·cm-1). Photosynthetic rate, stomatal conductance, and transpiration rate were also found to be affected by EC levels. Down regulation of photosynthesis, as indicated by chlorophyll fluorescence results, were observed when potato plantlets were cultured under nutrient solution of higher EC level. Plantlet growth and photosynthetic rate increased as photosynthetic photon flux (PPF) levels increased from 50 to 250 μmol·m-2·s-1. Particularly, increasing PPF level had a more distinctive effect on plantlet growth than CO2 enrichment condition. It was apparent from this study that nutrient solution of pH 6.0 and 0.15 S·cm-1 EC in combination with high PPF level (250 μmol·m-2·s-1) were suitable for hydroponic culture of potato plantlets as it would maximize net photosynthetic rate, and achieve the highest growth rates.

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M. Carmen González-Mas, M. José Llosa, Antonio Quijano, and M. Angeles Forner-Giner

. Biochem. 41 839 845 Calatayud, A. Iglesias, D.J. Talón, M. Barreno, E. 2004 Response of spinach leaves ( Spinacia oleracea L.) to ozone measured by gas exchange, chlorophyll a fluorescence, antioxidant systems, and lipid peroxidation Photosynthetica 42

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Francisco García-Sánchez and J.P. Syvertsen

Three-month-old citrus rootstock seedlings of the Cl- excluder Cleopatra mandarin (Citrus reticulata Blanco) and the Cl- accumulator Carrizo citrange [C. sinensis (L.) Osb. × Poncirus trifoliata L.] were fertilized with nutrient solution with or without additional 50 mm NaCl and grown at either ambient CO2 (360 μL·L-1) or elevated CO2 (700 μL·L-1) in similar controlled environment greenhouses for 8 weeks. Elevated CO2 increased plant growth, shoot/root ratio, leaf dry weight per area, net assimilation of CO2, chlorophyll, and water-use efficiency but decreased transpiration rate. Elevated CO2 decreased leaf Ca2+ and N concentration in non-salinized Cleopatra. Salinity increased leaf Cl- and Na+ in both genotypes. Carrizo had higher concentrations of Cl-but lower Na+ in leaves than Cleopatra. Salinity decreased plant growth, shoot/root ratio, net gas exchange, water use, and root Ca+2 but increased root N in both genotypes regardless of CO2 level. Neither salinity nor elevated CO2 affected leaf chlorophyll fluorescence (Fv/Fm). Carrizo had higher Fv/Fm, leaf gas exchange, chlorophyll, N, and Ca2+ than Cleopatra. Salinity-induced decreases in leaf osmotic potential increased leaf turgor especially at elevated CO2. The increase in leaf growth at elevated CO2 was greater in salinized than in nonsalinized Carrizo but was similar in Cleopatra seedlings regardless of salt treatment. In addition, salinity decreased water-use efficiency more at elevated CO2 than at ambient CO2 in Cleopatra but not in Carrizo. Elevated CO2 also decreased leaf Cl- and Na+ in Carrizo but tended to increase both ions in Cleopatra leaves. Based on leaf growth, water-use efficiency and salt ion accumulation, elevated CO2 increased salinity tolerance in the relatively salt-sensitive Carrizo more than in the salt-tolerant Cleopatra. In salinized seedlings of both genotypes, Cl- and Na+ concentration changes in response to eCO2 in leaves vs. roots were generally in opposite directions. Thus, the modifications of citrus seedling responses to salinity by the higher growth and lower transpiration at elevated CO2 were not only species dependent, but also involved whole plant growth and allocations of Na+ and Cl-.

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D. Michael Glenn

-oxidative stress responses in leaves J. Exp. Bot. 53 1249 1254 Hacker, J. Spindelböck, J.P. Neuner, G. 2008 Mesophyll freezing and effects of freeze dehydration visualized by simultaneous measurement of IDTA and differential imaging chlorophyll fluorescence Plant

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María A. Equiza and David A. Francko

well as labor-intensive and time-consuming. More recently, chlorophyll fluorescence analysis has been used to evaluate plant responses to different environmental stresses ( Baker and Rosenqvist, 2004 ; Maxwell and Johnson, 2000 ). Chlorophyll

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

present study were to 1) compare the thinning responses of apple and peach to different concentrations of foliar-applied metamitron; 2) use the dark-adapted chlorophyll fluorescence parameter Fv/Fm to describe the effects of this PSII inhibitor on the

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Sorkel Kadir, Michael Von Weihe, and Kassim Al-Khatib

The photosystem II reaction center is the most sensitive reaction center in photosynthesis to heat stress ( Wen et al., 2005 ). Heat stress decreases photosynthetic electron transport activity and variable fluorescence and maximum fluorescence (Fv

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

optimize greenhouse production ( Baker and Rosenqvist, 2004 ) and to monitor crop responses to light ( Pocock, 2015 ). For example, Janka et al. (2015) used chlorophyll fluorescence measurements to monitor diurnal and dynamic fluctuations in Φ PSII of

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Fan Zhang, Zi Wei, Peter Jeranyama, Carolyn DeMoranville, and Harvey J.M. Hou

in vivo. Therefore, Chl fluorescence is proven to be an intriguing tool and reveals information on plant performance and responses through non-intrusive measurements, especially addressing the effects of plant leaves under environmental stress