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

fluorescence, and 15 to 20 plots were used for the measurements of sugar content and enzyme activities. Measurement of photosynthetic parameters and chlorophyll fluorescence. Photosynthetic gas exchange and chlorophyll fluorescence response of five

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John Jifon, Kevin Crosby, and Daniel Leskovar

High temperature stress is a major limitation to commercial production of habanero pepper (Capsicum chinense Jacq.) in tropical and subtropical regions. The ability to sustain physiological activity under stress is an important trait for newer varieties. We evaluated leaf thermotolerance [based on the cell membrane stability (CMS) test] of three habanero pepper varieties to: 1) determine genetic variability in CMS among the genotypes studied; and 2) to assess correlations between CMS, photosynthesis and chlorophyll fluorescence [(CF), an indicator of membrane-dependent photosystem II quantum efficiency, ΦPSII]. The genotypes evaluated were TAM Mild Habanero (TMH, a recently developed mild habanero pepper) and its closely related parents (Yucatan and PI 543184). Net CO2 assimilation rate (An) of intact leaves was measured in the field and leaf samples collected and exposed to heat stress (55 °C for 20 min) in temperature-controlled water baths under dim light conditions. The CF was assessed before and after the heat treatment. The CMS was highest in PI 543184, lowest in TMH and intermediate in Yucatan. All genotypes maintained high An rates in the field (25 ± 6 μmol·m-2·s-1); however, correlations between An and CMS were weak. The Φ values were similar among the genotypes (∼0.8) under nonstress conditions, but differed significantly following stress exposure. PI 543184 had the highest post-stress ΦPSII values (0.506 ± 0.023), followed by Yucatan (0.442 ± 0.023) and TMH (0.190 ± 0.025). Observed differences in CMS and ΦPSII indicate plasticity in the response to heat stress among these genotypes.

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Sorkel Kadir

High temperature adversely affects photosynthetic rates and thylakoid activities in many species, but photosynthesis response to heat stress is not well defined in grapes (Vitis L.). Genotypes within species respond differently to high temperatures, indicating a genetic variability for the trait. The objective of this study was to determine the physiological responses of two grape species to high temperature, at the whole-plant level and at the cellular level. Gas exchange, relative chlorophyll content, and chlorophyll fluorescence of intact leaves and thermostability of extracted thylakoids of the American (V. aestivalis Michx.) `Cynthiana' and European (V. vinifera L.) `Semillon', `Pinot Noir', `Chardonnay', and `Cabernet Sauvignon' wine grapes were evaluated. One-year-old vines were placed in controlled environmental chamber held at 20/15, 30/25, or 40/35 °C day/night for 4 weeks. Net CO2 assimilation (A) rate, stomatal conductance (gs), transpiration (E) rate, chlorophyll content, and chlorophyll fluorescence of intact leaves were measured at weekly intervals. Chlorophyll fluorescence of thylakoids extracted from V. aestivalis `Cynthiana' and V. vinifera `Pinot Noir' subjected to temperatures ranging from 20 to 50 °C was measured. Optimal temperatures for photosynthesis were 20/15 °C for `Cynthiana' and `Semillon' and 30/25 °C for the other three V. vinifera cultivars. The A, gs, E, chlorophyll content, and chlorophyll fluorescence values at 40/35 °C were lower in `Cynthiana' than `Pinot Noir'. In general, reduction of A coincided with decline in gs in `Cynthiana', whereas no strong relationship between A and gs was observed in V. vinifera cultivars. Variable chlorophyll fluorescence (Fv) and the quantum efficiency of photosystem II (Fv/Fm) of intact leaves for all the cultivars decreased at 40/35 °C, with severe decline in `Cynthiana' and `Cabernet Sauvignon,' moderate decline in `Semillon' and `Chardonnay', and slight decline in `Pinot Noir'. A distinct effect of high temperature on Fv and Fv/Fm of `Cynthiana' was exerted after 2 weeks of exposure. Prolonged-exposure to 40/35 °C led to 78% decrease in Fv/Fm in `Cynthiana', compared with 8% decrease in `Pinot Noir'. In general, Fv and Fv/Fm of extracted thylakoids declined as temperature increased, with more decline in `Cynthiana' than in `Pinot Noir'. Based on A rates and Fv/Fm ratios, results showed that `Cynthiana' has lower optimal temperature for photosynthesis (20/15 °C) than `Pinot Noir' (30/25 °C). Chlorophyll fluorescence responses of intact leaves and extracted thylakoids to high temperatures indicate that `Pinot Noir' possess higher photosynthetic activity than `Cynthiana'. Results of this work could be used in selection programs for the development of heat resistant cultivars in the warmest regions.

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Wayne A. Mackay, Brent Pemberton, Joseph Maxim, and Suresh D. Pillai

communication of novel application of food irradiation J. Food Science and Nutrition 6 253 256 Jovanić, B.R. Dramićanin, M.D. 2003 In vivo monitoring of chlorophyll fluorescence response to low-dose γ-irradiation in

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John Erwin, Ken Altman, and Fran Esqueda

fluorescence responses for shade-tolerant cactus Hylocereus undatus under current and doubled CO 2 concentrations Physiol. Plant. 93 505 511 Roberts, E.H. Summerfield, R.J. 1987 Measurement and prediction of flowering in annual crops, p. 17–50. In: J

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

ETR; these parameters were ≈60%, 48%, and 30% lower than the controls when measured 1, 3, and 5 d after treatment, respectively. Fig. 3. Effects of a non-ionic surfactant (Silwet L-77) on the fluorescence responses of ‘Cameo’/M7 apple leaves to 200 mg

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Derek J. Plotkowski and John A. Cline

calibration samples, with repeats being run if necessary. Fluorescence response factors were calculated as the proportion of the average integrated area of the standard chromatogram peaks to the concentrations of the amino acids found in the authentic

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

cold storage in sitka spruce and douglas-fir seedlings Can. J. For. Res. 21 890 901 Mena-Petite, A. Robredo, A. Alcalde, S. Duñabeitia, M.K. González-Moro, M.B. Lacuesta, M. Muñoz-Rueda, A. 2003 Gas exchange and chlorophyll fluorescence responses of

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James Mattheis and David R. Rudell

-5214(02)00187-4 Zanella, A. Cazzanelli, P. Panarese, A. Coser, M. Cecchinel, M. Rossi, O. 2005 Fruit fluorescence response to low oxygen stress: Modern storage technologies compared to 1-MCP treatment of apple Acta Hort. 682 1535 1542 doi: 10.17660/ActaHortic.2005.682.204

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Qingqing Duan, Ye Lin, Wu Jiang, and Danfeng Huang

. Dunabeitia, M.K. Gonzalez-Moro, M.B. Lacuesta, M. Munoz-Rueda, A. 2003 Gas exchange and chlorophyll fluorescence responses of Pinus radiata D. Don seedlings during and after several storage regimes and their effects on post-planting survival Trees Struct