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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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Burcu Begüm Kenanoglu, Ibrahim Demir, and Henk Jalink

resulting chlorophyll fluorescence, and linking it with the quality of the seeds. This has been performed with seeds of cabbage ( Brassica oleracea ) ( Dell’Aquila et al., 2002 ; Jalink et al., 1998 ), tomato ( Solanum lycopersicum ) ( Jalink et al., 1999

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Madhulika Sagaram and Jacqueline K. Burns

consequence of starch accumulation in citrus leaves affected by HLB may be an impact on photosynthesis. Light energy absorbed by chlorophyll molecules can be used to drive photosynthesis, dissipated as heat, or re-emitted as light (chlorophyll fluorescence

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D. Michael Glenn

. Chlorophyll fluorescence and the photochemistry of photosystem II (PSII) can be imaged using cameras, sophisticated data capture techniques, and synchronized light sources ( Baker, 2008 ). Both baseline chlorophyll fluorescence and the Fv/Fm can be imaged and

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D.H. Willits and M.M. Peet

Chlorophyll fluorescence was measured under both laboratory and greenhouse conditions in an effort to develop a quick, reliable, and inexpensive laboratory procedure capable of predicting heat stress experienced by tomato (Lycopersicon esculentum Mill.) under greenhouse conditions. The laboratory tests consisted of measurements of the ratio of variable to maximal chlorophyll fluorescence (Fv/Fm) performed on leaf discs taken from whole tomato leaves and placed on a temperature controlled plate. Comparisons were made with greenhouse measurements of the same parameter conducted on intact leaves of whole plants exposed to different temperature treatments imposed by manipulation of the aerial environment of the greenhouse. Dark adaption periods ranging from 15 min to all day in the greenhouse and temperature exposure periods ranging from 5 min to 60 min in the laboratory were compared to find the best correlation between the two tests. Best agreement was obtained with 60 min treatment times in the laboratory and 60 min dark adaption periods in the greenhouse. Fv/Fm decreased quadratically with increasing leaf temperature in a similar fashion in both tests, suggesting that the laboratory approach can adequately predict plant response to greenhouse heat stress.

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Julián Miralles-Crespo, Juan Antonio Martínez-López, José Antonio Franco-Leemhuis, and Sebastián Bañón-Arias

excitation pressure may occur as a consequence of a reduction in PSII antenna size ( Huner et al., 1998 ). These mechanisms avoid damage to photosystems but result in a decrease in photosynthesis ( D'Ambrosio et al., 2006 ). Hence, chlorophyll fluorescence is

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

peach have not been described. Photochemistry, chlorophyll fluorescence, and heat dissipation represent three competing de-excitation pathways for the light energy absorbed by chlorophyll in plant leaves ( Maxwell and Johnson, 2000 ). A reduction in the

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

fluorescence. Chlorophyll fluorescence measurements can be used to quickly and reliably determine Φ PSII ( Maxwell and Johnson, 2000 ). Generally, a decrease in Φ PSII indicates that either plants dissipate an increasing fraction of the absorbed light energy

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Sarah E. Bruce, D. Bradley Rowe, and James A. Flore

Chlorophyll fluorescence over the course of stem cutting propagation was examined in 10 cultivars of Taxus ×media (Taxus baccata L. × T. cuspidata Sieb. & Zucc.), including `Brownii', `Dark Green Pyramidalis', `Dark Green Spreader', `Densiformis', `Densiformis Gem', `Hicksii', `L.C. Bobbink', `Runyan', `Tauntoni', and `Wardii'. The fluorescence value measured was the ratio of variable over maximum chlorophyll fluorescence (Fv/Fm). This value reflects the maximum dark-adapted photochemical efficiency of photosystem II (PSII) reaction centers involved in photosynthesis and is an indirect measure of plant stress. The objective of this study was to examine Fv/Fm as a method for stock plant selection and for monitoring rooting progress of various cultivars. Fv/Fm varied significantly (P ≤ 0.05) among cultivars, initially and over time. However, there was significant overlap among some cultivars. The Fv/Fm decreased dramatically during cold storage, but usually returned to original levels after several weeks in the propagation beds. This appeared to be a reflection of the reduction of water stress as the cuttings formed roots. Initial stock plant Fv/Fm was not correlated (P ≤ 0.05) with rooting percentage, root number, root dry weight, or root length, indicating that Fv/Fm is not a reliable indicator of stock plant rooting potential. Visual assessment is just as reliable.

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Jinhong Yuan, Man Xu, Wei Duan, Peige Fan, and Shaohua Li

upper part of trees. Measurement of gas exchange and chlorophyll fluorescence. Mature leaves from the upper part of six trees per treatment were selected for measurements of gas exchange and chlorophyll fluorescence. Gas exchange was measured everyday