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B.M. Cregg, M.W. Duck, C.M. Rios, D.B. Rowe, and M.R. Koelling

We assessed variable chlorophyll fluorescence (Fv/Fm) and needle chlorophyll concentration of seedlings of Maccedonia fir (Abies borisii regis Mattfeld), subalpine fir [A. lasiocarpa (Hooker) Nuttall], Sakhalin fir [A. sachalinensis (Schmidt) Mast.], Siberian fir [A. sibirica (Lebed.)], and Veitch fir (A. veitchii Lindl.) grown under varying soil media pH. Soil media pH was modified using liquid flowable dolomitic limestone, resulting in five pH levels (3.4, 4.0, 5.4, 6.0, and 6.8). Increasing media pH significantly reduced Fv/Fm and needle chlorophyll concentration in all of the species tested. The effect of pH on photochemistry was due to depressed nutrient uptake of P, Mn, B, and Cu. Because photosynthetic quantum yield may be related to deficiencies of several elements affected by pH, Fv/Fm may serve as a criterion to select for improved pH tolerance. Among the species examined, A. veitchii and A. lasiocarpa were most tolerant of increased pH based on Fv/Fm and needle chlorophyll concentration.

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Hussein Al-Amier, Robert Lussier, Ming Coler, Margaret Stoltzman, and Lyle Craker

The stress level in a plant may be directly associated with the intensity of the Kautsky effect (the sudden increase in fluorescence emission by chlorophyll following a dark adaptation). The decrease in photosynthetic efficiency, linked with the rate of photochemistry of plants under stress, provides a definitive signature (graphical pattern) that can be quantified and monitored, even for plants that have no visible stress symptoms. Using a prototype GrowScanner®, signature differences in plants under nitrogen and water stress, as compared with plants not under stress, could be detected and measured. Returning stressed plants to a nonstressed condition returned the stress signatures to that of control plants not under stress. Development of the technology may provide a relatively quick, presymptomatic methodology for detecting plant stress without sacrificing plant tissue.

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James A. Hardin, Michael W. Smith, Paul R. Weckler, and Becky S. Cheary

precision agriculture practices in pecan production. Much of the N in a leaf is partitioned in chlorophyll; thus, a sensor that measures chlorophyll can often be used to quantify the amount of N in a leaf ( Filella et al., 1995 ). The basis for most optical

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Charalambos I. Siminis and Manolis N. Stavrakakis

Iron (Fe) is an essential nutrient for plants, which catalyzes crucial cellular functions such as chlorophyll synthesis, chloroplast development, and antioxidative cell protection ( Marschner, 1995 ). Despite being abundant in soils, Fe mainly

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

about how P n is limited and whether there are changes in energy fluxes in the photosynthetic apparatus. The status of the photosynthetic apparatus may be investigated in vivo using fast chlorophyll a fluorescence transient analysis ( Strasser and

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Robert E. Rouse, Sandra P. Perez, and Sally B. Davenport

The Minolta chlorophyll meter SPAD-502 (Minolta Camera Company, 101 Williams Drive, NJ 07446, USA) was evaluated as an accurate, nondestructive means to measure chlorophyll content in citrus leaves. Meter readings from leaves of sweet orange and grapefruit citrus cultivars were used to develop a standard curve for citrus. A significant correlation value of 0.96 was calculated between the chlorophyll meter readings and actual chlorophyll extraction levels. The development of a standard curve using the SPAD-502 chlorophyll meter had not been established on citrus. The SPAD-502 chlorophyll meter proved to be a quick, accurate, simple, and nondestructive way to determine chlorophyll content in citrus leaves.

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Lingyan Chen, Jinli Lai, Tianyou He, Jundong Rong, Muhammad Waqqas Khan Tarin, and Yushan Zheng

variegated leaves provide suitable materials for studying the mechanism of chlorophyll biosynthesis and biodegradation, the chloroplast structure, and the photosynthetic process. The biosynthesis of chlorophyll is a complex process, which involves chemical

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Burcu Begüm Kenanoglu, Ibrahim Demir, and Henk Jalink

variation in seed maturity results in variation in plant growth and development. Therefore, separating out less mature seeds would enhance the overall quality of a seed lot. Chlorophyll content of the seedcoat in many species decreases as seed matures

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Dean A. Kopsell, Carl E. Sams, Dennis E. Deyton, Kristin R. Abney, David E. Kopsell, and Larry Robertson

chlorophylls as valuable phytochemicals ( Ferruzzi and Blakeslee, 2007 ). Recent evidence is also suggesting that dietary chlorophylls may possess biological activities associated with cancer prevention, antimutagenic activity, and induction of apoptosis in

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Zhou Li, Yan Peng, and Bingru Huang

, 2004 ; Pessarakli, 2007 ). Drought and heat stress injury are typically characterized by leaf dehydration, reflected as a decline in leaf water content or accelerated leaf senescence due to loss of chlorophyll and photosynthetic activities, as well as