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Nadia Hakam, Jennifer R. DeEll, Shahrokh Khanizadeh, and Claude Richer

Chlorophyll fluorescence (CF) was evaluated as a technique to assess chilling injury of rose (Rosa sp.) leaves exposed to low temperatures. In the more susceptible genotypes, variable fluorescence (Fv) decreased dramatically as the temperature was lowered. In the less susceptible genotypes, Fv was more stable and decreased more slowly as temperature fell. Our results suggest that measurement of CF may provide a rapid method to prescreen genotypes for chilling susceptibility, as required in plant breeding.

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G.E. Bell, B.M. Howell, G.V. Johnson, W.R. Raun, J.B. Solie, and M.L. Stone

Differences in soil microenvironment affect the availability of N in small areas of large turfgrass stands. Optical sensing may provide a method for assessing plant N needs among these small areas and could help improve turfgrass uniformity. The purpose of this study was to determine if optical sensing was useful for measuring turfgrass responses stimulated by N fertilization. Areas of `U3' bermudagrass [Cynodon dactylon (L.) Pers.], `Midfield' bermudagrass [C. dactylon (L.) Pers. × C. transvaalensis Burtt-Davy], and `SR1020' creeping bentgrass (Agrostis palustris Huds.) were divided into randomized complete blocks and fertilized with different N rates. A spectrometer was used to measure energy reflected from the turfgrass within the experimental units at 350 to1100 nm wavelengths. This spectral information was used to calculate normalized difference vegetation index (NDVI) and green normalized difference vegetation index (GNDVI). These spectral indices were regressed with tissue N and chlorophyll content determined from turfgrass clippings collected immediately following optical sensing. The coefficients of determination for NDVI and GNDVI regressed with tissue N averaged r 2 = 0.76 and r2 = 0.81, respectively. The coefficients of determination for NDVI and GNDVI regressed with chlorophyll averaged r 2 = 0.70 and r 2 = 0.75, respectively. Optical sensing was equally effective for estimating turfgrass responses to N fertilization as more commonly used evaluations such as shoot growth rate (SGR regressed with tissue N; r 2 = 0.81) and visual color evaluation (color regressed with chlorophyll; r 2 = 0.64).

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Ritu Dhir, Richard L. Harkess, and Guihong Bi

temperatures inhibit photosynthesis ( Sharkey et al., 2001 ) and the response to high temperatures can vary significantly within a species ( Reynolds et al., 1990 ). High temperatures influenced chloroplast development, chlorophyll biosynthesis, and the

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Mayashree Chinsamy, Manoj G. Kulkarni, and Johannes Van Staden

. Photosynthetic pigment (chlorophyll a, b, and total chlorophyll) content was extracted by homogenizing fresh leaf samples (5 g) of treated and control seedlings in 80% acetone (20 mL) using a homogenizer. The resultant solution was filtered through Whatman No. 1

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Naoki Yamauchi and Alley E. Watada

Pigments in stored parsley leaves (Petroselinum crispum Nym.) were monitored to determine if degradative products of chlorophyll (chl) differed while under different types of atmosphere. The leaves were stored in a closed container under a stream of humidified air at 20C with or without 10 ppm ethylene and with or without 10 percent oxygen and 10 percent carbon dioxide. Analysis of pigments with HPLC showed that chl a and b decreased sharply with or without ethylene and the decrease was considerably less under CA. Chlorophyll a-1, the oxidized form of chl a, was initially low, and the level decreased slightly with all of the storage conditions. Chlorophyllide was also low, but it increased slightly during storage. Xanthophyll derivatives, which appeared to be the esterified xanthophylls, increased slightly during storage. These results indicate that chl degradation in stored parsley leaves was hastened by ethylene or suppressed by CA condition and the pathway of chl degradation did not appear to be altered by the different storage atmospheres.

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Nazir Mir, Michael Wendorf, Rufino Perez, and Randolph M. Beaudry

The relationship between chlorophyll fluorescence of `Cortland', `Redchief Delicious', and `Empire' apple (Malus ×domestica Borkh.) fruit and the development of superficial scald was studied during 120 days of refrigerated air (RA) storage at 0 °C and during 7 days of poststorage holding at 22 °C. Minimal fluorescence (Fo), maximal fluorescence (Fm), photochemical efficiency (Fv/Fm, where Fv=Fm=Fo) and coefficient of photochemical fluorescence quenching (qp) were measured. During storage, while Fv/Fm and Fm declined in `Cortland' and `Redchief Delicious' fruit over time, these two measures of chlorophyll fluorescence remained stable in `Empire' fruit. Of the three cultivars, only `Empire' is resistant to and did not develop superficial scald. A decline in Fv/Fm preceded scald development in `Cortland' and `Redchief Delicious' fruit. After 30 days of storage, qp began to decrease in fruit from all three cultivars. Prestorage diphenylamine (DPA) application had no effect on Fv/Fm, Fo, and Fm and only marginally improved maintenance of qp, but completely prevented the development of superficial scald. Poststorage holding at 22 °C accelerated the rate of change in most fluorescence measurements. The decline in the Fv/Fm ratio and/or qp with storage time may be in response to senescence-related factors that also enhance scald susceptibility, however, Fv/Fm does not appear to be directly related to superficial scald susceptibility per se.

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Yuji Yamada, Masayoshi Nakayama, Hiromitsu Shibata, Sanae Kishimoto, and Takashi Ikeda

activities in the fruit of the cultivar Mavras, which are dark purple when immature, and Tequila, which are lilac when immature. We also studied the synchrony between content changes in anthocyanins and both chlorophylls (green pigments) and carotenoids (red

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Yiguang Wang, Chao Zhang, Bin Dong, Yaohui Huang, Zhiyi Bao, and Hongbo Zhao

the most important. In addition to the chlorophylls commonly found in green tissues, flavonoids and carotenoids are main pigments determining the colors of plants ( Tanaka et al., 2008 ). Anthocyanins are the most important flavonoids that affect the

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Panayiotis A. Nektarios, Ioannis Amountzias, Iro Kokkinou, and Nikolaos Ntoulas

separated from the substrate by rinsing with water. The fresh weight of the aerial plant portion was determined by weighing, and then all plant parts were placed in a drying oven at 70 °C for 4 d to determine leaf and stem dry weights. SPAD and chlorophyll

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Eleni Tsantili, Miltiadis V. Christopoulos, Constantinos A. Pontikis, Pantousis Kaltsikes, Chariklia Kallianou, and Michalis Komaitis

for chlorophyll determination, Ca and Mg concentrations, and ≈350 olives per tree were collected for the rest of the fruit measurements. At this stage, all fruits were at the black-ripe climacteric stage. All fruits and leaves collected were