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Chenping Xu and Beiquan Mou

; Konica Minolta Sensing, Tokyo, Japan). Leaf maximum photochemical efficiency (F v /F m ), photochemical yield [Y(II)] and electron transport rate (ETR) were measured with a fluorometer (MINI-PAM-II; Heinz Walz, Effeltrich, Germany) on the four largest

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

changes in photochemical efficiency and heat dissipation; low Fv/Fm values in plants under stress indicate damage to the PSII reaction center. Chlorophyll fluorescence is used to determine the effects of environmental stresses on photosynthesis in plants

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Zhongjie Ji, James J. Camberato, Cankui Zhang, and Yiwei Jiang

). GABA is a nonprotein amino acid that is well recognized as an endogenous plant signaling molecule ( Kinnersley and Turano, 2000 ). Exogenous application of GABA enhanced photosynthesis, leaf photochemical efficiency, and enzymatic antioxidant activity

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Marjorie Reyes-Diaz, Miren Alberdi, and Maria de la Luz Mora

parameters. Chlorophyll fluorescence parameters were used to determine the photochemical efficiency of PSII in leaves. The basic protocol of Reyes-Díaz et al. (2005) was followed. Fluorescence of attached nonshaded leaves was measured using a portable

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Jinyu Wang, Patrick Burgess, Stacy A. Bonos, William A. Meyer, and Bingru Huang

declined to 0.733–0.823 or 0.775–0.796, respectively. Fig. 5. Photochemical efficiency of ( A ) chewings fescue, ( B ) hard fescue, ( C ) sheep fescue and slender creeping red fescue, and ( D ) strong creeping red fescue as affected by heat stress compared

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Mahalaxmi Veerasamy, Yali He, and Bingru Huang

comparison with the heat-stressed plants. Measurements. Two parameters, including leaf chlorophyll content and photochemical efficiency, were measured to evaluate leaf senescence and the severity of heat injury. All measurements were made on leaves at

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Lijian Liang, Yanming Deng, Xiaobo Sun, Xinping Jia, and Jiale Su

biological replicates. Fig. 3. Effects of nitric oxide (NO) pretreatment on photochemical efficiency ( F v / F m ) in anthurium under chilling stress. Anthurium plants used in this study were grown in a growth chamber for 20 d and then pots with established

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Thomas E. Marler and Patrick D. Lawton

Leaflets of `Arkin', `B-10', `Kary', and `Sri Kembangan' carambola (Averrhoa carambola L.) trees were restrained in a horizontal position for 3.5 h during midday under full sun conditions to determine the influence of overriding natural leaflet movement on adaxial chlorophyll fluorescence and temperature. Induced chlorophyll fluorescence obtained after 30 minutes of dark adaptation following the period of full sun exposure was affected by leaflet movement. Restrained leaflets exhibited a variable fluorescence (Fv)/peak fluorescence (Fm) of 0.48, while that of unrestrained leaflets was 0.65. Adaxial leaflet temperature of restrained leaflets was 6C higher than that of leaflets that were allowed to move. The influence of leaflet movement on temperature or chlorophyll fluorescence was not different among the four cultivars. However, mean Fv/Fm of `Kary' and `Sri Kembangan' was lower than that of `B-10'. Our results indicate that the ability of carambola to change leaflet angle leads to lower temperature and higher photochemical efficiency than occurs when leaflets are not allowed to move naturally (vertically orient) under full sun conditions.

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Erik H. Ervin, Xunzhong Zhang, and John H. Fike

Plants possess various constitutive and inducible defense mechanisms such as pigment and antioxidant systems for protection against stresses such as ultraviolet-B (UV-B; 290 to 320 nm) radiation. Our previous research has indicated that higher chlorophyll, carotenoid, and anthocyanin concentrations were associated with greater tolerance of UV-B stress by `Georgetown' kentucky bluegrass (Poa pratensis L.). The objectives of this study were to determine if kentucky bluegrass cultivars with darker leaf color possessed greater pigment and antioxidant defense systems and if such increases were associated with greater resistance to UV-B. Eight cultivars exhibiting a range of green color intensity (`Apollo', `Brilliant', `Julius', Limerick', `Midnight', `Moonlight', `Nuglade', and `Total Eclipse') were selected and subjected to continuous, artificial UV-B radiation (70 μmol·m-2·s-1). UV-B irradiation reduced turf quality (55% to 62%) and photochemical efficiency (37% to 70%) when measured 5 days after initiation of UV-B exposure. Significant differences in turf color, photochemical efficiency, chlorophyll a, chlorophyll b, chlorophyll a+b, and carotenoids were found among the cultivars. `Moonlight' had greatest photochemical efficiency, chlorophyll, carotenoids, and turf quality. Positive correlations of pigment concentration with photochemical efficiency and turf color were observed under UV-B radiation stress, with correlation coefficients ranging from 0.49 to 0.62. The results of this study suggests that selecting cultivars with higher concentrations of chlorophyll and carotenoids and photochemical efficiency may be an effective way for turfgrass managers and sod producers to improve sod establishment and quality in environments with higher UV-B radiation.

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Vijaya Shukla, Yingmei Ma, and Emily Merewitz

, 1981 ). Membrane health attributes were estimated by measuring the following parameters. Leaf photochemical efficiency (F v /F m ) and quantum yield of photochemical energy conversion in PSII (YII) were determined with a fluorometer system (OSp5; Opti