• Journal of Plant Biology
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• v.30 no.3
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• pp.181-187
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• 1987

Copper inhibited PSII-mediated O2 evolution (H2OlongrightarrowDCIP, H2OlongrightarrowSiMo) but not PSImediated O2 uptake(DCIP. Asc.longrightarrowMV) in isolated Chinese cabbage chloroplasts. Copper toxicity on PSII-mediated O2 evolution was higher at alkaline condition than at acidic condition and was inhanced by light illumination after copper treatment. The increased toxicity by light illumination was not recovered by subsequent dark treatment. The inhibitory effect of copper on H2OlongrightarrowDCIP reaction was higher than that on H2OlongrightarrowSiMo reaction. This result suggests that there may be another inhibitory site of copper on PSII other than water oxidizing side of PSII.

• Korean Journal of Environmental Agriculture
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• v.25 no.2
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• pp.109-117
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• 2006

Photoinhibition and photoprotection of PSII in the leaves of hot pepper (Capsicum annuum L.) grown in Hoagland solution and Tap water were compared. Though changes in the rates of $O_2$ evolution as a function of photon fluence rate (PFR) were comparable, the rates of respiration in the dark was 3 times higher in the Hoagland solution grown leaves than in the Tap-water grown ones. Compared to Hoagland solution grown plane, PSIIs of Tap water grown pepper leaves were more susceptible to photoinhibitory light treatment. In order to inactivate functional PSII to the same extents, Hoagland solution grown plants required almost 2-fold high light $(1600{\mu}molm^{-2}s^-)$ treatment than those of Tap water $(900{\mu}molm^{-2}s^-)$. Interestingly, the remaining fraction of PSII in Hoagland grown pepper was able to survive under prolonged illumination in the presence of lincomycin, which probably means that the growth condition of plant seemed to have an effect on the recovery of PSII from light stress. When PSII was severly photoinactivated at a chilling temperature, recovery was observed only if the residual functional PSII were not inhibited with DCMU, Nigericin and MV during recovery. In conclusion, PSIIs grown in the Hoagland solution was more resistant to excess light than in the Tap water grown one and the recovery of PSII from photodamage was more efficient in Hoagland grown pepper leaves than Tap water grown one, which means that the increased dark respiration may play a important role in the protection of PSII from photoinhibition by helping repair photosynthetic proteins (in particular, the D1 protein of PSII) degraded by photoinhibition.

• Rapid Communication in Photoscience
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• v.2 no.1
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• pp.18-23
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• 2013

The photosystem II (PSII) light harvesting complex (LHC) consists of a variety of pigment protein complexes which are involved in structural organization and regulation of photosynthetic unit. These LHC proteins encoded by a group of Lhcb genes are essential for the structural integrity of PSII supercomplex, the channeling the excitation energy to the reaction center of PSII and its redistribution to photosystem I by state transitions. Numerous studies with the help of recent technological advancements have enabled a significant progress in our understanding on the structure of PSII-LHCII supercomplexes and their mobilization under various light conditions. Here, we present a mini-review on the latest concepts and models depicting the structure of PSII-LHCII supercomplexes and the role of Lhcb proteins in their supra-molecular organization. Also we will review on the current understandings and remaining problems involved in the mobilization of the supercomplexes during state transitions and during high light illumination for controlling light energy distribution between the two photosystems.

• Journal of Photoscience
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• v.9 no.3
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• pp.65-70
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• 2002

In the rice leaves treated with methyl viologen (MV), the photochemical efficiency of PSII (or $F_{v/}$F $m_{m}$) was significantly decreased, and significant portion of the photoinactivation process was reversible during the dark-recovery. The dark-reactivation process was relatively slow, reaching its plateau after 2-2.5 h of dark incubation. The damaged portion of functional PSII was 13％, based on the value of I/ $F_{o}$- I/ $F_{m}$ after this dark-recovery period. The reversible photoinactivation process of PSII function in the MV-treated leaves consisted of a xanthophyll cycle-dependent development of NPQ and a xanthophyll cycle-independent process. The latter process was reversible in the presence of nigericin. As well as the increase in the values of Chl fluorescence parameters, the epoxidation process during the dark-recovery after the MV-induced photooxidation was very slow. These results suggest that the photooxidative effect of MV is partly protected by the down-regulation of PSII before inducing physical damages in core proteins of PSII.I.I.I.I.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.3
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• pp.390-399
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• 2010

Non-photochemical quenching (NPQ) values for utilizing them to detect osmotic tolerance in plants were examined with two different soybean cultivars, an osmotic tolerant soybean (Shinpaldalkong 2) and a control soybean (Taekwangkong). Two different stresses were applied to the cultivars as the restricted irrigations of 200 and 50 ml water $pot^{-1}\;d^{-1}$ for 5 days for a control and a drought stress, respectively, and a sodium chloride solution of 200 mmol for 6 days for a salt stress. The intact leaves of the two cultivars after treatment were used to measure chlorophyll fluorescence parameters, maximum efficiencies of photosystem II photochemistry (Fv/Fm), efficiencies of photosystem II photochemistry (${\Phi}_{PSII}$), $CO_2$ assimilation rate ($P_N$), and NPQ. Leaf water potentials of the two cultivars decreased from - 0.2 to - 0.8MPa by a drought treatment and from - 0.7 to - 1.7MPa by a salt treatment. Leaf water content of Shinpaldalkong 2 after a salt treatment was less decreased than that of Taekwangkong. $F_v/F_m$ values of both cultivars were not changed, while ${\Phi}_{PSII}$ and $P_N$ were decreased proportionally to leaf water potential decrease. The response of NPQ was occurred in Shinpaldalkong 2 under the drought and salt stresses. With Taekwangkong cultivar, only drought stress referred NPQ response. The cultivar differences on chlorophyll fluorescence parameters were found in the relationships between ${\Phi}_{PSII}$ and $P_N$, and between NPQ and ${\Phi}_{PSII}$. Although the positive relationships between ${\Phi}_{PSII}$ and $P_N$ were established on all treatments of both cultivars, the decreasing rate of ${\Phi}_{PSII}$ to $P_N$ was smaller in Shinpaldalkong 2 than Taekwangkong. The NPQ was increased according to the decrease of ${\Phi}_{PSII}$ by osmotic treatments in Shinpaldalkong 2. The complementary relationships between NPQ and ${\Phi}_{PSII}$ were well maintained at all treatments in Shinpaldalkong 2, while these relationships were lost at a salt treatment in Taekwangkong. Taken together, the results suggest that analysis of complementary relationships between ${\Phi}_{PSII}$ and NPQ could be more valuable and applicable for determining osmotic tolerance than single analysis of each parameter such as $F_v/F_m$, ${\Phi}_{PSII}$ and NPQ.

• Analytical Science and Technology
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• v.15 no.3
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• pp.229-235
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• 2002

Plasma source ion implantation (PSII) technique was utilized to improve the wettability of polystyrene surfaces. It is well known that treated surfaces undergo aging, leading to hydrophobic recovery with time. We investigated the aging effect of polystyrene thin film on the various molecular weights. Polystyrenes with several molecular weights ($M_w$ = 760, 2430, 31600, 115700, 280000, 903600) were treated in different experimental conditions including gas species and pulse energy, and their hydrophilicity was measured by contact angle goniometer. To study wettability decay as a function of the molecular weight, PSII-treated samples were aged at different temperatures. Hydrophobic recovery of high molecular weight polystyrene was much slower than that of low molecular weight, even at high temperatures. The methods used to characterize treated surfaces were water contact angle measurement, TOF-SIMS, XPS, SEM and AFM.

• Proceedings of the Korean Vacuum Society Conference
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• 1997.02a
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• pp.20-20
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• 1997

• Journal of Photoscience
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• v.9 no.2
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• pp.385-387
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• 2002

Direct EPR evidence of the photo-generation of superoxide radicals ( $O_2$$^{-.}$) was obtained by using spin trapping techniques in spinach photosystem II (PSII) membranes. $O_2$$^{-.}$ was detected by following the formation of 5-diethoxyphosphoryl-5-methyl-1 -pyrroline-N-oxide (DEPMPO) superoxide adducts, DEPMPO-OOH. The significant increase of the EPR signal amplitude of DEPMPO-OOH in N$H_2O$H-, CaC $l_2$- and NaCl-treated PSII membranes showed that the oxygen-evolving system has a close relation to the $O_2$$^{-.}$ production. PSII membranes with inactivated donor side could not prevent the $O_2$$^{-.}$ production efficiently. Treatments on PSII donor side also influence the maximum level and the kinetics of Chlorophyll (Chi) a fluorescence. Results suggested that manganese cluster and extrinsic proteins might affect Chi a fluorescence in ways different from that happens at the acceptor side of PSII.SII.SII.

• Journal of Photoscience
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• v.7 no.3
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• pp.87-95
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• 2000

As sunlight not always optimized for every terrestrial plant in terms of light quality, quantity and duration, some plants suffer detrimental effects of sunlight exposure under certain conditions. Photoinhibition of photosynthesis is a typical phenomenon representing harmful light effects, commonly observed in many photosynthetic organisms. It is generally accepted that functional, structural loss of photosystem II complex(PSII) is the primary event of photoinhibition. Accumulating data also suggest that singlet oxygen($^1$O$_2$) is the main toxic species directly involved in it. There are two different views on the specific site and mechanism of $^1$O$_2$ production in the photosynthetic membrane. One of them favors the PSII reaction center, where the primary charge pairs recombination occurs as a prerequisite for the generation of $^1$O$_2$, and the other inclines to photosensitized $^1$O$_2$ formation by a substance located outside PSII. This article describes how we, as the advocators of the latter concept, have arrived at the conclusion that $^1$O$_2$ immediately involved in PSII photodamage is largely generated from the Rieske center of the cytochrome b$_{6}$/f complex and diffuses into PSII, attacking the reaction center subunits.s.

• Journal of Plant Biology
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• v.39 no.4
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• pp.301-307
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• 1996

The disassembly of Chl-protein complexes during dark-induced senescence (DIS) was investigated using detached third and fourthleaves of 21$\pm$1 day-old Arabidopsis thaliana. Although Chl content decreased linearly after 1 d, a significant decrease of photochemical effeciency (Fv/Fm) was observed after 2 d. In experiments using native green gel electrophoresis of Chl-protein complexes combined with additional two-dimensional SDS-PAGE analysis, we could observe the degradation of both photosystems after 2 d. Although light-harvesting complex(LHC) for PSI (LHCI) was degraded first in PSI complex, small PSII apoproteins including CP47/CP43 and D1/D2 apoproteins were degraded first in PSII complexes. LHC for PSII (LHCII) trimers were stable until 4 d. The level of LHCII monomers was increased until 3 and decreased thereafter, resulting in the increase of free pigments. These results suggest that the disassembly process of PSI is different from that of PSII.