Inhibition of quantum yield of PS II electron transport in Spirulina platensis by osmotic stress may be explained mainly by an increase in the proportion of the QB-non-reducing PS II reaction centres

1998 ◽  
Vol 25 (6) ◽  
pp. 689 ◽  
Author(s):  
Congming Lu ◽  
Jianhua Zhang ◽  
Avigad Vonshak
Keyword(s):  
Electron Transport ◽  
Quantum Yield ◽  
Osmotic Stress ◽  
Spirulina Platensis ◽  
Fluorescence Induction ◽  
Photochemical Quenching ◽  
Ps Ii ◽  
Reaction Centres ◽  
Induction Kinetics ◽  
Fluorescence Induction Kinetics

Modulated chlorophyll fluorescence and fluorescence induction kinetics were used to evaluate the PS II photochemistry in Spirulina platensis exposed to osmotic stress (0–0.8 M mannitol). Osmotic stress decreased the efficiency of excitation energy capture by open PS II reaction centres (Fv′/Fm′) and more significantly, decreased photochemical quenching (qP). Osmotic stress also decreased the maximal efficiency of PS II photochemistry (Fv/Fm). There was no significant change in non-photochemical quenching (qN), indicating that the decreased Fv′/Fm′ was not due to an increase in qN. Analyses of the fast fluorescence induction kinetics indicated that osmotic stress caused a significant increase in the proportion of the QB-non-reducing PS II reaction centres. Based on the results in this study, we suggest that a substantial increase in the proportion of the QB-non-reducing PS II reaction centres may be responsible for the decrease in qP and Fv′/Fm′, of which both resulted in the decrease in the quantum yield of PS II electron transport (ΦPSII ).

Kinetic response of photosystem II photochemistry in the cyanobacterium Spirulina platensis to high salinity is characterized by two distinct phases

1999 ◽  
Vol 26 (3) ◽  
pp. 283 ◽  
Author(s):  
Congming Lu ◽  
Giuseppe Torzillo ◽  
Avigad Vonshak
Keyword(s):  
Electron Transport ◽  
Quantum Yield ◽  
Photosystem Ii ◽  
Spirulina Platensis ◽  
High Salinity ◽  
Photochemical Quenching ◽  
Second Phase ◽  
Ps Ii ◽  
Reaction Centres ◽  
Two Phases

The kinetic response of photosystem II (PS II) photochemistry in Spirulina platensis(Norstedt M2 ) to high salinity (0.75 M NaCl) was found to consist of two phases. The first phase, which was independent of light, was characterized by a rapid decrease (15–50%) in the maximal efficiency of PS II photochemistry (Fv /Fm), the efficiency of excitation energy capture by open PS II reaction centres (Fv′/Fm′), photochemical quenching (qp) and the quantum yield of PS II electron transport (Φ PS II) in the first 15 min, followed by a recovery up to about 80–92% of their initial levels within the next 2 h. The second phase took place after 4 h, in which further decline in above parameters occurred. Such a decline occurred only when the cells were incubated in the light, reaching levels as low as 45–70% of their initial levels after 12 h. At the same time, non-photochemical quenching (qN) and Q B -non-reducing PS II reaction centres increased significantly in the first 15 min and then recovered to the initial level during the first phase but increased again in the light in the second phase. The changes in the probability of electron transfer beyond QA (ψo) and the yield of electron transport beyond QA (φ Eo), the absorption flux (ABS/RC) and the trapping flux (TRo /RC) per PS II reaction centre also displayed two different phases. The causes responsible for the decreased quantum yield of PS II electron transport during the two phases are discussed.

scholarly journals Integrated high-resolution phenotyping, chlorophyll fluorescence induction kinetics and photosystem II dynamics under water stress and heat in Wheat (Triticum aestivum)

2019 ◽  
Author(s):  
Arun K. Shanker ◽  
Robert Coe ◽  
Xavier Sirault
Keyword(s):  
Chlorophyll Fluorescence ◽  
Water Stress ◽  
Quantum Yield ◽  
Photosynthetic Efficiency ◽  
Fluorescence Induction ◽  
Chlorophyll Fluorescence Induction ◽  
Maximum Quantum Yield ◽  
Induction Kinetics ◽  
Fluorescence Induction Kinetics ◽  
Chlorophyll Fluorescence Induction Kinetics

AbstractAn experiment was conducted in controlled conditions in three varieties of wheat under water stress, heat and heat +water stress treatments with the objective of studying Chlorophyll a fluorescence, chlorophyll fluorescence induction kinetics and the function of Photosystem II by plant phenotyping as affected by stress. We hypothesised that during stress, specific adaptive strategies are employed by plants, such as structural and functional changes in PS II by which they acquire new homeostasis which may be protective adaptations. Water stress stress treatment was imposed on Water stress and Heat +Water stress treatments at 43 DAS. Heat treatment was imposed on 48 DAS. Maximum quantum yield of primary photochemistry was measured with PAM 2500 and OJIP was measured with FluorPen FP 100 after the onset of stress at four observation times on two days viz., pre-dawn and afternoon during stress. In addition continuous monitoring of photosynthetic efficiency was done with Monitoring PAM. Heat +Water stress stress was more detrimental as compared to Heat or Water stress alone in terms of maximum quantum yield of photochemistry. This could have been due to higher decrease in connectivity between PSII and its antennae resulting in lower photosynthetic efficiency resulting in the impairment and disruption of the electron transport. K step was observed in heat stress and heat +Water stress stress which may be because of damage to Oxygen Evolving Complex indicating that low thermostability of the complex. The stress treatments had a reduction in the plastoquinone pool size as indicated by the reduced area above the OJIP curve. Our study indicated that the instrument PAM 2500 sensed both stresses separately and combined earlier than the other instruments, so in terms of sensitivity PAM 2500 was more effective than FluorPen FP 100 and MultispeQ. Rapid screening of stress was more effectively with FluorPen FP 100 and MultispeQ than by PAM 2500.

scholarly journals Effects of Heavy Metals on the Fast Chlorophyll Fluorescence Induction Kinetics of Photosystem II: a Comparative Study

1999 ◽  
Vol 54 (9-10) ◽  
pp. 735-739 ◽  
Author(s):  
M. Ciscato ◽  
J. Vangronsveld ◽  
R. Valcke
Keyword(s):  
Time Course ◽  
Fluorescence Induction ◽  
Chlorophyll Fluorescence Induction ◽  
Ps Ii ◽  
Induction Kinetics ◽  
Fluorescence Induction Kinetics ◽  
Bean Plants ◽  
Chlorophyll Fluorescence Induction Kinetics ◽  
Toxic Concentrations ◽  
Kinetics Of

The effects of toxic concentrations of Cu, Zn and Cd on the fast induction kinetics of fluorescence from photosystem(PS)II were investigated in a comparative way. The fast fluorescence transient from primary leaves of metal-treated bean plants was studied. During several days after metal application, the time course of the changes induced by the different metals was monitored. The results evidenced not only a different time course of the changes in fluorescence related parameters for the three metals, but also different effects on the fluorescence induction kinetics, which could possibly be linked to different mechanisms of action of the metals

Thermostability of photosystem II is increased in salt-stressed sorghum

1998 ◽  
Vol 25 (3) ◽  
pp. 317 ◽  
Author(s):  
Congming Lu ◽  
Jianhua Zhang
Keyword(s):  
High Temperature ◽  
Photosystem Ii ◽  
Salinity Stress ◽  
Fluorescence Induction ◽  
Maximum Efficiency ◽  
Photochemical Quenching ◽  
Fluorescence Parameters ◽  
Induction Kinetics ◽  
Fluorescence Induction Kinetics ◽  
Psii Photochemistry

Modulated chlorophyll fluorescence and rapid fluorescence induction kinetics were used to evaluate the functions of photosystem II (PSII) photochemsitry in sorghum leaves exposed to salinity (0–100 mM NaCl) and/or high temperature stress (30–50°C). No differences were detected in the steady- state fluorescence parameters and rapid fluorescence induction kinetics in salt-stressed leaves, indicating that PSII was highly resistant to salinity stress alone. However, salinity stress modified the responses of PSII to high temperature. When the temperature was above 45°C, the thermostability of PSII was strongly enhanced in salt-stressed leaves, which was reflected in a smaller decrease in maximum efficiency of PSII photochemistry, coefficients of photochemical and non-photochemical quenching, and efficiency of excitation capture by open PSII reaction centres, and in a smaller increase in the proportion of the QB-non-reducing PSII centres in salt-stressed leaves than in control leaves. This increased thermostability in salt-stressed leaves exposed to high temperature seemed to be independent of the imposed salt concentration since there were no significant variations in the above fluorescence parameters among the salt-stressed plants treated with different salt concentrations. The results are discussed in terms of the physiological significance of such increased resistance of PSII to high temperature.

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