Recovery of photosynthesis and photosystem II fluorescence in Chlamydomonas reinhardtii after exposure to three levels of high light

Abstract

Falk, S. and Samuelsson, G. 1992. Recovery of photosynthesis and photosystem II fluorescence In Chlamydomonas reinhardtii after exposure to three levels of high light. -Physiol. Plant. 85: 61-68.Recovery from 60 min of photoinhibitory treatment at photosynthetic photon flux densities of 500, 14t)0 and 2200 [imol m"* s^' was followed In cells of the green alga Chlamydomonas reinhardtii grown at 125 [imol m"-s^^. These light treatments represent photoregulation, moderate photoinhibition and strong photoinhibition, respectively. Treatment in photoregulatory light resulted in an increased maximal rate of oxygen evolution (P^aJ ^^^ ^^ increased quantum yield (•!*), but a 15% decrease In Fv/F^. Treatment at moderately photoinhibitory light resuhed In a 30% decrease in Fv/Ej, and an approximately equal decrease in i. Recovery in dim light restored Fv/F^ within 15 and 45 min after high light treatment at 500 and 1400 [imol m"^ s~\ respectively. Convexity (0), a measure of the extent of co-limitation between PS II turnover and whole-chain electron transport, and <t > approached, but did not reach the control level during recovery after exposure to 1400 fimol m~^ s"', whereas P^,, increased above the control. Treatment at 2200 nmol m"' s"' resulted in a strong reduction of the modeled parameters (t, 0 and ?"". Subsequent recovery was initially rapid but the rate decreased, and a complete recovery was not reached within 120 min. Based on the results, it is hypothesized that exposure to high light results in two phenomena. The first, expressed at all three light intensities, involves redistribution within the different aspects of PS II heterogeneity rather than a photoinhibitory destruction of PS II reaction centers. The second, most strongly expressed at 2200 ^mol m"-s^\ is a physical damage to PS 11 shown as an almost total loss cf PS !!" and PS II Qu-reducing centers. Thus recovery displayed two phases, the first was rapid and the only visible phase in algae exposed to 500 and 1 400 fijnol m'~ s^'. Tbe second phase was slow and visible only in the later part of recovery in cells exposed to 2200 nmol m"^ s"'.

Photosynthetic Light Utilization Efficiency, Photosystem II Heterogeneity, and Fluorescence Quenching in Chlamydomonas reinhardtii during the Induction of the CO2-Concentrating Mechanism

“…Durin cence quenching, noncyclic electron transport, and photosynthetic light utilization efficiency in C reinhardtii cells inducing the CCM. In several ways, these changes resemble earlier reported changes of the photosynthetic apparatus in C. reinhardtii cells exposed to a mild photoinhibitory treatment (6,7,16). In this context, it is important to emphasize that even though low-Ci cells of C reinhardtii can accumulate CO2 up to 40 times the concentration of an air-equilibrated medium (3), which has a C02(aq) concentration of 10 to 12 Mm, this would still only represent 20 to 30% of the CO2 concentration of a medium in equilibrium with 50 mL L1 C02(g), which has a CO2(aq) concentration of 1600 AM.…”

“…For photoinhibited cells of C. reinhardtii, it has previously been shown that a reduced PSII activity is correlated with a decline in the curvature parameter 0 of the photosynthetic light-response curve (6,7,16). Thus, it can be hypothesized that the low 0 observed in C reinhardtii cells with a fully induced CCM (Fig.…”

“…This inefficiency is generally most pronounced in the transition zone of photosynthetic light-, C02-, or temperature-response curves, where there is a change from one limiting step to another (5, 8). It has recently been shown that changes in one of these steps, namely the characteristics of PSII, such as antenna size and the ability to photoreduce the QB2 site of the DI protein, were tightly coupled with changes in the shape of the photosynthetic light response curve in photoinhibited cells of Chlamydomonas reinhardtii (6,7,16). This relationship was described by a model consisting of a quadratic equation having three independent variables: 4, Pmax 0 (5, 16).…”

Photosynthetic Response of Two Rice Field Cyanobacteria to Pesticides

“…The primary site of photoinhibition is the reaction centre (D1 protein) of PS II (Demming and Bjorkman, 1987;Jordan, 1996). Photoinhibition is manifested as a decrease in oxygen evolution (Krause, 1988) and photochemical efficiency (Falk and Samuelsson, 1992). The data on the measurement of Fv/Fm during the laboratory incubation of the different samples (Table 10 and 11) show similar kinetics like that off the photosynthetic pigment and protein accumulation and loss and DCPIP photoreduction of both the BGA in control and treated (pesticide) samples.…”

Effect on Biochemical Parameters of Cyanobacterium Anabaena Sp Under Lead Stress.

“…The primary site of photo inhibition is the reaction centre (D1 protein) of PS II (Demming and Bjorkman, 1987). Photo inhibition is manifested as a decrease in oxygen evolution (Krause, 1988) and photochemical efficiency (Falk and Samuelsson, 1992). Photosynthetic functions also have been found to be affected directly or indirectly by heavy metals since thylakoids lamelle of cyanobacterialcells contain all chlorophylls and carotenoids, which are disassembled in the presence of heavy metals (Baszynski and Krupa, 1995;Prasad etal., 2002).…”