Photoinhibition of photosynthesis in Antarctic lichen Usnea antarctica. I. Light intensity- and light duration-dependent changes in functioning of photosystem II

The paper deals with the differences in sensitivity of Antarctic lichen to photoinhibition. Thalli of Usnea antarctica were collected at the James Ross Island, Antarctica (57 deg 52 57 W, 63 deg 48 02 S) and transferred in dry state to the Czech Republic. After rewetting in a laboratory, they were exposed to 2 high light treatments: short-term (30 min), and long-term (6 h). In short-term treatment, the sample were exposed to 1000 and 2000 micromol m-2 s-1 of photosynthetically active radiation (PAR). In long-term experiment, PAR of 300, 600, and 1000 micromol m-2 s-1 were used. Photosynthetic efficiency of U.antarctica thalli was monitored by chlorophyll fluorescence parameters, potential (FV/FM) and actual (Phi PSII) quantum yield of photochemical processes in photosystem II in particular. In short-term treatments, the F0, FV and FM signals, as well as the values of FV/FM, and Phi PSII showed light-induced decrease, however substantial recovery after consequent 30 min. in dark. Longer exposition (60 min) to high light led to more pronounced decrease in chlorophyll fluorescence than after 30 min treatment, however dark recovery was faster in the thalli treated before for longer time (60 min). Long-term treatment by high light caused gradual decrease in FV/FM and Phi PSII with the time of exposition. The extent of the decrease was found light dose-dependent. The time course was biphasic for FV/FM but not for Phi PSII. The study showed that wet thalli of Usnea antarctica had high capacity of photoprotective mechanisms to cope well either with short- or long-term high light stress.Článek se zabývá rozdíly v citlivosti antarktických lišejníků na fotoinhibici. Stélky Usnea Antarktidy byly odebrány na Ostrově Jamese Rosse v Antarktidě (57 stupňů 52 57 W, 63 stupňů 48 02 S) a přeneseny v suchém stavu do ČR. Po ovlhčení v laboratoři byly vystaveny krátkodobé (30 min) a dlouhodobé (6 h) fotoinhibici. V krátkodobém experimentu byly vzorky se vystaveny 1000 a 2000 micromol m-2 s-1 fotosynteticky aktivního záření (PAR). Při dlouhodobém experimentu, PAR 300, 600, a 1000 micromol m-2 s-1 byly použity. Fotosyntetická účinnost U.antarctica stélek byla sledována podle parametrů fluorescence chlorofylu, potenciální (FV / FM) a efektivní (Phi PSII) kvantový výtěžek fotochemických procesů v fotosystému II.The paper deals with the differences in sensitivity of Antarctic lichen to photoinhibition. Thalli of Usnea antarctica were collected at the James Ross Island, Antarctica (57 deg 52 57 W, 63 deg 48 02 S) and transferred in dry state to the Czech Republic. After rewetting in a laboratory, they were exposed to 2 high light treatments: short-term (30 min), and long-term (6 h). In short-term treatment, the sample were exposed to 1000 and 2000 micromol m-2 s-1 of photosynthetically active radiation (PAR). In long-term experiment, PAR of 300, 600, and 1000 micromol m-2 s-1 were used. Photosynthetic efficiency of U.antarctica thalli was monitored by chlorophyll fluorescence parameters, potential (FV/FM) and actual (Phi PSII) quantum yield of photochemical processes in photosystem II in particular. In short-term treatments, the F0, FV and FM signals, as well as the values of FV/FM, and Phi PSII showed light-induced decrease, however substantial recovery after consequent 30 min. in dark. Longer exposition (60 min) to high light led to more pronounced decrease in chlorophyll fluorescence than after 30 min treatment, however dark recovery was faster in the thalli treated before for longer time (60 min). Long-term treatment by high light caused gradual decrease in FV/FM and Phi PSII with the time of exposition. The extent of the decrease was found light dose-dependent. The time course was biphasic for FV/FM but not for Phi PSII. The study showed that wet thalli of Usnea antarctica had high capacity of photoprotective mechanisms to cope well either with short- or long-term high light stress. The paper deals with the differences in sensitivity of Antarctic lichen to photoinhibition

Photoinhibition of photosynthesis in Antarctic lichen Usnea antarctica. II. Analysis of non-photochemical quenching mechanisms activated by low to medium light doses

The paper focus sensitivity of an Antarctic lichen Usnea antarctica to photoinhibition studied under controlled laboratory conditions. Main emphasis was given to the analysis of quenching mechanisms, i.e. deexcitation pathways of absorbed light energy exploited in non-photochemical processes. Thalli of U. antarctica were collected at the James Ross Island, Antarctica (57°52´57´´ W, 63°48´02´´ S) and transferred in dry state to the Czech Republic. After rewetting in a laboratory, they were exposed to medium light intensities (300, 600 and 1000 mmol m-2 s-1 of photosynthetically active radiation) for 6 h. Before and during photoinhibitory treatments, chlorophyll fluorescence parameters, photoinhibitory (qI), state 1-2 transition (qT), and energy-dependent quenching (qE) in particular were measured to evaluate dose- and time-dependent changes in these parameters. The results showed that among the components forming non-photochemical quenching (qN), qI contributes to the largest extent to qN, while qE and qT contribute less. This finding differs from our earlier studies made in a short term-, and high light-treated U. antarctica that found qE together with qI is the most important part of non-photochemical quenching. Possible explanation is that photoinhibition in PS II in U. ant-arctica, when induced by low to medium light, activates qE to only limited extend and for a relatively short time (tens of minutes). With prolonged high light treatment lasting several hours, qE tends to be reduced to the values close to zero and qI then forms a major part of qN

Photoinhibition of photosynthesis in Antarctic lichen Usnea antarctica. I. Light intensity- and light duration-dependent changes in functioning of photosystem II

The paper deals with the differences in sensitivity of Antarctic lichen to photoinhibition. Thalli of Usnea antarctica were collected at the James Ross Island, Antarctica (57°52´57´´W, 63°48´02´´S) and transferred in dry state to the Czech Republic. After rewetting in a laboratory, they were exposed to 2 high light treatments: short-term (30 min), and long-term (6 h). In short-term treatment, the sample were exposed to 1000 and 2000 µmol m-2 s-1 of photosynthetically active radiation (PAR). In long-term experiment, PAR of 300, 600, and 1000 µmol m-2 s-1 were used. Photosynthetic efficiency of U. antarctica thalli was monitored by chlorophyll fluorescence parameters, potential (FV/FM) and actual (FPSII) quantum yield of photochemical processes in photosystem II in particular. In short-term treatments, the F0, FV and FM signals, as well as the values of FV/FM, and FPSII showed light-induced decrease, however substantial recovery after consequent 30 min. in dark. Longer exposition (60 min) to high light led to more pronounced decrease in chlorophyll fluorescence than after 30 min treatment, however dark recovery was faster in the thalli treated before for longer time (60 min). Long-term treatment by high light caused gradual decrease in FV/FM and FPSII with the time of exposition. The extent of the decrease was found light dose-dependent. The time course was biphasic for FV/FM but not for FPSII. The study showed that wet thalli of Usnea antarctica had high capacity of photoprotective mechanisms to cope well either with short- or long-term high light stress. This might be of particular importance in the field at the James Ross Island, particularly at the begining of growing season when melting water is available and, simultaneously, high light stress may happen on fully sunny days

Photoinhibition of photosynthesis in Antarctic lichen Usnea antarctica. I. Light intensity- and light duration-dependent changes in functioning of photosystem II

The paper deals with the differences in sensitivity of Antarctic lichen to photoinhibition. Thalli of Usnea antarctica were collected at the James Ross Island, Antarctica (57°52´57´´W, 63°48´02´´S) and transferred in dry state to the Czech Republic. After rewetting in a laboratory, they were exposed to 2 high light treatments: short-term (30 min), and long-term (6 h). In short-term treatment, the sample were exposed to 1000 and 2000 µmol m-2 s-1 of photosynthetically active radiation (PAR). In long-term experiment, PAR of 300, 600, and 1000 µmol m-2 s-1 were used. Photosynthetic efficiency of U. antarctica thalli was monitored by chlorophyll fluorescence parameters, potential (FV/FM) and actual (FPSII) quantum yield of photochemical processes in photosystem II in particular. In short-term treatments, the F0, FV and FM signals, as well as the values of FV/FM, and FPSII showed light-induced decrease, however substantial recovery after consequent 30 min. in dark. Longer exposition (60 min) to high light led to more pronounced decrease in chlorophyll fluorescence than after 30 min treatment, however dark recovery was faster in the thalli treated before for longer time (60 min). Long-term treatment by high light caused gradual decrease in FV/FM and FPSII with the time of exposition. The extent of the decrease was found light dose-dependent. The time course was biphasic for FV/FM but not for FPSII. The study showed that wet thalli of Usnea antarctica had high capacity of photoprotective mechanisms to cope well either with short- or long-term high light stress. This might be of particular importance in the field at the James Ross Island, particularly at the begining of growing season when melting water is available and, simultaneously, high light stress may happen on fully sunny days

Comparative analysis of heterogeneity of primary photosynthetic processes within fruticose lichen thalli: Preliminary study of interspecific differences

Two species of fruticose lichens from different habitats and of distinct color, Usnea antarctica and Stereocaulon vesuvianum, were compared using chlorophyll fluorescence imaging in order to study the distribution of primary photosynthetic processes within the thalli. The thallus of U. antarctica is yellow with black tips: in this species chlorophyll containing cells were mostly located in the middle region of the thallus and the highest PS II efficiency was detected in the middle to basal region, as shown by the FV/FM and PhiPSII values. No chlorophyll fluorescence was detected in the apical part of the thallus, indicating that little or no photosynthesis takes place in these tissues. The lichen S. vesuvianum is homogeneously pale grayish green and chlorophyll containing cells are distributed along the thallus with maximum concentration in the middle region. In S. vesuvianum, the highest PS II efficiency was detected in the apical to middle region of the thallus, while the basal portion was found to have the lowest efficiency of primary photochemical reactions. Quenching analysis data confirmed the uneven patterns of primary photosynthetic processes within the thalli of these fruticose lichens.Byly porovnany primarni fotosynteticke procesy dvou druhu lisejniku s kerickovitym morfotypem stelky.Two species of fruticose lichens from different habitats and of distinct color, Usnea antarctica and Stereocaulon vesuvianum, were compared using chlorophyll fluorescence imaging in order to study the distribution of primary photosynthetic processes within the thalli. The thallus of U. antarctica is yellow with black tips: in this species chlorophyll containing cells were mostly located in the middle region of the thallus and the highest PS II efficiency was detected in the middle to basal region, as shown by the FV/FM and PhiPSII values. No chlorophyll fluorescence was detected in the apical part of the thallus, indicating that little or no photosynthesis takes place in these tissues. The lichen S. vesuvianum is homogeneously pale grayish green and chlorophyll containing cells are distributed along the thallus with maximum concentration in the middle region. In S. vesuvianum, the highest PS II efficiency was detected in the apical to middle region of the thallus, while the basal portion was found to have the lowest efficiency of primary photochemical reactions. Quenching analysis data confirmed the uneven patterns of primary photosynthetic processes within the thalli of these fruticose lichens

Comparative analysis of heterogeneity of primary photosynthe-tic processes within fruticose lichen thalli: Preliminary study of interspecific differences ( Short Communication )

Two species of fruticose lichens from different habitats and of distinct color, Usnea antarctica and Stereocaulon vesuvianum, were compared using chlorophyll fluorescence imaging in order to study the distribution of primary photosynthetic processes within the thalli. The thallus of U. antarctica is yellow with black tips: in this species chlorophyll containing cells were mostly located in the middle region of the thallus and the highest PS II efficiency was detected in the middle to basal region, as shown by the FV/FM and ΦPSII values. No chlorophyll fluorescence was detected in the apical part of the thallus, indicating that little or no photosynthesis takes place in these tissues. The lichen S. vesuvianum is homogeneously pale grayish green and chlorophyll containing cells are distributed along the thallus with maximum concentration in the middle region. In S. vesuvianum, the highest PS II efficiency was detected in the apical to middle region of the thallus, while the basal portion was found to have the lowest efficiency of primary photochemical reactions. Quenching analysis data confirmed the uneven patterns of primary photosynthetic processes within the thalli of these fruticose lichens

Phenotypic characterization of <i>Synechocystis</i> sp. PCC 6803 substrains reveals differences in sensitivity to abiotic stress - Fig 6

<p>Batch growth of <i>Synechocystis</i> sp. PCC 6803 substrains GT-L (white circles), GT-B (red triangles) and PCC-B (blue squares) in BG11 medium (A) and BG11 medium supplemented with 0.5 M NaCl at the beginning of the batch cultivation (B). The plotted values represent averages of at least three independent experiments, the error bars represent standard errors.</p

Growth rates of <i>Synechocystis</i> sp. PCC 6803 substrains GT-L (white circles), GT-B (red triangles) and PCC-B (blue squares) under increasing red, blue and white light.

<p>A, B–Red light was set to intensities of 25–660 μmol(photons) m^-2 s^-1 and it was supplemented with 25 μmol(photons) m^-2 s^-1 of blue light. The experiments were performed at 32°C (A) and 35°C (B). C–Red light of 220 μmol(photons) m^-2 s^-1 was supplemented with 25–220 μmol(photons) m^-2 s^-1 of blue light under 32°C. D–Red light of 220–8 μmol(photons) m^-2 s^-1 was supplemented with white light of 0–790 μmol(photons) m^-2 s^-1 (at 32°C) in order to keep the red photons (as a combination of red light and part of the white spectra) constant at 220 μmol(photons) m^-2 s^-1 (according to [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0189130#pone.0189130.ref019" target="_blank">19</a>]). All experiments were carried out in a quasi-continuous regime as described in the main text under growth saturating CO₂ concentration of 5 000 ppm. Each point represents average of at least four independent experiments, error bars represent standard errors. The dashed lines in panels A and B represent fitting of the data points by the function derived by Platt et al. (1980) [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0189130#pone.0189130.ref051" target="_blank">51</a>]. The dashed lines in panels C and D represent linear fitting of the data points by the least squares method. Legend in panel D represents particular combinations of white light (W) and red light (R) in units of μmol(photons) m^-2 s^-1.g.</p

Phenotypic characterization of <i>Synechocystis</i> sp. PCC 6803 substrains reveals differences in sensitivity to abiotic stress - Fig 4

<p>Cell size (A), dry weight (B), and glycogen content (C) of <i>Synechocystis</i> substrains GT-L (white bars), GT-B (red bars) and PCC-B (blue bars) under 25, 220 and 660 μmol(photons) m^-2 s^-1 of red light complemented with 25 μmol(photons) m^-2 s^-1 of blue light. The cells were cultivated at 32°C under input CO₂ concentration of 5 000 ppm in a quasi-continuous regime as described in the main text. Each value represents average from at least three independent experiments, error bars represent standard errors. Differences in cell size, dry weight and glycogen content among <i>Synechocystis</i> substrains are marked by letters above the particular columns (Tukey’s HSD post-hoc test following one-way ANOVA: p<0.05).</p