ILM for Dryad

Raw data used to produce figures in the manuscript

Suspension Images

Unprocessed chlorophyll emission images at different excitation wavelengths in zooxanthellae suspension

Discosoma Images

Unprocessed chlorophyll emission images at different excitation wavelengths in Discosoma

Results of tank experiment.

<p>(a) Chl <i>a</i> concentration per algae (in black) and (b) algae numbers (in gray), of <i>S. pistillata</i> subjected to six different treatments (chilling the tank water to 21°C, hitting the tank water to 29–30°C, feeding once a day with <i>Artemia nauplius</i>, filtration of sea water via 0.2 µm mash creating conditions of starvation, High PFD of ∼135 µmol quanta cm⁻² s⁻¹ and Low PFD of ∼20 µmol quanta cm⁻² s⁻¹), T0 represent a measurement taken on the day the fragments were plucked, “Ctrl” is the control and “Trans” are the fraq1agments from transplantation experiment. n = 5 fragments per each treatment, control treatment includes 10 fragments. Bars represent standard deviation.</p

A schematic presentation of electron transport within PSII and the resulting TL bands.

<p>The Q_A and Q_B quinones, P₆₈₀ and the Mn cluster S-states are shown. Forward electron transport is represented by plain arrows and back electron transport by blue arrows. Changes in the peak temperature observed in TL experiments can be used as an estimate for the recombination energy of the Q_B⁻S₂/Q_BS₁ and Q_B⁻S₃/Q_BS₂ (B-band) or Q_A⁻S₂/Q_AS₁ (Q-band) redox pairs. To observe the Q band emission, reduction of the Q_B site was blocked by herbicides that bind specifically to this site. The electron released from P₆₈₀ by light excitation at subzero temperatures can reach the Q_A site and, in the presence of herbicides that bind to the Q_B site, recombine upon warming with the oxidized S₂ state by back electron flow producing the Q band. Since the energy gap between Q_A⁻ and P₆₈₀<i>⁺</i> is smaller than that from Q_B⁻ to P₆₈₀<i>⁺</i> (B band), lower activation energy is required for this recombination and thus the Q band is observed at lower temperatures.</p

Temperature-dependence of TL emissions of <i>Synechocysti</i>s (A) and <i>Microcoleus</i> cells (B).

<p>Measurements were carried out as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0011000#s4" target="_blank">Materials and Methods</a>. Note the significantly smaller difference in the maximal Q and B bands temperatures in <i>Microcoleus</i> as compared to those observed in <i>Synechocystis</i> used as a “model organism”. The intensities of the Q bands are partially quenched by the herbicides used <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0011000#pone.0011000-Gleiter1" target="_blank">[29]</a>.</p

Fluorescence yield in <i>Microcoleus</i> inhabiting desert sand crusts as affected by time and moisture.

<p>Fluorescence emitted from 4 crust samples was measured using a PAM 2500 (Walz, Effertlich, Germany). Two plates were sprayed with water to prevent dehydration. The experiments were repeated 4 times with minor variations in the results.</p

Kinetics of Q_A⁻ oxidation in the presence of DCMU following exposure to excess light.

<p><b>A–C.</b> Cell suspensions (7.5 µg chl ml⁻¹) were exposed to 2000 µmol photons m⁻² s⁻¹ for 0–35 min, at 25°C. Q_A⁻ oxidation was measured using the FL 3000 fluorimeter following 2 min dark adaptation in the presence of 10 µM DCMU. The t_½ time of Q_A⁻ oxidations was 0.2–0.4 ms and 1.3–2.0 s for the fast and slow phases, respectively. Flash intensity was 2300 µmol photons m⁻² s⁻¹; flash duration 30 µs. The first sampling point was recorded 215 µs after the flash to minimize the contribution of the flash decay, 5 points per decade and 20% voltage of the measuring beam. Furthermore, since all measurements were performed with the same instrument and setting, the contribution of instrumental artifacts, if any, would equally occur in all the measurements. For the sake of clarity, we provide full data sets for the 0 and 35 min time point in (<b>A</b>) and the Fv values and the ratio of fast to slow decay kinetics, as a function of time of exposure to the excess light in (<b>B</b>), calculated from data such as presented in (<b>A</b>). (<b>C</b>) Same conditions as above but with the cells exposed for 17 min to various light intensities (250 to 2000 µmol photons m⁻² s⁻¹). (<b>D</b>) Same conditions as in (<b>A</b>) but the QA⁻ re-oxidation was measured at 15°C. The t_½ time of Q_A⁻ oxidations was 0.32–0.45 ms and 3.1–7.1 s for the fast and slow phases, respectively. Note the large rise in the extent of the fast phase and that the t_1/2 of the fast phase was little affected by lowering the temperature from 25°C (<b>A–C</b>) to 15°C (<b>D–E</b>), whereas that of the slow phase declined by about 3-fold (compare with (A).</p

Absorption changes in high light-exposed <i>Microcoleus</i> cells.

<p>Cells suspension was exposed to 1500 µmol photons m⁻² s⁻¹ for 40 min followed by 60 min recovery at 50 µmol photons m⁻² s⁻¹, which resulted in the recovery of the Ft–Fo values (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0011000#pone-0011000-g003" target="_blank">Fig. 3B</a>). Elapsed time (min) from the beginning of the experiment is shown in the box. <b>Top panel</b>: Absorptions in the visible range during the entire experiment. <b>Bottom panel</b>: Absorptions changes calculated from the differences between the light exposed and zero time control. O.D.₈₀₀ was used for normalization. Wavelengths are indicated where maximal absorption differences were observed. Differential absorption measurements were made using a Cary 300bio UV-visible spectrophotometer (Varian, Palo Alto, USA). Integration time was set to 0.5 s, the slit to 2 nm and the wavelength increment to 2 nm.</p

Loss of variable fluorescence, even in the presence of DCMU, DBMIB and FCCP following excess light treatment.

<p><b>A.</b> Cells suspensions (7.5 µg chl ml⁻¹) were exposed to 2000 µmol photons m⁻² s⁻¹, 2.2 cm optical path, for the indicated times in the presence of 10 µM DCMU, a concentration which completely blocked CO₂-dependent O₂ evolution. Fv was measured after dark adaptation for 2 min using the FL 3000 fluorimeter; optical path 0.5 cm. After 15 min of excess illumination the light intensity was reduced to 50 µmol photons m⁻² s⁻¹ for 50 min. <b>B.</b> Fluorescence emission kinetics of dark-adapted cells in the presence or absence of 10 µM DCMU. The cells were exposed for 950 s to 530 µmol photons m⁻² s⁻¹ of blue light using the IMAG-MAX PAM. Note that in its setup, this light intensity is the maximal but it is not saturating. <b>Insert:</b> Rate of fluorescence decline at the 150–900 s range for cultures exposed to varying light intensities (100–530 µmol photons m⁻² s⁻¹). <b>C</b>. The experiment was performed as in (A), 2000 µmol photons m⁻² s⁻¹, 2.2 cm optical path, but with 10 µg chl ml⁻¹ and 0.15 µM DBMIB instead of DCMU. Note that DBMIB itself is a fluorescence quencher and the procedure used to minimize this effect is explained in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0011000#s4" target="_blank">Materials and Methods</a> section. <b>D.</b> Experiment performed as in (C) but in the presence of 10 µM FCCP.</p