FIGURE LEGENDS
FIGURE 1. Effect of long-term stress acclimation on partitioning of PSII (a) and PSI (b) in UWO 241 and SAG 49.72 grown under control and long term stress conditions. Φ NO, non-regulated energy dissipation; Φ NPQ, non-photochemical energy quenching; ΦPSII, PSII quantum yield; ΦPSI, PSI quantum yield; ΦND, donor side limitation; ΦNA, acceptor side limitation. C, Control; HL, High Light; LT, Low Temperature; HS, High Salt. Values are means with standard deviations (n=3).
FIGURE 2. Capacity for nonphotochemical quenching in UWO 241 (UWO) and SAG 49.72 (SAG) grown under control and high stress conditions. C, Control; HL, high light; LT, low temperature; HS, high salt. Letters - a, statistical significance between control vs. stress within one algal species; b, statistical significance between UWO 241 vs. SAG 49.72 when grown under same treatment (n=3; p<0.05).
FIGURE 3. 77K Chl a fluorescence emission spectra of the mesophile SAG 49.72 (a) and the psychrophile UWO 241 (b) and acclimated to control and long-term stress treatments. C, Control; HL, high light; LT, low temperature; HS, high salt.
FIGURE 4. Photosystem I (P700) oxidation/reduction of the mesophile SAG 49.72 and the psychrophile UWO 241 grown under control and long-term stress conditions. a. Oxidation state of P700. b. Re-reduction kinetics of P700+. P700oxidation/reduction was monitored in the presence of far red light. Letters - a, statistical significance between control vs. stress within one algal species; b, statistical significance between UWO 241 vs. SAG 49.72 when grown under same treatment (n=3; p<0.05). C, Control; HL, high light; LT, low temperature; HS, high salt; ND, not detectable.
FIGURE 5. Photosystem I oxidation/reduction kinetics in UWO 241 grown under control and long-term stress conditions. P700 oxidation/reduction was monitored in the presence of red actinic light following DCMU pretreatment. (a) Oxidation state of P700. (b) Re-reduction kinetics of P700+. Letters statistical significance between control vs. stress (n=3; p<0.05). C, Control; HL, high light; LT, low temperature; HS, high salt.
FIGURE 6. Activity of AsA-GSH pathway enzymes, ascorbate peroxidase (APX, a) and glutathione reductase (GR, b) the mesophile SAG 49.72 and the psychrophile UWO 241 grown under control and long-term stress conditions. Letters - a, statistical significance between control vs. stress within one algal species; b, statistical significance between UWO 241 vs. SAG 49.72 when grown under same treatment (n=3; p<0.05). C, Control; HL= high light; LT, low temperature; HS, high salt.
FIGURE 7. Photoinhibition and recovery in the mesophile SAG 49.72 and the psychrophile UWO 241. Cultures grown under control conditions exposed to either high light (HL, 300 μmol m­-2s-1) or low temperature LT, (2oC) short-term stress for 60 min then returned to control conditions for 120 min to recover. (a) Percent photoinhibition was determined by loss of photochemical ability (FV/FM) relative to time zero. (b) Photochemical quenching, qL. C. nonphotochemical quenching, NPQ (n=3).
FIGURE 8. Production of reactive oxygen species in UWO 241 (P) vs. SAG 49.72 (M) during short-term incubation in low temperature (5oC) or high light (300 μmol m-2s-1) stress. Algal samples were incubated for 1 hour in the presence of NBT dye to detect superoxide. Data is normalized to time 0. Letters - a, statistical significance between control vs. stress within one algal species; b, statistical significance between UWO 241 vs. SAG 49.72 when grown under same treatment (n=3; p<0.05).
Table 1. Growth conditions for UWO 241 and SAG 49.72 used in this study.