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.