Simultaneous measurements of PSII activity and thallus temperature during linear cooling. A method to assess interspecific differences in photosynthetic processes in lichens from polar regions.
|Year of publication||2014|
|MU Faculty or unit|
|Description||A comparison of cryoresistance of isolated lichen photobiont and polar lichens is presented. Several species were chosen for this experiment: (1) algal cultures of Trebouxia glomerata, Trebouxia sp. (2) thalli of Usnea antarctica, Usnea aurantiaco-atra, Usnea longissima, Umbilicaria decussata, Umbilicaria cylindrica. All the samples were exposed to temperatures linearly decreasing from +20 °C to -40 °C under controlled conditions. During the experiment, sample temperature and two parameters of chlorophyll fluorescence – (1) potential (FV/FM) and (2) effective quantum yield of photochemical processes in photosystem II (YieldPSII) – were measured simultaneously. Cooling was provided by a KRYO 560-16 (PLANER, United Kingdom) device. For majority of samples, two cooling rates were used: 6 °C min-1 (fast) and 2 °C min-1 (slow) were used. The chlorophyll fluorescence was measured by a PC-linked PAM 2000 fluorometer (H. Walz, Germany). Measurements of YieldPSII were made every 30 s. For all samples, the response of FV/FM and YieldPSII to declining temperature showed an „S curve“ with critical temperatures, indicating high level of cryoresistance of the samples. In an individual sample, critical temperature for FV/FM was typically lower than for YieldPSII.|