Effect of high light on the efficiency of photochemical energy conversion in a variety of lichen species with green and blue-green phycobionts

Abstract

Exposure to high light induced a quantitatively similar decrease in the rate of photosynthesis at limiting photon flux density (PFD) and of photosystem II (PSII) photochemical efficiency, FV/FM, in both green and blue-green algal lichens which were fully hydrated. Such depressions in the efficiency of photochemical energy conversion were generally reversible in green algal lichens but rather sustained in blue-green algal lichens. This greater susceptibility of blue-green algal lichens to sustained photoinhibition was not related to differences in the capacity to utilize light in photosynthesis, since the light-and CO2-saturated rates of photosynthetic O2 evolution were similar in the two groups. These reductions of PSII photochemical efficiency were, however, largely prevented in lichen thalli which were fully desiccated prior to exposure to high PFD. Thalli of green algal lichens which were allowed to desiccate during the exposure to high light exhibited similar recovery kinetics to those which were kept fully hydrated, whereas bluegreen algal lichens which became desiccated during a similar exposure exhibited greatly accelerated recovery compared to those which were kept fully hydrated. Thus, green algal lichens were able to recover from exposure to excessive PFDs when thalli were in either the hydrated or desiccated state during such an exposure, whereas in blue-green algal lichens the decrease in photochemical efficiency was reversible in thalli illuminated in the desiccated state but rather sustained subsequent to illumination of thalli in the hydrated state.

Ecophysiological responses of desiccation-tolerant cryptobiotic crusts

“…Cryptobiotical crusts derived from Tanzania showed an unusually high Fv/Fm fluorescence value, approximately 0.8, after 80 min of rehydration. This value corresponded to the observation in healthy leaves of higher plants that is about 0.8 [47] and higher than the highest value observed in cyanobacterial lichens, 0.62 [48]. However, the crusts did not contain just cyanobacteria but green algae also, which might explain the values of variable fluorescence.…”

“…Longterm rehydration (3 hours) resulted in lower and steadystate values of Fv/Fm, between 0.4 and 0.6 compared with 10 min of rehydration due to the complete recovery of photosynthetic system ( Figure 6). Many studies observed similar results for cyanobacteria that reflect a steady-state condition of photochemistry [21,48]. The relatively high qP, even at high light intensities, is related to the ability of cyanobacteria to remove electrons from PSII and maintain the centres open [21,49].…”

Photosynthetic field capacity of cyanobacteria of a tropical inselberg of the Guiana Highlands

“…11). In contrast, cyanobacteria grown under artificial laboratory conditions sustained damage to the photosynthetic apparatus and did not recover for several days after sudden transfer to high light (Demmig-Adams et al, 1990b). Survival in the extremely high-light habitat of the inselbergs, therefore, requires other mechanisms to protect U.…”

Differences in photosynthetic performance between cyanobacterial and green algal components of lichen photosymbiodemes measured in the field

“…The equipment was identical to that of Lange et al (1993) and similar to that of Lange et al (1990). Three different instruments were used to measure lichen photosynthesis and dark respiration.…”