THE EFFECT OF DESICCATION ON CELL SHAPE IN THE LICHEN <i>PARMELIA SULCATA</i> TAYLOR

Brown, D. H.; Rapsch, Sonia; Beckett, A.; Ascaso, Carmen

doi:10.1111/j.1469-8137.1987.tb00867.x

Cited by 44 publications

(20 citation statements)

References 6 publications

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“…In our experiments, cytorrhysis occurred in all photobiont cells studied, as previously reported by various authors using LTSEM (Brown et al 1987;Honegger 1993;Scheidegger 1994) and by conventional SEM after rapid destruction of the semipermeability of the membranes prior to dehydration (Biidel and Lange 1991). Cytorrhysis also occurs in appressoria (Honegger 1993) and medullary hyphae of Nephroma resupinatum at low water content (Scheidegger 1994), while medullary and cortical hyphae of other lichens do not collapse, even at very low water contents.…”

Section: Discussionsupporting

confidence: 59%

“…They mentioned that during desiccation thick-walled cells suddenly become gas-filled, findings which were later confirmed by Ried (1960) for crustose species. In recent years, the effects of desiccation and rehydration at the cellular level have been studied by destroying the semipermeability of the membranes immediately prior to dehydration (Biidel and Lange 1991), or by low-temperature scanning electron microscopy (LTSEM; Brown et al 1987;Scheidegger 1993Scheidegger , 1994Honegger and Peter 1994) and transmission electron microscopy after freeze substitution (Honegger and Peter 1994). Regardless of which protocol is followed, it is essential that contact with water-containing fixatives is avoided during the preparation of water-stressed or desiccated structures (Bewley and Krochko 1982) so as to prevent rehydration during the preparation steps.…”

Section: Introductionmentioning

confidence: 99%

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Structural and functional processes during water vapour uptake and desiccation in selected lichens with green algal photobionts

Scheidegger

Schroeter

Frey

1995

Planta

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Abstract. Structural alterations of the photobiont and mycobiont cells of lichens have been related to CO2-gas exchange during experiments involving water vapour uptake and desiccation of liquid-water-saturated thalli. Increasing water vapour uptake of air dry lichens led to a gradual unfolding of the photobiont cells in Lobaria pulmonaria, Pseudevernia furfuracea, Ramalina maciformis and Teloschistes lacunosus as studied by low-temperature scanning electron microscopy. The data indicated that globular, probably turgid, cells and also slightly infolded or even heavily collapsed cells contributed to positive net photosynthesis, which was reached after water vapour uptake by the four species studied. During desiccation of fully water-saturated thalli of L. pulmonaria, extrathalline water films gradually evaporated before maximum values of CO2-gas exchange were measured and before photobiont cells started to shrivel. In contrast, in P. furfuracea the CO2-gas exchange maximum was reached when a considerable percentage of photobiont cells had already collapsed and while other parts of the thalli were still covered with liquid water. Further desiccation led to cavitation of the cortical cells in both species, this occurring at water contents at which net photosynthesis was still positive.

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Section: Discussionsupporting

confidence: 59%

Section: Introductionmentioning

confidence: 99%

Structural and functional processes during water vapour uptake and desiccation in selected lichens with green algal photobionts

Scheidegger

Schroeter

Frey

1995

Planta

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“…aprina below -5-4 °C leads to extracellular freezing of symplastic and apoplastic water and this translocation of water leads to a rapid dehydration of the protoplast. Structural changes occurring during extracellular freezing are similar to processes observed during dehydration at ambient temperatures (Brown et al, 1987;Blidel & Lange, 1991;Honegger, 1993;Scheidegger, 1994). The photobiont cells compensate the considerable reduction of the cell \'olume by cytorrhysis (Oertli, 1989), whereas the cortical and medullary hyphae with their rigid cell walls build up a highly negative turgor until cavitation occurs within the protoplasts (Scheidegger et al, 1995).…”

Section: Discussionmentioning

confidence: 57%

Water relations in lichens at subzero temperatures: structural changes and carbon dioxide exchange in the lichen Umbilicaria aprina from continental Antarctica

Schroeter

Scheidegger

1995

New Phytologist

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SUMMARY Photosynthetic activity and structural changes at subzero temperatures were monitored in the foliose lichen Umbilicaria aprina Nyl. from continental Antarctica. Carbon dioxide gas exchange measurements revealed that net photosynthesis and dark respiration occurred at subzero temperatures regardless of whether a lichen thallus saturated with liquid water was exposed to subzero temperatures, or if a dry thallus was re‐hydrated only from snow at subzero temperatures. When water‐saturated thalli of U. aprina were slowly cooled at subzero temperatures ice nucleation activity could be detected at — 5·4 °C, indicating extracellular freezing of water. Using low‐temperature scanning electron microscopy (LTSEM) it was demonstrated that extracellular ice formation leads to cytorrhysis in the photobiont cells and to cavitation in the mycobiont cells. Both processes were reversible if the lichen thallus was re‐warmed. When dry lichen thalli were covered with snow at subzero temperatures a substantial re‐hydration from snow could be observed in LTSEM micrographs and measured gravimetrically. The final thallus water content was strongly dependent on the temperature regime and gave water contents between 20% d. wt at — 21 °C and 56% d. wt at —4·5 °C after 16 h exposure. Carbon dioxide gas exchange measurements revealed that metabolic activity was initiated during re‐hydration from snow at subzero temperatures. It is proposed that water uptake from snow at subzero temperatures occurs in the gaseous phase and depends only on the temperature‐related differences in water potential between the cell contents and the surrounding atmosphere in equilibrium with snow. Photosynthetic activity and re‐hydration from snow at subzero temperatures are of great ecological importance for primary production in extreme environments such as Antarctica where metabolic activity is severely limited by water availability and low temperatures.

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“…Unlike vascular plants, lichens lack active mechanisms for controlling water content. As a result, their water content tends to fluctuate widely based on water availability in the environment [1]. Indeed, lichens can lose water rapidly when the environment is dry and they can also rapidly recover to normal water content when water becomes available [2].…”

mentioning

confidence: 99%

Comparative transcriptome analysis of the lichen-forming fungus Endocarpon pusillum elucidates its drought adaptation mechanisms

Wang

Zhang

Zhou

et al. 2014

Sci. China Life Sci.

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The lichen-forming fungus was isolated from the desert lichen Endocarpon pusillum that is extremely drought resistant. To understand the molecular mechanisms of drought resistance in the fungus, we employed RNA-seq and quantitative real-time PCR to compare and characterize the differentially expressed genes in pure culture at two different water levels and with that in desiccated lichen. The comparative transcriptome analysis indicated that a total of 1781 genes were differentially expressed between samples cultured under normal and PEG-induced drought stress conditions. Similar to those in drought resistance plants and non-lichenized fungi, the common drought-resistant mechanisms were differentially expressed in E. pusillum. However, the expression change of genes involved in osmotic regulation in E. pusillum is different, which might be the evidence for the feature of drought adaptation. Interestingly, different from other organisms, some genes involved in drought adaption mechanisms showed significantly different expression patterns between the presence and absence of drought stress in E. pusillum. The expression of 23 candidate stress responsive genes was further confirmed by quantitative real-time PCR using dehydrated E. pusillum lichen thalli. This study provides a valuable resource for future research on lichen-forming fungi and shall facilitate future functional studies of the specific genes related to drought resistance. lichen, mycobiont, dehydration, drought adaption, drought resistant Citation:Wang YY, Zhang XY, Zhou QM, Zhang XL, Wei JC. Comparative transcriptome analysis of the lichen-forming fungus Endocarpon pusillum elucidates its drought adaptation mechanisms.

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THE EFFECT OF DESICCATION ON CELL SHAPE IN THE LICHEN PARMELIA SULCATA TAYLOR

Cited by 44 publications

References 6 publications

Structural and functional processes during water vapour uptake and desiccation in selected lichens with green algal photobionts

Structural and functional processes during water vapour uptake and desiccation in selected lichens with green algal photobionts

Water relations in lichens at subzero temperatures: structural changes and carbon dioxide exchange in the lichen Umbilicaria aprina from continental Antarctica

Comparative transcriptome analysis of the lichen-forming fungus Endocarpon pusillum elucidates its drought adaptation mechanisms

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