Low‐temperature scanning electron microscopy of birch leaves after exposure to ozone

Scheidegger, Christoph; Günthardt‐Goerg, Madeleine S.; Matyssek, Rainer; Hatvani, P.

doi:10.1111/j.1365-2818.1991.tb03075.x

Cited by 36 publications

(27 citation statements)

References 21 publications

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“…The latter method resulted in a brightly stained callose, whereas cellulose wails and stainable protoplasmic contents were only palely stained ( viewed under phase contrast). For low-temperature scanning electron microscopy, excised leaf discs were immediately frozen in liquid nitrogen (for further procedure see Scheidegger et al 1991).…”

Section: Methodsmentioning

confidence: 99%

Ozone-induced microscopical changes and quantitative carbohydrate contents of hybrid poplar (Populus � euramericana)

Landolt

Günthardt‐Goerg

Pfenninger

et al. 1994

Trees

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Summary. Cuttings of hybrid poplar (Populus • euramericana var. "Dorskamp") were exposed to ozone (80 ]xg/m 3 from 2100 hours to 0700 hours, 180 [.tg/m 3 from 0700 hours to 2100 hours) for 3 months. Ozone reduced the starch content in leaves and stem bark, whereas starch granules accumulated in bundle sheath cells along small leaf veins. At the same time, sucrose and inositol content increased in the leaves. Mesophyll cells in the vicinity of the stomata were injured first, and droplet-like material appeared on their walls. In the sieve plates of fumigated trees, the pores showed a higher degree of narrowing than those of the control treatment. Cell collapse in the leaves was accompanied by water loss and an increase in air space. In the stems, the ozone treatment led to a reduced radial width, particularly in the xylem tissue. These results are discussed in relation to reduced or inhibited phloem loading and ozone-induced drought stress. The plants injured by ozone showed quite distinct patterns of metabolite responses as well as enzyme activities (PEP-and RubPcarboxylase) in the leaves from the top to the bottom. There were also remarkable differences in the reaction of sucrose and inositol between leaves and stem bark. Future research should therefore increasingly follow a whole-plant approach for a better understanding of complex plant reactions.

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Section: Methodsmentioning

confidence: 99%

Ozone-induced microscopical changes and quantitative carbohydrate contents of hybrid poplar (Populus � euramericana)

Landolt

Günthardt‐Goerg

Pfenninger

et al. 1994

Trees

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show abstract

“…This problem was overcome if frozen specimens were mounted with the low-temperature cryoglue but in this case the detection of extrathalline water films was no longer unambiguously possible. Mounted specimens were cooled to 196'~C and then transferred to the cold stage of the preparation chamber of a dedicated scanning cryo unit SCU 020 (BAL-TEC; Miiller et al 1991;Scheidegger et al 1991). The specimens were fractured with a microtome at -9ff'C or -120~ when mounted with DMSO and partially freeze-dried in a high vacuum (P < 2 x 10 4 Pa) at -90"C for 1 min.…”

Section: Ramalina Maciformis (Delile) Bory and Teloschistes Lacunosusmentioning

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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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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“…A detailed description of the method and equipment can be found in Muller et al (1991) and Scheidegger et al (1991).…”

Section: Low-temperature Scanning Electron Microscopy Studiesmentioning

confidence: 99%

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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Low‐temperature scanning electron microscopy of birch leaves after exposure to ozone

Cited by 36 publications

References 21 publications

Ozone-induced microscopical changes and quantitative carbohydrate contents of hybrid poplar (Populus � euramericana)

Ozone-induced microscopical changes and quantitative carbohydrate contents of hybrid poplar (Populus � euramericana)

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

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