Short-Term Changes in Heat Tolerance in the Alpine Cushion Plant Silene acaulis ssp. excapa [All.] J. Braun at Different Altitudes

Abstract

The habit of cushion growth positively affects plant temperature but at the same may increase the risk of occasional overheating. In order to determine the adaptive response to short-term heat stress, we exposed S. acaulis cushions at field sites to controlled heat treatments using infrared lamps. Natural diurnal changes in heat tolerance were monitored at alpine sites and at a site distinctly below the natural distribution boundary, where higher temperatures were expected.

The range of heat tolerance limits in summer, 45.5 - 54.5 °C (9 K), exceeded that reported for other alpine species (0.1 - 5 K) and even that for total seasonal changes (5 - 8 K). Heat tolerance either increased or decreased on most days (80 %). The maximum diurnal increase was + 4.7 K. Under the experimental conditions heat hardening started at leaf temperatures around 30 °C and proceeded at mean rates of 1.0 ± 0.5 K/h. The onset of functional disturbances in photosystem II also occurred at 30 °C. Heating rates exceeding those naturally found above 30 °C (> 10 K/h) appeared to retard heat hardening.

During summer average leaf temperature maxima were 12.4 K (600 m) and 13.0 K (1945 m) higher than air temperature which corroborates the heat trapping nature of cushion plants. At 600 m, as compared to 1945 m, cushions experienced significantly higher leaf temperature maxima (+ 8.8 K) and exceeded 30 °C on most days (80 %). This resulted in a significantly higher heat tolerance (LT₅₀) at 600 m (51.7 ± 0.2 °C) than at 1945 m (49.8 ± 0.2 °C).

The fast short-term changes of heat tolerance in summer help S. acaulis to cope with the occasional diurnal short-term heat stress associated with cushion growth.

Abbreviations

F_v/F_m: potential efficiency of photosystem II

LT₀: highest temperature sustained without heat damage

LT₅₀: temperature at 50 % heat damage

PS II: photosystem II

Heat survival - high temperature stress - thermostability - photoinhibition - short-term heat hardening

References

• 01 Alexandrov,  V. Y.. (1977) Cells, molecules and temperature. Berlin; Ecol. Studies 21, Springer pp. 330
• 02 Biebl,  R.. (1968);  Über Wärmehaushalt und Temperaturresistenz arktischer Pflanzen in Westgrönland.  Flora. 157 327-354
• 03 Dahl,  E.. (1951);  On the relation between summer temperature and the distribution of alpine vascular plants in the lowlands of Fennoscandia.  Oikos. 3 22-52
• 04 Gauslaa,  Y.. (1984);  Heat resistance and energy budget in different Scandinavian plants.  Holarct. Ecol.. 7 1-78
• 05 Havaux,  M.. (1992);  Stress tolerance of photosystem II in vivo. Antagonistic effects of water, heat, and photoinhibition stresses.  Plant Physiol.. 100 424-432
• 06 Havaux,  M.. (1998);  Carotenoides as membrane stabilizers in chloroplasts.  Trends in Plant Sci.. 34 147-151
• 07 Havaux,  M., and Strasser,  R. J.. (1992);  Antagonistic effects of red and far-red lights on the stability of photosystem II in pea leaves exposed to heat.  Photochemistry and Photobiology. 55 621-624
• 08 Kainmüller,  C.. (1974) Die Temperaturresistenz von Hochgebirgspflanzen. University Innsbruck; PhD thesis
• 09 Kappen,  L.. (1964);  Untersuchungen über den Jahreslauf der Frost-, Hitze- und Austrocknungsresistenz von Sporophyten einheimischer Polypodiaceen (Filicinae).  Flora. 155 123-166
• 10 Kappen,  L.. (1981) Ecological significance of resistance to high temperature. Physiological Plant Ecology I. Responses to the physical environment. Lange, O. L., Nobel, P. S., Osmond, C. B., and Ziegler, H., eds. Berlin, Heidelberg, New York; Springer pp. 439-474
• 11 Kjelvik,  S.. (1976);  Varmeresistens og varmeveksling for noen planter, vesentlig fra Hardangervidda.  Blyttia. 34 211-226
• 12 Körner,  C.. (1999) Alpine plant life. Functional plant ecology of high mountain ecosystems. Berlin; Springer pp. 338
• 13 Körner,  C., and Cochrane,  P.. (1983);  Influence of plant physiognomy on leaf temperature on clear midsummer days in the snowy mountains, south-eastern Australia.  Acta Oecologia. 4 17-124
• 14 Körner,  C., and De Moraes,  J. A. P. V.. (1979);  Water potential and diffusion resistance in alpine cushion plants on clear summerdays.  Oecol. Plant. 14 109-120
• 15 Körner,  C., and Larcher,  W.. (1988) Plant life in cold climates. Plants and temperature. Long, S. and Woodward, F. I., eds. Cambridge; Comp. Biol. Ltd. pp. 25-57
• 16 Lange,  O. L.. (1961);  Die Hitzeresistenz einheimischer immer- und wintergrüner Pflanzen im Jahreslauf.  Planta. 56 666-683
• 17 Lange,  O. L., and Lange,  R.. (1962);  Untersuchungen über Blatttemperatur, Transpiration und Hitzeresistenz an Pflanzen mediterraner Standorte (Costa Brava, Spanien).  Flora. 153 387-425
• 18 Larcher,  W.. (1973) Limiting temperatures for life functions. Temperature and Life. Precht, H., Christophersen, J., Hensel, H., and Larcher, W., eds. Berlin, Heidelberg, New York; Springer pp. 195-231
• 19 Larcher,  W.. (1980);  Klimastreß im Gebirge - Adaptationstraining und Selektionsfilter für Pflanzen.  Rheinisch-Westf. Akad. Wiss.. Vortr.-Nr. 291 49-80
• 20 Larcher,  W.,, Holzner,  M.,, and Pichler,  J.. (1989);  Temperaturresistenz inneralpiner Trockenrasen.  Flora. 183 115-131
• 21 Larcher,  W., and Wagner,  J.. (1976);  Temperaturgrenzen der CO₂-Aufnahme und der Temperaturresistenz der Blätter von Gebirgspflanzen im vegetationsaktiven Zustand.  Oecol. Plant. 11 361-374
• 22 Mooney,  H. A., and Billings,  W. D.. (1961);  Comparative physiological ecology of arctic and alpine populations of Oxyria digyna. .  Ecol. Monogr.. 31 1-29
• 23 Neuner,  G.,, Braun,  V.,, Buchner,  O.,, and Taschler,  D.. (1999);  Leaf rosette closure in the alpine rosette plant Saxifraga paniculata Mill.: significance for survival of drought and heat under high irradiation.  Plant, Cell and Environment. 22 1539-1548
• 24 Neuner,  G., and Buchner,  O.. (1999);  Assessment of foliar frost damage: a comparison of in vivo chlorophyll fluorescence with other viability tests.  Journal of Applied Botany. 73 50-54
• 25 Nijs,  I.,, Kockelberg,  F.,, Teughels,  H.,, Blum,  H.,, Hendrey,  G.,, and Impens,  I.. (1996);  Free air temperatures increase (FATI): a new tool to study global warming effects on plants in the field.  Plant, Cell and Environ.. 19 495-502
• 26 Sakai,  A., and Larcher,  W.. (1987) Frost survival of plants. Responses and adaptation to freezing stress. Berlin; Ecol. Studies 62 Springer pp. 321
• 27 Salisbury,  F. B., and Spomer,  G. G.. (1964);  Leaf temperatures of alpine plants in the field.  Planta. 60 497-505
• 28 Schreiber,  U., and Berry,  J. A.. (1977);  Heat-induced changes of chlorophyll fluorescence in intact leaves correlated with damage of the photosynthetic apparatus.  Planta. 136 233-238
• 29 Seemann,  J. R.,, Downton,  W. J. S.,, and Berry,  J. A.. (1986);  Temperature and leaf osmotic potential as factors in the acclimation of photosynthesis to high temperature in desert plants.  Plant Physiol.. 80 926-930
• 30 Weis,  E.. (1982);  Influence of metal cations and pH on the heat sensitivity of photosynthetic oxygen evolution and chlorophyll fluorescence in spinach chloroplasts.  Planta. 154 41-47
• 31 Weis,  E., and Berry,  J. A.. (1988) Plants and high temperature stress. Plants and Temperature. Long, S. P. and Woodward, F. I., eds. Cambridge; Comp. Biol. Ltd. pp. 329-346

Section Editor: M. Riederer