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Freezing Resistance (freezing + resistance)

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Life Sciences100%

Selected Abstracts

Freezing resistance varies within the growing season and with elevation in high-Andean species of central Chile

NEW PHYTOLOGIST, Issue 2 2009
Angela Sierra-Almeida
Summary ,,Predicted increases in the length of the growing season as a result of climate change may more frequently expose high-elevation plants to severe frosts. Understanding the ability of these species to resist frosts during the growing season is essential for predicting how species may respond to changes in temperature regimes. ,,Here, we assessed the freezing resistance of 24 species from the central Chilean Andes by determining their low temperature damage (LT50), ice nucleation temperature (NT), freezing point (FP) and freezing resistance mechanism (i.e. avoidance or tolerance). ,,The Andean species were found to resist frosts from ,8.2 to ,19.5°C during the growing season, and freezing tolerance was the most common resistance mechanism. Freezing resistance (LT50) varied within the growing season, decreasing towards the end of this period in most of the studied species. However, the FP showed the opposite trend. LT50 increased with elevation, whilst FP was lower in plants from lower elevations, especially late in the growing season. ,,Andean species have the potential to withstand severe freezing conditions during the growing season, and the aridity of this high-elevation environment seems to play an important role in determining this high freezing resistance. [source]

Reduced early growing season freezing resistance in alpine treeline plants under elevated atmospheric CO2

GLOBAL CHANGE BIOLOGY, Issue 3 2010
MELISSA MARTIN
Abstract The frequency of freezing events during the early growing season and the vulnerability to freezing of plants in European high-altitude environments could increase under future atmospheric and climate change. We tested early growing season freezing sensitivity in 10 species, from four plant functional types (PFTs) spanning three plant growth forms (PGFs), from a long-term in situ CO2 enrichment (566 vs. 370 ppm) and 2-year soil warming (+4 K) experiment at treeline in the Swiss Alps (Stillberg, Davos). By additionally tracking plant phenology, we distinguished indirect phenology-driven CO2 and warming effects from direct physiology-related effects on freezing sensitivity. The freezing damage threshold (lethal temperature 50) under ambient conditions of the 10 treeline species spanned from ,6.7±0.3 °C (Larix decidua) to ,9.9±0.6 °C (Vaccinium gaultherioides). PFT, but not PGF, explained a significant amount of this interspecific variation. Long-term exposure to elevated CO2 led to greater freezing sensitivity in multiple species but did not influence phenology, implying that physiological changes caused by CO2 enrichment were responsible for the effect. The elevated CO2 effect on freezing resistance was significant in leaves of Larix, Vaccinium myrtillus, and Gentiana punctata and marginally significant in leaves of Homogyne alpina and Avenella flexuosa. No significant CO2 effect was found in new shoots of Empetrum hermaphroditum or in leaves of Pinus uncinata, Leontodon helveticus, Melampyrum pratense, and V. gaultherioides. Soil warming led to advanced leaf expansion and reduced freezing resistance in V. myrtillus only, whereas Avenella showed greater freezing resistance when exposed to warming. No effect of soil warming was found in any of the other species. Effects of elevated CO2 and soil warming on freezing sensitivity were not consistent within PFTs or PGFs, suggesting that any future shifts in plant community composition due to increased damage from freezing events will likely occur at the individual species level. [source]

Freezing resistance varies within the growing season and with elevation in high-Andean species of central Chile

NEW PHYTOLOGIST, Issue 2 2009
Angela Sierra-Almeida
Summary ,,Predicted increases in the length of the growing season as a result of climate change may more frequently expose high-elevation plants to severe frosts. Understanding the ability of these species to resist frosts during the growing season is essential for predicting how species may respond to changes in temperature regimes. ,,Here, we assessed the freezing resistance of 24 species from the central Chilean Andes by determining their low temperature damage (LT50), ice nucleation temperature (NT), freezing point (FP) and freezing resistance mechanism (i.e. avoidance or tolerance). ,,The Andean species were found to resist frosts from ,8.2 to ,19.5°C during the growing season, and freezing tolerance was the most common resistance mechanism. Freezing resistance (LT50) varied within the growing season, decreasing towards the end of this period in most of the studied species. However, the FP showed the opposite trend. LT50 increased with elevation, whilst FP was lower in plants from lower elevations, especially late in the growing season. ,,Andean species have the potential to withstand severe freezing conditions during the growing season, and the aridity of this high-elevation environment seems to play an important role in determining this high freezing resistance. [source]

Ecophysiology of Antarctic vascular plants

PHYSIOLOGIA PLANTARUM, Issue 4 2002
Miren Alberdi
Most of the ice and snow-free land in the Antarctic summer is found along the Antarctic Peninsula and adjacent islands and coastal areas of the continent. This is the area where most of the Antarctic vegetation is found. Mean air temperature tends to be above zero during the summer in parts of the Maritime Antarctic. The most commonly found photosynthetic organisms in the Maritime Antarctic and continental edge are lichens (around 380 species) and bryophytes (130 species). Only two vascular plants, Deschampsia antarctica Desv. and Colobanthus quitensis (Kunth) Bartl., have been able to colonize some of the coastal areas. This low species diversity, compared with the Arctic, may be due to permanent low temperature and isolation from continental sources of propagules. The existence of these plants in such a permanent harsh environment makes them of particular interest for the study of adaptations to cold environments and mechanisms of cold resistance in plants. Among these adaptations are high freezing resistance, high resistance to light stress and high photosynthetic capacity at low temperature. In this paper, the ecophysiology of the two vascular plants is reviewed, including habitat characteristics, photosynthetic properties, cold resistance, and biochemical adaptations to cold. [source]