Ice Propagation in Dehardened Alpine Plant Species Studied by Infrared Differential Thermal Analysis (IDTA)

Hacker, Jürgen; Neuner, Gilbert

doi:10.1657/1523-0430(07-077)[hacker]2.0.co;2

Cited by 59 publications

(61 citation statements)

References 37 publications

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“…The reproductive shoots of the investigated cushion plants S. bryoides , S. caesia , S. moschata and S. acaulis showed unique freezing patterns at all reproductive stages (bud, anthesis, fruit development). Each single reproductive shoot froze independent from each other and needed an autonomous ice nucleation event, which corroborated the findings of separate freezing events in vegetative shoots of a cushion of S. acaulis [11]. The detected ice barrier is not a structural one, which could be demonstrated for a loosened S. acaulis cushion.…”

Section: Discussionsupporting

confidence: 82%

Inflorescences of alpine cushion plants freeze autonomously and may survive subzero temperatures by supercooling

et al. 2011

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Freezing patterns in the high alpine cushion plants Saxifraga bryoides, Saxifraga caesia, Saxifraga moschata and Silene acaulis were studied by infrared thermography at three reproductive stages (bud, anthesis, fruit development). The single reproductive shoots of a cushion froze independently in all four species at every reproductive stage. Ice formation caused lethal damage to the respective inflorescence. After ice nucleation, which occurred mainly in the stalk or the base of the reproductive shoot, ice propagated throughout that entire shoot, but not into neighboring shoots. However, anatomical ice barriers within cushions were not detected. The naturally occurring temperature gradient within the cushion appeared to interrupt ice propagation thermally. Consequently, every reproductive shoot needed an autonomous ice nucleation event to initiate freezing. Ice nucleation was not only influenced by minimum temperatures but also by the duration of exposure. At moderate subzero exposure temperatures (−4.3 to −7.7 °C) the number of frozen inflorescences increased exponentially. Due to efficient supercooling, single reproductive shoots remained unfrozen down to −17.4 °C (cooling rate 6 K h−1). Hence, the observed freezing pattern may be advantageous for frost survival of individual inflorescences and reproductive success of high alpine cushion plants, when during episodic summer frosts damage can be avoided by supercooling.

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Section: Discussionsupporting

confidence: 82%

Inflorescences of alpine cushion plants freeze autonomously and may survive subzero temperatures by supercooling

et al. 2011

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“…In contrast, fully developed vegetative parts of woody alpine plant species, such as stem, bark, and leaves can tolerate extracellular ice formation down to a species-specific low temperature during the summer months without damage (Taschler and Neuner, 2004). Once ice formation is initiated somewhere inside a vegetative part of a plant, it can propagate rapidly (up to 27 cm.s -1 ) throughout the vascular system in all plant parts colder than 0°C (Hacker and Neuner, 2007, 2008; Hacker et al, 2008). …”

Section: Reproductive Shoots In Summermentioning

confidence: 99%

“…The same is true for the effect of frost on reproductive tissues, which can have a dramatic impact on overall reproductive success. Improvements in imaging methods to study the freezing processes in plants, such as infrared differential thermal analysis (IDTA; Hacker and Neuner, 2007, 2008; Hacker et al, 2008; Neuner et al, 2010; Kuprian et al, 2014), has led to significant advances in our current understanding of ice propagation, ice barriers, and supercooling in plants. IDTA can provide more precise information on tissue-specific mechanisms of frost survival and on the basis of frost damage.…”

Section: Introductionmentioning

confidence: 99%

Frost resistance in alpine woody plants

Neuner

2014

Front. Plant Sci.

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This report provides a brief review of key findings related to frost resistance in alpine woody plant species, summarizes data on their frost resistance, highlights the importance of freeze avoidance mechanisms, and indicates areas of future research. Freezing temperatures are possible throughout the whole growing period in the alpine life zone. Frost severity, comprised of both intensity and duration, becomes greater with increasing elevation and, there is also a greater probability, that small statured woody plants, may be insulated by snow cover. Several frost survival mechanisms have evolved in woody alpine plants in response to these environmental conditions. Examples of tolerance to extracellular freezing and freeze dehydration, life cycles that allow species to escape frost, and freeze avoidance mechanisms can all be found. Despite their specific adaption to the alpine environment, frost damage can occur in spring, while all alpine woody plants have a low risk of frost damage in winter. Experimental evidence indicates that premature deacclimation in Pinus cembra in the spring, and a limited ability of many species of alpine woody shrubs to rapidly reacclimate when they lose snow cover, resulting in reduced levels of frost resistance in the spring, may be particularly critical under the projected changes in climate. In this review, frost resistance and specific frost survival mechanisms of different organs (leaves, stems, vegetative and reproductive over-wintering buds, flowers, and fruits) and tissues are compared. The seasonal dynamics of frost resistance of leaves of trees, as opposed to woody shrubs, is also discussed. The ability of some tissues and organs to avoid freezing by supercooling, as visualized by high resolution infrared thermography, are also provided. Collectively, the report provides a review of the complex and diverse ways that woody plants survive in the frost dominated environment of the alpine life zone.

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“…For example, anatomical zones for massive ice accumulation have been identified in the midribs of cold-acclimated Eucalyptus pauciflora where ice deposits form in intercellular spaces of parenchyma strands located on the upper and lower side of the vascular bundle (Ball et al 2004). In recent years, the employment of high-resolution infrared differential thermal analysis has allowed to further link leaf anatomy with ice nucleation and propagation pathways in evergreen leaves (Hacker and Neuner 2007;Hacker and Neuner 2008). Whereas in deciduous species ice propagated inside the leaf from the petiole following the venation network, in 1-year old leaves of the evergreen Buxus sempervirens, ice nucleation took place in a lacunar space separating palisade and spongy mesophyll, followed by the formation of a central ice lens.…”

Section: Structural Adaptations For Frost Tolerancementioning

confidence: 99%

Photosynthetic ecophysiology of evergreen leaves in the woody angiosperms – a review

Wyka¹,

Oleksyn²

2014

Dendrobiology

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Abstract:Evergreen plants are an important component of many ecosystems of the world and occur in numerous evolutionary lineages. In this article we review phenotypic traits of evergreen woody angiosperms occurring in habitats that regularly experience frost. Leaf anatomical traits such as sclerenchymatic tissues or prominent cuticles ensure mechanical strength while often enhancing tolerance of water deficit. The low ratio of photosynthetic to nonphotosynthetic tissues as well as modified cell wall structure and nitrogen allocation patterns in evergreen leaves result in lower mass-based photosynthetic rate and photosynthetic nitrogen use efficiency in comparison with deciduous leaves. Their photosynthetic apparatus is adapted for the survival of frost in a down-regulated state with potential for photosynthetic activity in winter during periods of permissive temperatures. Leaf structure interacts with the mechanisms of frost survival. Stem xylem in evergreen plants tends to contain smaller diameter conduits incurring greater resistance to freeze/ thaw induced cavitation than in deciduous plants, although at the cost of reduced hydraulic efficiency. In contrast, no such differences in hydraulic conductivity have been documented at the leaf level. There is evidence for reduced structural plasticity of evergreen leaves in response to variability in irradiance, however photosynthetic downregulation occurs in mature leaves in response to self shading. Some evergreen species exhibit slow leaf development and "delayed greening", while in many species aging is also a very protracted process. Finally, evergreen leaves may participate in carbohydrate and, less obviously, in nitrogen storage for the support of spring shoot and foliage growth, although the importance of this function is under debate. In conclusion, the evergreen leaf habit is correlated with numerous structural and functional traits at the leaf and also at the stem level. These correlations may generate trade-offs that shape the ecological strategies of evergreen plants.Additional key words: internal conductance to CO 2 , leaf anatomy, sclerophylly, winter photosynthesis, winter photoinhibition.

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Ice Propagation in Dehardened Alpine Plant Species Studied by Infrared Differential Thermal Analysis (IDTA)

Cited by 59 publications

References 37 publications

Inflorescences of alpine cushion plants freeze autonomously and may survive subzero temperatures by supercooling

Inflorescences of alpine cushion plants freeze autonomously and may survive subzero temperatures by supercooling

Frost resistance in alpine woody plants

Photosynthetic ecophysiology of evergreen leaves in the woody angiosperms – a review

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