ABSTRACT Summer frost resistance and ice nucleation temperatures for 33 alpine plant species were measured in situ to avoid the shortcomings of laboratory tests. Species selected investigate relationship between stature upper distribution boundary, freezing patterns. The tested on average 1.1 K (± 0.2, SE) hardier than Frost (LT 50 ) ranged from −4.5 −14.6 °C appeared insufficient protect against air temperature minima, corroborating reports natural damage. All tolerated extracellular...

We studied ice propagation in stems and leaves of various angiosperm deciduous evergreen trees shrubs gymnosperms by differential thermal analysis (DTA) images captured with a digital infrared camera. This so-called DTA (IDTA) technique should elucidate the smallest freezing exotherms plant tissues. After intrinsic nucleation stem, spread into leaves. On leaf lamina, it was possible to differentiate between initial veins subsequent mesophyll. The followed venation could usually be tracked...

In alpine species the classification of various mechanisms underlying seed dormancy has been rather questionable and controversial. Thus, we investigated 28 to evaluate prevailing types dormancy. Embryo type water impermeability coats gave an indication potential class. To ascertain actual class level, performed germination experiments comparing behavior seeds without storage, after cold-dry cold-wet scarification. We also tested light requirement for in some species. Germination was...

In temperate-zone mountains, summer frosts usually occur during unpredictable cold spells with snow-falls. Earlier studies have shown that vegetative aboveground organs of most high-mountain plants tolerate extracellular ice in the active state. However, little is known about impact frost on reproductive development and success. common plant species from European Alps (Cerastium uniflorum, Loiseleuria procumbens, Ranunculus glacialis, Rhododendron ferrugineum, Saxifraga bryoides, S....

Over-wintering reproductive buds of many woody plants survive frost by supercooling. The bud tissues are isolated from acropetally advancing ice the presence barriers that restrict growth. Plants living in alpine environments also face risk formation summer months. Little knowledge exists, how structures protected injury during episodic frosts. In order to address this question, resistance three common dwarf shrubs, Calluna vulgaris, Empetrum hermaphroditum and Loiseleuria procumbens was...

Abstract Questions How frost resistant are the early development stages (seeds, seedlings, plantlets and juveniles) of alpine plant species? Do summer frosts impair establishment species typical different successional on a central glacier foreland? Location Rotmoos foreland, A ustrian C entral lps ( O bergurgl, T yrol, ustria). Methods Seeds 12 were collected in foreland either sown directly field or growth chamber (25/10 °C, 16/8 h) grown to investigated stages. Frost resistance adult was...

Abstract The impact of sublethal heat on photosynthetic performance, pigments and free radical scavenging activity was examined in three high mountain species, R hododendron ferrugineum , S enecio incanus anunculus glacialis using controlled situ applications stress, both darkness under natural solar irradiation. Heat treatments applied the dark reversibly reduced performance maximum quantum efficiency photosystem II ( F v /F m ), which remained impeded for several days when plants were...

Green algae of the genus Zygnema form extensive mats and produce large amounts biomass in shallow freshwater habitats. Environmental stresses including freezing may perturb these mats, which usually have only annual character. To estimate limits survival at subzero temperatures, resistance young sp. (strain MP2011Skan) cells pre-akinetes was investigated. Young, 2-week-old cultures were exposed to temperatures 0 - 14 °C 2-K steps, whereas 8-month-old frozen from 10 70 10-K intervals. Cell...

Alpine environments in Europe are increasingly affected by more erratic precipitation patterns, and frequent drought heat waves. Heat-hardening capacity is a key feature for survival of these abiotic stress factors, but it poorly understood how affect plant performance when combined. The main objectives this study were (1) to determine maximum hardening 14 selected species (2) alpine plants respond combined compared alone. (3) For risk assessment leaf temperatures measured the field (4)...

Effects of winter snow cover on photoinhibition and possible interactions with desiccation were investigated in situ an evergreen subalpine woody species, Rhododendron ferrugineum L., at the alpine timberline (1950 m a.s.l.). Timing duration complete markedly influenced potential efficiency photosystem II (PSII; F(v) /F(m)). Lack led to severe but mostly reversible F(v)/F(m) values as low 0.05. Complete immediately stopped further reductions PSII efficiency. Snow promoted recovery from...

Frost resistance and ice nucleation temperatures of leaves, from bud swelling until after full expansion, were measured in situ for five major woody timberline species with recently developed field freezing equipment. determined on leaves attached twigs was significantly higher than values detached laboratory tests (e.g., the temperature at which incipient frost damage observed (LTi) 1.2 degrees C Picea abies (L.) Karst.). all changed during shoot expansion changes 7.2 11 Rhododendron...

Infrared differential thermal analysis (IDTA) was used to study ice propagation and whole plant freezing patterns in dehardened intact individuals of various alpine species, including a shrub (Rhododendron ferrugineum), herbaceous (Senecio incanus), cushion (Silene acaulis), two graminoids (Poa alpina Juncus trifidus). Freezing differed markedly among species reflected peculiarities the shoot structure vascular system. In graminoids, each single leaf required separate nucleation event, as...

The freezing pattern and frost killing temperatures of apple (Malus domestica Borkh.) xylem were determined by differential thermal analysis infrared (IDTA). Results from detached or attached twigs in controlled experiments during natural field trees compared. Non-lethal apoplastic water as monitored winter frosts the occurred at −1.9 ± 0.4 °C did not change seasonally. whole tree was variable specific to environmental conditions. On high-temperature exotherms (HTEs) 2.8 K below temperature...

The photoprotective mechanisms of desiccation tolerance and freezing their relation to molecular mobility (cell vitrification) were assessed in a single model: the exceptional subalpine resurrection plant Ramonda myconi . Dehydrated leaves showed drop maximal photochemical efficiency PSII ( F v / m ) accompanied by synthesis zeaxanthin (Z), even dark, which was limited cell vitrification after complete desiccation. recovery severe drying treatment (7 days at 50% relative humidity) confirmed...

In temperate climates, overwintering buds of trees are often less cold hardy than adjoining stem tissues or evergreen leaves. However, data scarce regarding the freezing resistance (FR) and underlying functional frost survival mechanism that in case supercooling can restrict geographic distribution. Twigs 37 woody species were sampled midwinter 2016 Austrian Inn valley. After assessment FR, infrared-video-thermography cryo-microscopy used to study pattern around vegetative buds. Only four...

The frequency and severity of night frosts increase during the summer in alpine environment as elevation increases. Intra-specific, temporal, elevational variability freezing resistance (FR) plants active growing period has not been documented, especially regards to intra-specific distribution at their upper limits growth. FR leaves 13 species was investigated regular intervals from June through August, 2017 elevations between 600 3200 m. examined have different lower range limits, either...

Extracellular ice nucleation usually occurs at mild subzero temperatures in most plants. For persistent supercooling of certain plant parts barriers are necessary to prevent the entry from already frozen tissues. The reproductive shoot Calluna vulgaris is able supercool down below -22°C throughout all developmental stages (shoot elongation, flowering, fruiting) despite an established xylem conductivity. After localization barrier between and vegetative base pedicel by infrared differential...

Climate change increases the intensity and duration of heatwaves. Heat limits for plants are commonly determined by a 30-minute test. This neglects effect heat-dose (intensity x exposure-duration) on heat limits, which has been poorly studied. dysfunction (PSII efficiency) damage were measured after exposure to various heat-doses (34–64 °C 1–512 min) five alpine species. The ecological significance was tested based natural episodes. With increasing exposure-duration 5% decreased 11.2–17.5 K....

Heat and drought stresses are increasingly relevant topics in the context of climate change, particularly Alps, which warming faster than global average. Previously, we have shown that alpine plants, including Primula minima, can be gradually heat hardened under field conditions situ to achieve maximum tolerance within a week. Here, investigated antioxidant mechanisms P. minima leaves had been (H) without or with (H+D) additional stress. Lower free-radical scavenging ascorbate concentrations...

Freezing and high temperature thresholds of photosystem 2 (PS2), ice formation frost heat damage were measured in leaves evergreen subalpine plants under conditions naturally low (winter) to (summer) PS2 efficiencies (F V /F M ). The temperature‐dependent change basic Chl fluorescence 0 ) (T‐F technique that is usually used assess the threshold a new approach was applied test freezing PS2. T‐F curves (+5 °C −10 at K h −1 revealed significant, sudden increase F on extracellular (−4.0 or −5.5...