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Establishing a baseline of current Arctic vascular plant diversity and distribution is critical, given the rapid and major environmental changes occurring in the Arctic ecozone in response to climate change. Here, we report the results of a floristic study of vascular plant diversity of Dorset and Mallik islands in the Canadian Arctic Archipelago, Nunavut, Canada. These two small islands lie off the coast of the Foxe Peninsula of southwestern Baffin Island, and they are part of the Circumpolar Arctic bioclimate Subzone C. The hamlet of Kinngait (formerly Cape Dorset) is located on Dorset Island, and Nunavut’s Mallikjuak Territorial Park encompasses all of Mallik Island. The study is based on a specimen-based dataset comprising 876 unique collections from the two islands gathered over the last century, including 268 new ones collected in 2015. Results are presented in an annotated checklist. The vascular plant flora of the study area comprises 26 families, 71 genera, 150 species and three infraspecific taxa; 139 species are recorded on Dorset Island and 102 on Mallik Island. Eleven taxa are newly recorded from the study area in six families: Carex rupestris, Eriophorum scheuchzeri subsp. scheuchzeri, E. triste (Cyperaceae); Diapensia lapponica (Diapensiaceae); Equisetum arvense subsp. alpestre (Equisetaceae); Oxytropis deflexa var. foliolosa (Fabaceae); Potentilla arenosa subsp. arenosa, P. hyparctica subsp. hyparctica (Rosaceae); Antennaria friesiana subsp. friesiana, Askellia pygmaea, and Taraxacum phymatocarpum (Asteraceae).

Dwarf shrubs of the family Ericaceae are common in arctic and alpine regions. Many of these plants are associated with ericoid mycorrhizal (ERM) fungi, which allow them to take nutrients and water from the soil under harsh environmental conditions and, thus, affect host plant survival. Despite the importance of ERM fungi to alpine plant communities, limited information is available on the effects of microhabitat and host identity on ERM fungal communities. We investigated the communities of putative ERM fungi isolated from five dwarf shrub species (Arcterica nana, Diapensia lapponica, Empetrum nigrum, Loiseleuria procumbens, and Vaccinium vitis-idaea) that co-occur in an alpine region of Japan, with reference to distinct microhabitats provided by large stone pine (Pinus pumila) shrubs (i.e. bare ground, the edge of stone pine shrubs, and the inside of stone pine shrubs). We obtained 703 fungal isolates from 222 individual plants. These isolates were classified into 55 operational taxonomic units (OTUs) based on the sequencing of internal transcribed spacer regions in ribosomal DNA. These putative ERM fungal communities were dominated by Helotiales fungi for all host species. Cistella and Trimmatostroma species, which have rarely been detected in ERM roots in previous studies, were abundant. ERM fungal communities were significantly different among microhabitats (R2=0.28), while the host effect explained less variance in the fungal communities after excluding the microhabitat effect (R2=0.17). Our results suggest that the host effect on ERM fungal communities is minor and the distributions of hosts and fungal communities may be assessed based on microhabitat conditions.

This work aims to select the potentially vulnerable plant species against climate change at alpine and subalpine belts of Mts. Sorak, Jiri, and Halla, from central, southern, southern insular high mountains of the Korean Peninsula, respectively. The selection of global warming related vulnerable plants were performed by adapting various criteria, such as flora, endemicity, rarity, floristically specific and valuable species, species composition at mountain summits, horizontal and vertical ranges of individual species, and their distributional pattern in the Korean Peninsula. Line and quadrat field surveys along the major trails from all directions at height above 1,500 meters above sea level of Mts, Sorak, Jiri and Halla were conducted each year during spring, summer, and autumn from 2010 to 2011. Based upon above mentioned eight criteria, high level of climate change related potentially vulnerable arboral plants, such as Rhododendron aureum ,Taxus caespitosa ,Pinus pumila ,Oplopanax elatus , Vaccinium uliginosum , and Thuja koraiensis are noticed from at subalpine belt of Mt. Sorak. Species of Abies koreana ,Rhododendron tschonoskii ,Oplopanax elatus ,Taxus cuspidata ,Picea jezoensis , and Juniperus chinensis var. sargentii belong to climate change concerned vulnerable species at subalpine belt of Mt. Jiri. High level of climate change related species vulnerability is found at alpine and subalpine belts of Mt. Halla from Diapensia lapponica var. obovata ,Salix blinii ,Empetrum nigrum var. japonicum , Vaccinium uliginosum , Juniperus chinensis var. sargentii , Taxus cuspidata , Rhamnus taquetii , Abies koreana , Hugeria japonica , Prunus buergeriana , and Berberis amurensis var. quelpartensis . Countermeasures to save the global warming vulnerable plants in situ are required.

We compared allozyme variation in the two arctic–alpine plants Diapensia lapponica var. obovata and Empetrum nigrum var. japonicum between Sakhalin Island in Russian Far East, within their range core, and the Korean island of Jeju, their world’s southernmost distribution. For D. lapponica var. obovata, Sakhalin populations harbored moderate levels of within-population genetic variation and low among-population divergence, whereas extremely low levels of within-population genetic diversity and high among-population differentiation were found in Jeju Island populations. In contrast, we found moderate levels of within-population variation and low among-population differentiation in E. nigrum var. japonicum in both northern populations (those of Sakhalin and an additional population from northern Japan) and Jeju Island populations. Under a similar scenario of immigration history of arctic–alpine plants on Jeju Island during the glacial periods of the Pleistocene and local persistence through glacial/interglacial cycles, the contrasting genetic structure between D. lapponica var. obovata and E. nigrum var. japonicum is mainly attributable to their different life-history, ecological, and demographic traits: (1) hermaphroditic versus monoecious, dioecious or polygamous, (2) seeds with no adaptations for long-distance dispersal versus berry-like drupes dispersed by animals and birds, and (3) a very small patch near the peak of Mt. Halla with a few hundred individuals versus a relatively continuous distribution around the peak of Mt. Halla with numerous individuals. From a conservation perspective, in situ and ex situ conservation measures should be strengthened for D. lapponica var. obovata on Jeju Island given their extreme rarity there.

Endophytic bacteria inhabit internal plant tissues, and have been isolated from a large diversity of plants, where they form nonpathogenic relationships with their hosts. This study combines molecular and culture-dependent approaches to characterize endophytic bacterial communities of three arcto-alpine plant species (Oxyria digyna, Diapensia lapponica and Juncus trifidus) sampled in the low Arctic (69 degrees 03'N). Analyses of a 325 bacterial endophyte isolates, as well as seven clone libraries, revealed a high diversity. In particular, members of the Actinobacteria, Bacteroidetes, Firmicutes, Acidobacteria, and Proteobacteria were found. The compositions of the endophytic bacterial communities were dependent on host-plant species as well as on snow cover at sampling sites. Several bacterial genera were found to be associated tightly with specific host-plant species. In particular, Sphingomonas spp. were characteristic for D.lapponica and O.digyna, and their phylogenetic grouping corresponded to the host plant. Most of the endophyte isolates grew well and retained activity at +4 degrees C, and isolate as well as clone library sequences were often highly similar to sequences from bacteria from cold environments. Taken together, this study shows that arctic plants harbour a diverse community of bacterial endophytes, a portion of which seems to be tightly associated with specific plant species.

According to previous phylogeographic studies, high mountains at low latitudes are important areas for the study of the evolutionary history of arctic–alpine plants in surviving the Pleistocene climatic oscillations. To evaluate this hypothesis, we elucidated the genetic structure of the arctic–alpine plant, Loiseleuria procumbens, in the Japanese archipelago, which corresponds to one of the southernmost limits of its distribution, using 152 individuals from 17 populations that covered the entire distribution of the Japanese archipelago and Sakhalin, in addition to samples from Sweden. Based on 854 bp of chloroplast DNA, we detected eight haplotypes. Along with haplotype distribution, strong genetic differentiation between populations in central and northern Japan was elucidated by a neighbour-joining tree (100%) and spatial analysis of molecular variance (79%), which is consistent with other alpine plants in Japan, regardless of the species' range. In addition, the southernmost populations from northern Japan showed specific genetic structure, although the remaining areas of northern Japan and Sakhalin harboured an homogenous genetic structure. Our results suggest that the populations in central Japan persisted for a long time during the Pleistocene climatic oscillation and that genetic divergence occurred in situ, supporting our hypothesis in conjunction with a previous study of another arctic–alpine plant, Diapensia lapponica subsp. obovata. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97, 403–412.

Previous phylogeographic studies of arctic-alpine plants have partly elucidated that alpine areas at the southernmost edges of their distribution have been one of the most important areas for the survival of populations through Quaternary climatic oscillations. To reveal the genetic structure of arctic-alpine plants near the southern edge of their range in East Asia, 159 samples of Diapensia lapponica subsp. obovata (Diapensiaceae) were collected from 22 populations in Japan. Based on 1,134 bp of chloroplast DNA (cpDNA), we determined 10 haplotypes. Neighbor-joining (NJ) analysis, including D. lapponica from Sweden and Schizocodon soldanelloides, revealed that all haplotypes in Japan were monophyletic. Genetic differentiation between populations of central Honshu and northern Japan was strongly supported by the NJ tree (100%), analysis of molecular variance (AMOVA, 68%), and Monmonier’s algorithm (>95%). The most ancestral haplotype rarely occurred in Japan, which implied that the extant genetic structure was not caused by genetic divergence during colonization. Thus, these results suggest that the arctic-alpine plant D. lapponica subsp. obovata survived climatic oscillations in central Honshu. This finding supports the hypothesis that high mountains in temperate regions were important for survival of arctic-alpine plants during Quaternary climatic oscillations.

 Premise of the study: Most alpine plants in the Northeast United States are perennial and fl ower early in the growing season, extending their limited growing season. Concurrently, they risk the loss of reproductive efforts to late frosts. Quantifying longterm trends in northeastern alpine fl ower phenology and late-spring/early-summer frost risk is limited by a dearth of phenology and climate data, except for Mount Washington, New Hampshire (1916 m a.s.l.).  Methods: Logistic phenology models for three northeastern US alpine species ( Diapensia lapponica , Carex bigelowii and Vaccinium vitis-idaea ) were developed from 4 yr (2008–2011) of phenology and air temperature measurements from 12 plots proximate to Mount Washington’s long-term summit meteorological station. Plot-level air temperature, the logistic phenology models, and Mount Washington’s climate data were used to hindcast model yearly (1935–2011) fl oral phenology and frost damage risk for the focal species.  Key results: Day of year and air growing degree-days with threshold temperatures of �4 ° C ( D. lapponica and C. bigelowii ) and �2 ° C ( V. vitis-idaea ) best predicted fl owering. Modeled historic fl owering dates trended signifi cantly earlier but the 77-yr change was small (1.2–2.1 d) and did not signifi cantly increase early-fl owering risk from late-spring/early-summer frost damage.  Conclusions: Modeled trends in phenological advancement and sensitivity for three northeastern alpine species are less pronounced compared with lower elevations in the region, and this small shift in fltiming did not increase risk of frost damage. Potential reasons for limited earlier phenological advancement at higher elevations include a slower warming trend and increased cloud exposure with elevation and/or inadequate chilling requirements.

Premise of the study: Most alpine plants in the Northeast United States are perennial and flower early in the growing season, extending their limitedgrowing season. Concurrently, they risk the loss of reproductive efforts to late frosts. Quantifying long-term trends in northeastern alpine flower phenology and late-spring/early-summer frost risk is limited by a dearth of phenology and climate data, except for Mount Washington, New Hampshire (1916 m a.s.l.). Methods: Logistic phenology models for three northeastern US alpinespecies (Diapensia lapponica, Carex bigelowii and Vaccinium vitis-idaea) were developed from 4 yr (2008–2011) of phenology and air temperature measurements from 12 plots proximate to Mount Washington’s long-term summit meteorological station. Plot-level air temperature, the logistic phenology models, and Mount Washington’s climate data were used to hindcast model yearly (1935–2011) floral phenology and frost damage risk for the focal species. Key results: Day of year and air growing degree-days with threshold temperatures of −4°C (D. lapponica and C. bigelowii) and −2°C (V. vitis-idaea) best predicted flowering. Modeled historic flowering dates trended significantly earlier but the 77-yr change was small (1.2–2.1 d) and did not significantly increase early-flowering risk from late-spring/early-summer frost damage. Conclusions: Modeled trends in phenological advancement and sensitivity for three northeastern alpine species are less pronounced compared with lower elevations in the region, and this small shift in flower timing did not increase risk of frost damage. Potential reasons for limited earlier phenological advancement at higher elevations include a slower warming trend and increased cloud exposure with elevation and/or inadequate chilling requirements.

Determinants of reproductive success (measured as capsule mass) in Diapensia lapponica, an early-flowering pollen-risker dependent on insects for pollination, were evaluated in an exposed subarctic-alpine population in northern Sweden. The species was protogynous and self-compatible, but self-deposition of pollen was inefficient. Hand-pollination increased capsule mass significantly, indicating that reproductive success was severely pollen limited. An experiment designed to test the relative importance of insect pollination in comparison to water availability (precipitation) and shelter (temperature and wind), revealed that exclosure of insects decreased capsule mass significantly, as did watering, whereas shelter tended to increase capsule mass. Pollination was the most important determinant of reproductive success, and the study suggests that pollen limitation may be particularly severe for early-flowering species, i.e. pollen-riskers, in exposed locations.

To determine if canopy gaps offer “safe sites” for recruitment and persistence of arctic-alpine plants, we compared seedling densities in frost boils and closed vegetation, and examined persistence of Diapensia lapponica within frost boils. Seedling density was greater within frost boils, and D. lapponica numbers increased in resurveyed frost boils, suggesting persistence. Lower seed bank size combined with higher seedling numbers confirmed that frost boils represent favorable sites for germination.

The overall net photosynthesis potential of Diapensia lapponica was very low. It was highest at the end of August (11.1 μmol CO 2 (μmol chlorophyll) −1 hr −1 ) and decreased during the autumn and winter, reaching a minimum in February (0.6 μmol CO 2 (μmol chlorophyll) −1 hr −1 ). In March, with increased light in the subarticum, the potential rose temporarily, and after another minimum at the beginning of May, the potential slowly rose to the summer level (2.3–6.5 μmol CO 2 (μmol chlorophyll) −1 hr −1 ). Ihe seasonal fluctuation pattern of the potential of net photosynthesis was the same when calculated on a dry weight basis. Seasonal changes also occurred in the chlorophyll content and in the contents of polar lipids, particularly DGDG (digalactosyl diacygglycerols) and PC (phosphatidyl choline) and less clearly in MGDG (monoglactosyl diacylglycerols), PE (phosphatidyl ethanolamine) and PG (phosphatidyl glycerols). The contents of chlorophylls, DGDG and PC increased during autumn and early winter during the hardening process and decreasing light and temperature. Their contents decreased in late winter and spring in response to dehardening and increased light and temperature in the subarcticum. Thus, the molar ratios of MGDG:DGDG and PE:PC varied throughout the year, being lowest in winter. In addition, fatty acids of individual lipid classes showed seasonal fluctuation. In both MGDG and DGDG, the proportion of linolenic acid was higher in summer than in winter and that of linoleic acid was vice versa . In both PC and PE, the proportion of palmitic acid was highest in summer and lowest in winter,and, particularly in PC, this variation was compensated for by changes in linoleic acid and less clearly in linolenic acid, and, in PE, by the long-chain behenic acid. In PG, the proportions of trans -16:1 and oleic acid were higher in summer than in winter, whereas the proportions of palmitic and linoleic acids were higher in winter than in summer. Thus, there was not a clear increase in the degree of unsaturation of fatty acids during winter-time.

Growth and flowering in an evergreen, cushion-forming, circumpolar, arctic-alpine plant, Diapensia lapponica, was followed for five years, 1990–1994, at the Latnjajaure Field Station, northern Swedish Lapland. This species is unusually suitable for age determination since plants grow radially from a central point of initiation. During the study period, the radial annual radial growth of cushions averaged 0.6 mm. The species exhibited a sigmoid pattern of growth in relation to the estimated age of cushions, and at least 400–year old plant individuals are present within the study area. Plants of Diapensia become reproductive at an average age of about 18 years, and may continue to flower for centuries. Recruitment to the seedling population takes place during cold periods (sequences of cold summers), and there is a negative correlation between recruitment and mean annual temperature in the Abisko area since 1913. The oldest stock of the present population at Latnjajaure was recruited during the Little Ice Age.

Day length control can effectively limit seed germination to favorable seasons, but this phenomenon has been studied in relatively few wild plants. I tested species from interior Alaska for day length control of germination under controlled conditions, and I also monitored germination phenology in natural habitats. Unstratified and cold-stratified seeds were germinated on short (13 h) and long (22 h) day length and in the dark at constant and alternating temperatures. On long day length, unstratified Ledum decumbensand Saxifraga tricuspidata seeds germinated from 5 8 Ct o 20 8C, but on short day length few or no seeds germinated at 58C and 108C and germination was reduced at higher temperatures. Unstratified seeds of Diapensia lapponica and Chamaedaphne calyculatagerminated only at 158C and 208C on long day length, and short day length completely inhibited germination. Cold stratification widened the temperature range for germination on both long and short day lengths, but germination was still lower on short than long day length. Germination phenology in natural habitats was consistent with germination in controlled conditions. In these species, short day length and low temperatures interact to inhibit germination in the fall. After overwintering, seeds germinate in the spring at low temperatures and on long day lengths. The inhibitory effect of short day length is not important in the spring because day length is already long at snowmelt.

Owerwintering strategy of the sub-arctic evergreen Diapensia lapponica has been studied by examining storage substances in the stem cells throughout different seasons. Stem segments were taken from 5 and 20 mm behind the shoot tip, fixed in glutaraldehyde/formaldehyde and embedded in Epon. Semithin sections were stained with Toluidine blue for general observation, Sudan black for lipids, Amido black for proteins and periodic acid-Schiff s reagent (PAS) for carbohydrates. Lipids occurred abundantly throughout the year and seem to be the main storage substances. They were particularly common in mid-winter in the lower part of the shoot. The highest lipid content was found in the pith cells and parenchyma cells of the conductive tissues. Large amyloplasts appeared in mid-summer in higher amounts in the cortex than in the pith of the upper shoot, but vice versa in the lower stem. Starch was almost entirely lacking from November to April. Amido black staining did not indicate presence of protein bodies at any season. The occurrence of lipids and starch grains in the stem of Diapensia is in general similar to the occurrence of these substances in the leaves throughout the annual cycle.

Diapensia lapponica Linnaeus, Species Plantarum 1: 141. 1753. "Habitat in alpibus Lapponicis." RCN: 1140. Lectotype (Barrie in Jarvis & al., Regnum Veg. 127: 42. 1993): Herb. Linn. No. 195.1 (LINN). Generitype of Diapensia Linnaeus (vide Hitchcock, Prop. Brit. Bot.: 128. 1929). Current name: Diapensia lapponica L. (Diapensiaceae)., Published as part of Jarvis, Charlie, 2007, Chapter 7: Linnaean Plant Names and their Types (part D), pp. 474-489 in Order out of Chaos. Linnaean Plant Types and their Types, London :Linnaean Society of London in association with the Natural History Museum on page 480, DOI: 10.5281/zenodo.291971

Field studies in the Hudson Bay Lowland ecoregion of northern Ontario during 2010 resulted in the discovery of four native vascular plant species not previously confirmed from the province: Arctic Bellflower (Campanula uniflora; Campanulaceae), Lapland Diapensia (Diapensia lapponica; Diapensiaceae), Alpine Azalea (Kalmia procumbens; Ericaceae), and Alpine Brook Saxifrage (Saxifraga rivularis; Saxifragaceae). These four species are widespread arctic plants occurring in both North America and Eurasia and were found on the Sutton Ridges, a Precambrian bedrock inlier surrounded by the extensive wetlands of the Hudson Bay Lowland.

Preface P. S. Karlsson and T. V. Callaghan Introduction The Abisko Scientific Research Station N. A. Andersson, T. V. Callaghan and P. S. Karlsson Subarctic plant communities and their environment Holocene forest dynamics and climate changes in the Abisko area, northern Sweden - the Sonesson model of vegetation history reconsidered and confirmed B. E. Berglund, L. Barnekow, D. Hammarlund, P. Sandgren and I. F. Snowball Modelling and measuring evapotranspiration in a mountain birch forest M. Ovhed and B. Holmgren The resource economy of subarctic plants and ecosystems Nutrient cycling in subarctic and arctic ecosystems, with special reference to the Abisko and Tornetrask region S. Jonasson and A. Michelsen Resource dynamics within arctic clonal plants I. S. Jonsdottir, T. V. Callaghan and A. D. Headley Treeline ecology of mountain birch in the Tornetrask area B. Sveinbjornsson, H. Kauhanen and O. Nordell Relationships between nitrogen economy and performance in the mountain birch Betula pubescens ssp. Tortuosa P. S. Karlsson and M. Weih Peat formation and mass balance in subarctic ombrotrophic peatlands around Abisko, northern Scandinavia N. Malmer and B. Wallen A cross-continental comparison of phenology, leaf dynamics and dry matter allocation in arctic and temperate zone herbaceous plants from contrasting altitudes S. Prock and C. Korner Hazards to a mountain birch forest - Abisko in perspective O. Tenow The significance of carnivory for three Pinguicula species in a subarctic environment P. S. Karlsson, B. M. Svensson and B. A. Carlsson Photosynthetic characteristics of subarctic mosses and lichens B. Schipperges and C. Gehrke Population processes in subarctic plants Resource investment in reproduction and its consequences for subarctic plants L. M. Thoren, A. M. Hemborg and P. S. Karlsson Some apparently paradoxical aspects of the life cycles, demography and population dynamics of plants from the subarctic Abisko area T. V. Callaghan, B. A. Carlsson and B. M. Svensson A comparison of photosynthetic performance and leaf carbon gain of temperate and subarctic genotypes of Geum rivale and Ranunculus acris in northern Sweden M. Diemer Interactions between hemiparasitic angiosperms and their hosts in the subarctic M. C. Press and W. E. Seel Global change Summer air temperatures and tree line dynamics at Abisko B. Holmgren and M. Tjus Photo documentation of landscape change in northern Swedish mountains A. Rapp Direct and indirect effects of increasing temperatures on subarctic ecosystems S. Jonasson, J. A. Lee, T. V. Callaghan, M. Havstrom and A. N. Parsons Effects of enhanced ultraviolet-B radiation on terrestrial subarctic ecosystems and implications for interactions with increased atmospheric CO2 C. Gehrke, U. Johansson, D. Gwynn-Jones, L. O. Bjorn, T. V. Callaghan and J. A Lee Monitoring and modelling of the radiation climate at Abisko L. O. Bjorn and B. Holmgren Climatic impacts on flowering, growth, and vigour in an arctic-alpine cushion plant, Diapensia lapponica, under different snow cover regimes U. Molau Conclusion Plant ecology in subarctic Swedish Lapland: summary and conclusions T. V. Callaghan and P. S. Karlsson

The effects of weather on the flight and flower-visiting activity of bumblebees and butterflies were studied at a subarctic-alpine site in northern Swedish Lapland. The study focused on the insects' role as potential pollinators and the effect of bumblebee flight and foraging activity on plant reproductive success. The activity rates of both bumblebees and butterflies were significantly correlated with ambient air temperature and solar radiation, and as a consequence, both bumblebees and butterflies exhibited a regular diurnal activity pattern. The butterflies' activity was more constrained by low temperature and solar radiation then the bumblebees' activity, and small worker bees were more affected by the weather than the larger queens. Only 1% of the butterflies observed were visiting flowers, as compared to 69% of the bumblebees. Thus, butterflies seem to be less important pollinators for the alpine plant community than bumblebees. Short-term micrometeorological impact on the reproduction of two bumblebee-pollinated plant species, Bartsia alpina and Diapensia lapponica, was also studied. In both species, reproductive success, measured as seed production, was significantly reduced during a spell of cold weather in comparison to a warmer period.

Leaf specimens of evergreen Diapensia lapponica were collected monthly in Northern Finland (ca 70°N) in order to study seasonal changes in the ultrastructure of the chloroplasts of the palisade mesophyll. The volume fraction of chloroplasts per cell was lowest in summer and increased towards autumn and winter. However, the relative size seemed to be higher in summer than in other seasons. Length/width (L/W) ratio was calculated as an index of the chloroplast shape. The shape varied from elongated (usually concavo-convex in profile), with an L/W ratio from 1.9 to 2.5 in summer, to roundish or irregular (L/W ratio from 1.2 to 1.4) in midwinter. In autumn the chloroplasts were most elongated (LW ratio 2.6). The starch content was highest at the end of June when it constituted 38% of the volume of chloroplast. It decreased from then till November and was absent during the rest of the winter. Changes in the thylakoid system involved an increase in the number of partitions from an average of three in early summer to 11 in autumn and a decrease to M again towards winter. In spring it was up to 7 again. The large grana and high portion of stroma thylakoids observed in late August - September (the period of rhythmic light) are consistent with the high photosynthesis activity reported previously in D. lapponica in laboratory conditions.

Summary Diurnal temperature courses were measured with thermistores at different depths of Diapensia lapponica cushions in Swedish Lapland. With summerly radiation conditions the peripheral cushion layers warm up considerably more than the air, which causes a steep temperature gradient toward the centre; at night the cushions cool off more than the air; a gentle gradient from the centre towards the periphery may persist over an extended period of time. The diurnal temperature amplitude in the cushions close to the surface may exceed that in the soil considerably. Whereas the temperatures in the peripheral cushion layers vary immediately with intake and loss of energy through radiation and wind, the interior of the cushion is less responsive thermally. Some measurements in Loiseleuria procumbens show the diurnal temperature variations in a cushion-like dwarf shrub to be similar in type if less in extent than those in a genuine cushion plant. Warming up of cushions due to their shape and structure is discussed with a view to their water balance and productivity in arctic and alpine environments.

Seasonal fluctuations in storage lipids in the cushion plant Diapensia lapponica, growing in Northern Finland (70°N 27°E), were studied by microscopy and chemical analysis. Lipid bodies in the mesophyll cells were stained with Sudan Black for quantitative observation by light microscope. Electron microscope observations were made using aldehyde prefixed and osmium tetroxide postfixed sections of leaf blades. Thin layer and gas capillary chromatographic techniques were used to analyse total lipids and total fatty acids in green shoots of Diapensia. Free sugars and starch were extracted separately and determined by the anthrone method. A mesophyll cell was characterized by a large lipid body (storage lipid) in summer but by several small spherules in winter. Total surface area of the cross-sectioned lipid globules was at its lowest from April to September; the maximal value was in March. The amount of total lipids in the leafy tops of D. lapponica was 91–200 mg g-1 dry weight. Values were lowest at the end of June, when the total carbohydrate level was at its highest. Accordingly, the decrease in the total lipid level in the early growing season, when new leaves were developing, can be attributed primarily to the increase in the level of carbohydrates, particularly starch. The amount of total fatty acids varied from 21 to 30 mg g-1 dry weight. The level increased in the early growing season and remained elevated throughout the summer. Like the total lipids, the total fatty acids are derived from structurally different parts of the sclerophyllous leaves, including the well-developed cuticle and epicuticular wax layer. The discrepancies in the results obtained from microscopic and chemical analyses are discussed.

Summary A review of the nomenclature of the Diapensiaceae is presented with a brief discussion of some of the interesting aspects of this ancient family. The status of the pink-flowered form of Diapensia lapponica from Alaska has been changed (D. lapponica subsp. obovata f. rosea (Hult.) stat. nov.). Rs viable seed production is greatly decreased by fungal attack which occurs before and after capsule dehiscence (Day, 1978). McNair (1945), in studies relating plant fats and evolution, found the Diapensiales to

During the growing season alpine plants on Mt. Kurodake (1,984 m) in the Taisetsu mountain range in Hokkaido, Japan, survived freezing to only —5° to —7°C. Even after exposure to 0° and —3°C for 2 weeks, the resistance to freezing of these plants increased only slightly. During the winter, however, most alpine plants studied survived freezing at temperatures below —30°. Salix pauciflora, Diapensia lapponica, mosses, an lichens resisted freezing down to —70°C. They also retained viability after immersion in liquid nitrogen following prefreezing at —30°C. Furthermore, there did not appear to be an essential difference in the hardening effect between willows growing in high mountains and in low altitudes in Hookaido. Alpine plants may be characterized by their dwarf form, short growth period, and high freezing resistance of subterranean stems, crowns, and roots. See full-text article at JSTOR

1. Organography and vascular anatomy of the flower and certain aspects of embryology are reported for eight members of the family Diapensiaceae: Diapensia lapponica, D. lapponica subsp. obovata, Galax aphylla, Pyxidanthera barbulata, P. brevifolia, Schizocodon soldanelloides, Shortia galacifolia, and S. uniflora. 2. The flowers are actinomorphic, essentially hypogynous, and pentamerous except for the tricarpellate pistil. There are five fertile stamens opposite the sepals, and, in all but Diapensia and Pyxidanthera, five staminodes opposite the petals. The stamens and, to a varying extent, the staminodes are epipetalous except in Galax in which the petals are almost completely free and the stamens and staminodes monadelphous. Differences occur in length, orientation and number of pollen sacs, plane of dehiscence, and occurrence of appendages. Placentation is basically axile but may approach parietal in the top of the ovary. Ovules are few to many. 3. The sepals receive three traces in most species, but in...

(1952). Diapensia Lapponica L. in Scotland. Transactions of the Botanical Society of Edinburgh: Vol. 36, No. 1, pp. 34-36.

Diapensia lapponica, spec. nov. 1. Diapensia floribus pedunculatis. Diapensia. Fl. lapp. 88. t. 1. f. 1. * Fl. suec. 172. Habitat in alpibus Lapponicis . ���, Published as part of Linnaeus, Carolus, 1753, Species plantarum: exhibentes plantas rite cognitas, ad genera relatas, cum differentiis specificis, nominibus trivialibus, synonymis selectis, locis natalibus, secundum systema sexuale digestas, Stockholm :Laurentius Salvius on page 141, DOI: 10.5281/zenodo.3931989

Cushion plants can have positive impacts on plant richness in severe environments and possibly across trophic levels on arthropods, an under-studied topic. This study examined whether soil communities under cushions have higher richness and abundance of soil microarthropods than adjacent non-cushion vegetation, and whether differences in collembolan and mite abundance and species richness between cushions and adjacent vegetation increase with elevation. Paired soil samples were taken under cushions ofSilene acaulisalong the elevation gradient (1000, 1100, 1200, 1300, 1400 m a.s.l.), under cushions ofDiapensia lapponicaon the exposed ridge above the treeline (1000 m a.s.l.), and under adjacent non-cushion plant vegetation. In total, 5853 individuals of collembolans (n = 1705) and mites (n = 4148) were obtained from soil samples and identified to order/species level.S. acauliscushions had a positive effect on species richness and abundance of collembolans, with richness effects from 1100 m a.s.l. upwards. Oribatid mite richness and abundance were also higher under cushions compared with adjacent vegetation. Species richness of collembolans and oribatids declined with increasing elevation from 1200 m a.s.l. Collembolan abundance peaked at mid-elevation (1200 m a.s.l.) under cushions and adjacent vegetation, while oribatid mite abundance peaked at 1300 m a.s.l. under both vegetation types.D. lapponicacushions on the exposed ridge had significant positive effects on species richness, abundance and diversity index of collembolans, and abundance of oribatids. Cushion plants play an important role in supporting the biodiversity of soil fauna in severe alpine environments, with the positive effects of cushion plants increasing with environmental severity.

1 Alpine vascular plants seem to use other strategies in surviving a cold environment than reducing the reflectance in level leaves. Pubescence in alpine plants has small effect upon total reflectance, but may increase the amount of photosynthetic active radiation within the sheltered canopy. Alpine cushion plants like Silene acaulis, Diapensia lapponica and Loiseleuria procumbens maximize the absorptance of radiant energy with minimum heat losses, probably as an effect of the dense canopy structure. The young inflorescences of Eriophorum vaginatum were found to be extremely efficient absorbators, while the reflectance in Salix catkins was close to that of green leaves. 2 In lichens, a great variation both in visible (400–700 nm) and infrared (700–1400 nm) reflectance was found: (A) The Pseudephebe pubescence group consists of species with very low reflectance at all measured wavelengths. The species are chionophobous, probably because of the high absorptance which makes growth possible during the cold season. (B) The Sticta sylvatica group, characterized by very low visible reflectance and very high infrared reflectance, is well adapted to shade. (C) The Cetraria nivalis group consists of fruticose species with high reflectance both in the visible and the near infrared. The intense visible reflectance probably makes net photosynthesis possible in well protected layers of the canopy. (D) The Nephroma arcticum group with spectral properties resembling green leaves in vascular plants. (E) The Haematomma ventosum group and the Parmelia perlata group with spectral properties intermediate between group C and D. 3 A modified method determining lethal temperatures and energies of activation in the process leading to death during a heat shock, is described. The two parameters are rather species specific in many of the 118 Scandinavian plants investigated. The lethal temperatures completely overlap the values in hotter parts of the world. However, habitat specific lethal temperatures were found; low values in wet- or shade-growing species and high values in dry-growing species. In Picea abies lethal temperatures and energies of activation showed pronounced, but diverging, year cycles in 12 ecotypes from different parts of Europe. Only negligible differences between the ecotypes exist, and cycles are probably photoperiodically determined. 4 Heat hardening can be achieved quickly, both in an active and dormant stage, by increasing the temperature. A linear correlation between hardening temperature, both in the optimal and supraoptimal temperature range, and hardening capability was found. In most species, but especially in cold adapted species, the hardening capability at supraoptimal temperatures decreases with increasing cultivation temperature. 5 Diffusion resistances with open (rs) and closed stomata (rc) are measured on excised leaf samples in 72 species. A positive correlation between rs and rc was found. rc ranges from 2.2-62.5 s cm−1 in mesophytes and from 19-425 s cm−1 in xerophytes, the highest values were found in succulents. Some of the alpine species had extremely low rc, falling within the rs-range. Some habitat specific differences in rc were found, but the relatively few significant differences in rs between different habitats indicate that a lot of different drought avoidance mechanisms exist. The greatest variation in rc between different species was found in periodically dry habitats, though a few species like Epilobium alsinifolium (rc= 62.5 s cm−1) growing in constantly wet habitats had remarkably high rc. 6 In Saussurea alpina leaf size increases with improved moisture conditions. Calculations of leaf temperatures with closed stomata and somewhat extreme meteorological conditions showed that the mean leaf size in the wettest part of the transect was below, but very close to the size giving lethal leaf temperatures. In Rubus chamaemorus leaf size increases with increasing artificial shading. The leaves growing in sunexposed sites will be only 0.5°C below the lethal limit when the stomata are closed. All the shade-leaves would exceed the lethal limit if the screen was removed and closing of stomata occurred. The northern distribution of this species is probably due to its low ability to avoid heat stress. 7 In Silene acaulis heat damage was observed under natural conditions at an air temperature of only 21°C. Leaf temperatures about 20°C above air temperature was often found in prostrate alpine vascular plants during sunny periods. The highest overtemperature (25.5°C) was observed in the broad leaves of Rubus chamaemorus. A comparison with maximum leaf temperatures measured in different parts of the world revealed rather uniform maximum leaf temperatures in spite of very contrasting air temperatures. Thus, vascular plants seem to control the leaf temperatures to a great extent by means of morphological modifications. 8 Leaf temperatures in a hot and dry period were calculated and compared with the heat resistance in 69 Scandinavian, mainly alpine, plants. In 14 wet growing species the lethal limits were exceeded if closing of the stomata occurred. In the remaining species calculated temperatures in single leaves never exceeded the lethal limit. Most of these species have leaves densely crowded in cushions or prostrate rosettes. Hence they get warmer than indicated by the calculated temperatures in single leaves, and will probably be heated close to the lethal limit. A highly significant correlation between lethal temperatures and cuticular diffusion resistances was found, probably illustrating the importance of transpirational cooling during a hot period. A combination of cuticular diffusion resistances and lethal temperatures segregates the species better in natural groups than only one parameter alone. 9 Factors involved in limiting the downward distribution of alpine plants are discussed. Some species avoid lowlands since they are drought sensitive (low cuticular diffusion resistance), others, mainly cushion plants with low heat exchange capacity, are probably overheated in lowlands.