Early growth of Scots pine seedlings is affected by seed origin and light quality.

Plants have evolved a suite of photoreceptors to perceive information from the surrounding light conditions. The aim of this study was to examine photomorphogenic effects of light quality on the growth of Scots pine (Pinus sylvestris L.) seedlings representing southern (60 °N) and northern (68 °N) origins in Finland. We measured the growth characteristics and the expression of light-responsive genes from seedlings grown under two LED light spectra: (1) Retarder (blue and red wavelengths in ratio 0.7) inducing compact growth, and (2) Booster (moderate in blue, green and far-red wavelengths, and high intensity of red light) promoting shoot elongation. The results show that root elongation, biomass, and branching were reduced under Retarder spectrum in the seedlings representing both origins, while inhibition in seed germination and shoot elongation was mainly detected in the seedlings of northern origin. The expression of ZTL and HY5 was related to Scots pine growth under both light spectra. Moreover, the expression of PHYN correlated with growth when exposed to Retarder, whereas CRY2 expression was associated with growth under Booster. Our data indicates that blue light and the deficiency of far-red light limit the growth of Scots pine seedlings and that northern populations are more sensitive to blue light than southern populations. Furthermore, the data analyses suggest that ZTL and HY5 broadly participate in the light-mediated growth regulation of Scots pine, whereas PHYN responses to direct sunlight and the role of CRY2 is in shade avoidance. Altogether, our study extends the knowledge of light quality and differential gene expression affecting the early growth of Scots pines representing different latitudinal origins.

Contributions of day length, temperature and individual variability on the rate and timing of leaf senescence in the common lilac Syringa vulgaris.

Deciduous trees prepare for winter by breaking up chlorophyll and other nitrogen-rich compounds, which are resorbed for storage. Timing is important as senescence too early will waste growing season, while senescence too late risks the loss of the leaf resources to frost. While plants of temperate and boreal regions use decreasing day length as a cue of approaching winter, we show that decreasing temperature may also play a role in the variability of leaf senescence. We investigated the timing of autumnal decrease in photosynthetic efficiency and the concentration of chlorophyll and total carotenoids in nine common lilac (Syringa vulgaris L.) trees over two consecutive years. Day length explained a greater proportion of photosynthetic efficiency, but temperature had a significant additional role, which seems to be related to individual differences. Precipitation and cloudiness did not explain photosynthetic efficiency. Photosynthetic efficiency was higher outside the canopy and at high and middle elevations than inside and low elevations of the canopy. Late onset of senescence led to a steeper decline in photosynthetic efficiency than early senescence. The onset of decline in photosynthetic efficiency differed between years, but there was no difference in the steepest rate of change in photosynthetic efficiency with respect to sampling year or location. Contributions of day-length vs temperature to leaf senescence have important consequences for the adaptability and invasibility of deciduous trees in a changing climate, especially at the edge of species distributions.

Competitive success of southern populations of Betula pendula and Sorbus aucuparia under simulated southern climate experiment in the subarctic.

Global warming has been commonly accepted to facilitate species' range shifts across latitudes. Cross-latitudinal transplantations support this; many tree species can well adapt to new geographical areas. However, these studies fail to capture species' adaptations to new light environment because the experiments were not designed to explicitly separate species' responses to light and temperature. Here we tested reaction norms of tree seedlings in reciprocal transplantations 1,000 km apart from each other at two latitudes (60°N and 69°N). In contrast to past studies, we exposed our experimental plants to same temperature in both sites (temperature of 60°N growing site is recorded to adjust temperature of 69°N site in real time via Internet connection) while light environment (photoperiod, light quality) remained ambient. Shoot elongation and autumn coloration were studied in seedlings of two deciduous trees (Betula pendula and Sorbus aucuparia), which were expected to respond differently to day length. Sorbus as a member of Rosaceae family was assumed to be indifferent to photoperiod, while Betula responds strongly to day length. We hypothesized that (1) southern and northern populations of both species perform differently; (2) southern populations perform better in both sites; (3) autumn phenology of southern populations may delay in the northern site; (4) and Sorbus aucuparia is less dependent on light environment. According to the hypotheses, shoot elongation of northern population was inherently low in both species. An evolutionary consequence of this may be a competitive success of southern populations under warming climate. Southern population of B. pendula was delayed in autumn coloration, but not in growth cessation. Sorbus aucuparia was less responsive to light environment. The results suggest that light provides selection pressure in range shifts, but the response is species dependent.

Targeted use of LEDs in improvement of production efficiency through phytochemical enrichment.

Based on available literature, ecology and economy of light emitting diode (LED) lights in plant foods production were assessed and compared to high pressure sodium (HPS) and compact fluorescent light (CFL) lamps. The assessment summarises that LEDs are superior compared to other lamp types. LEDs are ideal in luminous efficiency, life span and electricity usage. Mercury, carbon dioxide and heat emissions are also lowest in comparison to HPS and CFL lamps. This indicates that LEDs are indeed economic and eco-friendly lighting devices. The present review indicates also that LEDs have many practical benefits compared to other lamp types. In addition, they are applicable in many purposes in plant foods production. The main focus of the review is the targeted use of LEDs in order to enrich phytochemicals in plants. This is an expedient to massive improvement in production efficiency, since it diminishes the number of plants per phytochemical unit. Consequently, any other production costs (e.g. growing space, water, nutrient and transport) may be reduced markedly. Finally, 24 research articles published between 2013 and 2017 were reviewed for targeted use of LEDs in the specific, i.e. blue range (400-500 nm) of spectrum. The articles indicate that blue light is efficient in enhancing the accumulation of health beneficial phytochemicals in various species. The finding is important for global food production. © 2017 Society of Chemical Industry.

Decreased frost hardiness of Vaccinium vitis-idaea in reponse to UV-A radiation.

The aim of this study was to investigate plant frost hardiness responses to ultraviolet (UV) radiation, since the few results reported are largely contradictory. It was hypothesized that functional adaptation of life forms could explain these contradictions. Dwarf shrubs and tree seedlings, representing both evergreen and deciduous forms, were tested (Vaccinium vitis-idaea, Vaccinium myrtillus, Pinus sylvestris, Betula pubescens and its red form f. rubra). The research was performed in Sodankylä, Northern Finland (67°N), with enhanced UV-B- and UV-A-radiation treatments between 2002 and 2009. Plant frost hardiness was determined using the freeze-induced electrolyte leakage method in early autumn, during the onset of the frost hardening process. Additional physiological variables (malondialdehyde, glutathione, total phenols, C and N contents) were analyzed in V. vitis-idaea to explain the possible responses. These variables did not respond significantly to UV-radiation treatments, but explained the frost hardiness well (r² = 0.678). The main finding was that frost hardiness decreased in the evergreen shrub V. vitis-idaea, particularly with enhanced UV-A radiation. No significant responses were observed with the other plants. Therefore, this study does not support the idea that enhanced UV radiation could increase plant frost hardiness.

Optimization of protein extraction from Hypericum perforatum tissues and immunoblotting detection of Hyp-1 at different stages of leaf development.

Sample preparation is crucial for obtaining high-quality proteins for the purpose of electrophoretic separation and further analysis from tissues that contain high levels of interfering compounds. Hypericum perforatum is a medicinal plant that contains high amounts of phenolic compounds, of which hypericins, hyperforins, and flavonoids contribute to the antidepressant activities of the plant. This study focuses on obtaining optimized amounts of high-quality proteins from H. perforatum, which are suitable for electrophoretic analyses. From the tested protein extraction solutions, sodium borate buffers at pH 9 and 10 gave the best protein yields from mature H. perforatum leaves. With these buffers, relatively high protein yields could also be obtained from roots, stems, and flower buds. The protein extracts of all organs were well resolved in SDS-PAGE after an efficient removal of non-protein contaminants with PVPP, phenol extraction, and methanolic ammonium acetate precipitation. The method was suitable for high-quality protein extraction also from other tested species of genus Hypericum. The applicability of the protocol for immunoblotting was demonstrated by detecting Hyp-1 in H. perforatum leaves at different stages of development. Hyp-1, which has been suggested to attend to the biosynthesis of hypericin, accumulated in high amounts in H. perforatum leaves at mature stage.

Impacts of extreme winter warming events on plant physiology in a sub-Arctic heath community.

Insulation provided by snow cover and tolerance of freezing by physiological acclimation allows Arctic plants to survive cold winter temperatures. However, both the protection mechanisms may be lost with winter climate change, especially during extreme winter warming events where loss of snow cover from snow melt results in exposure of plants to warm temperatures and then returning extreme cold in the absence of insulating snow. These events cause considerable damage to Arctic plants, but physiological responses behind such damage remain unknown. Here, we report simulations of extreme winter warming events using infrared heating lamps and soil warming cables in a sub-Arctic heathland. During these events, we measured maximum quantum yield of photosystem II (PSII), photosynthesis, respiration, bud swelling and associated bud carbohydrate changes and lipid peroxidation to identify physiological responses during and after the winter warming events in three dwarf shrub species: Empetrum hermaphroditum, Vaccinium vitis-idaea and Vaccinium myrtillus. Winter warming increased maximum quantum yield of PSII, and photosynthesis was initiated for E. hermaphroditum and V. vitis-idaea. Bud swelling, bud carbohydrate decreases and lipid peroxidation were largest for E. hermaphroditum, whereas V. myrtillus and V. vitis-idaea showed no or less strong responses. Increased physiological activity and bud swelling suggest that sub-Arctic plants can initiate spring-like development in response to a short winter warming event. Lipid peroxidation suggests that plants experience increased winter stress. The observed differences between species in physiological responses are broadly consistent with interspecific differences in damage seen in previous studies, with E. hermaphroditum and V. myrtillus tending to be most sensitive. This suggests that initiation of spring-like development may be a major driver in the damage caused by winter warming events that are predicted to become more frequent in some regions of the Arctic and that may ultimately drive plant community shifts.

Drought tolerance of juvenile and mature leaves of a deciduous dwarf shrub Vaccinium myrtillus L. in a boreal environment.

The difference between drought tolerance of juvenile and mature leaves of the winter-deciduous dwarf shrub bilberry (Vaccinium myrtillus L.) from a northern boreal environment was investigated. It was hypothesised that mature leaves are more drought sensitive than juvenile leaves. Bilberry plants were allowed to dry out by excluding irrigation when leaves were at juvenile and mature stages. Tissue water content decreased at both phenological stages, but the response was more pronounced in the mature leaves. Anthocyanin concentrations increased as the tissue water content decreased, and again this occurred to a greater extent in the mature leaves. Chlorophyll concentrations decreased only marginally at the juvenile stage, while the decrease was significant in the mature leaves. Chlorophyll degradation was enhanced by drought stress. Soluble proteins decreased and protein oxidation increased in the mature leaves, and degradation of oxidised proteins increased in the drought-stressed plants. The results suggest that leaves of bilberry are more sensitive to drought stress at the mature stage, and that drought stress accelerates senescence at the mature stage. The significance of the results is that dry periods during the juvenility of leaves are not as detrimental as they may be later in summer. In addition, the strategy of a winter-deciduous plant is obviously to protect its perennial parts from severe drought by accelerated leaf senescence at the mature stage. Therefore, the deciduous life form may provide an excellent adaptation against drought also in northern ecosystems. The role of anthocyanins in photoprotection under drought stress is also discussed.

Improved elongation of Scots pine seedlings under blue light depletion is not dependent on resource acquisition.

Removal of blue light (400-500 nm) induced shoot elongation of 2-year-old Scots pine (Pinus sylvestris L.) seedlings, which was not related to resource acquisition (carbohydrates, C/N ratio and soluble proteins) and frost hardening. The seedlings were grown in northern Finland (64°N) in plexiglass chambers, either orange in colour or transparent, during elongation and cold hardening periods in 2001. The orange chamber removed the blue wavelengths. The results suggest that the growth inhibiting effect of blue light on Scots pine elongation is probably a photomorphogenic regulation response; the removal of blue light did not affect the gas exchange and accumulation of growth resources. In addition, the removal of blue light also did not affect the physiological parameters (pigment composition, chlorophyll fluorescence and lipid peroxidation) measured during the preparation for winter.

Metal stress consequences on frost hardiness of plants at northern high latitudes: a review and hypothesis.

This paper reviews the potential of trace/heavy metal-induced stress to reduce plant frost hardiness at northern high latitudes. The scientific questions are first outlined prior to a brief summary of heavy metal tolerance. The concepts of plant capacity and survival adaptation were used to formulate a hypothesis, according to which heavy metal stress may reduce plant frost hardiness for the following reasons: (1) Heavy metals change membrane properties through impaired resource acquisition and subsequent diminution of the cryoprotectant pool. (2) Heavy metals change membrane properties directly through oxidative stress, i.e. an increase of active oxygen species. (3) The involved co-stress may further increase oxidative stress. (4) The risk of frost injury increases due to membrane alterations. An opposite perspective was also discussed: could metal stress result in enhanced plant frost hardiness? This phenomenon could be based on the metabolism (i.e. glutathione, polyamines, proline, heat shock proteins) underlying a possible general adaptation syndrome of stress (GAS). As a result of the review it was suggested that metal-induced stress seems to reduce rather than increase plant frost hardiness.

Biodiversity, distributions and adaptations of Arctic species in the context of environmental change.

The individual of a species is the basic unit which responds to climate and UV-B changes, and it responds over a wide range of time scales. The diversity of animal, plant and microbial species appears to be low in the Arctic, and decreases from the boreal forests to the polar deserts of the extreme North but primitive species are particularly abundant. This latitudinal decline is associated with an increase in super-dominant species that occupy a wide range of habitats. Climate warming is expected to reduce the abundance and restrict the ranges of such species and to affect species at their northern range boundaries more than in the South: some Arctic animal and plant specialists could face extinction. Species most likely to expand into tundra are boreal species that currently exist as outlier populations in the Arctic. Many plant species have characteristics that allow them to survive short snow-free growing seasons, low solar angles, permafrost and low soil temperatures, low nutrient availability and physical disturbance. Many of these characteristics are likely to limit species' responses to climate warming, but mainly because of poor competitive ability compared with potential immigrant species. Terrestrial Arctic animals possess many adaptations that enable them to persist under a wide range of temperatures in the Arctic. Many escape unfavorable weather and resource shortage by winter dormancy or by migration. The biotic environment of Arctic animal species is relatively simple with few enemies, competitors, diseases, parasites and available food resources. Terrestrial Arctic animals are likely to be most vulnerable to warmer and drier summers, climatic changes that interfere with migration routes and staging areas, altered snow conditions and freeze-thaw cycles in winter, climate-induced disruption of the seasonal timing of reproduction and development, and influx of new competitors, predators, parasites and diseases. Arctic microorganisms are also well adapted to the Arctic's climate: some can metabolize at temperatures down to -39 degrees C. Cyanobacteria and algae have a wide range of adaptive strategies that allow them to avoid, or at least minimize UV injury. Microorganisms can tolerate most environmental conditions and they have short generation times which can facilitate rapid adaptation to new environments. In contrast, Arctic plant and animal species are very likely to change their distributions rather than evolve significantly in response to warming.

Responses to projected changes in climate and UV-B at the species level.

Environmental manipulation experiments showed that species respond individualistically to each environmental-change variable. The greatest responses of plants were generally to nutrient, particularly nitrogen, addition. Summer warming experiments showed that woody plant responses were dominant and that mosses and lichens became less abundant. Responses to warming were controlled by moisture availability and snow cover. Many invertebrates increased population growth in response to summer warming, as long as desiccation was not induced. CO2 and UV-B enrichment experiments showed that plant and animal responses were small. However, some microorganisms and species of fungi were sensitive to increased UV-B and some intensive mutagenic actions could, perhaps, lead to unexpected epidemic outbreaks. Tundra soil heating, CO2 enrichment and amendment with mineral nutrients generally accelerated microbial activity. Algae are likely to dominate cyanobacteria in milder climates. Expected increases in winter freeze-thaw cycles leading to ice-crust formation are likely to severely reduce winter survival rate and disrupt the population dynamics of many terrestrial animals. A deeper snow cover is likely to restrict access to winter pastures by reindeer/caribou and their ability to flee from predators while any earlier onset of the snow-free period is likely to stimulate increased plant growth. Initial species responses to climate change might occur at the sub-species level: an Arctic plant or animal species with high genetic/racial diversity has proved an ability to adapt to different environmental conditions in the past and is likely to do so also in the future. Indigenous knowledge, air photographs, satellite images and monitoring show that changes in the distributions of some species are already occurring: Arctic vegetation is becoming more shrubby and more productive, there have been recent changes in the ranges of caribou, and "new" species of insects and birds previously associated with areas south of the treeline have been recorded. In contrast, almost all Arctic breeding bird species are declining and models predict further quite dramatic reductions of the populations of tundra birds due to warming. Species-climate response surface models predict potential future ranges of current Arctic species that are often markedly reduced and displaced northwards in response to warming. In contrast, invertebrates and microorganisms are very likely to quickly expand their ranges northwards into the Arctic.

Anthocyanins and glutathione S-transferase activities in response to low temperature and frost hardening in Vaccinium myrtillus (L.).

Anthocyanin (Acy) contents and GST activities of bilberry (Vaccinium myrtillus L.) were investigated in two experiments conducted in June (Exp. I: active growth) and in August September (Exp. II: beginning of frost hardening) in Northern Finland (65 degrees N). Bilberry plants were subjected to +2 degrees C and +18 degrees C in Exp. I or +5/0 degrees C (day/night) and +18/+13 degrees C (day/night) in Exp. II. GST activities were assessed using either 1-chloro-2,4-dinitrobenzene (CDNB) or trans-cinnamic acid (tCA) as substrates. We found temperature to have no effect on Acy during either active growth or frost hardening. Acy increased several-fold from active growth to the beginning of frost hardening, but no increment was observed during the development of frost hardening. This suggests a role of Acy in photoprotection at low temperatures rather than their direct involvement in the development of freezing tolerance. The lack of response of GST activity to frost hardening and to temperature in autumn may indicate an indirect role of GSTs in frost hardening as protective enzymes. GST activity was the same with the two substrates studied (CDNB, tCA), supporting the assumption that GSTs could catalyze reactions with endogenous phenylpropanoids.

Acceleration of frost hardening in Vaccinium vitis-idaea by nitrogen fertilization.

Vaccinium vitis-idaea L. plants were grown in open-top chambers in northern Finland under CO2 enrichment (600-700 ppm) with or without elevated (double ambient) O3. Half of the plants received ammonium nitrate fertilizer equivalent to 200 kg N ha-1 year-1. Frost hardiness during the period of frost hardening was determined three times after the end of the experiment, at the beginning of August, September and October. The results indicate that frost hardening of the Vaccinium vitis-idaea is accelerated by N fertilization. However, CO2 and O3 enrichment had no measurable effect on frost hardiness.

Changes in cellular structures and enzymatic activities during browning of Scots pine callus derived from mature buds.

Visible browning is a typical feature of callus cultures derived from shoot tips of mature Scots pine (Pinus sylvestris L.). Because the ability of callus to regenerate is low, we determined the effect of browning on growth and changes in cellular structure during culture. Striking alterations in cellular structure were detected by LM (light microscopy), EM (electron microscopy) and SEM (scanning electron microscopy). Accumulation of phenolic substances was shown by histochemical staining. Staining for beta-glucosidase activity of soluble proteins that had been subjected to polyacrylamide gel electrophoresis indicated lignification of cells. The measured growth rate of callus was low compared with a hypothetical growth curve. Peroxidase activity increased rapidly soon after the start of the culture period, but especially between the second and third weeks of culture. At this time, the degradation of cell membranes and browning began coincident with the loss of chlorophyll. We conclude that browning is associated with cell disorganization and eventual cell death, making tissue culture of mature pine especially difficult.