Changing Environmental Effects on Frost Hardiness of Scots Pine During Dehardening

The effects of raised temperature and extended photoperiod onthe dehardening of quiescent and winter-hardy Scots pine saplingswere examined in an open-top-chamber experiment. The saplingswere exposed during winter to natural, square-curve fluctuating(between 1 and 11 °C with a 14 d interval), and constant(6 °C) temperatures with a natural and an extended (17 h)photoperiod. Frost hardiness of needles was determined by controlledfreezing tests and visual damage scoring. The constant 6 °Ctemperature treatment caused a gradual dehardening of needleswhereas under fluctuating temperatures the level of frost hardinessfluctuated. Trees exposed to extended photoperiods were lesshardy than under natural photoperiods after the initiation ofshoot elongation, but before this there were no clear differencesin frost hardiness between different photoperiodic treatments.The results indicate that the frost hardening competence ofScots pine changes during quiescence. Climate change; frost hardiness; hardening competence; photoperiod; Pinus sylvestris, Scots pine; temperature     

A Second-order Dynamic Model for the Frost Hardiness of Trees

The development of frost hardiness in forest trees is describedby a dynamic model in which the input variables are the prevailingenvironmental conditions and the developmental stage of trees.The assumption of the model is that for each temperature andphotoperiod there is a discrete stationary level of frost hardiness,which is attained if these environmental factors remain constant.The dependence of the stationary level on temperature and photoperiodis assumed to be piece-wise linear and additive. The rate ofacclimation, i.e. frost hardening or dehardening, is describedas a second-order dynamic process with two time constants, thesecond of which changes depending on the stage of the annualdevelopment of the trees. The frost hardiness model was calibratedand tested using experimental data from Douglas fir [Pseudotsugamenziesii var. glauca (Beissn.) Franco] seedlings. The resultssuggest that the second-order model describes the changes infrost hardiness better than the first-order model with onlyone time constant.Copyright 1995, 1999 Academic Press Acclimation, developmental stage, Douglas fir, dynamic model, frost hardiness, photoperiod, Pseudotsuga menziesii, temperature     

Frost Damage Resulting from Ice Crystal Formation in Seedlings of Spruce and Pine

The influence of ice crystal formation in tissues of unhardened and hardened seedlings of Pinus silvestris L. and Picea abies (L.) Karst. was determined. An apparatus for this purpose was constructed. Unhardened seedlings of spruce collapsed completely as a result of ice crystal formation in their shoots, while unhardened seedlings of pine survived ice crystal formation with or without injury to the needles. After a hardening period of 4–5 weeks, seedlings of spruce and pine survived ice formation but injuries occurred in spruce. For pine, on the contrary, the temperature after ice formation had a decisive effect on the extent of the injuries. Observed injuries are discussed in terms of inter- and intracellular ice crystal formation.     

Patterns of Forest Decline and Regeneration Across Scots Pine Populations

To predict future changes in forest ecosystems, it is crucial to understand the complex processes involved in decline of tree species populations and to evaluate the implications for potential vegetation shifts. Here, we study patterns of decline (canopy defoliation and mortality of adults) of four Scots pine populations at the southern edge of its distribution and characterized by different combinations of climate dryness and intensity of past management. General linear and structural equation modeling were used to assess how biotic, abiotic, and management components interacted to explain the spatial variability of Scots pine decline across and within populations. Regeneration patterns of Scots pine and co-occurring oak species were analyzed to assess potential vegetation shifts. Decline trends were related to climatic dryness at the regional scale, but, ultimately, within-population forest structure, local site conditions, and past human legacies could be the main underlying drivers of Scots pine decline. Overall, Scots pine regeneration was negatively related to decline both within and between populations, whereas oak species responded to decline idiosyncratically across populations. Taken together, our results suggest that (1) patterns of decline are the result of processes acting at the plot level that modulate forest responses to local environmental stress and (2) decline of adult Scots pine trees seems not to be compensated by self-recruitment so that the future dynamics of these forest ecosystems are uncertain.     

A Functional and Structural Mongolian Scots Pine (Pinus sylvestris var. mongolica) Model Integrating Architecture, Biomass and Effects of Precipitation

Mongolian Scots pine (Pinus sylvestris var. mongolica) is one of the principal tree species in the network of Three-North Shelterbelt for windbreak and sand stabilisation in China. The functions of shelterbelts are highly correlated with the architecture and eco-physiological processes of individual tree. Thus, model-assisted analysis of canopy architecture and function dynamic in Mongolian Scots pine is of value for better understanding its role and behaviour within shelterbelt ecosystems in these arid and semiarid regions. We present here a single-tree functional and structural model, derived from the GreenLab model, which is adapted for young Mongolian Scots pines by incorporation of plant biomass production, allocation, allometric rules and soil water dynamics. The model is calibrated and validated based on experimental measurements taken on Mongolian Scots pines in 2007 and 2006 under local meteorological conditions. Measurements include plant biomass, topology and geometry, as well as soil attributes and standard meteorological data. After calibration, the model allows reconstruction of three-dimensional (3D) canopy architecture and biomass dynamics for trees from one- to six-year-old at the same site using meteorological data for the six years from 2001 to 2006. Sensitivity analysis indicates that rainfall variation has more influence on biomass increment than on architecture, and the internode and needle compartments and the aboveground biomass respond linearly to increases in precipitation. Sensitivity analysis also shows that the balance between internode and needle growth varies only slightly within the range of precipitations considered here. The model is expected to be used to investigate the growth of Mongolian Scots pines in other regions with different soils and climates.     

Frost hardiness of mycorrhizal (Hebeloma sp.) and non-mycorrhizal Scots pine roots

The frost hardiness (FH) of mycorrhizal [ectomycorrhizal (ECM)] and non-mycorrhizal (NM) Scots pine (Pinus sylvestris) seedlings was studied to assess whether mycorrhizal symbiosis affected the roots’ tolerance of below-zero temperatures. ECM (Hebeloma sp.) and NM seedlings were cultivated in a growth chamber for 18 weeks. After 13 weeks’ growth in long-day and high-temperature (LDHT) conditions, a half of the ECM and NM seedlings were moved into a chamber with short-day and low-temperature (SDLT) conditions to cold acclimate. After exposures to a range of below-zero temperatures, the FH of the roots was assessed by means of the relative electrolyte leakage test. The FH was determined as the inflection point of the temperature-response curve. No significant difference was found between the FH of mycorrhizal and non-mycorrhizal roots in LDHT (?8.9 and ?9.8 °C) or SDLT (?7.5 and ?6.8 °C). The mycorrhizal treatment had no significant effect on the total dry mass, the allocation of dry mass among the roots and needles or nutrient accumulation. The mycorrhizal treatment with Hebeloma sp. did not affect the FH of Scots pine in this experimental setup. More information is needed on the extent to which mycorrhizas tolerate low temperatures, especially with different nutrient contents and different mycorrhiza fungi.     

A Structured Threshold Model for Mountain Pine Beetle Outbreak

A vigor-structured model for mountain pine beetle outbreak dynamics within a forest stand is proposed and analyzed. This model explicitly tracks the changing vigor structure in the stand. All model parameters, other than beetle vigor preference, were determined by fitting model components to empirical data. An abrupt threshold for tree mortality to beetle densities allows for model simplification. Based on initial beetle density, model outcomes vary from decimation of the entire stand in a single year, to inability of the beetles to infect any trees. An intermediate outcome involves an initial infestation which subsequently dies out before the entire stand is killed. A model extension is proposed for dynamics of beetle aggregation. This involves a stochastic formulation.     

Indirect Measurement of Pore Size and Permeability in Scots Pine and Norway Spruce

Five experiments to investigate the water relationships of Scotspine and Norway spruce sapwood are described. Field exposureof stakes, and their moisture characteristic relating wood moisturecontent to the water potential of the surroundings showed thatspruce had a lower moisture content than pine under the sameconditions. A pore size distribution derived from the characteristicsshowed more large pores in spruce than in pine, but in sprucethere were also more small pores. The inference was that thelarge pores of spruce were readily accessible to water, allowinga fast rate of water uptake, as found in the wick action andswelling investigations, while the small pores were not accessible,resulting in a low rate of water uptake and a low rate of swelling.The possibility is briefly discussed that it is the pore sizedistribution of the two woods which determines their water relationships,and the difference in pore size which determines their treatability. Key words: Pinus sylvestris L, Picea abies (L) Karst, Pore size, Water uptake     

Evolutionary Aspects of Functional and Pseudogene Members of the Phytochrome Gene Family in Scots Pine

According to the neutral theory of evolution, mutation and genetic drift are the only forces that shape unconstrained, neutral, gene evolution. Thus, pseudogenes (which often evolve neutrally) provide opportunities to obtain direct estimates of mutation rates that are not biased by selection, and gene families comprising functional and pseudogene members provide useful material for both estimating neutral mutation rates and identifying sites that appear to be under positive or negative selection pressures. Conifers could be very useful for such analyses since they have large and complex genomes. There is evidence that pseudogenes make significant contributions to the size and complexity of gene families in pines, although few studies have examined the composition and evolution of gene families in conifers. In this work, I examine the complexity and rates of mutation of the phytochrome gene family in Pinus sylvestris and show that it includes not only functional genes but also pseudogenes. As expected, the functional PHYO does not appear to have evolved neutrally, while phytochrome pseudogenes show signs of unconstrained evolution.     

Distribution of Cren- and Euryarchaeota in Scots Pine Mycorrhizospheres and Boreal Forest Humus

Archaeal 16S rRNA gene sequences have been found in a variety of moderate-temperature habitats including soil and rhizospheres. In this study, the differences of archaeal communities associated with Scots pine (Pinus sylvestris L.) short roots, different types of mycorrhizospheric compartments, and uncolonized boreal forest humus were tested by direct DNA extraction, polymerase chain reaction–denaturing gradient gel electrophoresis (PCR–DGGE), and sequencing. The results indicated that mycorrhizal colonization of Scots pine roots substantially influence the archaeal community of pine rhizospheres. Colonization of short roots by most mycorrhizal fungi tested increased both archaeal frequency and diversity. Most of the archaeal sequences encountered in mycorrhizas belonged to the phylum Euryarchaeota, order of Halobacteriales. The difference in archaeal diversity between the mycorrhizospheric compartments and humus was profound. Most compartments with fungal components contained euryarchaeotal 16S rRNA gene sequences, whereas a high diversity of crenarchaeotal sequences and no euryarchaeotal sequences were found in forest humus outside mycorrhizospheres.     

Long and Short Term Development of Frost Hardiness in Pinus silvestris, and Heavy Particle Adenosine Triphosphatase

The effect of different growth temperatures, of transfer between them, and of changes in outside temperature on frost hardiness and ATPase activity of Scotch pines (Pinus silvestris L.) were studied. Plants which had been grown in the greenhouse and transported to outside “remembered” something of their earlier growing circumstances during a long period. They differed from the plants continuously grown outside in the level of hardiness, although changes in temperature caused similar fluctuations in the hardiness of both groups. It is evident that two mechanisms are present, the one causing a long term determination of the level of frost hardiness obtainable, the other causing a short term adaption. The heavy particle ATPase activity as investigated below 20°C grouped itself according to the main temperature groups of the experiment. Above 30°C, the pretreatments had given rise to differences within the temperature groups. The level of the ATPase activity increased as the growing season came closer.     

The Influence of Photoperiod and Temperature on the Development of Frost Hardiness in Seedlings of Pinus silvestris and Picea abies

The influence of short days and low temperature on the development of frost hardiness in seedlings of Scots pine (Pinus silvestris L.) and Norway spruce [Picea abies (L.) Karst.], grown for 6 months in glasshouses and climate chambers, was investigated. The degree of hardiness was estimated by freezing the shoots of the seedlings to predetermined temperatures. After 8 weeks in a glasshouse the viability of the seedlings was determined by establishing bud flushing. The most effective climate for the development of frost hardiness was short days (SD) and low temperature (2°C); the next most effective was SD and room temperature (20°C). However, long days (LD) and low temperature also had a marked effect on the development of hardiness. A combination of 3 weeks’treatment with SD and 20°C, and 3 weeks with SD and 2°C gave the same results as 6 weeks with SD and 2°C. The results clearly demonstrate the importance of the photoperiod prior to low temperature for the development of frost hardiness. In conclusion both short days and low temperature induce frost hardiness development. Probably this occurs by initiation of different processes in the two cases. The degree of frost hardiness development appears to depend on the sum of these different processes and on the timing between them.     

Cold Hardiness of Pine Needles and Apple Bark as Affected by Alteration of Day Length and Temperature

Cold hardiness of pine needles and apple bark was determined in a series of experiments. Plants were exposed to 0°C and 20°C and exposed to day length conditions of 9 and 14 h. All 16 possible combinations were investigated by transfer of the plants from the original condition to each of the other conditions. In order to interpret the results, it was necessary to distinguish between a single and a dual environmental factor change. In pine plants at 20°C, a change in two factors decreased cold hardiness contrary to a single change in temperature or day length. In plants at 0°C, the effects of a change in day length and temperature were additive. Differences in pine and apple are discussed in relation to natural conditions and to geographical distribution. It is suggested that for increased hardiness shortening of day length should precede a low temperature regime and that reversal of this order may upset the signal system, resulting in dehardening.     

Characterization of the Proteinases Present in Germinating Seeds of Scots Pine, Pinus sylvestris

Methods were developed to determine proteinase activity in germinating seeds of Scots pine. The assays were based on the liberation of TCA-soluble peptides from haemoglobin at pH 3.7 and from casein at pH 5.4 and pH 7.0; the reaction products were determined by the Lowry method. — Endosperms separated from seeds at the time of rapid storage protein mobilization (seedling length between 20 and 50 mm) showed high proteinase activities in all three assays. Experiments with different inhibitors suggested that at least four enzymes were involved. One of the enzymes resembled mammalian and microbial pepsin-like acid proteinases: the pH optimum was 3.7 and the enzyme was inhibited by pepstatin.—The proteinase activities in the endosperms were high enough to account for the mobilization of the reserve proteins during germination. Moreover the activities at pH 3.7.5.4. and 7.0 in the endosperms were 10-, 25-, and 50-fold the corresponding activities in the growing seedlings (a “reference” tissue). Consequently, it seems that both the acid and neutral proteinases take part in the mobilization of storage proteins in the germinating seed.     

Localization and Activity of Naphthylamidases in Germinating Seeds of Scots Pine, Pinus sylvestris

Extracts prepared from endosperms of germinating seeds of Scots pine, Pinus sylvestris L., rapidly hydrolysed the β-naphthylamides of L-phenylalanine and L-leucine optimally at pH 6.5 and that of L-arginine at pH 7.7. Disc electrophoresis followed by activity staining showed that the activities were due to two naphthylamidases (aminopeptidases) with different substrate specificities. Seeds were allowed to germinate at 20°C on agar gel in the dark and the activities on the three substrates were assayed from separated endosperms and seedlings at various stages of germination. The activities in the endosperm of resting seeds were relatively high and they remained unchanged throughout the period of reserve protein mobilization (seedling length up to 50 mm), after which they began to decrease. The activities of the naphthylamidases are rather small compared with those of the two alkaline peptidases of pine, contributing about 17% of the total amino-peptidase activity in the endosperm of germinating seeds. The total aminopeptidase activity is sufficient to account for the rate of storage protein mobilization during germination. In the seedlings the naphthylamidase activities (per seedling) increased continuously during germination, and activities per g dry weight were higher than those in the endosperm.     

Rotational Activity of Trunk Parts in Scots Pine Trees: Seasonal Dynamics and Patterns

Doklady Biological Sciences - The seasonal dynamics and relationships between the characteristics of the angles of rotation of outer sapwood layers in trunks of Scots pine (Pinus sylvestris L.)...     

Freeze Thaw: A Simple Approach for Prediction of Optimal Cryoprotectant for Freeze Drying

The present study evaluates freeze thaw as a simple approach for screening the most appropriate cryoprotectant. Freeze–thaw study is based on the principle that an excipient, which protects nanoparticles during the first step of freezing, is likely to be an effective cryoprotectant. Nanoparticles of rifampicin with high entrapment efficiency were prepared by the emulsion-solvent diffusion method using dioctyl sodium sulfosuccinate (AOT) as complexing agent and Gantrez AN-119 as polymer. Freeze–thaw study was carried out using trehalose and fructose as cryoprotectants. The concentration of cryoprotectant, concentration of nanoparticles in the dispersion, and the freezing temperature were varied during the freeze–thaw study. Cryoprotection increased with increase in cryoprotectant concentration. Further, trehalose was superior to fructose at equivalent concentrations and moreover permitted use of more concentrated nanosuspensions for freeze drying. Freezing temperature did not influence the freeze–thaw study. Freeze-dried nanoparticles revealed good redispersibility with a size increase that correlated well with the freeze–thaw study at 20% w/v trehalose and fructose. Transmission electron microscopy revealed round particles with a size ∼400 nm, which correlated with photon correlation spectroscopic measurements. Differential scanning calorimetry and X-ray diffraction suggested amorphization of rifampicin. Fourier transfer infrared spectroscopy could not confirm interaction of drug with AOT. Nanoparticles exhibited sustained release of rifampicin, which followed diffusion kinetics. Nanoparticles of rifampicin were found to be stable for 12 months. The good correlation between freeze thaw and freeze drying suggests freeze–thaw study as a simple and quick approach for screening optimal cryoprotectant for freeze drying.