Period Of Active Growth Research Articles

Satellite detection of increasing Northern Hemisphere non-frozen seasons from 1979 to 2008: Implications for regional vegetation growth

The landscape freeze–thaw (FT) signal from satellite microwave remote sensing is closely linked to vegetation phenology and land–atmosphere trace gas exchange where seasonal frozen temperatures are a major constraint to plant growth. We applied a temporal change classification of 37GHz brightness temperature (Tb) series from the Scanning Multichannel Microwave Radiometer (SMMR) and Special Sensor Microwave Imager (SSM/I) to classify daily FT status over global land areas where seasonal frozen temperatures influence ecosystem processes. A temporally consistent, long-term (30year) FT record was created, ensuring cross-sensor consistency through pixel-wise adjustment of the SMMR Tb record based on empirical analyses of overlapping SMMR and SSM/I measurements. The resulting FT record showed mean annual spatial classification accuracies of 91 (+/−8.6) and 84 (+/−9.3) percent for PM and AM overpass retrievals relative to in situ air temperature measurements from the global weather station network. The FT results were compared against other measures of biosphere activity including CO2 eddy flux tower measurements and satellite (MODIS) vegetation greenness (NDVI). The FT defined non-frozen season largely bounds the period of active vegetation growth and net ecosystem CO2 uptake for tower sites representing major biomes. Earlier spring thawing and longer non-frozen seasons generally benefit vegetation growth inferred from NDVI spring and summer growth anomalies where the non-frozen season is less than approximately 6months, with greater benefits at higher (>45°N) latitudes. A strong (P<0.001) increasing (0.189daysyr−1) trend in the Northern Hemisphere mean annual non-frozen season is largely driven by an earlier (−0.149daysyr−1) spring thaw trend and coincides with a 0.033°Cyr−1 regional warming trend. The FT record also shows a positive (0.199daysyr−1) trend in the number of transitional (AM frozen and PM non-frozen) frost days, which coincide with reduced vegetation productivity inferred from tower CO2 and MODIS NDVI measurements. The relative benefits of earlier and longer non-frozen seasons for vegetation growth under global warming may be declining due to opposing increases in disturbance, drought and frost damage related impacts.

Sharka in plums: Diagnostics and management

Sharka or plum pox is the most destructive disease of plums and other stone fruits belonging to genus Prunus, worldwide. The disease is incited by plum pox virus (PPV), a member of the genus Potyvirus and family Potyviridae. Timelydetection of PPV in fruit trees is necessary prior to embracing an appropriate management tool for containment of the disease to keep the crop loss sufficiently below the economic threshold level. PPV can be diagnosed by visual examination, particularly, during the period of active growth. Traditionally, cultural methods have been used to isolate and identify this dreaded pathogen. Alternatively, molecular detection techniques are also available which, can generate accurate results rapidly enough to be useful for disease management decisions. With the herald of new frontiers of science such as functional genomics and metabolomics, the development of more cost effective novel tools with exceptional sensitivity in real time is not a distant dream to be realized.

Use of carnauba based carrier for copper sprays reduces infection by &amp;lt;i&amp;gt;Xanthomonas citri&amp;lt;/i&amp;gt; subsp. &amp;lt;i&amp;gt;citri&amp;lt;/i&amp;gt; and &amp;lt;i&amp;gt;Diaporthe citri&amp;lt;/i&amp;gt; in Florida commercial grapefruit groves

Citrus canker, caused by Xanthomonas citri subsp. citri (Xcc), is a bacterial disease of citrus and results in peel blemishes rendering fresh fruit unsalable. Xcc is most active in warm, wet Florida summers where tissues are infected during periods of active growth. Melanose, caused by Diaporthe citri, is common in citrus producing countries, but, like canker, is only important for fresh market fruit. To control canker and melanose, Florida growers spray trees with copper formulations (Cu), but these sprays are removed by strong rains and intense radiation of Florida summers. A study was undertaken in FL commercial grapefruit groves in 2009 and 2010 to assess the efficiency of a spray combining copper with a specially formulated, hydrating wax (WashGard?) (WG). Using a 21-day spray schedule for the season, fruit were sprayed with WG + Cu, Cu and Control (no spray). Fruit from trees sprayed with WG + Cu had approximately 10 and17% more canker free fruit in 2009 and 2010 respectively compared to trees sprayed with copper alone. Compared to control trees the canker free fruit incidence was increased by ≈10% in 2009 and 57% in 2010. For melanose there was 40% more disease free fruit (treated) over fruit from trees with no treatment in 2009 and approximately 20% more in 2010. Controlling infection with this spray significantly reduces citrus canker and melanose, increasing the percentage of marketable fruit.

Responses to winter dormancy, temperature, and plant hormones share gene networks

Gene networks modulated in winter dormancy (WD) in relation to temperature and hormone responses were analyzed in tea [Camellia sinensis (L.) O. Kuntze]. Analysis of subtracted cDNA libraries prepared using the RNA isolated from the apical bud and the associated two leaves (two and a bud, TAB) of actively growing (AG) and winter dormant plant showed the downregulation of genes involved in cell cycle/cell division and upregulation of stress-inducible genes including those encoding chaperons during WD. Low temperature (4°C) modulated gene expression in AG cut-shoots in similar fashion as observed in TAB during WD. In tissue harvested during WD, growth temperature (25°C) modulated gene expression in the similar way as observed during the period of active growth (PAG). Abscisic acid (ABA) and gibberellic acid (GA(3)) modulated expression of selected genes, depending upon if the tissue was harvested during PAG or WD. Tissue preparedness was critical for ABA- and GA(3)-mediated response, particularly for stress-responsive genes/chaperons. Data identified the common gene networks for winter dormancy, temperature, and plant hormone responses.

Alpha-tubulin (CsTUA) up-regulated during winter dormancy is a low temperature inducible gene in tea [Camellia sinensis (L.) O. Kuntze

The present manuscript describes cloning and expression characterization of alpha-tubulin (CsTUA) gene in an evergreen tree tea [Camellia sinensis (L.) O. Kuntze] in response to winter dormancy (WD), abiotic stresses (sodium chloride, polyethylene glycol, and hydrogen peroxide) and plant growth regulators [abscisic acid (ABA), gibberellic acid (GA(3)), indole-3-butyric acid (IBA), and 6-benzylaminopurine (BA)]. CsTUA encoded a putative protein of 449 amino acids with a calculated molecular weight of 49.6kDa and an isoelectric point (pI) of 5.09. CsTUA shared 76-84 and 90-95% identity at nucleotide and amino acid level, respectively with TUA genes from other plant species. During the period of active growth (PAG), CsTUA showed maximum expression in floral buds as compared to leaf, stem, fruit and root. Though the transcript was not detectable in the younger leaf tissue during the PAG, the expression was induced within 24h of the low temperature (LT) treatment. The expression was not modulated by the plant growth regulators either in the tissue harvested during PAG or during WD. It was interesting to record that the expression of CsTUA was up-regulated in response to sodium chloride, polyethylene glycol, and hydrogen peroxide. Data has been discussed on the possible role of CsTUA in imparting tolerance to stresses including to LT so that the tea does not exhibit deciduous nature during winters.

Annual variation in δ 13C values of maize and wheat: Effect on estimates of decadal scale soil carbon turnover

On sites where C4-plants have replaced C3-plants, changes in soil δ 13C allow the turnover of C3- and C4-derived C to be separated. Studies of decadal scale turnover of soil C following conversion to C4-plants generally lack δ 13C values for previous C4-residue inputs and assume that estimates of C4-derived soil C to be based on a fixed δ 13C value. Further assumptions are that changes in the initial (time-zero) soil δ 13C values are insignificant following conversion to C4-plants. We tested these assumptions by measuring: 1) the δ 13C of annual samples of silage maize biomass (C4-plant) and winter wheat grains (C3-plant) grown during 1988 to 2006, and 2) the δ 13C of soil kept under bare fallow during 1956 to 1983. The δ 13C of plants was related to climate variables, and the impact of maize δ 13C was based on estimates of maize-derived soil C using different approaches to establish the δ 13C in maize inputs. The δ 13C of both maize and wheat decreased with time, but the rate of change and annual variations were considerably larger for wheat than for maize. Maize as well as wheat δ 13C was best related to year (probably reflecting a decrease in atmospheric δ 13C) and the water balance during the active growth period. Using the smallest (−12.44‰) and the largest (−11.26‰) δ 13C measured during 1988 and 2006, estimates of maize-derived C in soil after 18 years ranged from 13.2% to 14.2% of the soil total C. Despite a loss of 31% of the soil C pool under bare fallow, the increase in soil δ 13C was significant only at P < 0.10. We conclude that annual variations in maize δ 13C values and changes in the δ 13C of the soil C fraction derived from the pre-conversion C3-vegetation have only little impact on estimates of maize-derived soil C that cover a few decades. For estimates covering several decades to centuries, the subtle but consistent changes in plant and soil δ 13C need to be accounted for. The variability in δ 13C in wheat grains suggest that the use of any fixed δ 13C value for C3-residues in estimates of C turnover in soils on which C4-plants have been replaced by C3-plants can be associated with considerable uncertainty.

A Survey of the Arthropod Pests and Plant Parasitic Nematodes Associated with Commercial Figs,Ficus carica(Moraceae), in South Africa

Edible figs originate from Arabia Felix, present-day Yemen (Eisen 1901) and have been cultivated in the Lower Jordan valley since 11 400-11 200 B.C. (Kislev et al. 2006). Genetic distinction of fig cultivars in Italian isles and natural populations occurring in the Mediterranean basin (Khadari et al. 2005), indicate introduction from the east Arabian Peninsula (Kislev et al. 2006). Eisen (1901) suggested that this introduction to Europe occurred around 800 B.C. by the Phoenicians and Greeks. Under Roman rule they spread to the rest of Europe, but only slowly towards the east, with the first documented edible figs appearing in China by A.D. 1550. At first the fig was considered a luxury for the rich, but it soon became a traded commodity, forming an integral part of the human diet. The ideal climate of Portugal for fig production secured the development of a superior industry there. With the explorations of the Spanish and Portuguese, figs were subsequently established in almost all countries they visited. Today figs are grown all over the world, but they especially favour a warm-temperate Mediterranean-type climate. Figs require sufficient moisture during the active growth period, but a warm dry climate when fruit are ripening (P. Botma, pers. comm.). The winter rainfall areas of South Africa, such as the Swartland and Klein Karoo in the Western Cape are therefore ideal for fig cultivation whereas fruit quality is negatively affected by higher fungal contamination in summer rainfall areas (M. Wohlfarter, pers. obs.).

Photosynthetic Characteristics of Indian Rhubarb (Rheum emodi Wall.): An Endangered Medicinal Plant

Rheum emodi Wall. ex Meissn (Polygonaceae) is a perennial herb distributed in altitudes ranging from 2800 to 3800m in the temperate and subtropical regions of Himalayas. The herb has been traditionally used to treat pathological ailments like fevers, ulcers, bacterial and fungal infections, jaundice and liver disorders. In addition to that, roots of R. emodi are reported to have biological activities such as laxative, diuretic, and in vivo inhibitory effect towards P388 leukemia in mice models. Due to commercial exploitation and its unscientific extraction from nature, Rheum emodi has been categorized as an endangered and top-priority species for conservation by Threatened Plants Species Committee of the Survival (TPSSC) of International Union for Conservation of Nature (IUCN). In this regard, strategies are being developed for the conservation and cultivation of this species at comparatively lower altitudes. In the present study, photosynthetic characteristics of R. emodi Wall were studied to assess its conservation and cultivation possibility at comparatively lower altitude. Plants of R. emodi, collected from its natural habitat (Tungnath, 3600m altitude), grown at lower altitude (550m) were examined for their growth and photosynthetic characteristics at different light (0, 100, 600, 900, 1200, 1500 and 2000µmol m-2 s-1), and temperature (10, 15, 20, 25, 30 oC) and CO2 (350 and 700µmol mol-2) concentrations. Optimum temperature for photosynthesis in this species was observed at 25 oC, which appears to be much higher than the average temperature of its natural habitat (3600m) during active growth period. A gradual increase in the rate of photosynthesis with light intensity up to 2000µmol m-2 s-1 at both (ambient and elevated) levels of CO2 indicates its adaptability potential to survive under high irradiance. Under optimum conditions, a considerable increase (˜ 30%) in its water use efficiency was observed when exposed to elevated CO2 concentration. Since lower altitude is normally characterized with higher temperature and CO2 conditions as compared to alpines, this species can perform much better at lower altitudes as it is able to acclimate under higher temperature and CO2 conditions. Within its limits, this study suggests that R. emodi can be cultivated at lower altitudes in sun-exposed sites for its conservation and cultivation to meet its ever increasing industrial demand.

L-Tryptophan Production by Auxotrophic and Analogue Resistant Mutants of Aureobacterium flavescens

A number of tyrosine plus phenylalanine double auxotrophic mutants were isolated by N-methyl-N-nitro-N-nitrosoguanidine (MNNG) treatment of a locally isolated strain of Aureobacterium flavescens of which 11A39 and 11A17 were selected on the basis of their tryptophan production in a mineral salt medium over other isolated mutant strains. The mutational block in the aromatic amino acid biosynthetic pathway of the selected double auxotrophs were determined. By controlling pH of the production medium to near neutrality, the active growth period could be extended up to 72 h and more tryptophan was accumulated compared to pH unregulated culture where the active growth ceased after 48 h. Further improvement of the tryptophan production has been achieved by stepwise isolation of a mutant strain resistant to the tryptophan analogues p-fluorotryptophan (FT) and 5-methyl tryptophan (MT) from the 11A39. Demand for L-tryptophan as food additive and therapeutic agent is increasing day by day throughout the World, particularly in the underdeveloped and developing countries like India. Still to date India depends on other countries for L-tryptophan. The aim of this work is to develop a potent high yielding, feed back insensitive mutant strain and optimization of its medium pH for maximum production of tryptophan.

Changes in the content of poplar isoplastocyanins a and b during vegetation cycle

Changes in the content of isoplastocyanins a (PCa) and b (PCb) in Populus nigra leaves were studied during complete vegetation cycle (from April 30 to October 28). Measurements were made every 7 days. The procedure included extraction and purification of total protein followed by analytical isoelectric focusing and densitometry of obtained isophoregrams. The positions of PCa and PCb were determined by comparison with the positions of the highly purified two isoforms. The PCb/PCa ratio was calculated from the areas of the corresponding densitometric peaks. The amount of PCb was one half of PCa amount in the earliest stage of the leaf formation as well as during the longer part of the summer, e.g., the second half of July, August, and September. During the most active period of the poplar growth, e.g., June and the first half of July, the ratio was about or above unity. This result could be important for understanding the specific functional significance of PCa and PCb.

Assessing the susceptibility of semiarid rangelands to wildfires using Terra MODIS and Landsat Thematic Mapper data

In order to monitor wildfires at broad spatial scales and with frequent periodicity, satellite remote sensing techniques have been used in many studies. Rangeland susceptibility to wildfires closely relates to accumulated fuel load. The normalised difference vegetation index (NDVI) and fraction of photosynthetically active radiation (fPAR) are key variables used by many ecological models to estimate biomass and vegetation productivity. Subsequently, both NDVI and fPAR data have become an indirect means of deriving fuel load information. For these reasons, NDVI and fPAR, derived from the Moderate Resolution Imaging Spectroradiometer on-board Terra and Landsat Thematic Mapper imagery, were used to represent prefire vegetation changes in fuel load preceding the Millennial and Crystal Fires of 2000 and 2006 in the rangelands of south-east Idaho respectively. NDVI and fPAR change maps were calculated between active growth and late-summer senescence periods and compared with precipitation, temperature, forage biomass and percentage ground cover data. The results indicate that NDVI and fPAR value changes 2 years before the fire were greater than those 1 year before fire as an abundance of grasses existed 2 years before each wildfire based on field forage biomass sampling. NDVI and fPAR have direct implication for the assessment of prefire vegetation change. Therefore, rangeland susceptibility to wildfire may be estimated using NDVI and fPAR change analysis. Furthermore, fPAR change data may be included as an input source for early fire warning models, and may increase the accuracy and efficiency of fire and fuel load management in semiarid rangelands.

The black holes of radio galaxies during the “Quasar Era”: masses, accretion rates, and evolutionary stage

We present an analysis of the AGN broad-line regions of 6 powerful radio galaxies at z>~2 (HzRGs) with rest-frame optical imaging spectroscopy obtained at the VLT. All galaxies have luminous (L(H-alpha)=few x 10^44 erg s^-1), spatially unresolved H-alpha line emission with FWHM>= 10,000 km s^-1 at the position of the nucleus, suggesting their AGN are powered by supermassive black holes with masses of few x 10^9 M_sun and accretion luminosities of a few percent of the Eddington luminosity. In two galaxies we also detect the BLRs in H-beta, suggesting relatively low extinction of A_V~1 mag, which agrees with constraints from X-ray observations. By relating black hole and bulge mass, we find a possible offset towards higher black-hole masses of at most ~0.6 dex relative to nearby galaxies at a given host mass, although each individual galaxy is within the scatter of the local relationship. If not entirely from systematic effects, this would then suggest that the masses of the host galaxies have increased by at most a factor ~4 since z~2 relative to the black-hole masses, perhaps through accretion of satellite galaxies or because of a time lag between star formation in the host galaxy and AGN fueling. We also compare the radiative and mechanical energy output (from jets) of our targets with predictions of recent models of "synthesis" or "grand unified" AGN feedback, which postulate that AGN with similar radiative and mechanical energy output rates to those found in our HzRGs may be nearing the end of their period of active growth. We discuss evidence that they may reach this stage at the same time as their host galaxies.

Variation in δ13C among species and sexes in the family Restionaceae along a fine‐scale hydrological gradient

AbstractConsistent, repeatable segregation of plant species along hydrological gradients is an established phenomenon that must in some way reflect a trade‐off between plants' abilities to tolerate the opposing constraints of drought and waterlogging. In C3 species tissue carbon isotope discrimination (δ13C) is known to vary sensitively in response to stomatal behaviour, reflecting stomatal limitation of photosynthesis during the period of active growth. However, this has not been studied at fine‐spatial scale in natural communities. We tested how δ13C varied between species and sexes of individuals in the family Restionaceae growing along a monitored hydrological gradient. Twenty Restionaceae species were investigated using species‐level phylogeny at two sites in the Cape Floristic Region, a biodiversity hotspot. A spatial overlap analysis showed the Restionaceae species segregated significantly (P &lt; 0.001) at both sites. Moreover, there were significant differences in δ13C values among the Restionaceae species (P &lt; 0.001) and between male and female individuals of each species (P &lt; 0.01). However, after accounting for phylogeny, species δ13C values did not show any significant correlation with the hydrological gradient. We suggest that some other variable (e.g. plant phenology) could be responsible for masking a simple response to water availability.

Variabilité interspécifique de trois algues rouges : Hypnea musciformis, Gracilaria multipartita et Gelidium sesquipedalen(Rhodophycées) de la côte atlantique marocaine

Interspecific variability of the red algae: Hypnea musciformis, Gracilaria multipartita and Gelidium sesquipedale (Rhodophyceae) of the Moroccan atlantic coastTotal analysis of the growth of three red algae species; Hypnea musciformis, Gracilaria multipartita and Gelidium sesquipedale were undertaken with an aim of determining interspecific variability within the same natural environment. The studied site is the beach of Mehdia located at the north of the Moroccan Atlantic coast. The results show specific differences in the growth rates of the three studied species. Gracilaria multipartita presents a significant development of the growth parameters like the size, the weight and the total ramification, especially for the aestival period compared to Gelidium sesquipedale and Hypnea musciformis. The active growth periods of Gracilaria multipartita are characterized by slightly important temperatures and light intensities and by high percentages of nitrates and phosphates. On the other hand, the growth of Hypnea musciformis shows fluctuations due to the variations of the environmental factors. The growth of Gelidium sesquipedale is slow and seems more under the influence of intrinsic factors than environmental factors.

Comparison of MODIS fPAR Products with Landsat-5 TM-Derived fPAR over Semiarid Rangelands of Idaho

While validation of the MODIS fPAR product is well behind that of the LAI product, it is recently receiving more attention. In this study, MODIS fPAR and Landsat-5 TM-derived fPAR (TM fPAR) were calculated and quantitatively compared using imagery from 2005 to 2008 for the semiarid rangelands of Idaho, USA. fPAR change maps were calculated between active growth and late-summer senescence periods. Accuracy of the MODIS fPAR and TM fPAR were determined indirectly by incorporating field-based measurements of above-ground forage biomass and percent ground cover from a variety of sites (n = 442).

MCP1 Directs Trafficking of Hematopoietic Stem Cell-Derived Fibroblast Precursors in Solid Tumor

Our previous studies have demonstrated that hematopoietic stem cells (HSCs) are a novel source of carcinoma-associated fibroblasts. However, the mechanisms regulating recruitment and homing of HSC-derived carcinoma-associated fibroblasts or their precursors to the tumor microenvironment are unknown. Herein, we demonstrate using a single cell transplantation model that circulating fibroblast precursors (CFPs) are of HSC origin. This population increased with tumor burden in vivo and functional in vitro studies showed that CFPs preferentially migrated and differentiated into fibroblasts in response to tumor, suggesting that HSC-derived CFPs serve as an intermediate between the bone marrow and tumor. Based on this chemotactic ability and our demonstration of a monocyte lineage origin for CFPs, we investigated the role of monocyte chemoattractant protein (MCP1) in mediating CFP recruitment/homing. Blocking tumor-produced MCP1 inhibited in vitro migration of CFPs in response to multiple tumor types, indicating broad biological significance for this CFP/chemokine interaction. In vivo, CCR2-expressing CFPs increased in circulation during the period of active tumor growth and stromal development. Inhibition of MCP1 during tumor development resulted in decreased tumor volume in tumor-bearing mice. Together these findings confirm an HSC origin for CFPs, demonstrate a role for MCP1 in regulating their contribution to the tumor microenvironment, and suggest a potential therapeutic target for limiting tumor growth.

Seasonal variability in gaseous mercury fluxes measured in a high-elevation meadow

Seasonal patterns of atmospheric mercury (Hg) fluxes measured over vegetated terrestrial systems can provide insight into the underlying process controlling emission and deposition of Hg to vegetated surfaces. Gaseous elemental Hg fluxes were measured for week-long periods in each season (spring, summer, fall, and winter) over an uncontaminated high-elevation wetland meadow in Shenandoah National Park, Virginia using micrometeorological methods. Mean net deposition was observed in the spring (−4.8 ng m −2 h −1), emission in the summer (2.5 ng m −2 h −1), near zero flux in the fall (0.3 ng m −2 h −1), and emission in the winter (4.1 ng m −2 h −1). Nighttime deposition (when stomata are closed) and the poor correlation between Hg fluxes and canopy conductance during periods of active vegetation growth suggest that stomatal processes are not the dominant mechanism for ecosystem-level GEM exchange at this site. The strong springtime deposition relative to summer implies that young vegetation is better at scavenging Hg, with the highest deposition occurring at night possibly via a cuticular pathway. These results suggest that spring is a period of GEM deposition while other seasons exhibit net emission, emphasizing the importance of capturing GEM flux seasonality when determining total Hg budgets.

Effect of Altitude on Photosynthetic and Biochemical Characteristics of Podophyllum hexandrum: An Alpine Endangered Medicinal Herb from Central Himalayas

Podophyllum hexandrum is a high value endangered medicinal plant from alpines of Central Himalaya. This study was conducted to explore its conservation and cultivation possibilities at comparatively lower altitudes. Seedlings of the same age, were selected from alpine medicinal crop nursery, Tungnath (3600m) and were planted at the nurseries located at 3600 and 550m altitudes. After well acclimatization at both the altitudes, plants were examined for gas exchange and biochemical characteristics during their active growth period. Our data shows that the foliage nitrogen content was higher and, P, K and C content were found lower in the plants grown at higher elevation as compared to lower altitude; however, these altitudinal variations were not found statistically significant. Chlorophyll a, Chl b, total Chl and Carotenoids were higher and Chl a/b ratio was lower at lower altitude as compared to plant grown at higher altitude. Level of protein and RUBP Carboxylase activity was higher and level of PEP Carboxylase activity was observed lower in the plants grown at high elevation as compared to their counterparts at lower altitude. Light optima for photosynthesis (PARopt) was observed around 2000µmolm–2s–1 at both the elevations in this species. A shift in optimum temperature for photosynthesis (Topt) was observed towards higher temperature in plants grown at lower altitude as compared to higher elevation, which indicates their potential to survive in the comparatively warmer environment. Topt was observed at 20°C in plants grown at higher altitude whereas, at lower altitude Topt was observed at 25°C for the plants of P. hexandrum. Conductance and transpiration was found slightly higher at high altitude as compared to plants grown at lower altitude. In view of these results, it can be concluded that these species can be cultivated at lower altitudes to meet their ever-increasing industrial demand.

Analysis of global changes in gene expression during activity-dormancy cycle in hybrid aspen apex

Perennial plants such as the long-lived trees of boreal forest cycle between periods of active growth and dormancy. Transition from active growth to dormancy is induced by short day (SD) signal. Once dormancy is established, prolonged exposure to low temperature is required for breaking dormancy before warm temperatures can induce growth. We have studied global changes in gene expression in the apex of model plant hybrid aspen during the distinct stages of activity-dormancy cycle. Our data shows that all stages of activity-dormancy cycle in the apex are associated with substantial modulation of the transcriptome. Detailed analysis of core cell cycle genes indicates that with the exception of plant specific B-type CDKs, all of the other CDKs are regulated post-transcriptionally during growth cessation. SD signal appears to target the expression of cyclin genes that are down regulated during growth arrest. Several of the cold hardiness related genes e. g. dehydrins are induced during transition to dormancy although temperature is not reduced and the up-regulation of the expression of these genes does not appear to rely on SD mediated induction of classical CBF transcription factors. Our results suggest that transcriptional control plays a key role in modulation of hormones such as ABA and GA that are known to play a central role in various processes during activity-dormancy cycle. Analysis of histone and DNA modification genes indicates that chromatin remodeling could be involved in coordinating global changes in gene expression during activity-dormancy cycle.

Dentaoalveolar changes in young adult patients with Class II/1 malocclusion treated with the Herbst appliance and an activator

Functional appliances can be used effectively in the treatment of skeletal Class II/1 malocclusions. The best treatment results are obtained during active period of facial growth when skeletal, as well as dentoalveolar, changes occur. In comparison with removable functional appliances, such as activator, that are effective only during adolescent period of growth, the Herbst fixed appliance is also successful at the end of the growth period. It also offers a shorter treatment time and a patient compliance is not necessary. The aim of this study was to analyze and compare dentoalveolar changes in the group of young adult patients with Class II/1 malocclusion treated with the Herbst appliance and an activator. The sample for this study consisted of 50 patients of both sexes, 14-21 years of age with Class II/1 malocclusion. For estimating the effect of functional appliances used, the following cephalometrics parameters were determined: inclination of the upper and lower incisors, interincisal angle, antero-posterior molars relationships, overjet and overbite. The results obtained were statistically tested. The cephalometric findings after the treatment indicated retroinclination of upper incisors (average value of 9 degrees) and proclination of lower incisors (average value of 7 degrees), mostly expressed in the patients treated by Herbst appliance (p < 0.001). Increased overjet and distocclusion were completely corrected in the group of patients treated with the Herbst appliance, while the correction of malocclusion in the activator group was only partially accomplished. No changes in the overbite were noticed at the end of the treatment in both groups. The results of this study revealed that the Herbst appliance is more effective in the treatment of Class II/1 malocclusion in young adults in comparison with the activator.