Growth Initiation Time Research Articles

Characterization of creep constraint effects on creep crack growth behavior by Q-type parameters

The effect of creep constraint on creep crack growth behavior and the stress field around the creep crack-tip was studied under different specimen geometry conditions. The correlation between the constraint parameters Q and Qm with the stress triaxiality under creep conditions was investigated. The results showed that the Q and Qm depend linearly on the stress triaxiality. Moreover, based on the existing constraint parameters Q∗ and Qm, a new load-independent constraint parameter Qm∗ was proposed to quantify the creep constraint effect. The Qm∗ was superior to Q∗ in quantifying higher out-of-plane creep constraints induced by specimen width and thickness. Furthermore, the Q∗ and Qm∗ were employed to correlate with the normalized creep crack growth rate and initiation time. Finally, the constraint-dependent creep crack growth prediction model based on constraint parameters Q∗ and Qm∗ had been established.

Extraction and Formulation of hydrolyzed-wool keratin solution for hair growth

Hair growth is controlled by hair Follicles which show patterns of cyclic activity with periods of active growth and hair production (anagen), apoptosis-driven involution (catagen) and relative resting (telogen). These transformations are regulated by different variations like endocrine, vascular, neural, age and nutritional. Keratin biomaterial has been used in regenerative medicine owing to its in-vivo and in-vitro biocompatibility. The present study aimed at extracting keratin from wool by sulfitolysis, filtration by dialysis tube and freeze drying. Qualitative analysis of the keratin extract powder ensured the presence of cysteine, Keratin powder formulated as solution dosage form and pharmaceutically evaluated, Keratin extract was topically applied on the synchronized depilated dorsal skin of telogenic 4 mice and promoted hair growth by changing Hair growth initiation and completion time and quality of hair result, in wool keratin extract solution-treated groups hair growth initiation and completion time reduced and the hair result was hard, long, thick and healthy. Besides, that the keratin extract solution was a safe agent for topical administration, our study demonstrated that keratin extract stimulating hair growth by inducing the growth phase. The topical application of keratin extract may represent a promising biomaterial for the management and applications of hair follicle disorder.

Carbon Dioxide Triggers Carbon Nanotube Nucleation: Isotope Labeling Study on the Growth Process of Individual Nanotubes

Growing long and high-density arrays of semiconducting single-walled carbon nanotubes is the key to building high-performance electronics. From the growth process perspective, the density and length of carbon nanotubes are determined by their nucleation probability from individual catalysts, subsequent growth rates, and growth lifetime. Here, we study the effects of additive oxygen-containing species on the growth process at the individual nanotube level during alcohol chemical vapor deposition. When tracing the growth process by isotope labeling techniques, the growth rates are slowed down upon the addition of CO2 due to carbon removal from catalysts. This simultaneously leads to a noticeable extension of the growth lifetime, which has the overall effect of lengthening the nanotube arrays. According to the relationship between the timing of CO2 supply and the growth initiation time of each nanotube, we surprisingly find that the oxidants also trigger the growth initiation, leading to the improvement of nanotube density. As all these effects of the additive oxidants can be explained by the tuning of the supersaturation level of carbon on catalysts, our results suggest the importance of choosing the appropriate balance of carbon sources and oxidants for the simultaneous control of density and length of carbon nanotube arrays.

Dynamics of seasonal growth in a long-lived southern hemisphere conifer are linked to early season temperature

Standard correlation approaches in dendroclimatology provide limited scope to elucidate differences between years in timing of growth initiation and cessation. In the Southern Hemisphere (SH), with relatively few long-term climate reconstructions, a clearer understanding of signals contained in ring width variation is of particular importance. In this study, we monitored growth in detail at two sites (low and high altitude) in Lagarostrobos franklinii (Huon pine) for five growing seasons. In concert, local environmental data were recorded, and cambial samples taken on several occasions. Season duration in Huon pine at low altitude lasted about six months, generally starting in September/October and ending in April. At higher altitude, season duration did not exceed about four months and generally started during November, ending in March. The shortest season and smallest rings were linked to cooler conditions compared to other years. On the other hand, an earlier growth onset in the 2011 growing season was evidently brought on by unusually warm conditions in late winter. Growth onset was linked to a running mean temperature of about 8.5 °C and 6.5 °C at the lower and higher altitude sites, respectively. While effects of limiting water on growth cessation were not universally clear, our results suggest that limiting water (during hotter, drier summers) may reduce growth rates, and precipitate earlier growth cessation.

Sensitivity of Spring Phenology Simulations to the Selection of Model Structure and Driving Meteorological Data

Accurate estimation of the timing of intensive spring leaf growth initiation at mid and high latitudes is crucial for improving the predictive capacity of biogeochemical and Earth system models. In this study, we focus on the modeling of climatological onset of spring leaf growth in Central Europe and use three spring phenology models driven by three meteorological datasets. The MODIS-adjusted NDVI3g dataset was used as a reference for the period between 1982 and 2010, enabling us to study the long-term mean leaf onset timing and its interannual variability (IAV). The performance of all phenology model–meteorology database combinations was evaluated with one another, and against the reference dataset. We found that none of the constructed model–database combinations could reproduce the observed start of season (SOS) climatology within the study region. The models typically overestimated IAV of the leaf onset, where spatial median SOS dates were best simulated by the models based on heat accumulation. When aggregated for the whole study area, the complex, bioclimatic index-based model driven by the CarpatClim database could capture the observed overall SOS trend. Our results indicate that the simulated timing of leaf onset primarily depends on the choice of model structure, with a secondary contribution from the choice of the driving meteorological dataset.

Tree growth patterns and diagnosis of water status based on trunk diameter fluctuations in fast-growing Populus tomentosa plantations

High resolution measurements of trunk diameter fluctuations (TDF) provide a means to study short-term and long-term stem radial variations and response to water stress of fruit trees. There is a lack of information, however, on the performance of TDF measurements on fast-growing poplar trees. To both clarify the intra-annual and inter-annual growth patterns and to diagnose water status of young poplar trees, we monitored TDF, leaf area index, soil matric potential, midday stem water potential (Ψstem) and main meteorological variables in a plantation with 3- and 4-year-old Populus tomentosa trees over two growing seasons (2016 and 2017). We had two irrigation treatments, well-watered (WW) and water-stressed (WS). For the first time for this species, we identified accurately and quantitatively the seasonal growth pattern and associated parameters (growth initiation and cessation time, growing season duration, maximum growth rate, etc.) of young P. tomentosa with four clear stages, based on the growth rate for both treatments. We identified that stage II (mid-April to mid-June), when trees showed the most active growth rate and less rainfall was recorded, is the most crucial stage for irrigation management, especially as trees grow larger and have a greater water demand. In the two experimental years, irrigation did not affect the timing of growth initiation and cessation. However, maximum growth rate was significantly higher and occurred earlier in the WW trees than in the WS trees. From the tested trunk diameter fluctuation indicators, trunk growth rate (TGR) showed a greater potential for assessing tree water stress than both maximum daily shrinkage (MDS) and daily growth (DG), being even more sensitive to the onset of water stress than midday Ψstem. We conclude that high resolution trunk dendrometers are useful to track growth and determine water stress, which make them a good candidate to schedule irrigation in fast-growing poplar plantations.

Seasonal Pattern of Stem Diameter Growth of Qinghai Spruce in the Qilian Mountains, Northwestern China

It is important to develop a better understanding of the climatic and soil factors controlling the stem diameter growth of Qinghai spruce (Picea crassifolia Kom.) forest. The results will provide basic information for the scientific prediction of trends in the future development of forests. To explain the seasonal pattern of stem diameter growth of Qinghai spruce and its response to environmental factors in the Qilian Mountains, northwest China, the stem diameter changes of 10 sample trees with different sizes and soil and meteorological conditions were observed from May to October of 2015 and 2016. Our results showed that the growth initiation of the stem diameter of Qinghai spruce was on approximately 25 May 2015 and 20 June 2016, and stem diameter growth commenced when the average air and soil temperatures were more than 10 °C and 3 °C, respectively. The cessation of growth occurred on approximately 21 August 2015 and 14 September 2016, and it was probably controlled by soil moisture. Stem diameter growth began earlier, ended later, and exhibited a larger growth rate as tree size increased. For the period May–October, the cumulative stem diameter growth of individual trees was 400 and 380 μm in 2015 and 2016, respectively. The cumulative stem diameter growth had a clear seasonal pattern, which could be divided into three growth stages, i.e., the beginning (from day of year (DOY) 120 to the timing of growth initiation with the daily growth rate of less than 2 μm·day−1), rapid growth (from the timing of growth initiation to the timing of growth cessation with the daily growth rate of more than 2 μm·day−1), and ending stages (from the timing of growth cessation to DOY 300 with the daily growth rate of less than 2 μm·day−1). The correlation of daily stem growth and environmental factors varied with growth stages; however, temperature, vapor pressure deficit (VPD), and soil moisture were the key factors controlling daily stem diameter growth. Overall, these results indicated that the seasonal variation in stem growth was regulated by soil and climatic triggers. Consequently, changes in climate seasonality may have considerable effects on the seasonal patterns of both stem growth and tree growth.

A Novel Effect of Acyclovir on Hair Growth in BALB/c Mice: A Promising Future for Finding a New Topical Drug for the Treatment of Hirsutism.

PurposeHirsutism (ie, terminal hair growth on the face and body in a male-like pattern in women) is a common dermatological disorder in women, with psychosocial implications. Consequently, there is demand for finding novel pharmacological treatments and agents that can safely reduce hair growth. This study aimed to investigate the potential effect of topical acyclovir on hair growth in mice.MethodsIn this study, twenty-four female BALB/c mice were randomly divided into three groups in order to evaluate the hair growth-reducing effects of acyclovir (control group, vehicle group, and acyclovir group). Topical acyclovir 5% was applied on the shaved denuded skin of mice. Topical application onto the backs of the animals was performed twice daily for 28 consecutive days. The time (in days) required for hair growth initiation as well as completion of hair growth in dorsal skin of animals were recorded. On day 28, horizontally cut biopsy samples were removed and the numbers of hair follicles were counted, and the diameter of hair follicles was measured under high-field microscopy by a specialist blinded to the treatments.ResultsHair growth initiation time was significantly increased with acyclovir, as compared to control and vehicle groups. The time required for complete hair growth in control and vehicle groups were 18±0.68 and 19±1.41 days, respectively; however, the hair growth completion in acyclovir-treated animals was not observed at the end of the experiment. Furthermore, the length of hairs in treatment group was significantly shorter than the control group at the end of the study (P < 0.001). In histologic examination, the count and the diameter of hair follicles in deep subcutis were significantly decreased.ConclusionThe results of this study, for the first time, showed that topical administration of acyclovir might have inhibitory effects on hair growth in experimental animals; however, further studies are required to understand its mechanism.

Evaluation of Hair Growth Promoting Activity of Maharanga bicolor and Hibiscus rosa sinensis

Alopecia is common and most frequently complaint dermatological disorder since the time immemorial. Various herbal and allopathic formulations are reported to have hair growth promoting activity. Minoxidil and Finasteride are only US FDA approved drugs for alopecia and hair loss. Maharanga bicolor and Hibiscus rosa sinensis are two ethnomedicinal herbs commonly used for hair growth promotion. Present study was conducted to determine hair growth promoting activity of petroleum ether extract of M. bicolor and H. rosa sinensis in Aloe vera gel. Minoxidil Sulphate and Different formulations of petroleum ether extract of M. bicolor and H. rosa sinensis was formulated in Aloe vera gel and applied to denuated area of rats for 30 days. Hair growth pattern, hair growth initiation, hair growth completion and length of hair was measured. M. bicolor (2%) formulation shows shortest hair growth initiation time on 6th day compared to 11th day in blank sample. Formulation containing 2% of each extract have shortest hair growth completion time on 19th day of sample application and showed potent hair growth pattern observed by blind investigation. The result suggests that petroleum ether extract of M. bicolor and H. rosa sinensis possess good hair growth promoting activity.&#x0D; Key words: Maharanga bicolor, Hibiscus rosa sinensis, Hair growth promotion, Activity

Phenology, flowering and fruit-set performance of six recent pear cultivars of Nordic origin

ABSTRACT Flowering performance and phenology of six new pear cultivars of Nordic origin were examined during a 12 year period. The seasonal timing of shoot growth and flower initiation were monitored in three years. The morphological floral stages of the flower bud formation process were examined for the cultivar ‘Celina’. Seven floral stages were identified and described. The date of full bloom varied between years as a function of the currently accumulated heat sum in early spring. Still, the earliness ranking of the cultivars was consistent across years for both flower initiation and blooming. The cultivars ‘Anna’ and ‘Ingeborg’ consistently initiated floral primordia 2–3 weeks earlier than ‘Celina’, ‘Clara Frijs’, ‘Fritjof’ and ‘Kristina’, and this was accompanied with 4–5 days earlier blooming in the following spring. The early flower initiation cultivars ‘Anna’ and ‘Ingeborg’ also had richer flowering than the late-blooming cultivars. ‘Fritjof’ was identified as a suitable pollinator for ‘Celina’ in the Nordic climate. Comparison of the flowering phenology of pear and apple cultivars showed that while the pears, on average, flowered a week ahead of the apples, they initiated flower primordia almost two weeks later, thus rendering the intervening period approximately three weeks longer in pear than in apple.

Evaluation of hair growth promoting activity of petroleum ether extract of Abrus precatorius Linn. on Wistar Albino rats

In present investigation was carried out to screening of hair growth promoting potentiality of petroleum ether extract of Abrus precatorius leaf. Preliminary chemical tests and TLC analysis revealed the presence flavonoids and saponins. Hair growth promoting activity of petroleum ether of Abrus precatorius was screened by considering different parameters which included time taken for covering bald patch, length of hair produced, percentage of hair follicles in anagen and telogen phases, time of hair growth initiation and completion and level of minerals in blood. The petroleum ether extract of Abrus precatorius showed a very good hair growth promoting activity at a dose of 300 mg/kg which was comparable to that of 2% minoxidil. After 30 days of treatment with test and standard drugs it was observed that, time taken for covering the bald patch, hair growth initiation and completion time and quantitative hair growth were found to be comparable to that of the standard drug. An increase in percentage of hair follicles turning from telogen phase to anagen phase was noted. The control treated group of animals showed poor hair growth for all the parameters.&#x0D; Keywords: Abrus precatorius Linn, Anagen, Catagen, Telogen, Minoxidil

Comparing hydrological frameworks for simulating crop biomass, water and nitrogen dynamics in a tile drained soybean-corn system: Cascade vs computational approach

Biophysical agricultural models are needed for assessing science-based mitigation options to improve the efficiency and sustainability of agricultural cropping systems. It is crucial that they can accurately simulate soil hydrology and nutrient flows which strongly influence crop growth, biogeochemical processes and water quality. The purpose of this study was to compare the performance of the DeNitrification DeComposition model (DNDC), which utilizes simplified hydrologic processes, to a more comprehensive water flow model, the Root Zone Water Quality Model (RZWQM2), to determine which processes are sufficient for simulating water and nitrogen dynamics and recommend improvements. Both models were calibrated and validated for simulating soil hydrology, nitrogen loss to tile drains and crop biomass using detailed observations from a corn (Zea mays L.) -soybean (Glycine max (L.) Merr.) rotation in Iowa, with and without cover crops. DNDC performed adequately across a wide range of metrics in comparison to a more hydrologically complex model. Soybean and corn yield, and corn biomass over the growing season were well simulated by both models (NRMSE < 25%). Soybean yields were also very well simulated by both models (NRMSE < 20%); however, soybean biomass was over-predicted by RZWQM2 in the validation treatments. The magnitude of winter rye biomass and N uptake was well simulated but the timing of growth initiation in the spring was inaccurate at times. The annual and monthly estimation of tile flow and nitrogen loss to tiles drains were well simulated by both models; however, RZWQM2 performed better for simulating soil water content, and the dynamics of daily water flow to tile drains (DNDC: NSE −0.32 to 0.24; RZWQM2: NSE 0.35–0.69). DNDC overestimated soil water content near the soil surface and underestimated it in the deeper profile. We recommend that developments be carried out for DNDC to include improved root density and penetration functions, a heterogeneous and deeper soil profile, a fluctuating water table and mechanistic tile drainage. However, the inclusion of computationally intensive processes needs to be assessed in context to improved accuracy weighed against the model’s broad applicability.

Creep-fatigue crack growth behavior of G115 steel under different hold time conditions

The creep-fatigue crack growth behavior and fracture mechanisms of G115 steel at 650 °C were studied using compact tension specimens in a constant load control mode. The crack growth length and load-line displacement analyses reveal that G115 steel is a creep-ductile material and the crack growth life and initiation time increase with increasing dwell time. Meanwhile, the parameter ΔK was used to characterize the crack growth behavior and the effect of dwell time on da/dN depends on ΔK. These data were also compared with those getting from P91 steel under 625 °C and P92 steel at 630 °C. When the crack growth rate, da/dtavg, is represented by Ctavg, all the data seem to collapse within a single narrow scatter band. Further, the approximate Nikbin-Smith-Webster (NSW) crack growth model was utilized to predict the creep-fatigue crack propagation behavior of G115 steel. And the microstructures of the cross-sections along the crack growth direction were studied through scanning electron microscopy to reveal the crack growth mechanisms of G115 steel.

Adaptive phenotypic plasticity of Avicennia officinalis L. across the salinity gradient in the Sundarbans of Bangladesh

Adaptive phenotypic plasticity of Avicennia officinalis across the salinity gradient in the Sundarbans of Bangladesh was studied. Propagule morphology was compared through use of a completely randomized design. Propagule growth initiation traits across the salinity gradient (from 0 to 35 ppt at 5 ppt interval) were studied by means of a randomized block design. Propagules showed variability in length, width, and weight across the salinity gradient in the Sundarbans. Propagule growth initiation time, mean growth initiation time, growth initiation index, and propagule growth initiation percentage of A. officinalis varied significantly with the increasing salinity and among low, medium, and high saline zones. However, propagules originating from the high and medium saline zones started their growth initiation more rapidly and vigorously at high salinities compared to those from the low saline zone. Therefore, A. officinalis exhibited adaptive phenotypic plasticity in terms of variability in propagule size and weight as well as physiologically adaptive plastic responses during propagule growth initiation across the salinity gradient in the Sundarbans. A. officinalis in high and medium saline zones of Sundarbans is the most salt-adapted phenotype, and a good knowledge about this will be widely useful for successful regeneration, coastal afforestation, and conservation of this species in increasing saline environments in the future.

Fine root phenology differs among subtropical evergreen broadleaved forests with increasing tree diversities

Fine root phenology represents ecological strategy of plants in utilizing soil resources and plays an essential role in carbon and nutrient cycling. Here, we aimed to understand how fine root phenology could change in subtropical broadleaved forests with increasing tree species diversity. Three 37–40 years old Castanopsis carlesii forests with low to high tree species diversity were selected in southern China: a plantation forest (PF), a secondary forest through the assisted regeneration (AR), and a secondary forest through natural regeneration (NR), with a nearby natural C. carlesii forest as a control. Fine root length production in these forests was measured monthly during January 2013 to December 2014 using minirhizotron, and fine root production phenology and its correlations with environmental factors were compared among these forests. No significant difference in fine root length production was found among these forests; however, there was distinct fine root phenology. The timing of fine root growth initiation and growth peak was quite stable across the two years in PF, while they were more flexible in AR and NR which were higher in tree species diversity. However, the timing of fine root growth cessation was quite fixed for all the forests. The duration and inter-annual stability of fine root growth both decreased with increasing tree species diversity. Moreover, the correlations of monthly fine root production with monthly air and soil temperature both increased with increasing tree species diversity. It is concluded that the timing of fine root growth in higher tree species diversity stand seems more flexible and more synchronous with seasonal and annual fluctuations of soil resources caused by weather variability, which helps our understanding of the relationships between tree diversity and ecosystem carbon and nutrient cycling.

Selective breeding of lodgepole pine increases growth and maintains climatic adaptation

Climate change is disrupting historical patterns of adaptation in temperate and boreal tree species, causing local populations to become maladapted. Tree improvement programs typically utilise local base populations and manage adaptation using geographically defined breeding zones. As climates shift, breeding zones are no longer optimal seed deployment zones because base populations are becoming dissociated from their historical climatic optima. In response, climate-based seed transfer (CBST) policies incorporating assisted gene flow (AGF) are being adopted to pre-emptively match reforestation seedlots with future climates, but their implementation requires accurate knowledge of genetic variation in climatically adaptive traits. Here we use lodgepole pine as a case study to evaluate the effects of selective conifer breeding on adaptive traits and their climatic associations to inform CBST and AGF prescriptions.Our approach compared 105 natural stand and 20 selectively bred lodgepole pine seedlots from Alberta and British Columbia grown in a common garden of ∼2200 seedlings. The effects of selection on phenotypic variation and climatic associations among breeding zones were assessed for growth, phenology and cold hardiness. We found substantial differences between natural and selected seedlings in growth traits, but timing of growth initiation was unaffected, growth cessation was delayed slightly (average 4days, range 0.7days to 10days), and cold injury was slightly greater (average 2.5%, range −7% to 11%) in selected seedlings. Phenotypic differentiation among breeding zones and climatic clines were stronger for all traits in selected seedlings. Height gains resulted from both increased growth rate and delayed growth cessation, but negative indirect effects of selection on cold hardiness were weak.Selection, breeding and progeny testing combined have produced taller lodgepole pine seedlings that are not adaptively compromised relative to their natural seedling counterparts. Selective breeding produces genotypes that achieve increased height growth and maintain climate adaptation, rather than reconstituting genotypes similar to populations adapted to warmer climates. While CBST is needed to optimise seedlot deployment in new climates, an absence of systematic indirect selection effects on adaptive traits suggests natural and selected seedlots do not require separate AGF prescriptions.

Using a Novel Absolute Ontogenetic Age Determination Technique to Calculate the Timing of Tooth Eruption in the Saber-Toothed Cat, Smilodon fatalis.

Despite the superb fossil record of the saber-toothed cat, Smilodon fatalis, ontogenetic age determination for this and other ancient species remains a challenge. The present study utilizes a new technique, a combination of data from stable oxygen isotope analyses and micro-computed tomography, to establish the eruption rate for the permanent upper canines in Smilodon fatalis. The results imply an eruption rate of 6.0 millimeters per month, which is similar to a previously published average enamel growth rate of the S. fatalis upper canines (5.8 millimeters per month). Utilizing the upper canine growth rate, the upper canine eruption rate, and a previously published tooth replacement sequence, this study calculates absolute ontogenetic age ranges of tooth development and eruption in S. fatalis. The timing of tooth eruption is compared between S. fatalis and several extant conical-toothed felids, such as the African lion (Panthera leo). Results suggest that the permanent dentition of S. fatalis, except for the upper canines, was fully erupted by 14 to 22 months, and that the upper canines finished erupting at about 34 to 41 months. Based on these developmental age calculations, S. fatalis individuals less than 4 to 7 months of age were not typically preserved at Rancho La Brea. On the whole, S. fatalis appears to have had delayed dental development compared to dental development in similar-sized extant felids. This technique for absolute ontogenetic age determination can be replicated in other ancient species, including non-saber-toothed taxa, as long as the timing of growth initiation and growth rate can be determined for a specific feature, such as a tooth, and that growth period overlaps with the development of the other features under investigation.

Probabilistic Models to Predict the Growth Initiation Time for Pseudomonas spp. in Processed Meats Formulated with NaCl and NaNO2.

This study developed probabilistic models to determine the initiation time of growth of Pseudomonas spp. in combinations with NaNO2 and NaCl concentrations during storage at different temperatures. The combination of 8 NaCl concentrations (0, 0.25, 0.5, 0.75, 1, 1.25, 1.5, and 1.75%) and 9 NaNO2 concentrations (0, 15, 30, 45, 60, 75, 90, 105, and 120 ppm) were prepared in a nutrient broth. The medium was placed in the wells of 96-well microtiter plates, followed by inoculation of a five-strain mixture of Pseudomonas in each well. All microtiter plates were incubated at 4, 7, 10, 12, and 15℃ for 528, 504, 504, 360 and 144 h, respectively. Growth (growth initiation; GI) or no growth was then determined by turbidity every 24 h. These growth response data were analyzed by a logistic regression to produce growth/no growth interface of Pseudomonas spp. and to calculate GI time. NaCl and NaNO2 were significantly effective (p<0.05) on inhibiting Pseudomonas spp. growth when stored at 4-12℃. The developed model showed that at lower NaCl concentration, higher NaNO2 level was required to inhibit Pseudomonas growth at 4-12℃. However, at 15℃, there was no significant effect of NaCl and NaNO2. The model overestimated GI times by 58.2±17.5 to 79.4±11%. These results indicate that the probabilistic models developed in this study should be useful in calculating the GI times of Pseudomonas spp. in combination with NaCl and NaNO2 concentrations, considering the over-prediction percentage.

Live imaging of developmental processes in a living meristem of Davidia involucrata (Nyssaceae).

Morphogenesis in plants is usually reconstructed by scanning electron microscopy and histology of meristematic structures. These techniques are destructive and require many samples to obtain a consecutive series of states. Unfortunately, using this methodology the absolute timing of growth and complete relative initiation of organs remain obscure. To overcome this limitation, an in vivo observational method based on Epi-Illumination Light Microscopy (ELM) was developed and tested with a male inflorescence meristem (floral unit) of the handkerchief tree Davidia involucrata Baill. (Nyssaceae). We asked whether the most basal flowers of this floral unit arise in a basipetal sequence or, alternatively, are delayed in their development. The growing meristem was observed for 30 days, the longest live observation of a meristem achieved to date. The sequence of primordium initiation indicates a later initiation of the most basal flowers and not earlier or simultaneously as SEM images could suggest. D. involucrata exemplarily shows that live-ELM gives new insights into developmental processes of plants. In addition to morphogenetic questions such as the transition from vegetative to reproductive meristems or the absolute timing of ontogenetic processes, this method may also help to quantify cellular growth processes in the context of molecular physiology and developmental genetics studies.

Intra-annual stem radial increment response of Qilian juniper to temperature and precipitation along an altitudinal gradient in northwestern China

Spring temperature is a major limiting factor at the beginning of the growing season, the timing of growth initiation can increase by about 7 days/°C. During the growing season, impacts of climate variables on radial growth are similar along an altitudinal gradient. Altitude is considered as an important factor affecting tree growth in mountain forest ecosystems. In this paper, the results of a 2-year field study along an altitudinal gradient in the cold and arid central Qilian Mountains, northwestern China, are reported. Twelve Qilian juniper trees (Sabina przewalskii Kom.) were monitored with high-resolution dendrometers at three altitudes ranging from 2,865 to 3,550 m. At each altitude, a local weather station was installed close to the studied trees. We identified correlations between intra-annual growth patterns derived from the Gompertz equation with local air temperature and precipitation data. The timing of growth initiation became earlier and the growing season duration increased with decreasing altitude. The onset of radial growth occurred between early May and early June, and the growing season terminated between mid-July and late August, resulting in a growing season duration that decreased from 107 to 41 days as elevation increased. June is the most important growth period at each altitude. Spring temperature, which is strongly associated with elevation, is a critical factor determining the initiation of radial growth. The timing of growth initiation was delayed by 3–4 days per 100 m elevation. When associated with the modeled altitudinal spring temperature lapse rate of −0.48 °C/100 m, the onset of the growing season increased by about 7 days/°C. However, during the growing season, daily stem radial increments showed a positive correlation with precipitation and a negative correlation with daily maximum air temperature at all altitudes. Our study provides new data revealing the basic growth processes of Qilian juniper trees and provides significant information to quantify the responses of tree growth to future global warming.