scholarly journals Assessment of Cambial Activity and Xylogenesis by Microsampling Tree Species: An Example at the Alpine Timberline

IAWA Journal ◽  
2006 ◽  
Vol 27 (4) ◽  
pp. 383-394 ◽  
Author(s):  
Sergio Rossi ◽  
Annie Deslauriers ◽  
Tommaso Anfodillo
Keyword(s):  
Cell Differentiation ◽  
Tree Ring ◽  
Cross Sections ◽  
Cambial Activity ◽  
Wall Thickening ◽  
Cell Production ◽  
Xylem Cell ◽  
Alpine Timberline ◽  
Xylem Formation ◽  
Secondary Cell Wall Thickening

Mechanisms of cell production and maturation and dynamics of xylem formation have been widely studied in trees in order to better characterize stem radial growth. Histological analyses have been used in this study to describe cambial activity and xylem cell differentiation in Larix decidua, Pinus cembra and Picea abies at the Alpine timberline. Wood microcores were collected weekly from April to October 2003 and cross sections prepared to distinguish xylem cells of the growing tree ring and to determine the number of cells in the cambial zone, radial cell enlargement, secondary wall thickening and lignification and the number of mature tracheids. The anatomical changes characterizing the phases of xylem cell production and differentiation during the year are described and discussed. All species showed the same trend of xylem formation. Three delayed bell-shaped curves and an S-shaped curve were observed for cambium, enlarging and wall thickening cells and mature cells, respectively. Cells divided in the cambial zones from April-May to August, depending on the species. From 100 to 130 days were required to complete cell differentiation. Tree-ring formation ended during September. The average periods spent on radial enlargement, and secondary cell wall thickening and lignification were estimated at 7–10 and 20–25 days, respectively.

Cutting time slices of tree rings —How intra-annual dynamics of wood formation help to decipher space for time conversion in tree-ring sciences

2020 ◽  
Author(s):  
Gonzalo Peres-De-Lis ◽  
Cyrille Rathgeber ◽  
Stéphane Ponton
Keyword(s):  
Cell Differentiation ◽  
Tree Ring ◽  
Isotope Composition ◽  
Growing Season ◽  
Wood Formation ◽  
Tree Level ◽  
Wall Thickening ◽  
North East ◽  
Common Signal ◽  
Kinetics Of

<p>Despite a long-standing interest in retrieving intra-annual environmental information from tree-ring features, none of the approaches developed so far for accurately dating intra-ring sector has been validated on observations. Here, we investigated space-for-time association across regular intra-ring sectors for which we estimated the timing of formation. For this purpose, a unique dataset containing quantitative wood anatomy measurements and kinetics of tracheid differentiation was compiled for 45 trees grown in North-East France (three years of wood formation monitoring, for five trees, from three different conifer species). Tracheid dimensions were measured directly on the best anatomical sections at the end of the growing season, while the kinetics of xylem cell differentiation were provided at tree-level by an empirical model of wood formation dynamics. Our results confirmed that the time taken to form sectors of the same width increased from earlywood (composed of wide thin-walled tracheids) to latewood (composed of narrow thick-walled tracheids). This mainly reflected the increase of the duration of cell wall deposition through the growing season, and, to a lesser extent, the augmentation of the number of tracheids per sectors. However, our results also show that regular intra-ring sectors, which were well separated in space, overlapped in time. The overlapping culminated during the summer period, reaching 40 % for 10 sectors. It could be reduced to approx. 30 % by increasing the number of sectors (from 10 to 25, for example), but it cannot be removed. Therefore, successive intra-ring sectors could not be attributed to a succession of separated time intervals by simply using their relative position along the ring. However, the formation of sectors of equivalent ranks were noticeably synchronous between the different trees and years, reaching 80 % of synchronicity for the process of wall thickening. This suggest that data from regular intra-ring sectors could be reliably used to build mean chronologies expressing the common signal of tree populations. Our results show the limits that the xylogenesis process itself imposes on the dating of intra-ring features. They also argue for an in-depth understanding of the association between cell differentiation processes (enlargement, wall thickening and lignification) and wood characteristics (density, anatomy, stable isotope composition).</p>

scholarly journals Origin of Intra-annual Density Fluctuations in a Semi-arid Area of Northwestern China

2021 ◽  
Vol 12 ◽  
Author(s):  
Jiani Gao ◽  
Sergio Rossi ◽  
Bao Yang
Keyword(s):  
Cambial Activity ◽  
Wood Formation ◽  
Density Fluctuations ◽  
Arid Ecosystems ◽  
Wall Thickening ◽  
Drought Event ◽  
Cell Enlargement ◽  
Xylem Formation ◽  
June July ◽  
Semi Arid

Intra-annual density fluctuation (IADF) is a structural modification of the tree ring in response to fluctuations in the weather. The expected changes in monsoon flow would lead to heterogeneous moisture conditions during the growing season and increase the occurrence of IADF in trees of the arid ecosystems of continental Asia. To reveal the timings and physiological mechanisms behind IADF formation, we monitored cambial activity and wood formation in Chinese pine (Pinus tabuliformis) during 2017–2019 at three sites in semi-arid China. We compared the dynamics of xylem formation under a drought event, testing the hypothesis that drought affects the process of cell enlargement and thus induces the production of IADF. Wood microcores collected weekly from April to October were used for anatomical analyses to estimate the timings of cambial activity, and the phases of enlargement, wall thickening, and lignification of the xylem. The first cells started enlargement from late April to early May. The last latewood cells completed differentiation in mid-September. Trees produced IADF in 2018. During that year, a drought in June limited cell production in the cambium, only 36% of the xylem cells being formed in IADF trees, compared to 68% in normal tree rings. IADF cells enlarged under drought in early July and started wall thickening during the rainfall events of late July. The drought restricted cell enlargement and affected wall thickening, resulting in narrow cells with wide walls. Cambium and cell enlargement recovered from the abundant rainfall, producing a new layer with large earlywood tracheids. IADF is a specific adaptation of trees to cope with water deficit events occurring during xylem formation. Our findings confirmed the hypothesis that the June-July drought induces latewood-like IADFs by limiting the process of cell enlargement in the xylem. Our finding suggests a higher occurrence of IADF in trees of arid and semi-arid climates of continental Asia if the changes to monsoon flows result in more frequent drought events during the earlywood formation in June.

scholarly journals Climatic and physiological regulation of the bimodal xylem formation pattern in Pinus pinaster saplings

2019 ◽  
Vol 39 (12) ◽  
pp. 2008-2018 ◽  
Author(s):  
Núria Garcia-Forner ◽  
Joana Vieira ◽  
Cristina Nabais ◽  
Ana Carvalho ◽  
Jordi Martínez-Vilalta ◽  
...  
Keyword(s):  
Water Availability ◽  
Growth Pattern ◽  
Pinus Pinaster ◽  
Cambial Activity ◽  
Fine Tuning ◽  
Wall Thickening ◽  
Physiological Variables ◽  
Second Growth ◽  
Xylem Formation ◽  
Number Of Cells

Abstract Seasonality in tree cambial activity and xylem formation encompass large variation in environmental conditions. Abiotic stressors such as warming or drought also modulate plant behavior at species and individual level. Despite xylem formation susceptibility to carbon (C) and water availability, it is still unknown which are the key physiological variables that regulate xylogenesis, and to what extent plant performance contributes to further explain the number of cells in the different phases of xylem development. Xylogenesis and physiological behavior was monitored in saplings of Pinus pinaster Aiton, a bimodal growth pattern species, distributed in different irrigation regimes. Xylogenesis and plant physiological behavior were compared between treatments and the relationship between climate, physiology and the number of cells in the cambium, enlargement and cell-wall thickening phases was evaluated. Xylogenesis regulation shifted from physiological to climatic control as cell differentiation advanced to mature tracheids. The number of cells in the cambium increased with assimilation rates and decreased with the water potential gradient through the plant. Enlargement was the most susceptible phase to plant relative water content, whereas no physiological variable contributed to explain the number of cells in the wall thickening phase, which declined as temperatures increased. All treatments showed a bimodal growth pattern with a second growth period starting when primary growth was completed and after plants had experienced the highest summer hydraulic losses. Our study demonstrates the importance of including physiological responses and not only climate to fully understand xylogenesis, with special attention to the enlargement phase. This is critical when studying species with a bimodal growth pattern because the second growth peak responds to internal shifts of C allocation and may strongly depend on plant hydraulic responses and not on a fine tuning of cambial activity with soil water availability.

Global ecological trends in wood cell production of coniferous trees

2020 ◽  
Author(s):  
Cyrille Rathgeber
Keyword(s):  
Physical Model ◽  
Tree Ring ◽  
Extended Period ◽  
Forest Productivity ◽  
Wood Formation ◽  
Site Conditions ◽  
Cell Production ◽  
Final Number ◽  
Xylem Cell ◽  
Number Of Cells

<p>As a consequence of recent climatic changes, many studies have reported an increase in tree growth, forest ecosystem net primary productivity, and terrestrial biosphere carbon up-take, making forests one of the largest carbon sink on Earth. Direct and remote observations, as well as eco-physiological models, have suggested that it is mainly the rise in temperature and the resulting extended period of growth that is responsible for forest enhanced productivity. However, up to now, there is no comprehensive observation-based study deciphering the respective roles of the length of the growing season versus its intensity, to confirm this interpretation. Based on a large wood-formation-monitoring dataset, encompassing numerous sites from Mediterranean to Boreal conifer forests, we tested the hypothesis that the length of the growing period is more important than the rate of growth to explain tree-ring width. Moreover, we explored the influence of the environmental conditions on the variation in both timings and rates of xylem cell production.</p><p>We collected data from more than 50 sites spread at various altitudes and latitudes, on three continents (America, Europe, Asia), in the extra tropical parts of the Northern Hemisphere (Boreal, Temperate and Mediterranean bioclimatic zones). Wood formation was monitored at a weekly time-step using histological sections of forming xylem collected from the stems of more than 15 conifer species. The critical dates of xylem phenology were assessed at tree level using logistic regressions, while the rates of cell production were computed using Gompertz models. A basic physical model was developed relating the total number of xylem cells with the rate and duration of its production. A sensitivity analyses was performed to reveal the global ecological patterns of tree-ring formation, while mixed effect models were used to quantify the influences of the environmental factors.</p><p>The basic physical model of xylem cell production was applied successfully to the whole dataset (including Mediterranean sites) explaining more than 80 % of the observed variability. The sensitivity analysis showed that the rate of xylem cell production contributed a bit more than the duration to the variation in the final number of cells. Trees presented contrasted strategies according to the bioclimatic zone they belong to: while Boreal trees grew at a high speed during a short time; Mediterranean trees proceeded slowly, but for an extended period of time. Nevertheless, even for Mediterranean trees, the rate of growth remained the first driver of the final number of cells. Moreover, we showed that xylem phenology was consistently explained by the change in thermal conditions occurring with altitude or latitude, while growth rate was more related to species effect and site conditions.</p><p>Our results confirm that recent global warming may have resulted in extended period of growth explaining the recent increase in forest productivity. However, we also showed that the rate of xylem cell production is indeed the first driver of tree radial growth, therefore species behavior and site conditions should be considered in vegetation models to assess the impact of climate changes on forest productivity.</p>

Interpolation of microtubules into cortical arrays during cell elongation and differentiation in roots of Azolla pinnata

1979 ◽  
Vol 37 (1) ◽  
pp. 411-442
Author(s):  
A.R. Hardham ◽  
B.E. Gunning
Keyword(s):  
Cell Differentiation ◽  
Cell Walls ◽  
Unit Length ◽  
Cell Types ◽  
High Rate ◽  
Wall Thickening ◽  
Cortical Microtubules ◽  
Azolla Pinnata ◽  
Outer Cortex ◽  
Cortical Cells

Longitudinal sections of roots of Azolla pinnata R. Br. were prepared for electron microscopy so that cortical microtubules could be counted along the longitudinal walls in cell files in the endodermis, pericycle, and inner and outer cortex, and in sieve and xylem elements. With the exception of the xylem, where there are no transverse cell divisions, each file of cells commences with its initial cell and then possesses a zone of concomitant cell expansion and transverse cell division, followed, after completion of the divisions, by a zone of terminal cell differentiation. The cells augment their population of cortical microtubules as they elongate and divide, showing a net increase of up to 0.6 micron of polymerized microtubule length per min. Two main sub-processes were found: (i) When a longitudinal wall is first formed it is supplied with a higher number of microtubules per unit length of wall than it will have later, when it is being expanded. This initial quota becomes diluted as the second sub-process commences. (ii) The cells interpolate new microtubules at a rate which is characteristic of the cell, and, in the endodermis, of the face of the cell, while the cell elongates. Most cell types thus maintain a set density of cortical microtubules while they elongate and divide. Comparisons of endodermal cells in untreated controls, and roots that had been treated with colchicine, low temperature, or high pressure indicate that the initial quota of microtubules, and the later interpolations, and differentially sensitive to microtuble perturbations. Three types of behaviour, all related to changes in the cell walls, were noted as cortex, xylem and sieve element cells entered their respective phases of cell differentiation. The cortical cells expanded in all dimensions, and the interpolation of microtubules diminished or ceased. The sieve elements continued to elongate, and interpolated at a high rate, reaching unusually high densities of microtubules when the cell walls were being thickened. During this period a net increase of 2.0 micron of polymerized microtubule length per min was calculated. Thereafter interpolation ceased and the density of microtubules declined. The sample applied to developing xylem except that, because wall-thickening is localized rather than widespread, the rise and subsequent fall in the density of microtubules was less marked. The data are discussed in relation to the participation of microtubules in wall deposition and to the hypothesis that cortical microtubules arise in discrete zones along the edges of cells.

scholarly journals Tree-Ring Growth of Larch (Larix decidua Mill.) in the Polish Sudetes—The Influence of Altitude and Site-Related Factors on the Climate–Growth Relationship

Forests ◽  
2018 ◽  
Vol 9 (11) ◽  
pp. 663 ◽  
Author(s):  
Małgorzata Danek ◽  
Monika Chuchro ◽  
Adam Walanus
Keyword(s):  
Tree Ring ◽  
Climatic Factors ◽  
Negative Relationship ◽  
Thermal Conditions ◽  
Cambial Activity ◽  
Negative Influence ◽  
Larix Decidua ◽  
Related Factors ◽  
Local Conditions ◽  
Negative Effect

In this paper, the first study of a regional character on the influence of climatic factors on the tree-ring growth of European larch (Larix decidua Mill.) growing in the Polish Sudetes is presented. The obtained results indicate the relatively high diversity of the climatic signal observed in the tree rings of larches growing in the Sudetes. The most significant differentiating factor is altitude. The results suggest that the possible influence of local conditions (e.g., summit proximity, soil and bedrock characteristics, and exposure to strong winds) could also be of importance. A positive relationship between tree-ring growth and May temperatures was noted throughout the area; this indicates the principal importance of thermal conditions during the initial stage of cambial activity and tree-ring formation in larches from the Sudetes. The negative effect of the temperatures in the previous summer upon the tree-ring growth of larch in the subsequent year was also observed. The studies also indicate the negative influence of the water stress in summer (particularly in July of the previous year) upon the growth of trees. The negative relationship between tree-ring growth and the previous November temperature could be explained by the need for a late-autumn cooling, which affects the development of assimilation apparatus in spring of the subsequent year, which indirectly affects the tree-ring growth in the same year.

scholarly journals Cambial Activity of Moringa peregrina (Forssk.) Fiori in Arid Environments

2021 ◽  
Vol 12 ◽  
Author(s):  
Holger Gärtner ◽  
Emad Farahat
Keyword(s):  
Photosynthetic Activity ◽  
Storage Capacity ◽  
Cambial Activity ◽  
Ring Formation ◽  
Arid Environments ◽  
Dry Tropics ◽  
Xylem Formation ◽  
Moringa Peregrina ◽  
Desert Regions ◽  
Environmental Adaptability

Moringa peregrina (Forssk.) Fiori, one of 13 species of the Moringaceae family widely distributed throughout the dry tropics, has the potential to become one of the most economically important medicinal plants in Egypt. However, despite its tolerance for drought and heat, it is also threatened by increasing temperatures and decreasing precipitation. Although the phenophase of this species is well documented, almost nothing is known about its period of cambial activity in desert regions. Ring formation and the general environmental adaptability of trees are affected by the timing of cambial activation. In our study site, we observe a distinct coupling of the development of new green leaves at the onset of vegetative growth in October and the phase of cambial activity (November–January). The onset of cambial activity seems to be related to a drop in temperature in October and the onset of torrential rains in the region. There might even be a short phase between the end of cambial activity and the onset of bud formation without xylem formation, but with photosynthetic activity. If so, we assume that all assimilates are stored as non-structural carbohydrates (NSC) in the parenchyma of the new ring. This potential gap opens new questions regarding the correlation between NSC storage capacity and the timing of remobilization for subsequent ring formation.

Fine structure of tissue bordering lesions induced by wounding and virus infection

1978 ◽  
Vol 56 (23) ◽  
pp. 2990-2999 ◽  
Author(s):  
G. Faulkner ◽  
Warwick C. Kimmins
Keyword(s):  
Cell Wall ◽  
Fine Structure ◽  
Secondary Cell Wall ◽  
Wall Material ◽  
Wall Thickening ◽  
Pinto Bean ◽  
Local Lesions ◽  
Virus Localization ◽  
Similar Appearance ◽  
Secondary Cell Wall Thickening

Tissue in Phaseolus vulgaris L. cv. Pinto bean bordering local lesions induced by tobacco mosaic virus showed cell wall deposition associated with paramural body formation in a narrow ring of viable cells extending one to three cell diameters around the lesions. Deposition, which led to secondary cell wall thickening, was greatest 3–4 days after inoculation, the time when the lesion stopped expanding. Secondary cell wall thickening, of similar appearance but less pronounced, was seen in tissue bordering local lesions which continued to expand; no significant secondary cell wall thickening was observed in leaves with a nonlocalized infection. Cells bordering mechanical lesions differed markedly in fine structure from cells bordering virus and chemical lesions. It is suggested that the deposition of extra cell wall material in the wall regions of cells bordering fully expanded local lesions is associated with virus localization.

scholarly journals Is size an issue of time? Relationship between the duration of xylem development and cell traits

2019 ◽  
Vol 123 (7) ◽  
pp. 1257-1265 ◽  
Author(s):  
Valentina Buttò ◽  
Sergio Rossi ◽  
Annie Deslauriers ◽  
Hubert Morin
Keyword(s):  
Cell Wall ◽  
Cell Differentiation ◽  
Tree Ring ◽  
Wall Thickness ◽  
Secondary Wall ◽  
Temporal Dynamics ◽  
Secondary Growth ◽  
Growth Equation ◽  
Wall Deposition ◽  
Secondary Wall Deposition

Abstract Background and Aims Secondary growth is a process related to the formation of new cells that increase in size and wall thickness during xylogenesis. Temporal dynamics of wood formation influence cell traits, in turn affecting cell patterns across the tree ring. We verified the hypothesis that cell diameter and cell wall thickness are positively correlated with the duration of their differentiation phases. Methods Histological sections were produced by microcores to assess the periods of cell differentiation in black spruce [Picea mariana (Mill.) B.S.P.]. Samples were collected weekly between 2002 and 2016 from a total of 50 trees in five sites along a latitudinal gradient in Quebec (Canada). The intra-annual temporal dynamics of cell differentiation were estimated at a daily scale, and the relationships between cell traits and duration of differentiation were fitted using a modified von Bertalanffy growth equation. Key Results At all sites, larger cell diameters and cell wall thicknesses were observed in cells that experienced a longer period of differentiation. The relationship was a non-linear, decreasing trend that occasionally resulted in a clear asymptote. Overall, secondary wall deposition lasted longer than cell enlargement. Earlywood cells underwent an enlargement phase that lasted for 12 d on average, while secondary wall thickness lasted 15 d. Enlargement in latewood cells averaged 7 d and secondary wall deposition occurred over an average of 27 d. Conclusions Cell size across the tree ring is closely connected to the temporal dynamics of cell formation. Similar relationships were observed among the five study sites, indicating shared xylem formation dynamics across the entire latitudinal distribution of the species.The duration of cell differentiation is a key factor involved in cell growth and wall thickening of xylem, thereby determining the spatial variation of cell traits across the tree ring.

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