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

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.

Download Full-text

Seasonal Dynamics of Wood Formation in Pinus Halepensis from Dry and Semi-Arid Ecosystems in Spain

IAWA Journal ◽

10.1163/22941932-90001651 ◽

2007 ◽

Vol 28 (4) ◽

pp. 389-404 ◽

Cited By ~ 97

Author(s):

Martín de Luis ◽

Jožica Gričar ◽

Katarina Čufar ◽

José Raventós

Keyword(s):

Pinus Halepensis ◽

Cambial Activity ◽

Wood Formation ◽

Arid Ecosystems ◽

Summer Drought ◽

Growth Rings ◽

False Rings ◽

Cambial Reactivation ◽

Resin Canals ◽

Semi Arid

The seasonal dynamic s of cambial activity, wood formation , occurrence of false rings (FR), and tangential bands of resin canals (RC) were investigated in Pinus halepensis from three Mediterranean dry and semi-arid ecosystems in Spain. We collected intact tissues of phloem, cambium, and outer xylem at monthly intervals throughout 2004 from each time six trees at the three sites. Cell divisions in the cambium in all trees started before our first sampling in mid-March and ceased between November and December. Cambial activity was characterized by two maxima; one in spring and another in autumn. Trees still grew in summer but at a very low rate. The first solitary RC were formed in May or June and tangential bands ofRC in June or July. In general , tangential bands ofRC were observed in wider growth rings . The formation of tangential bands of RC seems to be induced by drought in the second half of the growing season . FR were formed as a result of cambial reactivation in autumn and were observed in growth rings that contained more than 50 cells in a radial row.It appears that summer drought and early autumn precipitation play an important role in false-ring formation.

Download Full-text

Cambial Growth of Swietenia macrophylla King Studied under Controlled Conditions by High Resolution Laser Measurements

Holzforschung ◽

10.1515/hf.2003.029 ◽

2003 ◽

Vol 57 (2) ◽

pp. 196-206 ◽

Cited By ~ 5

Author(s):

O. Dünisch ◽

M. Schulte ◽

K. Kruse

Keyword(s):

High Resolution ◽

Cambial Activity ◽

Cell Enlargement ◽

Swietenia Macrophylla ◽

Cambial Growth ◽

Laser Measurements ◽

Cambial Reactivation ◽

Radial Cell ◽

Xylem Formation ◽

Kinetics Of

SummaryThe kinetics of phloem and xylem formation of two-year-old plants ofSwietenia macrophyllaKing (true mahogany) was studied in a model system along the shoot circumference (experiment 1) and along the shoot axis (experiment 2). The radius increment of the shoot was registered by high resolution laser measurements (accuracy: ±2 μm) in a spatial resolution of 7.8 to 41.3 μm along the stem circumference and 1.5 mm along the stem axis. The temporal resolution of the measurements was 2 s in experiment 1 and 20 s in experiment 2. The radius increment of the shoot detected by the laser measurements was predominately due to the radial enlargement of the phloem and xylem derivatives. On the phloem side the reinitiation of radial cell enlargement after a cambial dormancy occurred first in sieve tubes with contact to ray parenchyma cells, while on the xylem side the radial cell enlargement of vessels and paratracheal parenchyma was induced almost simultaneously along the shoot circumference. In the phloem and xylem derivatives, which were formed first after the cambial reactivation, radial cell enlargement was induced almost simultaneously along the shoot axis. In more advanced phases of phloem and xylem formation, radial cell enlargement of phloem and xylem derivatives was induced shoot downwards with a rate of approximately 13 mm per min. The mean rate of radial cell enlargement of the phloem and xylem derivatives was 2.26 and 4.37 μm per min, respectively. These findings suggest that the kinetics of cambial growth of tropical tree species differ significantly from kinetics observed in trees from temperate regions. The laser measurements might provide a useful experimental approach for studies of cambial activityin situ.

Download Full-text

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

Tree Physiology ◽

10.1093/treephys/tpz099 ◽

2019 ◽

Vol 39 (12) ◽

pp. 2008-2018 ◽

Cited By ~ 2

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.

Download Full-text

SEASONAL VARIATION IN WOOD FORMATION OF CEDRELA FISSILIS (MELIACEAE)

IAWA Journal ◽

10.1163/22941932-90000149 ◽

2006 ◽

Vol 27 (2) ◽

pp. 199-211 ◽

Cited By ~ 34

Author(s):

Carmen Regina Marcati ◽

Veronica Angyalossy ◽

Ray Franklin Evert

Keyword(s):

Secondary Xylem ◽

Cambial Activity ◽

Wood Formation ◽

General Term ◽

Dry Season ◽

Climate Data ◽

Wet Season ◽

Growth Rings ◽

Dormant Period ◽

Xylem Formation

Cambial activity and periodicity of secondary xylem formation in Cedrela fissilis, a semi-ring-porous species, were studied. Wood samples were collected periodically from 1996 to 2000. The phenology was related to climate data of the region. The cambium has one active and one dormant period per year. The active period coincides with the wet season when trees leaf-out. The dormant period coincides with the dry season when trees lose their leaves. Growth rings are marked by parenchyma bands that begin to be formed, together with the small latewood vessels, just before the cambium becomes dormant at the beginning of the dry season. These bands are added to when the cambium reactivates in the wet season. At this time, the large earlywood vessels of the growth rings are also formed. As these bands consist of both terminal and initial parenchyma, we suggest the general term marginal bands be used to describe them. The growth layers vary in width among and within the trees.

Download Full-text

Intra-annual dynamics of cambial and xylem phenology in subalpine conifers at Deogyusan National Park in the Republic of Korea

Journal of Wood Science ◽

10.1186/s10086-021-01950-2 ◽

2021 ◽

Vol 67 (1) ◽

Author(s):

Jun-Hui Park ◽

En-Bi Choi ◽

Hong-Chul Park ◽

Na-Yeon Lee ◽

Jeong-Wook Seo

Keyword(s):

Cell Wall ◽

National Park ◽

Cambial Activity ◽

Republic Of Korea ◽

Pinus Koraiensis ◽

Wall Thickening ◽

Cell Enlargement ◽

Xylem Development ◽

The Republic ◽

Number Of Cells

AbstractSubalpine conifers are highly sensitive to climatic changes. In these trees, the intra-annual dynamics of cambial activity and phenological process in xylem development are closely associated with climatic conditions. However, these scientific findings have not been verified for subalpine conifers in the Republic of Korea. Therefore, we initiated such a study with four subalpine conifers, viz. Abies koreana, Pinus koraiensis, Taxus cuspidata, and Picea jezoensis, growing between 1573 and 1594 m a.s.l. at Deogyusan National Park. Microcores (Ø 2 mm) of these trees were obtained using a mini borer, called as Trephor, every week between April 7 and September 25 in 2017 to monitor their growing seasons, the intra-annual dynamics of the cambial activity, and the number of cells during phenological phases of cell enlargement and cell-wall thickening. For the study, five trees were selected for each conifer species. Results showed that the cambial activity of A. koreana, P. koraiensis, and P. jezoensis required at least 73.8 heat-sum values, whereas the T. cuspidata needed 109.6 heat-sum. The durations of cambial activity of A. koreana, P. koraiensis, T. cuspidata, and P. jezoensis were 134 (127–144), 113 (92–128), 113 (106–120), and 100 (76–128) days, respectively. The intra-annual variations of the number of cells in the cambium, during the cell enlargement phase and cell-wall thickening phase showed predominantly a bell-shaped curve, with a delay of approximately 2–4 weeks between each other. On the other hand, the number of cumulated mature cells showed an S-shaped curve. Through this study, the first fundamental data on phenological process in xylem development of subalpine conifers in the Republic of Korea have been successfully presented.

Download Full-text

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

IAWA Journal ◽

10.1163/22941932-90000161 ◽

2006 ◽

Vol 27 (4) ◽

pp. 383-394 ◽

Cited By ~ 142

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.

Download Full-text