Báo cáo khoa học: "Variation of vessel lumen diameter in radial direction as an indication of the juvenile wood growth in oak"

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article Original Variation of vessel lumen diameter in radial direction as an indication of the juvenile wood growth in oak (Quercus petraea Liebl) L Heli&jadnr;ska-Raczkowska ul Department of Wood Science, Agricultural University, Wojska Polskiego, 38-42, Poznan, Poland 60-627 29 October 1992; accepted 8 January 1994) (Received Summary — Radial variations of vessel lumen diameters and number of vessels per unit area were investigated in sessile oak wood from 3 trees in the same stand. With increasing growth-ring age, the lumen diameters of earlywood and latewood vessels and the number of earlywood vessels per unit area increased, especially in the core zone of stem cross-section; the number of earlywood vessels per unit area decreased. Results of measurements of the variation in conductive elements in oak wood suggest that the juvenile (core) wood of the oak trees may contain approximately 30 growth rings. For the same annual rings from the pith, a very significant tree effect appeared for the vessel characteristics measured. Quercus petraea /vessel/ diameter / number per unit area Résumé—La variation radiale du diamètre du lumen des vaisseaux du bois, un indice de la durée de la période de croissance juvénile chez le chêne (Quercus petraea Liebl). On a examiné l’évo- lution du diamètre des lumens des vaisseaux et de leur nombre par unité de surface depuis la moelle jusqu’à l’écorce sur 3 chênes sessiles provenant d’un même peuplement. Lorsque l’âge du cerne compté depuis la moelle augmente, le diamètre des lumens des vaisseaux du bois de printemps aug- mente et leur nombre par unité de surface diminue. Dans le bois d’été, le diamètre des lumens et leur nombre par unité de surface augmente lorsque l’âge augmente. Cet effet de l’âge du cerne est très sensible au voisinage de la moelle. Les résultats de l’étude des variations des éléments conducteurs en fonction de l’âge depuis la moelle montrent que la zone de bois juvénile chez le chêne concerne à peu près les 30 premiers cernes depuis la moelle. Pour le même âge depuis la moelle, un effet indi- viduel (effet arbre) très significatif apparaît pour les caractéristiques des vaisseaux prises en considération dans l’étude. Quercus petraea vaisseaux / diamètre / nombre par unité de surface /
number of vessels per unit area in oak trees INTRODUCTION of even-aged stands with different growth characteristics were measured to fill the This paper is a continuation of studies on information gap. the variation in the structures and proper- ties of oak wood (Maeglin, 1976; Petri&jadnr; and &Scaron;&jadnr;ukanec, 1980; Nepveu, 1984a, 1984b, MATERIALS AND METHODS 1990; Gasson, 1985; Heli&jadnr;ska-Raczkowska, 1990; Heli&jadnr;ska-Raczkowska and Fabisiak, experimental site was located in a 78-year-old The 1991).An improved understanding of the (according to the management plan) even-aged laws governing changes in structural fea- oak stand (Quercus petraea Liebl) in the west- tures of wood in the function of wood cross- ern part of Poland (52°33’N and 16°50’E) on the section radii, as well as the relationship site of the experimental forests of the Agricultural University in Pozna&jadnr;. With reference to the mea- between these changes and conditions of sured diameters of trees, one experimental tree tree growth in a stand, is very important selected from each of the dominant, inter- was from the wood-application and silviculture- mediate, and suppressed classes (table I). Discs practice points of view. It should be noted experiments were taken at a height corre- for that only quantitative assessments of the sponding to the 1/4 height of the tree measured influence of different factors on wood for- from the butt-end (table II). Strips were cut along the northern radius of each disc (20 mm in width mation will provide the information needed along the tangential direction and 20 mm in height in silviculture practice so as to produce trees along the fibres). For the investigation, the fol- of a desired quality (Trotter, 1986; Wagen- lowing annual rings, counted from the pith, were führ et al, 1989). In previous studies, juvenile selected: 3, 6, 9, 12, 15, and further out towards wood produced by juvenile (immature) cam- the bark, every fifth ring. Permanent slides of bium was investigated, but little attention growth-ring transection were taken from each of these rings for measurements. has been paid to the hardwoods (Nepveu, The lumen diameter of earlywood and late- 1981; Zobel and van Buijtenen, 1989). In wood vessels was measured on samples to particular, a lack of reliable criteria for dis- include all the growth rings under study. Mea- tinguishing the juvenile and mature wood surements were made using the system in one tree appears to be very inconvenient. described before (Heli&jadnr;ska-Raczkowska, 1990). Therefore, in this study lumen diameters of For each of the annual rings studied, 15 mea- earlywood and latewood vessels and the surements of earlywood and latewood vessel
age it reached 90%. As the age of growth lumen diameter (inner diameter) were made. The maximal tangential inner diameter of the rings increased, the number of earlywood first row earlywood vessels in the growth ring vessels per unit area decreased (fig 1), the and latewood vessels located near the border variation of this characteristic being the of growth rings were measured. On the cross- greatest in the area from pith to about the section, the number of earlywood and latewood 30th growth ring. There was a negative cor- vessels per unit area, ie their number per 1 mm 2 relation between earlywood vessel lumen of the transection of earlywood and latewood part of the annual ring, was also determined. diameter and their number per unit area (fig However, the number of latewood vessels per 2), which means the greater the earlywood unit area was determined at the border of the vessel lumen diameters, the lower the num- annual ring. ber of the earlywood vessels per unit area. For example, for the vessel lumen diameter of 300 μm, their number per unit area was RESULTS AND DISCUSSION , 2 5/mm while for the diameter of 120 μm, the number of the vessels per unit area Statistical analysis of the measurements increased to 25/mm Such a relationship . 2 indicated that the mean coefficient of varia- between the diameter of vessel lumen and tion for earlywood vessel lumen diameter their number per unit area can be explained is 17 (8...32)%, while for latewood it is 18 by functional reasons (Bamber and Curtin, (10...29)%. Histograms of the diameters 1974; Baas, 1982; Ziemmermann, 1983; and a comparison of the arithmetical means Carlquist, 1988). It is also worth mention- and modal values suggest that the distribu- ing that the diameter of earlywood vessel tion of vessel lumen diameters is close to lumen was negatively correlated with the normal. width of annual rings for a given tree, ie the narrower the annual rings, the greater the Radial variation of vessel earlywood diameter of earlywood vessel lumen (fig 3, lumen diameter and the number of early- for example, for a dominant tree). For late- wood vessels per unit area is shown in fig- wood vessels, with increasing age of growth ure 1. It follows from these data that the rings, an increase in the lumen diameter increment of earlywood vessel lumen diam- and in the number of vessels per unit area eter increases continuously with the increase was observed (table III). However, an of cambial age of growth rings up to about increase in the diameter of latewood ves- 30 yr. The vessel lumen diameter remained sel lumina in the outerwood zone, in com- more or less constant with any further parison with the vessel in the corewood increase of the cambial age of growth rings. zone was significantly smaller than for ear- Increase in the earlywood vessel lumen lywood vessels, and on average it amounted diameter in the outerwood was significant to 30%. On the other hand, the number of compared with that in the pith area; on aver-
latewood vessels per unit area tended to Radial variation of the number of early- increase with the increasing age of the wood and latewood vessels per unit area growth ring, even reaching 300% in the out- varied (fig 4). The number of earlywood ves- erwood zone in comparison with the core- sels per unit area decreased as the age of wood zone. growth rings increased, while that of late-
wood vessels increased. It should be also noted that high variability exists between the dominant tree to 220 μm in the sup- individual trees for the number of earlywood pressed tree. Diameters of latewood ves- and latewood vessels per unit area. The sel lumina, on the other hand, exhibit an same is true for the diameter of earlywood inter-tree variability but this is lower than for the other above-mentioned characteristics. vessel lumina, which varies from 310 μm in
The absolute values of the vessel lumen would be about 30 yr on visual estimation. diameter measured were similar to those The same limit can be (visually) accepted reported in the literature (Wagenführ and for the 3 trees considered here. It is worth Scheiber, 1974; Wagenführ, 1984; Wagen- mentioning that the juvenile period of oak führ et al, 1989). As regards the number of development, determined on the basis of latewood vessels per unit area in the mature changes in earlywood vessel lumen diam- wood, the values obtained are closest to eter, overlaps the zone of juvenile wood those collected by Vichrov (1954). determined on the basis of radial variation in fibre length (Heli&jadnr;ska-Raczkowska and The curves of radial varation of early- Fabisiak, 1991).Moreover, it should be wood vessel lumen diameter or number per noted that the juvenile period of oak devel- unit area of vessels may be used as an indi- opment, determined on the basis of radial cator of the border between the juvenile variation in wood anatomical elements, cor- (corewood) and the mature wood (outer- responds to the juvenile period of tree devel- wood). The zone of juvenile wood may be opment established on the basis of the num- assumed to comprise growth rings from pith ber of years a tree needs to achieve to those that have either a constant diame- reproduction capabilities, which for Q robur ter of earlywood vessel lumen or a constant usually takes from 25 to 30 yr (Wareing and number per unit area. In other words, the Philips, 1985). number of years taken to reach a more or less constant earlywood lumen diameter or Juvenile oak wood was characterized its number per unit area may be used as a by wider growth rings than mature wood, junction between the juvenile and the mature a higher percentage of latewood, and a wood in oak. Due to the value of the deter- higher wood density (dry weight, green vol- mination coefficient R the diameter of the , 2 ume basis) by about 100 kg/m Average . 3 vessel lumen is preferable as the indicator. density differentiation of examined oak In the case considered here, the transition wood is given in table IV. However, an period of juvenile wood into mature wood attempt to use these parameters to differ-
is generally related to the age from the pith entiate between juvenile and mature wood failed. in the juvenile wood (corewood). With increasing age of growth rings, the diameter the results of studies Generally, our are of earlywood and latewood vessel lumina in agreement with the basic laws of eco- and the number of latewood vessels per unit logical and functional anatomy, by which area increases, while the number of early- the broadly understood influence we mean wood vessels per unit area decreases. The of climatic, biotic, and edaphic factors on zone of juvenile wood determined from the the variations in wood structure. According curves of radial variation in earlywood vessel to these laws, deteriorated conditions of tree lumen diameter consists of approximately growth may result in a decrease in the diam- 30 growth rings. For the same age from the eter of earlywood vessels and increase their pith, a very significant tree effect appears number per unit area (Carlquist, 1988; Van for the diameter of vessel lumen and the den Over et al, 1981; Baas, 1982). The com- number of vessels per unit area. parison between the 3 trees taken into con- sideration here (1 dominant, 1 intermedi- ate, 1 suppressed tree) seems to be in REFERENCES accordance with these bibliographic results but our sampling is not complete enough to confirm this point seriously. However know- Baas P (1982) Systematic, phylogenetic, and ledge of the laws mentioned above with ref- ecological wood anatomy - history and per- erence to hardwoods is limited (Denne and spectives. In: New Perspectives in Wood Anatomy (P Baas, ed) Martinus Nijhoff, Dr W Dood, 1981), which has also been evi- Junk Publ, Hague, 45 denced in this paper. Due to the scarcity of Bamber RK, Curtin RA (1974) Some properties of experimental material, this study should be wood Blackbutt trees of two ages. Austr For considered as an introductory. It seems 36, 226-234 necessary therefore to extend these studies Carlquist S (1988) Comparative Wood Anatomy. to other species from the Quercus genus Springer Series in Wood Science, Springer- and to other genera from the group of ring- Verlag, Berlin, 44-46, 54 porous wood (eg, Fraxinus, Ulmus and Denne MP, Dood RS (1981) The environmental Robinia). control of xylem differentiation. In: Xylem Cell Development (JR Barnett, ed) Castle House Publ Ltd, Tunbridge Wells, Kent, 236-253 CONCLUSIONS Gasson P (1985) Automatic measurements of vessel lumen area and diameter with particu- Radial variation of the diameter of earlywood lar reference to pedunculate oak and com- vessels in oak and their number per unit area mon beech. IAWA Bull ns 6, 219-237
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