Aggregate Rays in New Zealand Nothofagus Blume (Fagaceae) Stem Wood and Their Influence on Vessel Distribution

IAWA Bulletin n.s., Vol. 80),1987 53

AGGREGATE RAYS IN NEW ZEALAND NOTHOFAGUS BLUME (FAGACEAE) STEM WOOD AND THEIR INFLUENCE ON VESSEL DISTRIBUTION

T. M. Middleton Department of Plant and Microbial Sciences, University of Canterbury, Private Bag, Christchurch, New Zealand

Summary Materials and Methods Aggregate rays occur in the stern wood of The sapwood of more than fifty beech trees Nothofagus solandri var. cliffortioides (Hook. was examined under the scanning electron mi• f.) Poole (mountain beech), N. solandri var. so• croscope and measurements were made on landri (Hook. f.) Gerst. (black beech), N. trun• more than 1000 micrographs. Wood discs were cata (Col.) Ckn. (hard beech), and N. fusca preserved in formalin-aceto-a1cohol (F.A.A), (Hook. f.) Gerst. (red beech), but not in N. placed in a dish containing distilled water and menziesii (Hook. f.) Gerst. (silver beech). The left for a few minutes, and small cubes were composite structures visible in transversely cut using a new razor blade. The tangential lon• sawn wood consist of groups of narrow xylem gitudinal and transverse faces were clean cut. rays separated by fibres; vessels are frequently The cube was cut diagonally on a board to ob• absent. The influence of aggregate rays on ves• tain a pyramid with the required faces; the re• sei distribution was studied using scanning elec• mainder was discarded. All the cut specimens tron microscopy and tested statistically. In• were then placed in vials and cleared in sodium dented growth ring boundaries are associated hypo chlorite and put through the following de• with the presence of aggregate rays. Aggregate hydration series: 30%, 50%, 70%, 80%, 90%, rays occur in saplings. In larger trees aggregate 100% volume/volume ethanol for a minimum rays taper out beyond 6 cm from the stern time of one hour each, and then into 25%, 50 centre. %, 75%, 100% volume/volume amyl acetate Key words: Nothofagus, aggregate rays, New ethanol for a minimum of two hours each. The Zealand beech, vessel distribution. amyl acetate ethanol infiltrated specimens were then critical point dried, and mounted with the Introduction two clean cut faces at 45° to the surface of the Aggregate rays, sometimes called pseudo• stub using the technique of Exley et al. (1973, rays, are composite structures consisting of 1977). The specimens were gold palladium coat• axial as weil as ray tissue. Groups of small nar• ed and examined under the Cambridge Stereo• row xylem rays are separated by fibres and scan 250 Mark 2. sometimes a few vessels. Aggregate rays appear as large conspicuous broad rays in transverse Results and Discussion view, they may be evenly or unevenly spaced In transverse view the central region of the and appear to dilate from the centre of the aggregate ray is indented towards the centre of stern. the stern (Fig. I A-F). An indented growth ring Aggregate rays are present in some members boundary, associated with the presence of ag• of the Fagales, for example Quercus, Carpinus, gregate rays was reported in Fagus crenata Ainus and Fagus, but have not been reported Blume (Shimaji, 1953). Indented growth ring in New Zealand Nothofagus species. In his de• boundaries are present in all New Zealand No• scription of the wood .of Nothofagus solandri thofagus taxa except N. menziesii. Figures I & var. cliffortioides Parharn 0930, 1933) made 2 depict aggregate rays in the most recently only brief mention of zones of aggregations. formed sapwood of N. solandri var. cliffortioi• Aggregate rays were not noted in Dadswell's des, N. solandri var. solandri, N. truncata, and and Ingle's (954) descriptions of the New N. fusca. Although the presence of an inden ted Zealand members of section Calusparassus. cambial region is usually correlated with the Aggregate rays feature in only four of the five presence of aggregate rays, exceptions may oc• taxa of New Zealand Nothofagus: N. menziesii cur (Fig. 2F). Here the bark and cambial zone lacks aggregate rays. have been removed. There is no variation in the

Downloaded from Brill.com09/27/2021 11:06:43PM via free access 54 IAWA Bulletin n.s., Vol. 8 (1),1987 diffuse porous condition in the area of the in• The mean, mean square and standard devia• dentation. The aggregate ray in Figure 2A is tions are presented in Table 2. The greater used to compare the transverse view with the abundance of vessels per unit area noted in tangential view shown in Figure 2C. N. solandri var. cliffortioides coincides weil The outer external bark of beech trees con• with it having wider aggregate ray zones than taining aggregate rays tends to exhibit vertical those of N. fusca and N. solandri var. solandri. grooves. Donaldson (1982) observed aggregate On a statistical basis the results of Duncan's rays in Eucalypts and noted that the large rays New Multiple Range Test involving square root were associated with 'prominent dimples in the transformation of data indicate that the differ• out er tangential surface of the wood.' ence between the number ofvessels per I mm' Aggregate rays were observed in young sap• between species / variety is insignificant at p = lingsand poles with a circumference of approx• 0.05. A one way analysis of variance showed imately 20 cm ; there was a marked absence of there is no significant difference among species. aggregate rays in the wood developed beyond Table 3 gives the number of vessels outside 6 cm radius from the stern centre. Beech trees the aggregate ray zone for comparison with with large trunks lacked the characteristic ex• Table 2. ternaI grooves associated with the presence of Observations disclose the variation in the dis• aggregate rays. The spasmodic production of tribution of vessels within each aggregate ray vessels is the result of uneven circumferential zone to be too large to draw any specific con• growth of the cambium of sm all trees. c1usion . In so me aggregate ray zones, vessels are Table 'I gives the range and means of mea• concentrated near the growth ring boundary as surements in microns of the widths of aggre• shown in Figure I Fand in others, such as in gate ray zones in the transverse sections of N. Figure 2E, they are absent. Vessels mayaiso in• solandri var. cliffortioides (mountain beech), crease in number towards the sides of some ag• N. solandri var. solandri (black beech), N. trun• gregate ray zones or be more concentrated in cata (hard beech) and N. fusca (red beech). Ag• the middle of the aggregate ray zone so as to gregate ray zones are widest in N. solandri var. split it into two zones. Aggregate rays can cross cliffortioides (Fig. I A). Widths of aggregate ray several growth ring boundaries before tapering zones vary radially and axially along sterns and off (Fig. IC) . Development of vessels in the ag• also from tree to tree. gregate ray zone appears to be under seasonal The number of vessels in the aggregate ray influence. Observations of abnormally broad zones were counted. Because of the divergent xylem rays in hard and softwoods by Forsaith and tapering nature of the aggregate rays, Y. (1920), Fink (1982), Bhat (1983) etc. have led mm 2 was considered the most suitable area size to suggestions that these areas of very few ves• for counts. Values have been converted to sels are the product of a complex interaction square millimetres for comparison with vessel between genetical and environmental factors frequency outside the aggregate ray zone. and physiological processes.

Explanation of Figures 1 & 2:

Fig. I. Transverse view of aggregate rays in New Zealand Nothofagus species. - A, B & F: mountain beech(N. solandri var. cliffortioides). - C: hard beech (N. truncata). - D: red beech (N. fusca). - E: black beech (N. solandri var. solandri).

Fig. 2. Aggregate rays in New Zealand Nothofagus species. - A: note the indented cambial zone (arrowed); transverse view, black beech (N. solandri var. solandri) ; B: bark, C: cambium. - B: note the indented growth ring boundaries (arrowed); transverse view, hard beech (N. truncata). - C: tan• gentiallongitudinal view showing the absence of vessels in the aggregate ray zone (AR); mountain beech (N. solandri var. cliffortioides). - D: hard beech (N. truncata) ; detail of the bark showing the associated increase in phloem production and the wavy bands of fibres; see also Figs. 2A & B. - E: transverse view showing part of an aggregate ray zone (AR) in hard beech (N. truncata). - F: mountain beech (N. solandri var. cliffortioides); an exception where inden ted growth ring bounda• ries are not associated with the production of aggregate rays ; the bark has been removed. Note the diffuse vessel distribution.

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Figure 1

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Figure 2

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Table 1. Aggregate ray zone width in transverse view (in J..lm).

Taxa mean range

mountain beech 520J..lffi 400-600J..lm black beech 378J..lm 260-430J..lm hard beech 394 Jlm 220-560 J..lffi red beech 384 Jlm 240-450J..lm

Table 2. The number of vessels per mm 2 in the aggregate ray zones.

Taxa mean mean square standard deviation

mountain beech 72.0 629.19 25.08 black beech 48.0 122.79 11.08 hard beech 76.0 339.99 18.44 red beech 48.0 57.99 7.62

Table 3. The number ofvessels per mm 2 outside the aggregate ray zones.

Taxa mean mean square standard deviation

mountain beeeh 131.0 646.0 25.4 black beeeh 127.0 848.0 29.1 hard beech 89.0 561.8 23.7 red beeeh 82.0 229.6 15.2

Acknowledgements ~ , B.A. Meylan & B.G. Butterfield. 1977. A The author gratefully acknowledges Dr. B.G. technique for obtaining clean cut surfaces Butterfieid for expert guidance, Drs. P. Haase and on wood sampIes prepared for the scanning B. A. Meylan for providing three of the sampies, electron microseope. J. of Microscopy 110: 1.A. Donaldson for helpful comments and Dr. 75-78. 1.M.H. Middleton for assistanee in fieldwork. Fink, S. 1982. Adventitious root primordia - the eause of abnormally broad xylem rays Referenees in hard- and softwoods. IA WABulI. n. s. 3: Bhat, K. M. 1983. A note on aggregate rays of 31-38. Betula speeies.IAWA Bull. n.s.4: 183-185. Forsaith, C. C. 1920. Anatomical reduction in Dadswell, H. E. & H. D. Ingle. 1954. Wood anat• some alpine plants. Ecol. I: 124-135. omy of New Guinea Nothofagus. Aust. J. Parharn, B. E. V. 1930. An introductory study Bot. 2: 141-153. of the genus Nothofagus Blume. Thesis. Donaidson, 1. A. 1982. Abnormal rays in the Christehureh, Univ. of Canterbury. wood of Eucalypts. IA WA Bull. n. s. 3: ~ 1933. New Zealand beech timbers; their 214-215. structure and identifieation. New Zeal. J. Exley, R.R., B.G. Butterfield & B.A. Meylan. Sei. & Techno!. 14: 372-382. 1973. The preparation of wood speeimens Shimaji, K. 1953. Anatomical studies on the for the seanning eleetron mieroseope. J. of wood of some Fagus species. Bull. Tokyo Mieroseopy 101: 21-30. Univ. Forests 42: 181-195.

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