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Forestry and Forest Products Research Institute, Tsukuba Norin, P.O. Box 16, Ibaraki 305-8687, Japan; and Botanical Garden, Graduate School of Science, Tohoku University, Kawauchi, Aoba, Sendai 980-0862, Japan
Received for publication March 23, 2000. Accepted for publication June 22, 2000.
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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Key Words: alpine zone • Ericaceae • ontogeny • plant form • Rhododendron • subgenera • wood structure
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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1000 species divided into eight subgenera (Chamberlain et al., 1996
). In Nepal, 29 species of the two largest subgenera, Rhododendron and Hymenanthes, are distributed in the montane to the alpine zones. Subgenus Hymenanthes is characterized by the lack of scales and includes species of various plant forms from dwarf shrubs to large trees up to 30 m tall (Chamberlain, 1982
). Subgenus Rhododendron is characterized by scales at least on the young growth and the undersurface of the leaves and consists mostly of shrub species and rarely of subtree species such as R. cinnabarinum (Cullen, 1980
). In Nepal all tree and subtree species except for R. cinnabarinum belong to subgenus Hymenanthes and all shrubs to subgenus Rhododendron.
In the Nepalese Himalayas Rhododendron species are major elements of vegetation, especially in the alpine zone, and grow almost continuously from the upper part of the montane zone near to the vegetation limit (Noshiro and Suzuki, 1989
; Noshiro and Ohba, 1993
). Most species have an altitudinal range of 1000 m, usually corresponding to a vegetation zone, and four species, R. anthopogon, R. arboreum, R. lepidotum, and R. setosum, have a 2000–3000 m range, covering more than one vegetation zone (Noshiro, 1997
). Nepalese Rhododendron species vary from trees up to 20 m tall and 60 cm thick in stem diameter to small shrubs up to 0.1 m tall and 0.2 cm thick. Based on plant form and their position in vegetation zones, Nepalese Rhododendron species can be classified into tree, subtree, and shrub species (Noshiro and Suzuki, 1989
; Noshiro and Ohba, 1993
). Tree species usually have a distinct main stem and form the undergrowth of montane and subalpine forests, most typically in the subalpine Abies forests. Tree species, however, become shrubs in the uppermost part of their distribution ranges. Subtree species are generally in the form of large shrubs and occasionally become small trees up to 8 m tall. Subtree species grow as scattered or almost continuous scrubs in open spaces within subalpine forests and form continuous Rhododendron scrubs in the lower part of the alpine zone. Alpine shrubs less than 1 m tall grow throughout the alpine zone and often form Rhododendron scrubs on the northward slopes or grow sporadically in alpine meadows. Montane and subalpine shrubs are larger, up to 4 m tall, and grow usually as epiphytes on rocks or tree trunks or occasionally in open spaces in the montane or subalpine forests. Thus Nepal seems to be an ideal place to study wood structural diversity of Rhododendron species in relation to plant form, size, and habitat.
Nepalese Rhododendron species have diffuse-porous wood with distinct growth rings and evenly distributed small vessels and heterocellular rays (see Figs. 1–16; Suzuki and Noshiro, 1988
; Suzuki et al., 1999
). In Nepalese Rhododendron, quantitative features of the wood structure had clear ecological trends within the genus in relation to plant size and/or altitude of material trees (Noshiro, Suzuki, and Ohba, 1995
). Some features showed continuous trends within the genus, and others had trends differing between shrubs and trees plus subtrees. Transectional area of individual vessels, for example, showed a curvilinear exponential increase with stem diameter, and vessel element length showed a similar increase with plant height. On the contrary, vessel density varied greatly among shrubs, but was almost constant in trees and subtrees irrespective of stem diameter. Area percentage of multiseriate rays in a tangential section seemingly had a curvilinear increase with stem diameter, but this trend could also be interpreted as a combination of a steep linear increase among shrubs and a gentle linear increase in trees and subtrees. Within species, however, wood structure was less variable, and among four species that grow in an altitudinal range of 2000 m, only two to nine characters were significantly correlated with plant size and/or habitat altitude (Noshiro and Suzuki, 1995
). Thus in Nepalese Rhododendron, trends within the genus reflect wood structural diversification of species that have various plant size or form and habitat preference. However, it is not clear whether shrubby species have a basically different wood structure with respect to quantitative features than do trees plus subtrees, or whether the small size of shrubby species leads to apparently different wood structure than that of trees plus subtrees. Because specimens of tree and subtree species used in the genus-level study were all obtained from the outermost trunks of large individuals, study of shrub-sized stems of tree and subtree species is necessary for the strict comparison with shrub species.
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), we will infer ontogenetic trends of quantitative features from pith to fully mature wood in trees plus subtrees. We will finally compare trends among mature shrub species with the ontogenetic trends in trees plus subtrees, treating alpine shrubs and montane to subalpine shrubs separately. Thus we aim to clarify whether wood structure of shrubs conforms with or differs from that of trees and subtrees and whether there is wood structural diversification between alpine shrubs and montane to subalpine ones. |
MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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All features were measured for all specimens except for vessel element length, which was measured in five specimens of four species. Samples for measurement were from the longest radius of each specimen. Measurement was done at 1-cm intervals between 0.5 and 2.5 cm from the pith, and at 1–2 cm intervals afterwards. Except for vessel element length, measurement was done with an image analyzing system consisting of a CCD video camera (SONY XC-009, SONY, Shinagawa, Tokyo, Japan), a personal computer (Power Macintosh 8100, Apple Computer, Cupertino, California, USA), and an image analysis software (NIH Image version 1.62, National Institute of Health, Bethesda, Maryland, USA). Vessel density and individual vessel area were measured and averaged from one 640 x 480 µm area. Multiseriate ray density, multiseriate ray height, and multiseriate ray area percentage were measured and averaged from two or three 1280 x 960 µm areas. Vessel element length is reported as an average of 50 vessel elements, measured with an optical microscope from macerations.
Growth rings were counted along the stem radii of all the tree and subtree specimens for the ontogenetic study. Growth ring number was provisionally counted considering the continuity of growth ring boundaries and vessel size difference over growth ring boundaries for specimens having extremely narrow, discontinuous, or false growth rings. Growth rings of shrub species were counted for 17 specimens of nine species among the materials for the genus-level study (Noshiro, Suzuki, and Ohba, 1995
). Growth ring number of shrubs was plotted against stem diameter, because shrubs often had eccentric growth with depressions along the stem margin.
Data of mature individuals of tree and subtree species and those of shrub species are all from the genus-level study of Nepalese Rhododendron (Noshiro, Suzuki, and Ohba, 1995
): 14 samples of five tree species, 23 samples of eight subtree species, and 31 samples of 13 shrub species. However, R. cinnabarinum was treated with shrub species. A preliminary study showed that R. cinnabarinum had trends conforming to shrub species of subgenus Rhododendron and differing from other tree and subtree species of subgenus Hymenanthes. Rhododendron griffithianum was treated with trees plus subtrees. Its materials in the genus-level study were shrubs or subtrees to 4 m tall, but it normally grows to a tree up to 10 m tall (Chamberlain, 1982
). Thus in the present study all the shrub species plus one subtree species belong to subgenus Rhododendron and all the tree and subtree species to subgenus Hymenanthes. Shrubs are divided into two groups, alpine and montane, according to their habitat. Alpine shrubs include R. anthopogon, R. lepidotum, R. lowndesii, R. nivale, R. pumilum, and R. setosum. Montane to subalpine shrubs include R. cameliiflorum, R. cinnabarinum, R. dalhousiae, R. glaucophyllum, R. lindleyi, R. triflorum, and R. vaccinioides.
The quantitative features of trees plus subtrees and shrubs are plotted against stem diameter as scatter plots using the power curve fitting of the DeltaGraph version 4.5 (SPSS, Chicago, Illinois, USA). Curvilinear fittings are provided provisionally to illustrate trends in trees plus subtrees and shrubs. However, details or statistical evaluation of these fittings will not be given, because there are no mathematical models to explain quantitative features of wood structure and because evaluation of curvilinear fittings is complicated and not feasible without such models (Sokal and Rohlf, 1995
).
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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In tree and subtree specimens, growth ring number increased almost linearly with respect to measured stem radius (Fig. 17). Decrease of growth ring width in the outermost part of stems due to senescence was not detected among the specimens. Two specimens of R. arboreum growing <3000 m showed comparatively rapid growth. Some specimens of the other species grew very slowly and accumulated 100 growth rings at 6–7 cm stem radius.
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Ontogenetic trends in trees and subtrees
Vessel features had ontogenetic trends common between specimens. Density initially decreased between 0.5 and 1.5 cm radius and was nearly constant or variable (Figs. 1–4, 18). Exceptionally high density of >600 vessels/mm2 occurred only in extremely narrow rings of subtree species (Figs. 9, 10). Except for these extreme values, density ranged between 300 and 550 vessels/mm2 outward from 1.5 cm radius. Vessel area usually showed an initial increase between 0.5 and 1.5 cm radius and a gentle one afterwards (Fig. 18). Vessel area was not affected by the width of growth rings, and extremely narrow growth rings had vessel areas similar to that of normal growth rings. Vessel element length was nearly constant throughout the radii and ranged between 320 and 590 µm (Fig. 18). Except for one specimen showing an initial increase over 100 µm, vessel element length was nearly stable and fluctuated <100 µm along the stem radius of each species.
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Characterization of shrubs against trees plus subtrees
Shrub species generally had weakly defined growth ring boundaries, nearly stable vessel diameter within growth rings, and fewer and sporadic multiseriate rays (Figs. 11–16).
In trees plus subtrees, vessel density began at 500 vessels/mm2 and decreased gradually to 400 vessels/mm2 at the maximum stem diameter of 50 cm (Fig. 20). In shrubs vessel density varied widely from 300 to 2500 vessels/mm2 below 4 cm stem diameter and decreased afterwards more steeply than in trees and subtrees. Extremely high vessel density over 800 vessels/mm2 occurred exclusively in alpine shrubs and one montane epiphyte. All the other shrubs fit in the lower range of the ontogenetic trends of trees plus subtrees.
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300 to 500 µm2 out to a stem diameter of 5 cm and then gradually increased (Fig. 21). In shrubs, vessel size had an initial steep increase similar to trees plus shrubs from 100 µm2 close to the pith and then continuously increased up to the maximum stem diameter of 15 cm. Thus shrubs had no mature wood phase, while trees plus subtrees had. Most alpine shrubs had vessel areas <300 µm2, and montane to subalpine shrubs mostly had vessel areas of similar size to those of small or young individuals of trees and subtrees. Segregation of the alpine shrubs from trees, subtrees, and montane to subalpine shrubs was not so clear as it was in the case of vessel density, and all specimens could be treated as forming one curvilinear trend.
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400 µm near the pith to 500 µm at the maximum stem diameter (Fig. 22). Vessel element length varied from 200 to 300 µm in alpine shrubs, but montane to subalpine shrubs had vessel elements as long as small or young individuals of trees and subtrees. Similar to vessel density, vessel element length seemed to define alpine shrubs as a distinct group from others.
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). In shrubs, multiseriate ray density was mostly below 10 multiseriate rays/mm2 and gradually increased with increasing stem diameter. Multiseriate rays were not observed in two specimens. Alpine shrubs and montane to subalpine shrubs had similar ray densities, and ray density did not seem to have a correlation with ecology. Thus, trees plus subtrees tended to have more multiseriate rays per unit tangential area than did shrubs.
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10% (Fig. 25). In shrubs, multiseriate ray area percentage varied from 0 to 7% (to 11%) below 3.5 cm stem diameter, being 0% in two specimens, and gradually increased to 4%. Thus, multiseriate rays usually occupied a larger tangential area in trees plus subtrees than in shrubs. Values for alpine shrubs tended to be lower than those of montane to subalpine shrubs, but their ranges overlapped.
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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; Zobel and van Buijtenen, 1989
; Larson, 1994
; Lev-Yadun and Aloni, 1995
). The same set of vessel features as reported here seem to have been studied only for five South Indian species (Sebastine, 1958
). Ontogenetic decrease in vessel density and increase in vessel size in Rhododendron are common to five South Indian dicotyledonous species (Sebastine, 1958
) and to some Eucalyptus species (Wilkes, 1988
). Vessel density and size are usually inversely correlated following an exponential curve that is characteristic of each taxon (Noshiro and Baas, 1998
). These two features were significantly correlated at the 0.5% level in the tree and subtree specimens for the present ontogenetic study.
Vessel element length has been studied more extensively than have vessel density and size. Vessel element length of Nepalese Rhododendron was nearly constant among tree and subtree specimens for the ontogenetic study, but seemed to increase slightly in fully mature individuals (Fig. 22). The near constancy or the slight increase of vessel element length is common to other taxa such as those studied by Bailey and Tupper (1918)
, several Japanese species (Furukawa et al., 1983
), Shorea species (Aung, 1962
), Populus tremula (Hejnowicz and Hejnowicz, 1958
), and five South Indian species (Sebastine, 1958
), to cite a few examples. However, an initial increase in vessel element length in the innermost secondary xylem was not detected in trees and subtrees of Rhododendron, except for one specimen, and wood at 0.5 cm radius was already mature in terms of vessel element length.
In Nepalese Rhododendron, occurrence of multiseriate rays among the whole ray system was distinctly lower in shrub species than in others (Suzuki and Ohba, 1988
). The ontogenetic development of multiseriate rays has so far been studied in relation to the development of ray initials (Barghoorn, 1941
; Evert, 1961
; Cumbie, 1983
; review in Larson, 1994
, and Lev-Yadun and Aloni, 1995
), and multiseriate rays, separate from uniseriate ones, are rarely studied quantitatively. DeSmidt's (1922)
work on Ulmus fulva is the only comparative study we could find. Multiseriate ray features of tree and subtree species of Nepalese Rhododendron, however, usually had different trends than those in Ulmus fulva. Distinct trends of R. cinnabarinum of subgenus Rhododendron among other trees and subtrees of subgenus Hymenanthes (Fig. 19) rather indicated a systematic differentiation of multiseriate ray features in two subgenera of Nepalese Rhododendron. Although a significant correlation of ray features with growth ring width has been reported in several works reviewed by Larson (1994)
and Lev-Yadun and Aloni (1995)
, multiseriate ray features of Rhododendron materials did not have any significant correlation with stem growth. The fluctuation of stem growth of Rhododendron species, all <4.5 mm/yr, may not have been large enough for the variation of multiseriate rays to occur.
Subdivision of Nepalese Rhododendron based on wood structure
Trends in the wood anatomical features of trees plus subtrees and shrubs supported two different groupings for Nepalese Rhododendron. One is a systematic grouping of trees plus subtrees of subgenus Hymenanthes and shrubs including one subtree species, R. cinnabarinum, of subgenus Rhododendron. Another is an ecological grouping treating alpine shrubs as distinct from all others. Trends in vessel features allowed both systematic and ecological groupings, but trends in multiseriate ray features supported only the systematic one.
Vessel features reported for four Rhododendron species studied for within-species variation tend to support the ecological grouping clarified in the present study (Noshiro and Suzuki, 1995
). In their study, vessel density ranged from 590 to 2450 vessels/mm2 in two alpine shrub species, R. anthopogon and R. lepidotum, and from 210 to 560 vessels/mm2 in R. arboreum (tree species) and R. campanulatum (subtree species). The gap at 580 vessels/mm2 in these four species coincides with the gap between alpine shrubs and others shown in our scatterplot of vessel density (Fig. 20). In Noshiro and Suzuki's (1995)
study, vessel area ranged from 110 to 330 µm2 in the two alpine shrub species and 380 to 1130 µm2 in R. campanulatum and R. arboreum. Although there is an overlap in our scatterplot of vessel area (Fig. 21), alpine shrubs tend to have narrower vessels than 350 µm2. Vessel element length had a considerable overlap in Noshiro and Suzuki (1995)
and ranged from 210 to 400 µm in the two alpine shrubs and from 280 to 460 µm in R. campanulatum and from 360 to 610 µm in R. arboreum. In our scatterplot of vessel element length (Fig. 22), however, only alpine shrubs have shorter vessels than 300 µm. Shortening of vessel elements to 65–80% of those in the normal trees is found in dwarfed plants of several species having diffuse-porous and semi-ring-porous wood (Baas et al., 1984
) and agrees with the trends between plant height and vessel element length within Nepalese Rhododendron (Noshiro, Suzuki, and Ohba, 1995
).
There is a considerable overlap in multiseriate ray density and height of the four Rhododendron species studied for within-species variation (Noshiro and Suzuki, 1995
). Multiseriate ray density, for example, ranged from 0 to 7.5 multiseriate rays/mm2 in the two alpine shrubs, from 8.5 to 41.3 multiseriate rays/mm2 in R. campanulatum, and from 2.8 to 19.1 multiseriate rays/mm2 in R. arboreum. Individuals of R. arboreum growing below 2600 m tended to have sparse large multiseriate rays, <10 multiseriate rays/mm2 and 300–700 µm tall (Noshiro and Suzuki, 1995
). If we exclude individuals with >30 cm stem diameter in our scatterplot of multiseriate ray density (Fig. 23), trees plus subtrees of subgenus Hymenanthes tend to have >8 multiseriate rays/mm2 and shrubs of subgenus Rhododendron have less than that. In Noshiro and Suzuki's (1995)
study, multiseriate ray area percentage ranged from 0 to 6.6% in the two alpine shrubs and from 5.9 to 23.9% in R. campanulatum and R. arboreum. In spite of an overlap in their study and our scatterplot of the present study (Fig. 25), shrubs of subgenus Rhododendron tend to have multiseriate ray area percentages less than 7%, and trees plus subtrees of subgenus Hymenanthes tend to have percentages more than 6%.
In the present study, however, we could include no shrub species of subgenus Hymenanthes and only one subtree species of subgenus Rhododendron, and systematic grouping and plant form could not be analyzed separately. Further analyses with species growing outside Nepal is necessary to confirm the ecological significance of vessel features and the systematic significance of multiseriate ray features presented in this study.
Ecological characterization of alpine species
In the Nepalese Himalayas, the subalpine zone consisting mostly of Abies forests extends from 3000 to 3800 m (Ohsawa, Shakya, and Numata, 1973, 1986
). Above the forest limit at 3800 m, several subtree species of Rhododendron form alpine scrubs up to 4200 m, and only alpine shrubs grow above this altitude up to just over 5000 m near to the vegetation limit (Noshiro and Suzuki, 1989
; Noshiro and Ohba, 1993
). The ecological difference between the lower and the upper parts of alpine zones is yet to be clarified, but some kind of physiological or developmental threshold seems to exist that allows only alpine shrubs to grow in the upper alpine zone up to the vegetation limit.
Alpine shrub species of Nepalese Rhododendron were distinct from montane to subalpine shrubs, subtrees, and trees in having narrow, numerous vessels (Figs. 20, 21). The same trends in vessel features have been observed in dwarfed plants of the alpine timber line of the northern Appalachian Mountains (Forsaith, 1920
) and arctic shrubs of southeast Greenland (Miller, 1975
). Even in the woody flora of southern California, alpine shrubs and subshrubs have the most dense and narrowest vessels among 11 ecological groups (Carlquist and Hoekman, 1985
).
Narrow vessels are less vulnerable than are wide vessels to cavitation induced by freeze–thaw cycles (Sperry et al., 1994
; Sperry, 1995
), and numerous vessels can be a compensation for the low hydraulic conductance of narrow vessels (Zimmerman, 1983
). In the alpine zone of the Nepalese Himalayas, diurnal freeze–thaw cycles of air temperature occur on 160–170 d/yr at 4420 m and 190 d/yr at 5000 m, mostly in spring and autumn (Matsuoka, 1984
). Vessel features of alpine shrub species can be an adaptation for such frequent freeze–thaw cycles in the Nepalese Himalayas, although the actual number of freeze–thaw cycles that plants experience should be lower than the above counts because of snow cover in winter.
Another possible cause of narrow, numerous vessels in alpine shrub species is growth stress. Baas et al. (1984)
compared wood structure of normal trees with that of artificially induced or naturally occurring dwarf trees. They found that dwarf-growth plants tended to have more numerous, narrower vessels than did normal trees and interpreted the results as stress effects of extremely slow growth. Alpine shrub species in the upper part of the alpine zone grow up to a height of 50 cm between 4200 and 4800 m and up to 20 cm above 4800 m. The growing season is limited in the alpine zone of the Nepalese Himalayas, and 10-d mean air temperature measured at 4420 m exceeds 5°C only for 3 mo with midday air temperature <10°C (Inoue, 1976
). Apart from short summers, alpine species probably should have the low shrub habit to survive the winter under snow cover. Thus, the characteristic wood structure of alpine shrubs may only be the result of slow limited growth caused by the severe, short summer alpine environment, not by the need for a mechanism against embolism caused by freeze–thaw cycles.
The wood structure of Nepalese Rhododendron has a close correlation with plant form and habitat preference or with the systematic diversification within this large woody genus. Plant form of Rhododendron is a continuum from large trees to small shrubs, and distinction in plant form between subtrees and shrubs is problematic. Thus it is difficult to say whether the shrub form in Rhododendron is an adaptation based on a design strategy of small "throw-away" stems in high-stress environments or whether adaptations for survival in a high-stress environment impose the shrub form, as Wilson (1995)
hypothesized for the adaptive nature of the shrub form.
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FOOTNOTES |
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2 Author for correspondence (e-mail: noshiro{at}ffpri.affrc.go.jp
).
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LITERATURE CITED |
|---|
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
Baas, P., C. Lee, X. Zhang, K. Cui, and Y. Deng. 1984 Some effects of dwarf growth on wood structure. IAWA Bulletin, new series 5: 45–63
Bailey, I. W., and W. W. Tupper. 1918 Size variation in tracheary cells: I. A comparison between the secondary xylems of vascular cryptogams, gymnosperms and angiosperms. Proceedings of the American Academy of Arts and Sciences 54: 149–204[ISI]
Barghoorn, E. S., Jr. 1941 The ontogenetic development and phylogenetic specialization of rays in the xylem of dicotyledons. II. Modification of the multiseriate and uniseriate rays. American Journal of Botany 28: 273–282[CrossRef][ISI]
Carlquist, S., and D. A. Hoekman. 1985 Ecological wood anatomy of the woody southern Californian flora. IAWA Bulletin, new series 6: 319–347
Chamberlain, D. F. 1982 A revision of Rhododendron. II. Subgenus Hymenanthes. Notes from the Royal Botanic Garden Edinburgh 39: 209–486
———, R. Hyam, G. Argent, G. Fairweather, and K. S. Walter. 1996 The genus Rhododendron: its classification and synonymy. Royal Botanic Garden Edinburgh, Edinburgh, UK
Cullen, J. 1980 A revision of Rhododendron. 1. Subgenus Rhododendron sections Rhododendron & Pogonanthum. Notes from the Royal Botanic Garden Edinburgh 39: 1–207
Cumbie, B. G. 1983 Developmental changes in the wood of Bocconia vulcanica Donn. Smith. IAWA Bulletin, new series 4: 131–140
DeSmidt, W. J. 1922 Studies of the distribution and volume of the wood rays in slippery elm (Ulmus fulva Mich.). Journal of Forestry 20: 352–362
Evert, R. F. 1961 Some aspects of cambial development in Pyrus communis. American Journal of Botany 48: 479–488
Forsaith, C. C. 1920 Anatomical reduction in some alpine plants. Ecology 1: 124–135[CrossRef][ISI]
Furukawa, I., M. Sekoguchi, M. Matsuda, T. Sakuno, and J. Kishimoto. 1983 Wood quality of small hardwoods (II). Horizontal variations in the length of fibers and vessel elements in seventy-one species of small hardwoods. Hardwood Research 2: 103–134
Hejnowicz, A., and Z. Hejnowicz. 1958 Variations of length of vessel members and fibres in the trunk of Populus tremula L. Acta Societatis Botanicorum Poloniae 27: 131–159
Inoue, J. 1976 Climate of Khumbu Himal. Seppyo, special issue 38: 66–73
Larson, P. R. 1994 The vascular cambium. Springer, Berlin, Germany
Lev-Yadun, S., and R. Aloni. 1995 Differentiation of the ray system in woody plants. Botanical Review 61: 45–84
Matsuoka, N. 1984 Frost shattering of bedrocks in the periglacial regions of the Nepal Himalaya. Seppyo 46: 19–25
Miller, H. J. 1975 Anatomical characteristics of some woody plants of the Angmagssalik District of Southeast Greenland. Meddelelser om Grønland 198: 1–30
Noshiro, S. 1997 Distribution maps of Rhododendron in Nepal. Newsletter of Himalayan Botany 21: 21–28
———, and P. Baas. 1998 Systematic wood anatomy of Cornaceae and allies. IAWA Bulletin, new series 19: 43–97
———, and H. Ohba. 1993 Altitudinal distribution and tree form of Rhododendron in the Jaljale Himal, east Nepal. Journal of Japanese Botany 38: 193–198
———, and M. Suzuki. 1989 Altitudinal distribution and tree form of Rhododendron in the Barun Valley, east Nepal. Journal of Phytogeography & Taxonomy 37: 121–127
———, and ———. 1995 Ecological wood anatomy of Nepalese Rhododendron (Ericaceae). 2. Intraspecific variation. Journal of Plant Research 108: 217–233[CrossRef][ISI]
———, ———, and H. Ohba. 1995 Ecological wood anatomy of Nepalese Rhododendron (Ericaceae). 1. Interspecific variation. Journal of Plant Research 108: 1–9[CrossRef][ISI]
Ohsawa, M., P. R. Shakya, and M. Numata. 1973 On the occurrence of deciduous broad-leaved forests in the cool-temperate zone of the humid Himalayas in eastern Nepal. Japanese Journal of Ecology 23: 218–228
———, ———, and ———. 1986 Distribution and succession of West Himalayan forest types in the eastern part of the Nepal Himalaya. Moutain Research and Development 6: 143–157
Panshin, A. J., and C. de Zeeuw. 1980 Textbook of wood technology, 4th ed. McGraw-Hill, New York, New York, USA
Sebastine, K. M. 1958 Studies on the vessel variations in dicotyledonous trees. Journal of the Indian Botanical Society 37: 104–113
Sokal, R. R., and F. J. Rohlf. 1995 Biometry, 3rd ed. W. H. Freeman, New York, New York, USA
Sperry, J. S. 1995 Limitations on stem water transport and their consequences. In B. L. Gartner [ed.], Plant stems: physiological and functional morphology, 105–124. Academic Press, San Diego, California, USA
———, K. L. Nichols, J. E. M. Sullivan, and S. E. Eastlack. 1994 Xylem embolism in ring-porous, diffuse-porous, and coniferous trees of northern Utah and interior Alaska. Ecology 75: 1736–1752[CrossRef][ISI]
Suzuki, M., and S. Noshiro. 1988 Wood structure of Himalayan plants. In H. Ohba and S. B. Malla [eds.], The Himalayan plants, vol. 1, 341–379, pls. 52–96. University of Tokyo Press, Tokyo, Japan
———, ———, A. Takahashi, K. Terada, K. Yoda, and L. Joshi. 1999 Wood structure of Himalayan plants, III. In H. Ohba [ed.], The Himalayan plants, vol. 3, 119–170, pls. 49–103. University of Tokyo Press, Tokyo, Japan
———, and H. Ohba. 1988 Wood structural diversity among Himalayan Rhododendron. IAWA Bulletin, new series 9: 317–326
Wilkes, J. 1988 Variations in wood anatomy within species of Eucalyptus. IAWA Bulletin, new series 9: 13–23
Wilson, B. F. 1995 Shrub stems: form and function. In B. L. Gartner [ed.], Plant stems: physiological and functional morphology, 91–102. Academic Press, San Diego, California, USA
Zimmermann, M. H. 1983 Xylem structure and the ascent of sap. Springer, Berlin, Germany
Zobel, B. J., and J. P. van Buijtenen. 1989 Wood variation. Springer, Berlin, Germany
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