structure of wood and cambial varianf inthe stem of

IAWA Bulletin n.s., Vol. 11 (4), 1990: 379-391
STRUCTURE OF WOOD AND CAMBIAL VARIANf INTHE STEM OF DALBERGIA PANICULATA ROXB.
by
M. N. B. Nair and H. Y. Mohan Ram Department of Botany, University of Delhi, Delhi 110 007, India.
Summary The wood of Dalbergia paniculata is
unique as it consists of concentric layers of broad xylem, alternating with bands of nar row phloem. This anomaly results from the periodic formation of successive cambia in the secondary phloem. Some phloem paren chyma cells dedifferentiate to form a discon tinuous ring of cambium. Such parenchyma cells have higher succinate dehydrogenase activity than the neighbouring cells of sec ondary phloem. The newly differentiated cambial layer functions bidirectionally, and its products give rise to xylem internally and phloem externally. The phloem along with cambium present internal to the newly form ed xylem becomes included.
The wood is diffuse-porous and the inter vessel pits are vestured. The phloem has well differentiated sieve tube members and com panion cells. Key words: Cambial variant, successive bi
directional cambia, vestured pits, included phloem.
Introduction Wood produced by over a dozen species
of Dalbergia is commercially sold by the gen eral name rosewood and is highly valuable (Anonymus 1979). However, the wood of Dalbergia paniculata is unfit for use. The plant is widely distributed throughout south em, central and western India. It also extends northwards to the Siwaliks. The tree is erect and can attain a height of up to 20 m. The bark is smooth and greenish white. Among Dalbergia species the stem structure of D. paniculata is quite unusual. Gamble (1902), Brandis (1906) and Rao and Purkayastha (1972) reported that in this species broad concentric masses of wood alternate with
narrow layers of soft tissue. These authors observed that planks cut from the old trees often disintegrate due to separation in the region of soft layers. Hill (1901) examined cross sections of a dried trunk of Dalbergia paniculata and noted that the narrow soft layer in wood was phloem, with well-dif ferentiated sieve tubes and a certain amount of cambium. He was unable to study the exact mode of development of the anomaly because the material available to him was dry. As far as we are aware, there is no detailed anatomical study of the wood of this species. A few reports (Anonymus 1952; Thothathri 1987) indicate that the wood of D. paniculata is used as firewood, for construction of houses and in the manufacture of musical instruments. However, the latter uses seem most unlikely. Thothathri (1987) is of the opinion that D. paniculata cannot be con sidered as a separate species. He has merged it with D./anceolaria and has given it the rank of a subspecies. The objective of our work w.as to examine the structure of the wood, trace the function of the cambial variant, production of phloem, and its inclusion in the wood.
Materials and Methods Material for study was collected from
Dangs forest of Gujarat State, India. Wood samples were taken from branches (1 to 25 cm in diameter) and the main trunk (45 cm in diameter) from different felling sites. They were fixed immediately in FAA (formalin: acetic acid: 50% ethanol; 1: 1 : 9) and sec tioned on a sliding microtome, stained in 0.05% toluidine blue 0 in 0.1 M phosphate buffer, pH 6.8 (O'Brien et al. 1964), safra nin 0 and fast green FCF (Sass 1958).
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380 IAWA Bulletin n.s., Vol. 11 (4), 1990
Table 1. Wood characteristics of Dalbergia paniculata.
Vessel member length (11m)
Vessel member diameter <11m)
8.93
1136.74
127.30*
84.00*
9.42*
130.40*
79l.00*
l.70+
0.90+
l.35+
deviation
48.00
40.00
4.33
72.80
15l.00
0.21
0.22
0.24
Thickness of the bark at the time of initiation of first successive cambium 2.83+ 0.30
Distance from the normal cambium where the phloem cells first dedifferentiate into cambium (mm) 0.85+ 0.16
* = mean of 100 readings; + = mean of 25 readings.
A few samples were also fixed in parafor maldehyde-glutaraldehyde in 0.1 M caco dylate buffer pH 7.1 for one hour at room temperature (20-25°C). The blocks were trimmed to 2 mm 3, gently aspirated and again left in the fresh fixative for 4 hr in a refrigerator (4 ± 1°C). The samples were washed in the same buffer five times at 10 minute intervals. Post-fixation was done in 2% osmium tetroxide in 0.1 M cacodylate buffer pH 7.1 for 10-12 hr at 4 ± 1°C. After five washes in the same buffer, the materials were stained in 2% aqueous uranyl acetate for 30 minutes. After dehydration in acetone series, infiltration and embedding were car ried out in Spurr's low viscosity embedding medium (Spurr 1969). Sections of I-211m thickness were cut on a JB4 Dupont micro tome using glass knives. The sections were spread on 10% acetone, fixed on the slides by heating to 60-80°C over a hot plate and stained with methylene blue-azur II, basic
fuchsin (Humphrey & Pittmann 1974) and toluidine blue 0 (O'Brien & McCully 1981). Materials were prepared for scanning electron microscopy as described earlier (Nair 1987).
For localisation of enzymes, 10 cm long pieces of logs were sealed in polythene bags immediately after cutting and transported in a flask containing ice to the laboratory. Fresh sections were cut on a sliding microtome, and were collected in cold 0.1 M phosphate buffer, pH 7.6 for succinate dehydrogenase (E.C. 1.3.99.1) activity and in 0.1 M acetate buffer pH 4.5 for acid phosphatase (E. C. 3.1.3.2) activity according to the methods suggested by Bancroft (1975). Controls for enzyme reaction were maintained by incubat ing the sections after boiling them in distilled water for 5 minutes or by avoiding the sub strate in the incubating medium.
Measurements of wood elements were made in the sections as well as from macer ated materials. Vulnerability (mean vessel
Nair & Mohan Ram - Cambial variant in Dalbergia paniculata 381
member diameter divided by mean vessel frequency) and mesomorphy indices (vul nerability multiplied with mean vessel length) were calculated according to Carlquist (1977).
Results The wood is pale yellowish white and
heartwood is absent. Broad concentric bands of wood alternate with the narrow layers of soft tissue (Figs. 1, 28d). The dimensions of vessel members and other wood characteris tics are given in Table 1. The wood is diffuse porous (Figs. 1, 2). Axial parenchyma is paratracheal banded (Figs. 1-3). Rays are uniseriate to multi seriate (Fig. 4), mostly ho mocellular and rarely heterocellular (Fig. 5). Vessels are solitary, in radial multiple or rare ly in clusters (Figs. 1, 2). The perforation plates are transverse to oblique (Fig. 6) and simple (Fig. 7). There is a negative correla tion between vessel member length and ves sel member diameter (Fig. 29).
Legends of Figures 1-22:
The inteIVessel pits are bordered, alternate and vestured (Fig. 8). They belong to type 2i recognised by Nair and Mohan Ram (1989). Large vestures are present on the margin of the outer pit apertures, whereas small ves tures are seen towards the pit annulus (Fig. 8). Vestures are present in the inner pit aper tures also (Fig. 9). However, they are absent in the parenchyma cells and fibres. Occa sionally tyloses are obselVed in the vessels (Fig. 11).
The contact cells (parenchyma cells con tiguous with vessels) may also have bordered pits on the wall facing the vessel member (Fig. 10). Certain axial parenchyma cells and fibres are chambered and have large crystals in each chamber (Fig. 12).
Anomalous stem structure The wood contains wavy and anastomos
ing layers of phloem tissue (Figs. 1, 13, 14, 28d). Each ring of phloem is accompanied by
(text continued on page 386)
Fig. 1. Stem portion showing included phloem, x 70. PH = phloem. - Fig. 2. CS of wood, x 70. - Fig. 3. Magnified views of CS of wood, x 130. - Fig. 4. TLS of wood showing uniseriate to multiseriate rays, x 210.
Fig. 5. RLS of wood showing heterocellular rays, x 210. - Fig. 6. TLS showing vessel with extractives, x 110. VL = vessel- Fig. 7. Vessel member with simple perforation plate, x 190. PP = perforation plate. - Fig. 8. SEM showing vestured inteIVessel pits as viewed from outer surface of the vessel, x 2700. - Fig. 9. SEM of inner pit aperture with vestures as viewed from inside the vessel, x 3000. V = vestures. - Fig. 10. Contact cells with half-bordered pits, x 380. - Fig. 11. CS of wood showing tyloses in the vessel, x 210. T = tyloses. - Fig. 12. TLS of wood showing crystals in axial parenchyma and fibre (arrows), x 380.
Fig. 13. CS of stem showing interconnected included phloem layers, x 70. - Fig. 14. CS of stem showing disorganised growth pattern in wood, x 70. - Fig. 15. CS of wood with a portion of included phloem, x 80. - Fig. 16. Cambium associated with the included phloem, x 250. - Fig. 17. CS of phloem showing sieve plate and protein (at arrow), x 510. - PH = phloem; SP = sieve plate.
Figs. 18-20. CS of bark showing dedifferentiation of phloem parenchyma cells into cambium (arrows). - 18: x 140; 19: x 280; 20: x 210. PH = phloem. - Fig. 21. The dedifferentiating cells showing higher SDH activity as compared to neighbouring phloem parenchyma cells (Fig. 22), x 580. - Fig. 22. Phloem parenchyma cells with low SDH activity, x 580.
"0 >
.S Nair & Mohan Ram - Cambial variant in Dalbergia paniculata 383
386 IAWA Bulletin n.s., Vol. 11 1990
Figs. 23-25. CS of wood showing differentiation of xylem internally and phloem externally, from the cambium developed in the secondary phloem. - 23: x 120; 24: x 130; 25: x 70. PH = phloem; VL = vessels; XY = xylem. -- Fig. 26. CS of wood showing pith flecks, x 110. - Fig. 27. LS of pith flecks in the wood, x 230. - PF = pith flecks.
cambium internally (Figs. 15, 16). The pres ence of crushed cells along the periphery of four to six outer rings of included phloem indicate that the cambia accompanying them are active. Concentric rings of sclerenchyma,
interrupted by rays, alternate with the other phloem elements. The phloem consists of well-differentiated sieve elements with sieve plates (Fig. 17) and companion cells. The ini tial secondary growth of the vascular tissue
Figs. 23-25. CS of wood showing differentiation of xylem internally and phloem externally, from the cambium developed in the secondary phloem. - 23: x 120; 24: x 130; 25: x 70. PH = phloem; VL = vessels; XY = xylem. -- Fig. 26. CS of wood showing pith flecks, x 110. - Fig. 27. LS of pith flecks in the wood, x 230. - PF = pith flecks.
cambium internally (Figs. 15, 16). The pres ence of crushed cells along the periphery of four to six outer rings of included phloem indicate that the cambia accompanying them are active. Concentric rings of sclerenchyma,
interrupted by rays, alternate with the other phloem elements. The phloem consists of well-differentiated sieve elements with sieve plates (Fig. 17) and companion cells. The ini tial secondary growth of the vascular tissue
a
b
c
in Da/bergia panicu/ata is normal. However, the concentric layers of phloem and xylem are developed by the activity of successive layers of cambium formed in the secondary phloem. The initiation of cambium is first observed at certain loci in the secondary phloem in branches when their diameter reaches 2-3 cm.
Phloem parenchyma cells located about 850 Ilm away from the cambium start divid ing periclinally to form files of cells simu lating the cambium (Figs. 18-20). These cells show higher succinate dehydrogemise activity (Fig. 21) than the neighbouring secondary phloem cells (Fig. 22). The dedif ferentiation of parenchyma cells extends tan gentially so that a discontinuous cambial ring is formed (Figs. 20, 28a). This newly form ed cambium is bidirectional and produces phloem externally and xylem internally (Figs. 23-25, 28b-d). Thus the phloem present internal to the newly formed xylem becomes included between the xylem layers (Figs. 23-25, 28c, d). The differentiating cambial derivatives indicate a higher acid phospha tase activity than the neighbouring phloem parenchyma cells.
Fig. 28. Diagrammatic represen tation of initiation and func tioning of successive cambia resulting in the formation of con centric layers of phloem alter nating with xylem. CA = cam bium; PH = phloem; X = xylem.
c
lS0--t •
~ • • 100 • • ,
• :.s · , .. • .... SO • • • .8 • • .. .... • • E • .' . • • ... E 60 • • • -'0 r = - 0·5207 • ell
40 - • •• ell II) • e\. • ;.- p (%) = < 0 ·1 . " . •
20 <P = 100 .,. ..
0 I 0 20 40 60 SO 100 120 140 160 180 200
vessel member length in Jlrn
Fig. 29. Scatter diagram showing negative correlation between vessel member length and vessel member diameter.
The newly formed cambial cylinder may be discontinuous because contiguous second ary phloem cells do not invariably become meristematic. Consequently the inner and outer phloem layers become connected by patches of secondary phloem (Fig. 13). In such regions reorientation and readjustments of cells occur during the increase in stem girth (Fig. 14). Irregular patches of paren chyma generally known as pith flecks are also found in the wood (Figs. 26, 27).
Discussion Several modes of cambial variants (ano
malous secondary thickenings) have been reported in dicotyledonous stems and roots (Solereder 1908; Davis 1961; Balfour 1965; Philipson & Ward 1965; Studholme & Phi lipson 1966; Basson & Bierhorst 1967; Esau & Cheadle 1969; Dobbins 1971, 1981; Wheat 1977; Mikesell 1979; Zamski 1979; Bailey 1980. Carlquist 1988). The origin and func tion of cambial variants (anomalous cam-
bium) have been shown to vary in different species. Esau and Cheadle (1969) traced the anomalous secondary growth in Bougain villea to bidirectionally active cambium pro duced from the oldest phloem cells. Cambial variants are frequently reported in lianas (Met calfe & Chalk 1983; Wheeler et al. 1989). The term 'anomalous' is considered as a mis nomer as the included phloem and other cam bial variants are of regular occurrence in the taxa in which they are found (Wheeler et al. 1989). Carlquist (1988) has recognised three major types of cambial variants: 1) successive cambia; 2) a single cambium which produces interxylary phloem and xylem internally; 3) "cambia that begin as single (or in a few cases, multiple and simultaneous) nor mal cambia that produce phloem externally and xylem internally and have or develop a conformation other than cylindrical."
The alternating layers of xylem and phloem produced by successive cambia have been referred to as concentric type of 'included
phloem' or 'interxylary phloem' (Esau 1979; Metcalfe & Chalk 1983; Wheeler et al. 1989). Mikesell and Popham (1976) and Carlquist (1988) suggested to restrict these terms (in cluded phloem and interxylary phloem) to those situations in which a single (normal) cambium alternately produces xylem and phloem internally. We have used the term 'included phloem' in the present study with reservation as each phloem layer is included between the cambium from which it is pro duced and the xylem formed from the next cambium. The classification of cambial vari ants is debatable as it is generally based on topography rather than ontogeny.
Generally in plants characterised by the presence of successive cambia, the primary thickening meristem is formed from cortical parenchyma (Carlquist 1988). The further development of cambia is from the unligni fied parenchyma produced externally by the primary thickening meristem (Carlquist 1988). In the Papilionoideae the anomalous cambium is generally produced from the un lignified cortical parenchyma and pericycle (Solereder 1908). The successive cambia in Dalbergia paniculata are formed by dediffer entiation of phloem parenchyma cells and not from the cortical parenchyma. Each cambium functions normally, producing phloem exter nally and xylem internally.
Cambial variants may have arisen at dif ferent stages in evolution for attaining woodi ness (Metcalfe & Chalk 1983). Usually spe cies with winged or grooved stems produce cortical vascular bundles. The interxylary phloem in Strychnos is believed to have orig inated from ancestors with successive cambia (Joshi 1931). Joshi (1937) proposed that the occurrence of secondary thickening by suc cessive cambia in the Amaranthaceae and Chenopodiaceae is an ancestral character but that this feature has been lost in some species. Carlquist (1988) has suggested that succes sive cambia and interxylary phloem have originated independently.
There are 45 species of Dalbergia in Bang ladesh, Burma, China, India, Malaysia, Paki stan, Sri Lanka and Vietnam (Thothathri 1987). Wood structure of nine trees and five climbers/shrubs have been described by Gamble (1902). The structure of wood has
been described in six timber species by Pear son and Brown (1932). But only Gamble (1902) and Rao and Purkayastha (1972) noted anomalous structure in Dalbergia paniculata. Hill (1901) proposed that D. paniculata might have evolved from a liana and consequently inherited and retained the anomaly. It is necessary to investigate the stem structure of all the Dalbergia species to understand the precise affinities of the species and to draw phylogenetic conclu sions.
Fahn and Shchori (1967) have suggested that successive anastomosing layers of xylem and included phloem are of adaptive value in perennial desert plants. Dobbins and Fisher (1986) have suggested that the living tissue within the xylem is advantageous to lianas because it helps rapid and vigorous regener ation following wounding and girdling. Ano malies such as multiple vascular cylinders, convoluted or disjunct cambia, supernumer ary cambia, wide rays, and abundant xylem parenchyma provide a structurally efficient system for wound healing as the stems of lianas are under high risk to bark injury, vas cular interruption and girdling.
Carlquist (1988) has attempted to correlate cambial anomalies with habit and ecology. He has suggested that the products of succes sive cambia may provide channels for supply of photosynthates to storage structures. In the family Onagraceae a few species that have interxylary phloem show sudden flowering events (Carlquist 1988). It is presumed that to aid rapid formation of flowers and fruits interxylary phloem provides many distribu tion channels for efficient transport of photo synthates. It is also advantageous to plants if the vascular tissues remain functional over a period of years (Carlquist 1988). In Dalber gia paniculata alternating layers of phloem produced by successive cambia remain func tional as the cambium accompanying them also retains its activity.
Carlquist (1977, 1980, 1985, 1988) has proposed that low vulnerability and meso morphy values indicate xeromorphic wood with a capacity to resist water stress in the vessels. In Dalbergia paniculata these values are very high (see Table 1), suggesting their mesomorphic habitat. The relative importance
390
of negative correlation between vessel mem ber length and vessel member diameter in the conduction of water remains to be assessed cri ticall y.
Dalbergia paniculata has been treated as a distinct species in Indian and Burmese floras. In his recent taxonomic revision of the tribe Dalbergieae of the Indian subcontinent, Tho thathri (1987) has concluded that D. panicu lata cannot stand as a distinct species on ac count of its similarity with D. lanceolaria. He considers D. paniculata as a subspecies of D. lanceolaria. Thothathri (1987) has also stated that D. nigrescens described from Burma is con specific with D. paniculata and hence a synonym of D. paniculata.
Anomalous structure is always of diag nostic value because of its restricted occur rence (Metcalfe & Chalk 1983). Several ex amples have been cited by Carlquist (1988) to indicate that the presence of successive cambia is a significant criterion in systemat ics. Absence of successive cambia was one of the reasons for separating Bataceae from the Chenopodiaceae (Carlquist 1978, 1988). Occurrence of successive cambia lead to the removal of Simmondsia from the Buxaceae (Bailey 1980; Cariquist 1982) and Avicennia from the Verbenaceae (Studholme & Philip son 1966; Zamski 1979).
The stem structure is markedly different in D. paniculata and D. lanceolaria. Dalbergia paniculata is characterised by concentric rings of 'included phloem' in the wood, whereas D. lanceolaria does not show this feature. According to Gamble (1902) the wood of D. nigrescens has normal structure.
In our view an important character such as anomalous stem structure should be taken into consideration for taxonomic delimitation. We therefore propose that D. paniculata be retained as a separate species and not be merged with D.lanceolaria.
Acknowledgements This study was supported by the Univer
sity Grants Commission, New Delhi. The access to the scanning electron microscope provided by the Regional Electron Micro scope Facility, All India Institute of Medical Sciences, New Delhi, is gratefully acknowl edged.
IAWA Bulletin n.s., Vol. 11 1990
References Anonymus. 1952. The Wealth of India. A
dictionary of Indian raw materials and industrial products. Vol. 3. Pub!. & In form. Direct., C. S. I. R., Hillside Road, New Delhi, 1-12.
Anonymus. 1979. Tropical legumes: Re sources for the future. National Acad. of Sciences, Washington, D.C.
Bailey, D.C. 1980. Anomalous growth and vegetative anatomy of Simmondsia chi nensis. Amer. J. Bot. 67: 147-161.
Balfour, E. 1965. Anomalous secondary thick ening in Chenopodiaceae, Nyctaginaceae and Amaranthaceae. Phytomorphology 15: 111-122.
Bancroft, J. D. 1975. Histochemical tech niques. Butterworth, London.
Basson, P.W. & D.W. Bierhorst. 1967. An analysis of differential lateral growth in the stem of Bauhinia surinamensis. Bull. Torrey Bot. Club 94: 404-411.
Brandis, D. 1906. Indian trees. A. Constable & Co. Ltd., London.
Cariquist, S. 1977. Wood anatomy of Tre mandraceae; Phylogenetic and ecological implications. Amer.1. Bot. 64: 704-713.
Carlquist, S. 1978. Wood anatomy and rela tionships of Bataceae, Gyrostemonaceae and Stylobasiaceae. Allertonia 5: 297-330.
Carlquist, S. 1980. Further concepts in eco logical wood anatomy, with comments on recent work in wood anatomy and evolu tion. Aliso 9: 499-553.
Carlquist, S. 1982. Wood anatomy of Buxa ceae: correlations with ecology and phy logeny. Flora 172: 463-491.
Carlquist, S. 1985. Wood and stem anatomy of Mesodendraceae: systematic and eco logical conclusions. Brittonia 37: 58-75.
Carlquist, S. 1988. Comparative wood anat omy: systematic, ecological, and evolu tionary aspects of dicotyledon wood. Springer Verlag, Berlin.
Davis, E.L. 1961. Medullary bundles in the genus Dahlia and their possible origin. Amer. J. Bot. 48: 108 -113.
Dobbins, D.R. 1971. Studies on the anoma
lous cambial activity in Doxantha unguis cati (Bignoniaceae) II. A case of differ ential production of secondary tissues. Amer. 1. Bot. 58: 697-705.
Dobbins, D.R. 1981. Anomalous secondary growth in lianas of the Bignoniaceae is correlated with the vascular pattern. Amer. l Bot. 68: 142-144.
Dobbins, D.R. & J.B. Fisher. 1986. Wound responses in girdled stems of lianas. Bot. Gaz. 147: 278-289.
Esau, K. 1979. Phloem. In: Anatomy of the Dicotyledons, Vol. 1 (eds. C.R. Metcalfe & L. Chalk). Clarendon Press, Oxford.
Esau, K. & V.I. Cheadle. 1969. Secondary growth in Bougainvillea. Ann. Bot. 33: 807-819.
Fahn, A. & Y. Shchori. 1967. The organi zation of the secondary conducting tissue in some species of the Chenopodiaceae. Phytomorphology 17: 147-154.
Gamble, lS. 1902. A manual ofIndian tim bers. London.
Hill, T.G. 1901. On the anatomy of the stem of Dalbergia paniculata Roxb. Ann. Bot. 15: 183-186.
Humphrey, C.D. & F.E. Pittman. 1974. A simple methylene blue azur-II-basic fuch sin stain for epoxy embedded tissue sec tions. Stain Technol. 49: 9-15.
Joshi, A.C. 1931. Anomalous secondary thickenings in the stem of Rumex dentatus L. J. Indian Bot. Soc. 10: 209-212.
Joshi, A.C. 1937. Some salient points in the evolution of the secondary vascular cylin der of Amaranthaceae and Chenopodia ceae. Amer. J. Bot. 24: 3-9.
Metcalfe, C.R. & L. Chalk. 1983. Anatomy of the Dicotyledons. Ed. 2. Vol. II. Wood structure and conclusion of the general in troduction. Clarendon Press, Oxford.
Mikesell, J.E. 1979. Anomalous secondary thickening in Phytolacca americana L. (Phy tolaccaceae). Amer. J. Bot. 66: 997-1005.
Mikesell, J.E. & R.H. Popham. 1976. On togeny and correlative relationship of pri mary thickening meristem in four-o'clock plants (Nyctaginaceae) maintained under long and short photoperiods. Amer. J. Bot. 63: 427-437.
Nair, M.N.B. 1987. Occurrence of helical thickenings on the vessel element walls of dicotyledonous woods. Ann. Bot. 60: 23-32.
Nair, M.N.B. & H.Y. Mohan Ram. 1989. Vestured pits and vestured vessel mem ber walls in some Indian dicotyledonous woods. Bot. J. Linn. Soc. 100: 323-336.
O'Brien, T.P. & M.E. McCully. 1981. The study of plant structure. Principles and selected methods. Termarcarphi Pty. Ltd., Melbourne.
O'Brien, T.P., N. Feder & M.E. McCully. 1964. Polychromatic staining of plant cell walls by toluidine blue O. Protoplasrna 59: 367-373.
Pearson, R. S. & H. P. Brown. 1932. Com mercial timbers ofIndia, their distribution, supplies, anatomical structure, physical and mechanical properties and uses. Govt of India, Central Publ. Branch, Calcutta.
Philipson, W.R. & J.M. Ward. 1965. The ontogeny of vascular cambium in the stem of seed plants. BioI. Rev. 40: 534-579.
Rao, R. R. & S. K. Purkayastha. 1972. In dian woods. F. R. I. Press. Forest Res. Institute & Colleges, Dehra Dun.
Sass, lE. 1958. Botanical microtechnique. Iowa State College Press, Ames.
Spurr, A.R. 1969. A low viscosity epoxy resin embedding medium for electron mi croscopy. J. Ultra. Res. 26: 31-43.
Solereder, H. 1908. Systematic anatomy of the dicotyledons (English ed.), Vol. 1. Clarendon Press, Oxford.
Studholme, W.P. & W.R. Philipson. 1966. A comparison of the cambium in two woods with included phloem: Heimerlio dendron brunonianum and Avicennia resi nifera. New Zeal. J. Bot. 4: 355-365.
Thothathri, K. 1987. Taxonomic revision of the tribe Dalbergieae in the Indian subcon tinent. Bot. Surv. India, Calcutta.
Wheat, D. 1977. Successive cambia in the stem of Phytolacca dioica. Amer. l Bot. 64: 1209-1217.
Wheeler, E. A., P. Baas & P. E. Gasson. 1989. IA WA List of microscopic features for hardwood identification. IA WA Bull. n.s. 10: 219-332.
Zamski, E. 1979. The mode of secondary growth and the three dimensiomiJ. structure of the phloem in A vicennia. Bot. Gaz. 140: 67-76.
STRUCTURE OF WOOD AND CAMBIAL VARIANT IN THE STEM OF DALBERGIA PANICULATA ROXB
Summary
Introduction

structure of wood and cambial varianf inthe stem of

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