Tile Pafaeobofallisf, 28-29: 455-458, 1981.

CAMBIUM IN THE ROOTS OF SUPERBUM (ROXB.) CHEESMAN

T. S. MAHABALE Maharashtra Association for the Cultivation of Science, Law College Road, Pune-411 004, India

ABSTRACT

The plper gives an account of the secondary growth due to cambium noticed in the larger root, of EI/sefe s:/perbIlJn Ch~esman, previously known as Mllsa sllperba Roxb., a member of the Musaeeae found growing wild on the upper slopes and ravines of the Western Ghats - the Sahyadris.

Key-words - Ensefe, MlIsa, Secondary growth, Western Ghats (fndia).

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the lower part of rhizome and run a long distance and the smaller ones arise from ENSETEsome ,SUPERBUMoften growingis a lofty onhand•the slopes and in deep ravines of Western below the growing point and radiate Ghats - the Sahyadris. It belongs to the round the pseudostem. Both are endo• family . In Hooker's Flora of genous and have piliferous layer. The British India (Vol. VI, pp. 261-264), J.G. smaller roots are whitish in colour and Baker described six species of the genus ramify in the vicinity of the trunk. The and two of Lowia from India. Of older roots are larger, flabby and dark these, M. superba Roxb. (= M. textilis grey in colour. Root hairs on them often Grah.) is now considered to be Ensete fall away. A giant massive floral stalk or superbum (Roxb.) Cheesman. The peduncle arises from midst of a rosette grow in Ghats at higher altitudes of of leaves. It is 15-18 cm broad at the base SahYcldris and also in shady places. They close to rhizome, but only 5-10 cm above, grow sporadically, old and young ones as it emerges from the midst of leaves. It together, in the vicinity of running water bears numerous spathaceous bluish red streams. Fully grown plants have huge bracts in the axils of which the flowers are rhizome about 45 cm or more at the borne. The female flowers are mostly in base. But the young plants have a small the basal bracts and the m"lle ones are borne round rhizome hardly 7-10 cm broad. The in the axils of bracts above them. The leaf sheaths are persistent at the base and fem"lle flowers thus preceed the male ones. leave closely set scars on the rhizome. This sequence, however, may vary in Small and large numerous roots grow from different species of Musa. Sometimes there the rhizome radiating in all directions. is even a second row of female flowers with They are the first ones to be activated soon intervening deciduous bracts. The large after the rains and supply water to the floral stalk is often persistent and continues growing point of the rhizome, which proli• for more th'ln a year. The fruits are ferates into activity and forms plant rapidly. 12-15 cm long, more or less triangular, green Larger roots arise from the periphery of and have very little or no pulp. They have ~55 456 THE PALAEO BOTANIST

large, black oblong, subcoriaceous seeds The stele is thus polyarch with exarch which germinate in the vicinity of the old bundles in young roots. There is no cam• parent plant. The plant is propagated bium; but the pericycle and endodermis also by the vegetative buds on the rhizome. are visible. Pericycle becomes multilayered It is perennial. When the mud in the ledges and metaxylem cells in the pith form large of rocks in which it grows dries up, it cavities. They do not have protoxylem remains dormant in the soil during summer rows on them. Their number goes on months. Quite often the soil in ledges of increasing. As the root grows older one precarious slopes is held together by its notices as many as 20-25 large cavities of tuft of roots; when it gives way it is washed metaxylem in the pith which gets slowly down into the valley to the lower heights. compressed or crushed (PI. I, fig. 3). A The genus Musa is an ancient one in few mucilage cells are also seen in the central India and has persisted from the Tertiary pith as well as cortex. With further growth period (Mahabale, 1966). 1t occurs in of the root, endodermis becomes distorted the Deccan I ntertrappean Series at Mohgaon and lateral roots arise from the pericycle Kalan in Madhya Pradesh (Jain, 1963). pushing their way through the endodermis But the present wild species Ensete superbum and cortex. (M. superba) is different from the early As the width increases, parenchyma layers Tertiary species in the Deccan Intertrap• in the cortex also widen and the outer layer peans. In Mysore Ghats the plant grows of cells becomes lacunar by the formation loftier as the rain and humidity there are of schizogenous c::lVities (PI. 1, fig. 1). They greater than those in the Western Ghats are irregular and get crushed later. in Maharashtra. But at both places the About 4-5 parenchymatous layers and peri• plant has small and large roots of a derm lie outside this circle of schizogenous similar kind. The larger roots, as they cavities and the cortex follows schizogenous become older, form periderm and lose root cavity layer. A few layers of parenchyma hair. They appear to give mechanical and periderm constitute the outer cortex. strength to the plant and hold the plant The stele goes on expanding further and in its position. The larger roots appear the structure of the root completely changes to be formed only once in a season but the in the older root. smaller ones are produced continuously. They arise from the pericycle and have a OLDER ROOT structure typical of a monocot root. The outermost layer is generally piliferous layer The structure of older root is shown in or periderm. Both have similar structure PI. I ,figs 2 and 4. It has been observed with lot of variations. Cambium was ob• that the pith is full of 20-30 metaxylem served in the larger roots which form the cavities, due to which hardly any pith is subject matter of this paper. seen in the centre. Primary xylem strands are not visi ble as they are pushed to the SMALLER ROOTS periphery of the stele. Pericycle gets activated and by repeated division becomes Plate 1, figures 1 and 2 illustrate the multilayered (PI. 1, fig. 2). The endo• general structure of this root. In younger dermis is broken and the cortex gets stages the root is having a typical monocot considerably expanded by the formation root structure, having a wide cortex, small of several layers of parenchyma. Phloem pith and stele made up of radially elongated lies outside the cambium forming a con• linear xylem strands. In a medium sized tinuous ring (PI. 1, fig. 4), sometimes even root there are 20-25 xylem strands and 2 rings of cambium are formed (PI. 1, 4-5 medullary bundles in the central pith. fig. 3). The shape, method of division and The medullary bundles have large metaxy• position here is typical of cambium as in the lem cells with hardly a layer or two case of dicot roots. It is a regular feature of of conjunctive parenchyma. In a younger older roots in this plant. Obviously it is root 4-8 large medullary bundles and about due to the irregular secondary growth. 20 primary xylem strands are present. Examples of such irregular cambium There are only 2-3 cells of xylem on a radius are known to occur in some other mono• with exa,rch protoxylem (PI. I, figs 3, 4). cots also, e.g. we had noticed it in the roots MAHABALE - CAMBIUM IN THE ROOTS OF ENSETE SUPERBUM 457

of Aloe barbadel1se and in the suckers of Lugade. Generally new roots are formed a species of Commelil1a. How it develops below the meristem of stem or rhizome, from the meristem of the roots and how immediately after the rains, as the plant it gets connected to the structure of the begins to rejuvenate. older roots is not yet clear and will be des• Further work on the origin of these roots cribed later. It is being investigated by and their relation to stem meristem are Shri Govind Raj Rao and Mrs Shaila under investigation.

REFERENCES

JAIN, R. K. (1963). Studies in Musaceae-J. M/lsa MAHABALE,T. S. (1966). The flora of Deccan: cardiosperma sp. novo a fossil fruit from Presidential Address to Botany Section. 39th the Deccan Intertrappean Series, India. Palaeo• Indian Sci. Congr., Chandigarh. botanist, 12: 45-58.

EXPLANATION OF PLATE

PLATE 1 2. T. S. of a young root magnified to show the Ens3te sliperbllJn Cheesman showing secondary inner cortical region. X 600. 3. T. S. of old root with secondary growth. growth in the root. x 8. 1. T. S. of a young root without secondary growth. 4. A portion of root in fig. 3 enlarged to show x 10. secondary vascular tissues. x 120. 458 THE PALA EOBOTANIST

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