Ethnobotanical Leaflets 12: 139-149. 2008.
Epidermal Features and Petiolar Anatomy of Angiopteris evecta (Forst.) Hoffm. (Marattiaceae: Pteridophyta)
Department of Botany,
Epidermal features and petiolar anatomy of a known ethnomedicinal tree fern, Angiopteris evecta, were studied. The stipe receives eleven separate vascular strands from the rhizome which fuse together to form five strands during their upward course.
Key words: Angiopteris evecta, epidermal features, petiolar anatomy, vascular strands.
In the field of vascular anatomy of ferns it is necessary to study the successive stages through which the fern passes during its development. This procedure not only determines the position, interrelationship and structure of the different vascular components of the mature fern but also shows indications of phylogenetic relationship. The epidermal features of pinnae of different Pteridophytes have been studied in the past by Porsch (1905), Kondo (1962), Kondo and Toda (1965), Maroti (1958, 1961), Thurston (1969), Probst (1971) and others. Likewise the stipe characters which too have proved to be of great value (Tansley (1907, 1908), Sinnott (1911), Bower (1914, 1926), Kato (1972), Ogura (1972), Lucansky and White (1974), Linn and Devol (1977, 1978), Khare(1984), etc.) still remain to be studied in case of a number of fern species. With the same view point the epidermal features of pinnae and the exomorphic and internal details of the stipe of Angiopteris evecta have been investigated.
Materials and Methods
Plant materials of Angiopteris evecta for the present epidermal and anatomical
investigations were obtained from the fern house of Botany Department of
Epidermis of pinnae
The venation pattern of lamina is open dichotomous and a prominent mid vein is differentiated in the pinnae. The free ends of the veins are often swollen. Vein areas are devoid of stomata (Fig. 1A). The pinnae of Angiopteris evecta are hypostomatic i.e. having stomata only on the lower surface of the pinnae. Epidermal cells on both the faces of pinnae are sinuous walled and irregularly arranged. Near the margin they are less sinuous. The epidermis shows irregularly scattered groups of short, almost straight walled silica containing cells on their lower side. The number of silica containing cells can vary from 1 to 8. The stomata in pinnae are usually placed in the direction of the veins. Stomata are usually amphicyclic showing a ring of four or more clearly differentiated subsidiary cells are one or more rings of encircling cells. Mature guard cells are kidney shaped or slightly rectangular (Figs. 1B, C). The stomatal characters and frequencies of pinnae are mentioned in tables 1& 2.
Epidermis of petiole
In petiolar portion stomata are irregularly arranged. They are parallel to the surface cells. Each stoma is surrounded by four to six subsidiary cells. One or two cells of silica are also present. Epidermal cells are hexagonal in shape. Mature guard cells are kidney shaped or slightly rectangular (Fig. 1D) (Table 3).
Epidermis of rachis
The structures of epidermis of both primary and secondary rachis are the same. Both the primary and secondary rachis show irregularly arranged stomata. They are also parallel to the surface cells. Each stoma is surrounded by four to six subsidiary cells. One or two cells of silica are also present. Epidermal cells are hexagonal in shape like those of petiole. Mature guard cells are kidney shaped or slightly rectangular (Fig.1E, F).
The pulviuns of Angiopteris evecta is devoid of stomata. It consists of three types of parenchymatous cells. Outer cells are short with flat end walls. Middle region consists of cells which are narrow and elongated with tapering ends and the inner region consists of cells with comparatively thinner walls. Some of the cells contain tannin (Fig. 2H).
Anatomy of petiole
Transverse section of petiole shows single layered epidermis which consists of thin walled cells. The bulk of petiole is composed of ground tissue. It is differentiated into three zones. The outer most zones consist of 3-4 layers of cells which are made up of thin walled parenchymatous cells. The middle zone consists of 3-4 layers of cells made up of thick walled sclerenchymatous cells, being comparatively smaller in size than the cells of outer and inner zone (Plate1A; Fig.3A). Inner zone consists of large, thin walled polygonal cells filled with starch grains. Starch grains are usually large and spherical or oval in shape. The concentrations of these grains are more towards the base of petiole and gradually decrease towards the apex. At the top of the petiole and in the rachis cells are usually devoid of starch grains. Some of the cells of middle and inner zone contain tannin. Eleven widely separated vascular strands are present at the base of the petiole embedded in the parenchymatous ground tissue (Fig. 2G). Each strand has a single layered endodermis. Endodermis is followed by pericycle containing thin walled cells, which are 1-3 layers in thickness. Xylem lies in the centre of the vascular strand. It is plate like with several protoxylem points in exarch condition. Xylem is surrounded by phloem (Plate 1B, C, D). Phloem consists of sieve cells and parenchyma and xylem has simple tracheids of various sizes. Metaxylem tracheids have scalariform and pitted thickening while protoxylem tracheids have annular and spiral thickening (Fig.3B). The vascular strands in the petiole during their upward course gradually fuse with each other (Plates 1E, F; 2A, B, C, D,) and at last become five vascular strands at the tip. During the fusion, first the endodermis and at slightly higher level the pericycle and ultimately the phloem and xylem bundles of the two strands also fuse together. At this stage vascular strand becomes somewhat ‘C’ shaped. (Plate2E, F; Figs.2A, B, C, D, E, F, G; 3C).
Discussions and Results
Angiopteris evecta (Forsk.) Hoffam. is a threatened
species which is included in the endangered categories in the‘Red
Data Book’ of International union for conservation of Nature and Natural
Resources. Because of this it has become necessary to study about all parts
of this plant. The study of the petiolar anatomy
reveals their taxonomic significance. This study also reveals the vascular
supply to the petiole with respect to the number of leaf traces arising from
the stem stele and entering the petiole and whether they anastomoised,
divided or remain unchanged and discussed their bearing on the
interrelationships of various taxa. Although there are
about 100 species of Angiopteris
distributed all over the world, the genus is represented in
Fig. 1. Angiopteris evecta. A. A portion of pinna showing venation; B. A portion of upper epidermis; C. Lower epidermis of pinna showing silica bodies; D. Epidermis of petiole showing contiguous stomata and silica bodies; E. Epidermis of primary rachis showing silica bodies and stomata; and, F. Epidermis of secondary rachis showing silica bodies and stomata.
Fig. 2. Angiopteris evecta. A. Diagrammatic transection of petiole at the base showing five vascular strands; B. Diagrammatic transection of petiole a little above the base showing eight vascular strands; C. Diagrammatic transection of petiole more above the base showing eight vascular strands; D. Diagrammatic transection of petiole at its middle portion showing nine vascular strands; E. Diagrammatic transection of petiole a little above its middle portion showing nine vascular strands; F. Diagrammatic transection of petiole more above its middle portion showing ten vascular strands; G. Diagrammatic transection of petiole at its tip showing eleven vascular strands; and, H. Epidermis of pulvinus showing tannin cells.
Fig. 3. Angiopteris evecta. A . A portion of transection of petiole showing epidermis and ground tissue; B. Structural details of a vascular strand; and, C. Structural details of a C shaped vascular strand.
Plate 1. Angiopteris evecta. A. Transection of a portion of petiole showing epidermal cells and ground cells; and, B-F. Transection of petiole showing different types of structural details of vascular bundle.
Plate 2. Angiopteris evecta. A-F. Transection of petiole showing different types of structural details of vascular bundle.
Table1. Epidermal characters of A. evecta.
Table 2. Size and numbers of stomata and epidermal cells of A. evecta.
Table3. Size of Stomata and epidermal cells of petiole in A. evecta.
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