Home Archive Vol.36, No.4, 2010 Original Papers Histo-Anatomical Researches on the Leaf of Fraxinus excelsior L. Species

Histo-Anatomical Researches on the Leaf of Fraxinus excelsior L. Species

Monica Gabriela Tiţă(1), D. Lupuleasa(1), G. D. Mogoşanu(2)

(1)Faculty of Pharmacy, “Carol Davila” University of Medicine and Pharmacy, Bucharest; (2)Faculty of Pharmacy, University of Medicine and Pharmacy of Craiova

Abstract: In this paper, the authors present the results of the histo-anatomical researches on the leaf of Fraxinus excelsior L. species, from which the medicinal product Fraxini folium is obtained.

Keywords: Fraxinus excelsior, leaf, histo-anatomical researches


Introduction

Fraxinus excelsior L., ash, Oleaceae family, is a tree that reaches a height of 20 m. It is common in lowland and hill forests, but is also grown in parks, on roadsides. The tree trunk is covered with dark rhytidoma. It has black buds and opposite leaves, consisting of 7–15 oddly-pinnate leaflets, sessile, hairless, oval lanceolate, acuminate, toothed, with slightly asymmetrical base. The flowers are arranged in axillary hanging panicles, appearing before the leaves, are polygamous, hermaphrodite or unisexual. The hermaphrodite flower consists of 2–3 stamens and a bicarpellate gynoecium. The fruit is monosamara [1, 2].

The medicinal product Fraxini folium, leaflets obtained from the leaves, contain coumarin deri-vatives (fraxoside, fraxetol, isofraxetol), flavono-sides (rutin), catechic tannin, pentacyclic triter-penic acids (ursolic acid), mannitol, inositol, glucose, organic acids, volatile oil, gums [2–8].

It has diuretic, diaphoretic, laxative, analgesic, anti-inflammatory, and uricosuric properties, used in the treatment of gout, arthritis, arthrosis, rheumatism, lithiasis, into the formula of laxative purgative powder and rheumatic tea [2–9].

In the specialty papers, the histo-anatomical researches on the species are few [10, 11]. This reason and the medicinal value of the plant’s leaf have led us to perform the research.

Material and Methods

The vegetal material is represented by the leaves of F. excelsior trees harvested in May 2009 in Zăval Forest, Dolj County.

In terms of histo-anatomical study, the material passed through the following steps:

(a) Fixation and preservation in 70% alcohol.

(b) Manually sectioning, using hand microtome and botanical razor, with shock pith as support.

(c) Removal of cell content, with sodium hypo-chlorite for 20–35 minutes (depending on material), after which the cross sections were washed with distilled and acetic water.

(d) Staining of cross sections with iodine green and alum carmine red: conventional staining for the histo-anatomical studies of plants. Sections were first stained with iodine green (one minute), washed with 90% alcohol, and then stained with alum carmine red (20 minutes) and consecutively washed with distilled water [12].

(e) Making of permanent preparations: stained sections were mounted on glycerol-gelatine drops, added between the blade and slide.

(f) Valorization of the preparations: colour photographs at NOVEX photon microscope (Holland), with Canon A540 digital camera were made. Scale = 100 μm.

The interpretation of microscopic cross sections was performed in the manner of classic authors [11].

Results and Discussion

The petiole structure (Figure 1)

In cross section, the petiole is nearly circular shape, with flat adaxial side and modified by two latero-adaxial wings (Figure 1, a and b), that delimit a wide and deep ditch. The epidermis has isodiametric cells, with all thickened walls. A thin cuticle, fine ribbed, covers the external wall. Under the epidermis is a zone of two–three layers of collenchyma, whose thickness decreases towards the adaxial wings and increase in their peak. This hypodermic area continues with a meatus-type parenchyma, which bounds the con-ducting fascicles to their abaxial side.

The conducting tissues forming many libero-ligneous fascicles of collateral-type, very close together resulting a tortuous internal ring of xylem at the periphery of which the phloem ring appears interrupted from place to place of many scleren-chyma elements connecting periphloem mecha-nical cords and sclerified-lignified medullary rays.

(a)

(b)

(c)

(d)

Figure 1 – Aspects of cross sections through the petiole of F. excelsior.

Both conducting tissues have, in most part, secondary origin (Figure 1, c and d): the phloem consists of sieve-tubes, annex cells and fewer cells of phloem parenchyma; the xylem contains vessels of various diameters separated by numerous libriform fibres. At the periphery of all conducting fascicles, there is a continuous or discontinuous relatively thin ring of sclerenchyma elements with thick and intense lignified walls, as libriform fibres.

Centre of this stele is occupied by a meatus-type parenchyma, composed of large cells with very thin walls. The two latero-adaxial wings have the mesophyll easily differentiated in one layer of palisade tissue to the adaxial side and multi layered lacunose tissue. In both wings is one small conducting tissue, having only 1–2 sclerenchyma fibres at the phloem periphery.

The leaf’s limb structure (Figure 2)

The epidermis contain cells of irregular outline (Figure 2, a and b), with accentuated curled side walls. The anomocytic-type stomata are located only in the lower epidermis, so the leaf’s limb is hypostomatic. In the lower epidermis are present rare secretory hairs, which appear of circular shape, and numerous unicellular tector hairs rela-tively long and thick wall. Along the ribs, epidermal cells are highly elongated, with curled side walls.

(a)

(b)

Figure 2 – Aspects of cross sections through the leaf’s limb of F. excelsior (a and b).

In cross section, the median rib is prominent at the bottom side (Figure 2, c–e) and a broad and deep ditch is visible at the top.

The structure of the mid rib reminiscent of that of petiole, except that the conducting fascicles from adaxial are distinctive separate by sclerified and lignified rays, and the central parenchyma is lignified. Between lateral ribs, the upper epidermis has larger cells than the lower epidermis.

 (c)

(d)

(e)

(f)

Figure 2 – Aspects of cross sections through the leaf’s limb of F. excelsior (c–f).

The mesophyll is differentiated (Figure 2f) in one layer of palisade tissue on the upper side and multi layer of lacunose tissue on the lower side. Therefore, the leaf’s limb has bifacial heterofacial structure. At the level of lower epidermis are present rare unicellular tector hairs and, from place to place, secretory hairs.

Conclusions

The leaf’s petiole has nearly circular shape, with flat adaxial face having two wings. From outside to inside, in the leaf’s petiole structure it is found: a cuticle-covered epidermis, collenchy-matous hypodermis, meatus-type parenchyma, annular libero-ligneous conducting tissues, in most of the secondary origin, meatus-type medullary parenchyma.

The leaf’s limb has a bifacial heterofacial structure. The anomocytic-type stomata are located only in the lower epidermis, so the leaf’s limb is hypostomatic. On the lower epidermis are present tector and secretory unicellular hairs.

References

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Correspondence Adress: Pharm. Monica Gabriela Tiţă, PhD candidate, Dept. of Pharmaceutical Technology, Faculty of Pharmacy, “Carol Davila” University of Medicine and Pharmacy, 6 Traian Vuia Street, 020956 Bucharest, Romania; e-mail: monica_gabriela2007@yahoo.com


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