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Analele tiinifice ale Universitii Al. I. Cuza Iai Tomul LIII, s. II a. Biologie vegetal, 2007

RESEARCHES REGARDING THE MORPHOLOGY, STRUCTURE AND DISTRIBUTION OF LATICIFERS IN THE VEGETATIVE ORGANS OF SOME

EUPHORBIA SPECIES FROM ROMANIAS FLORA

RAMONA CRINA GALE1, C. TOMA1

Abstract: The study deals with the morphology, structure and distribution of laticifers in the vegetative organs of some Euphorbia species from the Romanian flora. Our histo-anatomical researches pointed out the presence of laticifers in all the vegetative organs (root, rhizome, aerial stem, leaf), being well represented in certain parenchymatous tissues and the secondary phloem. In all the analyzed organs, the laticifers of variable size have only primary wall, generally thicker than that of the adjacent cells. In the stem of certain investigated taxa, some laticifers resemble with the secretory ducts, because they are surrounded by two or more concentric layers of meristematic or mechanic cells. Key words: Euphorbia, anatomy, vegetative organs, laticifers

Introduction

Laticifers defined as a specialized cell or a row of cells containing latex (Fahn, 1979) (cf. Rudall, 1987) have been the object of intensive study since the early days of Plant Anatomy (De Bary, 1884; Sperlich, 1939) (cf. Esau, 1965) and among the plants with non-articulated laticifers, Euphorbia (Euphorbiaceae Juss.) is the most studied genus, the fundamental theory of the origin and development of the laticifers being established by Mahlberg & Sabharwal (1967) in Euphorbia marginata. Data concerning the morphology, structure and distribution of laticifers may be found in some ample papers which analyze the anatomy of Euphorbiaceae family (Gaucher, 1902; Metcalfe & Chalk, 1972; Esau, 1965). Until us (Gale & Toma, 2006), the Romanian literature of the field does not include any study exclusively on the morphology, structure and distribution of laticifers in Euphorbia species. The present paper follows our histo-anatomical researches on the laticifers, here being investigated over 8 Euphorbia taxa from the Romanian flora.

Material and Methods

The material used in the study belongs to 8 Euphorbia taxa (E. falcata ssp. acuminata (Lam.) Simonkai, E. maculata L., E. bazargica Prod., E. nicaeensis All., E. carniolica Jacq., E. agraria var. euboea (Halcsy) Hay, E.virgata W. et K., E. peplus L.) collected from different parts of Romania (Dobruja, Moldavia, Transylvania). The material subject to analysis (root, rhizome, aerial stem and leaf) has been fixed and preserved in 70% ethylic alcohol, cross-sectioned with Ranvier microtome and 1 Al. I. Cuza University, Faculty of Biology, Carol I Avenue, 20A, Iassy, 700506 ramonarotari@yahoo.com, ctoma@uaic.ro

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coloured with iodine green and ruthenium red. The surface sections of foliar limb were coloured with iodine green. For the evidence of the latex presence, some transverse sections were coloured with Sudan red solution. The permanent slides have been analyzed with a Novex (Holland) microscope and photographed on the same microscope with a Sanyo digital camera.

Results

Our histo-anatomical investigations pointed out that the laticifers are present in all the vegetative organs of all the analyzed taxa. Laticifers present constant characters (nonarticulated, ramified, polygonal shape in transverse section, cellulosic wall) as well as variable ones (the size, the thick of the walls, the distribution and the frequency in the plant tissues and organs, their presence in some particular structures). In the subterranean vegetative organs with secondary structure, the laticifers are bounded by a uniformly thick cellulosic wall and are localized in the inner part of the cortex and in the secondary phloem, being more numerous in the rhizome (Pl. I, fig. 1) than in the root (Pl. I, fig. 2). In the aerial stem, the laticifers are numerous in the cortex, being well represented in the inner part of the cortical parenchyma around the cordons of sclerenchymatous fibers or even in their thickness (Pl. I, fig. 3). A few laticifers may be observed in the secondary phloem and pith.

In the stem of E. virgata, laticifers are present in some particular structures as follows: 1. structures which look like the secretory ducts - placed in the medulary rays of the secondary xylem and formed by a laticifer surrounded by meristematic cells (Pl. I., fig. 4) or by a layer of parenchymatous cells and more concentric layers of mechanic elements with sclerified and lignified walls (Pl. II, fig. 5); 2. structures localized in the inner part of the cortical parenchyma which comprise a vascular bundle surrounded by laticifers and sclerenchymatous fibers (Pl. II, fig. 6). The stems laticifers have uniformly thick cellulosic walls, except for E. virgata, whose walls are thin; in the stems cortex of E. nicaeensis, the laticifers are grouped, the common wall of two adjacent laticifers presenting centripetal thickenings of buttonhole shape (Pl. II, fig. 7). In the foliar limb (Pl. II, fig. 8), the laticifers are localized in the median nervure (generally, in the close proximity of the phloem of median vascular bundle) as well as in the mesophylle (especially in the lacunary tissue, from where, branches of those penetrate in the palisadic tissue). The diameter of laticifers is variable in the different taxa, in the same taxa, in the same organ and even in the same tissue. In the root, the laticifers are in generally big. In the phloem of the rhizome, two types of laticifers may be observed some of them, which are localized in the outer part of the secondary phloem are very big and the other ones are very small. In the stem, laticifers are in generally big, except for of E. maculata (Pl. III, fig. 9), in which, in the cortex, there are laticifers of big and also very small size. In the foliar limb, the laticifers of the median nervure are bigger than those of the mesophyll.

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In the longitudinal section, the laticifers appear like long, nonarticulated and ramified tubes, (Pl. III, fig. 10). The mode of laticifers branching can be observed through transparency, in the surface section of foliar limb (Pl. III, fig. 11); their branches do not form a network. Generally, after the preparation of the vegetal material, the latex comes out from the sections. Thats way the majority of the laticifers appear as vide cells and only in some of them the latex persists; in the latest ones, after the coloration with Sudan red solution, the latex appears as a red mass of granular type (Pl. III, fig. 12).

Conclusions

In all the (subterranean and aerial) vegetative organs of the analyzed taxa, laticifers may be observed. The laticifers are always nonarticulated and ramified, generally being localized in the cortical parenchyma and in the secondary phloem and rarely in the secondary xylem and pith. The laticifers are numerous in all the vegetative organs, except for the root. The walls of the laticifers are cellulosic, being uniformly thick in the majority of the analyzed taxa, excepting E. virgata, in which they are thin. In E. nicaeensis the common wall of two adjacent laticifers presents centripetal thickenings of buttonhole shape. In E. virgata, the laticifers resemble with to secretory ducts.

BIBLIOGRAPHY

1. ESAU, KATHERINE, 1965 - Plant Anatomy (ed. 2), John Wiley and Sons, New York, London, Sydney, 318- 337 2. FINERAN,, B. A., 1981 - Distribution and organization of non-articulated laticifers in mature tissues of

Poinsettia (Euphorbia pulcherrima Willd.), Ann. Bot., 50: 207-220 3. FINERAN, B. A., 1983 - Differentiation of non-articulated laticifers in Poinsettia (Euphorbia pulcherrima

Willd.), Ann. Bot., 52: 279-293 4. GALE, RAMONA CRINA, TOMA, 2006 Morfologia i distribuia laticiferelor n organele vegetative ale

unor specii de Euphorbia L. din flora Romniei. Lucr. t. Univ. t. agr. i med. vet. Ion Ionescu de la BradIai, ser. Hortic., 1 (49): 21-26

5. GAUCHER, L., 1902 - Recherches anatomiques sur les Euphorbiaces, Ann. des Sci.Nat., sr.8, Bot., 15, 161-309 6. MAHLBERG P. G., SABHARWAL, P. S., 1967 Mitosis in non-articulated laticifer of Euphorbia marginata, Am. J. Bot., 54, 465-472 7. METCALFE, C. R., 1966 - Distribution of latex in the plant kingdom, Notes Jodrell Lab., 3:1-18 8. METCALFE, C. R., CHALK, L., 1972 - Anatomy of the Dicotyledons, II, Clarendon Press, Oxford, 1207-1235 9. NAPP-ZINN, Kl., 1973,1974 - Anatomie des Blattes. II. Angiospermen, In Handbuch der Pflanzenanatomie, Band VIII, A. 1-2., Gebrder Borntraeger, Berlin, Stuttgart 10. RUDALL, PAULA J., 1987, - Laticifers in Euphorbiaceae-a conspectus, Bot. J. Linn. Soc., 94:143-16 11. ERBNESCU-JITARIU, GABRIELA, TOMA, C. 1980 - Morfologia i anatomia plantelor, Ed. did. si ped.,

Bucureti 12. TOMA C., GOSTIN IRINA, 2000 - Histologie vegetal, Ed. Junimea, Iai

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Ramona Crina Gale, C. Toma Plate I Explanation of figures (orig. photos) (scale bars = 50 m) 1- Cross section of the E. nicaeensiss rhizom 2- Cross section of the E. virgata root 3- Cross section of the E. falcata ssp. acuminata aerial stem (upper level) 4 Cross section of the E. virgata aerial stem (upper level)

1 2

3 4

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Ramona Crina Gale, C. Toma Plate II Explanation of figures (orig. photos) (scale bars = 50 m) 5, 6 Cross sections of the E. virgata aerial stem (upper level) 7- Cross section of the E. nicaeensis aerial stem (upper level)

8- Cross section of the E. agraria var. euboea foliar limb

5 6

7 8

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Ramona Crina Gale, C. Toma Plate III Explanation of figures (orig. photos) (scale bars = 50 m) 9- Cross section of the E. maculata aerial stem (middle level) 10- Cross section of the of E. agraria var. euboea aerial stem (upper level)) 11- Surface section of the E. virgata foliar limb (adaxial side 12- Cross section of the E. agraria var. euboea aerial stem (middle level)

9 10

12 11

Analele tiinifice ale Universitii Al. I. Cuza Iai