Electron Microscopy Center, Babes - Bolyai University, Cluj-Napoca

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1 TYPES OF HAIRS OBSERVED ON THE SURFACE OF AERIAL ORGANS EPIDERMIS OF DROSERA ROTUNDIFOLIA L. VITROPLANTLETS Violeta TURCUŞ 1, Dorina CACHIŢĂ-COSMA 1, Constantin CRĂCIUN 2 1 Vasile Goldiş West University, Arad 2 Electron Microscopy Center, Babes - Bolyai University, Cluj-Napoca ABSTRACT. The electron microscope observations, made at the level of the aerial organs surface of D. rotundifolia vitroplantlets, allowed us to emphasize the fact that on their epidermis we found all types of hairs characteristic to the specie, three categories of glandular, cells hairs and, respectively, long pedicle hairs surnamed sensitive, tentacle hairs and short pedicle hairs, and sessile hairs, and, more rarely, a category of tector, cells hairs. It is interesting to notice that, although the D. rotundifolia vitroplantlets benefit from a complex of nutritive substrate, not so much of protein nature (their catabolism being oriented to use as energy source the sacharose present in the culture media), their glandular hairs did not regress as the stomata of the vitroplantlets suffering of hyper hydration. On the miniature leaflets, the glandular hairs have remained, as presence and structure, similar to those existing at Drosera plant in their natural environment. For the first time in scientific literature, we identified the presence of glandular, sessile hairs on the surface of vitro leaflets stipel epidermis, of the floral stems, of the floral peduncle and of the external side of the sepals and petals. Keywords: Drosera rotundifolia, bicolor rosette, stipel, hairs INTRODUCTION Carnivorous plants occupy a special place in the plant biology. The Drosera vitrocultures have an important role in the vegetal biotechnologies. The biomass resulting from Drosera vitroplantlets, cultivated in aseptic conditions in bioreactors serves as raw material for bio prepares processing, used in plant therapy. The Drosera vitroplantlets serve, however, as experimental models in a series of morphogenesis studies, in physiology, biochemistry and molecular biology. The carnivorous plants, in the case of D. rotundifolia vitroplantlets, have a common characteristic, respectively the presence on the epidermises of different types of glandular hairs, macro- or microscopic, with a complex role. In the case of Drosera species, the glandular hairs have several roles. They are called glandular, because part of the constitutive cells secretes protein lyses enzymes. These enzymes, in glandular, tentacle hairs, with sensitive and motility capacities, have the head covered with a viscous liquid, which shines in the sun as dew drops. This aspect gives the generic name of the specie Sky Dew. With this mucus, the tentacle hairs attract the insects and immobilize them. After sensing the presence of an insect on the leaf surface, they get curvy and the tentacles capture the prey. The glandular, tentacle hairs, with the enzymes secreted by the cells situated in the apex region, digest the captured insects proteins and afterward absorb the products resulting from their hydrolysis. Nevertheless, after Matušiková and collaborators (2005), the glandular hairs secrete not only protein lyses enzymes, *Correspondence: Violeta Turcuş, Vasile Goldiş West University, Arad, Department of Plant Biology, violeta_buruiana@yahoo.com Article received: november 2008; published: march 2009 but also chitin lyses, which serve plants to decomposing insects chitin. Part of the simple compounds, resulting from chitin degradation, serve to chitin lyses synthesis, and part makes up a nitrogen source, used by the plant to satisfy the metabolic requirements. Examining, in optic microscopy, the D. rotundifolia vitroplantlets epidermis, just like in the case of the Drosera species grown in nature or in greenhouse (described in 2008 by Stanescu), we identified the presence of three categories of glandular hairs on the leaflets surface. From drawings made with the clear chamber by Stanescu (2008), at the level of adult leaf epidermis of D. capensis L., originating in greenhouse culture, we extracted images of different types of hairs, which we assembled in another hierarchical order, according to their size fact which facilitates their better comparison (Figure 1, described by Stanescu, drawing modified by us). We identified these types of hairs at the level of D. rotundifolia L. leaflets too originating in vitrocultures. Our examinations were complex. They were executed with the optic microscope, the transmission electron microscope, and the scanning electron microscope. The purpose of our research has been to carry out an analysis of the types of hairs existing at the level of D. rotundifolia vitroplantlets organs epidermis, in the conditions of cultivating Drosera propaguls (mini rosettes) on Murashige-Skoog (1962) basis media, with classic growing regulators or with tidiazuron.

2 Turcuş V., Cachiţă-Cosma D., Crăciun C. MATERIALS AND METHODS The D. rotundifolia L. species micro propagation is easily done using propaguls. They consist in leaf mini rosettes (with roots or without). They result from primordial cultures, realized in aseptic regime, from stem apexes inoculated and grown on Murashige- Skoog (MS) (1962) media, using as growing regulators a mixture of beta indole acetic acid (AIA) with bensil adenine (BA), the compounds being added in concentration of 1mg/l each (Cachiţă et al., 1991). From these initial inoculs a colony of mini rosettes is regenerated (Fig. 2). Each mini rosette may be individualized resulting in a unit called propagul, which serves as inoculs in the micro propagation procedures. The Drosera propaguls may be periodically sub cultivated on MS media, with or without growth regulators. To test the Drosera vitrocultures reaction to tidiazuron (TDZ) added to the basis media MS, AIA and BA were substituted with TDZ in concentration of 2,5mg/l. the media recipients were sterilized by autoclavation, at 1.2 atmospheres, for 25 minutes. After media cooling, the recipients (with a diameter of 5cm and height of 10cm) were inoculated with a small Drosera rosette. The cultures growing was made at 22-24ºC, illuminated with fluorescent light, for a period of 16h/day. After three months in vitrocultures, part of the leaflets dissociated from the D. rotundifolia mini rosettes, originating in vitrocultures, were examined with the optic microscope, and the other part were studied with the stereomicroscope or the transmission or scanning electron microscope (Turcuş et al., 2008 a- d). Observations were made on sections in the foil lamina and peduncle. The most representatives images, made with different magnifications, were inserted in the present paper. Small fragments, drawn from vitroleaflets, were stained with glutar aldehyde 2,5% (prepared in phosphate tampon). The plant material was included in Epon 812. The block, after polymerization, was sectioned with the ultra microtome, using a diamond blade which allowed to obtain mixtures, compositions of micron thickness. The semi finite sections were stained for a minute with Epoxy tissue stain solution, warmed up, afterward the sections (on microscopy slides) were washed with distilled water (the water excess was removed with blotting paper). The resulted mixtures, compositions prepares were examined immediately with the optic microscope, or later fixation in Canada balm. RESULTS AND DISCUSSIONS As results of our biometric measurements (Turcuş et al., 2008 c), the number of secretive, tentacle hairs on the D. rotundifolia vitroleaflets epidermis was with 64,1% lower than the number of similar hairs on the superior epidermis of the leaf lamina from Drosera plants grown in greenhouse. On the other hand, on the superior epidermis of the vitroleaflets also, an increased number of secretive, sessile hairs, was identified (plus 24,6%), with respect to the Drosera plants grown in greenhouse. Nevertheless, in the case of inferior epidermis of the vitroleaflets, the number of secretive sessile hairs was decreased with about 6,2%, in the case of greenhouse plants. After examining in microscopy the epidermis surfaces of the vitroplantlets organs, we were surprised to observe different types of hairs in different areas of the organs. As mentioned in the introductive part of this paper, at D. rotundifolia vitroplantlets we identified all the four types of hairs described by Stanescu (2008) and Toma and Stanescu (2008), as being present on the leaf of different Drosera species originating from nature. It is interesting that, despite the fact that D. rotundifolia vitrocultures we worked with originate in a culture initiated by us in 1987 (results published by Cachita et al. in 1991), and maintained in the vitro plant basis of our laboratory operating subcultures at different time intervals (part of the D. rotundifolia vitrocultures being stocked at the Suceava Gene Bank for 4 years, (Turcuş et al., 2008 b), the clones obtained in vitro did not present a regression process of the glandular hairs, as in the case of other species vitroplantlets, to which in hypo hydric stress the stomata gets dysfunctional and even implodes. In most cases, the secretive, tentacle hairs are to be found only on the leaf lamina and the petiole in the vicinity of the insertion region to the leaf lamina (fig. 2 and 3). In the figures 4E and 6A and B there are illustrated electron microscope aspects of the short pedicle glandular hairs, and in the 3D, 4A and D and 6A and C-D figures, representative images of the glandular sessile hairs. Both hairs categories, numbered previously, are characterized by several cells, but they are reduced in size in comparison with the tentacle hairs. The short pedicle glandular hairs are more rare (fig. 6A), than the other two categories and they own in the apex area, secretive, a variable number of cells. The glandular, sessile hairs, are always formed from six cells 2 basal, 2 medial and 2 apical, the apical cells being the secretive cells; the apical cells seem to be fixed with the basis on the medial cells, with the peak free (fig. 6D and F). If the biological role of the glandular, tentacle hairs was already studied, the role of the glandular, short pedicle, hairs and that of the sessile hairs is still little known. It seems that, the mucus coming from the secretive, pedicle hairs, amplify the sessile gland reactions, with role in the absorption of the protein hydrolysis products (Toma and Stănescu, 2008). 152

3 Ttypes of hairs observed on the surface of aerial organs epidermis of Drosera rotundifolia L. vitroplantlets Fig. 1 Epidermal formations identified on the Drosera capensis L., plants leaf lamina, grown on aseptic media, where: A superior epidermal cells; B inferior epidermal cells; C tectorial hairs; D long tentacles, glandular hair; E pedicle glandular hairs; F sessile glandular hairs (Stănescu 2008, modified by us). A superior epidermal cells (s.ep; st stomata; ost osteole) B inferior epidermal cells (i.ep) C tectorial hairs D - long tentacles, glandular hair (s.c secretive cell of glandular, head; trh tracheids) E pedicle glandular hairs F sessile glandular hairs (s.gh) In our examinations of D. rotundifolia vitroplantlets, we observed that the secretive, sessile hairs distribution is on both epidermises of the leaf lamina and on the entire petiole length, and also on the flower stalk. At the same time, for the first time in the scientific literature, we signal the presence of these hairs on floral peduncle, and the sessile hairs on the inferior epidermis of sepals and petals (Turcuş et al., in print). In another paper of our group (Turcuş et al., 2008 b), we identified the presence of secretive sessile hairs on the external side of leaf ebose, regenerated from primordial tissue, at the level of Drosera plantlets vitroleaflets. In the experimental conditions realized by us, with Drosera vitrocultures in which we exchanged the growing regulators from the substrate with tidiazuron, red leaf rosettes appeared (fig. 2 B-D). Crowder et al. (1990) specify that at D. rotundifolia L. the hairs are red due to antocians contained in the vacuole juice. In our vitrocultures experiments with Drosera propaguls, the TDZ presence in the substrate induced the red color in all the leaf lamina tissues. But, it is interesting to notice that, in the same media, from initial propagul a mini rosette of red leaflets is formed, from which, a new rosette is regenerating at some distance, but which holds green leaflets (fig. 2B); other times, from the propagul two red mini rosettes regenerate (fig. 2C), or from a red rosette, in the superior part of the stem on which the rosettes are disposed, green leaflets are formed (fig. 3D). Such a transformation is based on accumulation or conversion of natural stain, originating in vacuoles, from an uncolored form as in the case of antocians in a red compound, reaction described by Cachiţă and Crăciun 153

4 Turcuş V., Cachiţă-Cosma D., Crăciun C. (1990) as being present in the petals of the flowers containing tell compounds in their vacuole juice. We mention that in the case of media on which plant inoculs grow, the media ph is regulated (before autoclavation) at 5.7. Fig. 2 Drosera rotundifolia L. vitroplantlets, cultivated on Murashige-Skoog (1962) basis media (A media missing growing regulators; B-D media with 2,5 mg/l tidiazuron) (where: l leaflet, m culture media; th tentacle hair; r root; fs floral stalk; a red rosette; b green rosette; D bicolor rosette. The results of our research show not only that entire glandular tentacle hairs are red colored (fig. 3A and C; 4C and D), but the short pedicle glandular hair vacuole too (fig. 4Eb and d), or the apical region, secretive, and to red individuals even the epidermis cells and the leaf mesofile have the same color (fig. 8 D-F). If we analyze the general aspect of the glandular tentacle hairs, green colored (fig. 3D-F), from D. rotundifolia vitroleaflets, we observe that in the pedicle we can distinguish chloroplasts, and by transparency in their length, in the central area a transport tissue, lignin can be seen (fig. 3E and D). In some cases (fig. 4B), plastids are less differentiated in chloroplasts, remaining as leucoplasts. At the red glandular tentacle hairs, the pedicle, the apex in the glandular region (fig. 4C and D) and in its cells doesn t have chloroplasts. On the tentacle hairs pedicle length (green or red), on optic microscopy we distinguish glandular, sessile hairs which usually are not colored, nevertheless in their vacuoles, sometimes, we distinguish dark color formations (fig 6Db), which examined in electron microscopy (Turcuş et al., 2008 a), after fixation with glutar aldehyde and 154 osmic acid staining, the vacuole content become electron dense and present phospholipid formations, described by us in the case of antocians. After examining with optical microscope the longitude sections through the glandular tentacle hairs apex (fig. 5Ab and B-D), of red vitroleaflets of Drosera, and also through their pedicle (fig. 5E and F), we distinguish very clearly in the images, a multitude of differences with respect to their histological structures, the red color being translated through aspects observed mostly in the epidermal cells vacuoles, of the hairs pedicle (fig. 5E and F). In the case of secretive apex cells, situated in the apex (fig. 5 A and B), of the tentacle hairs, the vacuom appears compact and dense, as long as on the other side of the apical region we can point out the presence of a dendritic conglomerate, of dot like formations, opposed to the first (fig. 5C and D), in the glandular region of the tentacle hair we distinguish two layers of secretive cells, missing dendritic formations. In the glandular cells layers (secreting mucus and digestive enzymes) a lignin tissue is located a rich (xylem), represented by a cluster of tracheids, which get down along the tentacle

5 Ttypes of hairs observed on the surface of aerial organs epidermis of Drosera rotundifolia L. vitroplantlets hair pedicle and gets connected to the leaf lamina strings, motive for which the tentacle hairs pedicle is considered as an expansion of the leaf lamina (upon Bruce, 1905, from Toma and Stănescu, 2008). As we mentioned previously, on the tentacle hairs tract, we observe the presence of glandular sessile hairs (fig. 3D, 4A and D, 5Fa and b), which contain in the vacuole juice of the apical cells dark color organic materials. Fig. 3 Drosera rotundifolia L. types of leaf (A leafs from nature, with glandular, tentacle hairs, with mucus; B green vitroleaflets and C red vitroleaflets, with secretive, tentacle hairs, with no secretion; D-F detail with glandular, tentacle, green secretive hairs, where: details D entire tentacle hairs; E tentacle hair apex, with glandular area, secretive gas and F tentacle hair basis; abbreviations: l leaf lamina, tr tracheid; lp leaf petiole; thp tentacle hair pedicle; sgh sessile glandular hair; cl chloroplasts). All the cytological elements described by us offer answers for the chemical composition complexity of these cells, which constitute the three types of glandular (secretive) hairs of Drosera, differences which confer the properties of these cells, and the hysto anatomic staining reactions used, especially Epoxytissue-stain, which in the case of red Drosera vitroplantlets gave an exceptional variety of cell types. These studies are pioneer like, and we believe that they should be continued and thoroughly researched, due to their cell relevance and it is special for carnivorous plants. After analyzing the obtained mixtures/compositions from D. rotundifolia (fig. 5A and 8D-f), we inferred/found out a color variability of the glandular hairs cells, especially tentacle, epidermis and leaf mesofile cells. The color difference is due, mainly, to the cell physiological role of these types of cells, the nature of the cytoplasmic and vacuole juice compounds (enzymes, mucus, natural stains, antocians), over which we use the reagent for structures staining. Both in figures 5A and D, and from images illustrated in figures 8D and F, even the cell walls, and the lignin structures on tracheids are colored in red; then, the vacuole content of the epidermis cells (fig. 5A-F and fig. 8D-F), which are fine granulated, of dark blue, emphasize a cell structure different of the one of the secretive cells and of the content of the vacuole juice in the leaf mesofile. In addition, in the assimilating parenchyma of the leaf lamina of vitroleaflets, red colored, the plastids represented by leucoplasts and 155

6 Turcuş V., Cachiţă-Cosma D., Crăciun C. not by chloroplasts have an aspect which has to be studied in the future. In general, according to Salageanu and Peterfi (1972), the glandular part of the tentacle hair of Drosera, has a red color, fact remarked by us too, in some vitrocultures of D. rotundiflora. Hook (2001), in experiments with Drosera cells suspensions, observed the presence of some naphtoquinones, in the collected biomass. In D. rotundifolia suspensions, on modified MS media, the authors remarked the presence of some small multicolor aggregates. At D. capensis, the green aggregates on modified MS media, with no growing regulators had a green color and a content of 0,33% 7-metiljuglone; on another culture media (McC- McCowns upon Lloyd and McCown, 1980), the aggregated contained 1,24% from the respective compound, the vitrocultures showing a rose color, and on modified MS and MC media, inoculs got a dark red color. Fig. 4 Secretive (glandular) hairs, identified through optical microscopy examinations, made at Drosera rotundifolia L. vitroleaflets level (A and D glandular, tentacle hair, observed at leaf level, see A, B, C and D at red leaf level; E short pedicle secretive hairs: a observed on green vitroplantlets and b-d observed on red leaf vitroplantlets, where: ep epidermis; pd pedicle; thp glandular, tentacle hair pedicle; gas tentacle hair glandular zone; pgz short pedicle secretive hair glandular zone; sgh sessile glandular hair). 156

7 Ttypes of hairs observed on the surface of aerial organs epidermis of Drosera rotundifolia L. vitroplantlets Fig. 5 Optical microscopy aspects of semi finite sections through glandular hairs present on the Drosera rotundifolia L. plantules red color vitroleaflets, where: A: a transversal section through the glandular, tentacle hair pedicle; b longitudinal section through the apical region, respectively through the secretive, tentacle hair head, B-D structure details of the tentacle hair head; E-F tissue structure details, observed in transversal sections through the tentacle hair pedicle: a adult; b immature, non differentiated; abbreviations: agc apical glandular cells; tr tracheids; lgc lateral glandular cells; ep epidermal cells; df dendrite formations; sgh sessile glandular hairs; x xylem (fig. A ob. 40; fig. B-E ob. 100). 157

8 Turcuş V., Cachiţă-Cosma D., Crăciun C. Fig. 6 Short pedicle hairs localization (A and B), or sessile hairs localization (C - F), on the green or red Drosera rotundifolia L. vitroplantlets; observations made in optical microscopy, where: A leaf lamina surface at red vitroleaflets; B floral peduncles with short pedicle glandular hairs with sphere liquid secretion; C-F sessile glandular hairs (abbreviations: a leaf lamina; b sessile glandular hair detail; ep epidermis; sgh sessile glandular hair; pgh pedicle glandular hair; thp tentacle hair pedicle). These researches bring forward some additional elements regarding the possible chemical compounds responsible of the red color of the D. rotundifolia leaflets, mostly those grown on MS media with TDZ. The short pedicle glandular hairs (fig. 4E a-d), at green vitroleaflets, may be uncolored (fig 4 Aa), or may be colored in the cell regions which constitutes the pedicle (fig. 4Eb and c), the red stain being present in their vacuole juice. Unlike the short pedicle glandular hairs, presented by Stănescu (2008) in the PhD thesis (fig 1E), referring to D. capensis leafs originating in nature, at D. rotundifolia vitroleaflets (red or green, fig. 4 Eb-d), the pedicle consists of single cell. In exchange, the transversal sections through the tentacle hairs pedicle offer images with cells which are found in different stages of vacuom loading with compounds which fill in completely or partially their content (fig. 5Ea and b), or maintain as dendritic formations (fig. 5C, D and F a and b). These aspects prove the complexity of the glandular apex cells, and of the cells which form the pedicle tissue of the tentacle hair. 158

9 Ttypes of hairs observed on the surface of aerial organs epidermis of Drosera rotundifolia L. vitroplantlets Fig. 7 Sessile glandular hairs, emphasized on Drosera rotundifolia L. vitroplantlets leaflets petiole, (where: ep epidermis; p leaf petiole; sgh sessile glandular hair; th tector hair; stip stipel). CONCLUSIONS Our optical microscopy examinations, on Drosera rotundifolia L. vitroplantlets, emphasized the morphoanatomical and cytological particularities of the epidermis formations of the analyzed organs, the inner cell aspects being different in the vitrocultures with green leaflets, with respect to those with red leaflets; the last ones contain cells with a vacuom which presents in Epoxy-tissue-stain diverse formations, consisting in corpuscle conglomerations, or in spheroid deposits, or which stain in red-blue color the entire vacuole. On the other hand, the cell walls and the lignin get stained in red color. It is undisputable the fact that in red vitroplantlets of Drosera, along the natural stain, endogen antocians, there exists another compound of unknown composition which at cell level changes the microscopic aspect of the examined cells at similar organs originating from green vitroplantlets. In red leaflets, the plastids are represented by leucoplasts, fact which shows that here the photosynthetic processes are absent. Nevertheless, in 159

10 Turcuş V., Cachiţă-Cosma D., Crăciun C. vitrocultures regime the plantlets benefit of the entire nutrient resources needed for their metabolism, as we observed, at a point in the middle of the red mini rosettes grow green leaflets. From a biological point of view, we consider that the cell physiology aspects and molecular biology aspects, which are the basis for Drosera plant function (respectively vitroplantlets), have to be studied to be clarified. It is worth mentioning the fact that, although in vitro, the D. rotundifolia plantlets have a heterotrophic regime (mostly in plantlets with red leaflets), or mixotrophic, they maintain the heterogeneity of the epidermal formations specific for the Drosera adult plants, grown in aseptic media, in the field or in greenhouse. Fig. 8 Optical microscopy aspects of Drosera rotundifolia L. vitroplantlets leaflets, originating in cultures made on Murashige-Skoog (1962) media, A-C missing growing regulators ( vitrocultures with green leafs A-C and D-V), media with 2,5mg/l tidiazuron (vitrocultures with red leafs); (where: ep epidermis; cl chloroplasts; l leucoplasts; ap assimilating parenchyma; sgh sessile glandular hairs; cw cell wall; ost osteole; st stomata; tr tracheids; V vacuole; ob 100). 160

11 Ttypes of hairs observed on the surface of aerial organs epidermis of Drosera rotundifolia L. vitroplantlets REFERENCES Cachiţă, C.D., Crăciun, C., 1990, Ultrastructural studie son some ornamentals. In: Handbook of Plant Cell Culture, vol V., Eds. Evans, P.A. et al, Ed. McGraw Hill Publ. Co. SUA. pp Cachiţă C.D., Zăpârţan M., & Grigoraş S., In vitro cultured Drosera rotundifolia a now biotest, The IVth-Nat. Symp. On Plant Cell and Tissue Culture, Cluj-Napoca, 7-9 dec Ed. Cachiţă C.D., Ed. West Side Computers Braşov, p Crower, A.A., Pearson, M.C., Grubb, P.J., Langlois, P.H., 1990, Drosera L., Biological flora of the British isles. Jaurnal of Ecology, 78, pp Darwin Ch., 1965, Plante insectivore. Editura Acad. R.S.R., Bucureşti (traducere din ediţia engleză Insectivorus plants, Ed. John Murray, London, 1875, de către E. Margulius şi revăzută de V.D. Mârza, N. Botnariuc, I.T. Tarnavschi, I. Fuhn. Hook, I., L. I., 2001, Naphthoquinone contents of in vitro cultured plants and cell suspensions of Dionaea muscipula and Drosera species. Plant Cell, Tissue and Organ Culture 67, Kluwer Academic Publishers, pp Lloyd, G., McCown, B., 1980, Commercially feasible micropropagation of mountain laurel, Kalmia latifolia by use of shoot tip culture. Int. Plant. Prop. Soc. Proc. 30. p Matusikova, I. Salaj, J., Morauccikova, J., Mlynarova, L., Nap, J.P., Libantova, J., 2005, Tentacles of in vitro-grown round leaf sundew (Drosera rotundifolia L.) show induction of chitinase activity upon mimicking the presence of prey. Planta, 222, pp Murashige, T., Skoog, F., 1962, A revised medium for rapid growth and bioassays with tobacco tissue cultures. Physiol. Plant 15, pp Sălăgeanu, N., Peterfi, St., 1972, Fiziologia plantelor, Ed. Did. şi Ped. Bucureşti. Stănescu I., Cercetări citologice şi histoanatomice asupra unor specii de plante carnivore, PhD Thesis, Alexandru Ioan Cuza University Iaşi. Turcuş, V., Cachiţă, C.D., Crăciun, C., Ardelean, A., Barbu-Tudoran,L., Mihali, C., 2008 a, Light and electron microscopy aspects of the glandular sessile hairs from the vitroplantlet leave of Drosera rotundifolia., 14th European Microscopy Congres, 1-5 September 2008, Aachen, Germany, pp Turcuş, V., Constantinovici, D., Cachiţă, C.D., Halmágyi, A., 2008 b, Vitrocultures of Drosera rotundifolia L. preserved in Suceava Gene Bank. Studia Universitas Vasile Goldiş Arad. Ser. Ştiinţele Vieţii, 18, pp Turcuş, V., Cachiţă, C.D., Crăciun, C., Stănescu, I., Toma, C., 2008 c, Studiu comparativ efectuat la nivelul epidermei frunzuliţelor de Drosera rotundifolia L., provenite din vitrocultură sau din seră. Studia Universitas Vasile Goldiş Arad. Ser. Ştiinţele Vieţii, 18, pp Turcuş, V., Stănescu, I., Cachiţă C.D., 2008 d, Aspecte histoanatomice comparative la plantele de Drosera, cultivate in vitro şi din natură. Analele St. Univ. Alex. I. Cuza din Iaşi (Serie nouă) Secţiunea II, a. Biologie Vegetală, tom. LIV, (Supliment), Ed. Univ. Alex.I.Cuza, Iaşi, pp Toma, C., Stănescu, I.E., 2008, Fascinanta lume a plantelor carnivore, Ed. Graphys, Iaşi. 161