MICROMORPHOLOGICAL AND ANATOMICAL STUDIES ON PETALS OF SOME TURKISH ONOSMA L Bangladesh J. Plant Taxon. 16(2): 157-164, 2009 (December) © 2009 Bangladesh Association of Plant Taxonomists MICROMORPHOLOGICAL AND ANATOMICAL STUDIES ON PETALS OF 11 TURKISH ONOSMA L. (BORAGINACEAE) TAXA ÖZNUR ERGEN AKÇIN1 Department of Biology, Faculty of Science & Arts, Ordu University, Ordu, Turkey. Keywords: Anatomy; Micromorphology; Onosma; Scanning Electron Microscope (SEM). Abstract The petal epidermis and petal anatomy of 11 taxa of Onosma L. were studied using light and scanning electron microscopy. Differences in epidermal patterns were observed on the dorsal surface. Domed epidermal cells and non-papillae epidermal cells were seen on the petal surface. Papillae types were lithops, cone-like, finger-like or skittle-cell type. Areolate and rugose types were observed on the non-papillae surface. Principal anatomical structures of petals were similar. Micromorphological features on dorsal surfaces of petals could be useful for species-level diagnosis along with other selected morphological and micromorphological features. Introduction The genus Onosma L. (Boraginaceae) is represented by more than 100 taxa (97 species) in Turkey (Riedl, 1978; Davis et al., 1988; Riedl et al., 2004; Binzet and Orcan, 2007). This genus is important in the Flora of Turkey because of its large number of species and endemism. Some Onosma species are used as vegetables, folk medicines and dyes. The flowers of some species are eaten as vegetables. Onosma species are grown in garden as ornamental plants because of their beautiful flowers (Oztürk and Ozçelik, 1991). There have been anatomical studies (Akçin and Engin, 2001, 2005; Akçin, 2004), karyological studies (Teppner, 1981, 1988), micromorphological studies (Akçin, 2007; Binzet and Akçin, 2009), and chemical studies (Khajuria and Jain, 1993; Ozgen et al., 2004) of many Onosma species. General corolla structures of O. isauricum Boiss. & Heldr. and O. stenolobum Hausskn. ex H. Riedl were studied with other anatomical features (Akçin and Engin, 2001). Petal morphology has major taxonomic importance in Onosma. Corolla colour, shape and size are used as taxonomic characters in this genus (Riedl, 1978). However, detailed observations of the micromorphology and anatomy of petals of Onosma species are lacking. The use of scanning electron microscopy (SEM) has greatly increased the knowledge of surface features of some vegetative and reproductive organs and has provided valuable taxonomic information (Barthlott, 1984; Stace, 1984; Özcan, 2002). According to Riedl (1978) most of the Turkish representatives of Onosma are poorly- defined and require additional characters for proper identification. In the present study, the anatomical and micromorphological features of petals were studied to provide more detailed information for 11 Onosma taxa. 1 E-mail: oakcin@odu.edu.tr; oakcin@gmail.com 158 AKÇIN Materials and Methods Plant specimens of 11 Onosma taxa were collected from north Anatolia, Turkey during 1997-2000 (Table 1). Voucher specimens are kept at Ordu University Herbarium. Samples for anatomical studies were fixed in 70% alcohol. Cross and surface sections of petals were excised by hand and they were covered with glycerin-gelatin (Vardar, 1987). Their photographs were taken with Nikon FDX-35 microscope. All measurements and observations were made using imaging software (NIS-Elements, Version 3.00 SP5). Epidermal terminology of petals was used as in Reule (1937), Stearn (1973) and Metcalfe and Chalk (1979). For SEM, dried corolla samples were mounted on stubs using double- sided adhesive tape. Samples were coated with 12.5-15 nm of gold. Coated leaves were examined and photographed with a JMS-6400 Scanning Electron Microscope. Table 1. Information on 11 examined Onosma taxa. Taxon Locality O. ambigens Lacaita Çorum: İskilip to Tosya, 450m, Ergen 1008. O. armenum DC. Ankara: Around Çubuk 2. Dam, 1150m, Barbaros 1007. O. bornmuelleri Hausskn. Kastamonu: Ilgaz, 890 m, Akçin 1031. O. bourgaei Boiss. Çankırı: Ilgaz, 2000m, Ergen 1010. O. bracteosum Hausskn. & Bornm. Samsun: Ladik, 950 m, Akçin 1016. O. intertextum Hub.- Mor. Tokat: Around Niksar, 350m, Akçin 1047. O. isauricum Boiss. & Heldr. Amasya: Akdag, 1150 m, Akçin 1015. O. roussaei DC. Samsun: Çakallı, 350 m, Akçin 1049. O. sericeum Willd. Ankara: Around Çubuk 2. Dam, 110m, Barbaros 1008. O. stenolobum Hausskn. ex H. Riedl Amasya: Vermiş village, 1200 m, Akçin 1010. O. tauricum var. tauricum Pallas ex Willd. Kastamonu: Tosya, 900 m, Akçin 1048. Results Morphological characteristics of the epidermal cells in abaxial surface of Onosma such as size, shape and pattern of anticlinal walls are studied. The epidermal cells of Onosma as seen under light micropcope are similar and usually polygonal, isodiametric- polygonal or polygonal-rectangular (Table 2). The pattern of anticlinal cells are straight to curved in all studied species. On dorsal surface, sizes of epidermis cells vary in the range 15-175 × 10-67.5 µm (Table 2). Onosma armenum has the longest cells (123.0± standard error of the mean 4.15 × 39.25±0.98 µm) and O. sericeum has the smallest cells (30±0.85 × 18±0.32 µm) (Table 2, Figs 1-11). Micromorphological properties of petal surfaces show some variations (Tables 2 & 3). Domed epidermal cells and non-papillae epidermal cells are seen on the surface of petals. Surface patterns are generally papillae type in studied species (Figs 13-14, 16-22). Papillae types are lithops, cone-like, finger-like or skittle-cell type (Table 3). Only in O. bourgaei, surface pattern is ribbed-rugose type; here ribbed-rugose structures are MICROMORPHOLOGICAL AND ANATOMICAL STUDIES ON PETALS 159 interconnected with each other (Fig. 15). These structures are generally arranged flexuous or longitudinally and latitudinally. There are a few papillae on the abaxial surface of O. ambigens (Fig. 12). In O. armenum, in contrast, the whole abaxial surface is covered by papillae. Domed epidermal cells are seen on the surface. Cell generally has a small, apically rounded papilla or smooth dome. Apical parts of papillae are generally slanted. Table 2. Petal epidermal features of 11 Onosma taxa studied under light microscope.   Epidermal cell size (Mean±SE*) Taxon Length Width No. of parenchyma layer Shape of epidermal cells O. ambigens 28.8 ± 3.07 22.0 ± 2.13 4-5 Isodiametric-polygonal O. armenum 123.0 ± 4.15 39.3 ± 0.98 5-6 Rectangular O. bornmuelleri 65.0 ± 3.87 48.3 ± 2.88 5-6 Polygonal-rectangular O. bourgaei 74.0 ± 1.05 34.8 ± 2.15 5-6 Rectangular O. bracteosum 31.4 ± 1.49 21.3 ± 1.40 5-6 Isodiametric-polygonal O. intertextum 68.8 ± 3.69 30.3 ± 2.28 4-5 Polygonal-rectangular O. isauricum 31.0 ± 1.66 21.8 ± 1.50 5-7 Rectangular O. roussaei 80.1 ± 0.65 30.4 ± 0.30 4 Rectangular O. sericeum 30.0 ± 0.85 18.0 ± 0.32 5-6 Isodiametric-polygonal O. stenolobum 63.5 ± 2.74 23.3 ± 1.62 4-5 Rectangular O. tauricum var. tauricum 91.3 ± 2.72 34.5 ± 0.64 4 Rectangular *SE = Standard error of the mean. Table 3. Petal epidermal features of 11 Onosma taxa studied under SEM. Taxon Surface pattern Papillae type Anticlinal wall of epidermis Trichome O. ambigens Areolate Rarely present Visible – O. armenum Papillae Lithops type Not visible Simple, porrect-stellate with ornamental wall O. bornmuelleri Papillae Skittle-cell type Not visible – O. bourgaei Ribbed- rugose – Visible Simple with ornamental wall O. bracteosum Papillae Skittle-cell type Not visible Simple with ornamental wall O. intertextum Papillae Skittle-cell type Not visible Simple with ornamental or smooth wall O. isauricum Papillae Cone-like papillae Not visible Simple with ornamental or smooth wall O. roussaei Papillae Skittle-cell type Visible Simple with ornamental wall O. sericeum Papillae Finger-like papillae Not visible Simple, densely arranged with ornamental wall O. stenolobum Papillae Skittle-cell type Visible Simple, short with ornamental wall O. tauricum var. tauricum Papillae Cone-like papillae with silica Not visible Simple with ornamental walls   160 AKÇIN There are also simple or porrect-stellate trichomes with ornamental walls on the epidermal cells (Fig. 13). In O. bracteosum, there are some cavities among papillae. Here cell walls are generally elevated (Fig. 16). In O. intertextum, apical parts of papillae are generally slanted and wider compared with the other skittle-cell types. Trichomes are in general adpressed and densely arranged (Fig. 17). Onosma isauricum generally has domed epidermal cells, usually smooth, and uncommonly non-papillose cells (Fig. 18). The outer periclinal walls of the epidermal cells are slightly bulged in O. roussaei (Fig. 19). In O. sericeum, densely and adpressed trichomes are present on the surface (Fig. 20). Figs 1-11. Epidermal cells on abaxial surface of petals of 11 Onosma taxa under light microscope. 1. O. ambigens; 2. O. armenum; 3. O. bornmuelleri; 4. O. bourgaei; 5. O. bracteosum; 6. O. intertextum; 7. O. isauricum; 8. O. roussaei; 9. O. sericeum; 10. O. stenolobum; 11. O. tauricum var. tauricum. (Bars: Figs 1, 5, 7, 9 = 30 µm; Figs 3, 6, 10 = 60 µm; Figs 4, 8 = 75 µm; Figs 2, 11 = 100 µm). MICROMORPHOLOGICAL AND ANATOMICAL STUDIES ON PETALS 161 Papillae do not cover the whole surface in O. stenolobum. Here boundaries of cells are seen clear (Fig. 21). The epidermal cells of O. tauricum var. tauricum contain silica (Fig. 22). The corolla of all examined species are clavate, cylindrical or campanulate. So they are seen as a lobed ring in transverse section. The principal architecture of all species is similar. The adaxial epidermal cells are larger than abaxial epidermal cells. Both adaxial Figs 12-22. Scanning electron micrographs of petal surface of 11 Onosma taxa. 12. O. ambigens; 13. O. armenum; 14. O. bornmuelleri; 15. O. bourgaei; 16. O. bracteosum; 17. O. intertextum; 18. O. isauricum; 19. O. roussaei; 20. O. sericeum; 21. O. stenolobum; 22. O. tauricum var. tauricum. (Bars: Fig. 12 = 10 µm; Figs 13-22 = 100 µm). 162 AKÇIN and abaxial epidermis are covered with cuticula. Mesophyll consists of oval or cylindrical and multilayered parenchymatic cells (Table 2). Parenchymatic cells have intercellular cavities. Large intercellular cavities are present in O. intertextum, O. isauricum, O. stenolobum and O. tauricum var. tauricum. Vascular bundles are small and consist of several xylem and phloem vessels. Bundle sheath generally surrounds each vascular bundle, and these are small parenchymatic cells (Figs 23-33). Figs 23-33. Cross-sections of petals of 11 Onosma taxa under light microscope. 23. O. ambigens; 24. O. armenum; 25. O. bornmuelleri; 26. O. bourgaei; 27. O. bracteosum; 28. O. intertextum; 29. O. isauricum; 30. O. roussaei; 31. O. sericeum; 32. O. stenolobum; 33. O. tauricum var. tauricum. ad, adaxial epidermis; p, parenchyma; ab, abaxial epidermis; pa, papillae; t, trichome. (Bars: Figs 23, 27 = 20 µm; Figs 26, 30 = 30 µm; Figs 24, 29, 31 = 35 µm; Figs 25, 33 = 40 µm; Figs 28, 32 = 45 µm). MICROMORPHOLOGICAL AND ANATOMICAL STUDIES ON PETALS 163 Discussion Petal morphology and micromorphology are distinctive features in taxa diagnosis (Metcalfe and Chalk, 1979; Özcan, 2002). The present micromorphological and anatomical studies on petals of some selected Onosma species provide more detailed information on these species. It appeared from the study that the morphological features of the petal epidermis under light microscope are constant with no apparent difference among the studied taxa. The pattern of anticlinal cells were straight to curved in all studied species. Nonetheless, some differences were seen in number of parenchymatic cell layers. Akçin and Engin (2001) studied anatomical structure of petals in O. isuricum and O. stenolobum. They reported that epidermal cells are covered with a cuticle layer with undulation. According to this study, epidermis cells in abaxial side were generally papillose, supporting the report of Metcalfe and Chalk (1979). The present study further support these findings. Micromorphological characters of petal surface, on the other hand, showed some variations in studied Onosma taxa. Papillae type was determined as a main type according to the ornamentation of the petal surface. Same surface type was seen in more than one species, but there was more or less difference in every species. The presence of crystals in Boraginaceae is an important feature (Metcalfe and Chalk, 1979). Azizian et al., (2000) reported that crystal (calcium carbonate) present in two forms in Onosma species: a) deposited in cell wall of hairs, and b) located in the base of large hairs. Crystals were clearly seen in the bases of trichomes in O. bracteosum and O. roussaei. According to the present study, micromorphological features of the dorsal surface of petal are important characters and can provide useful information on species-level diagnosis along with other selected morphological and micromorphological features. References Akçin, Ö.E. 2004. Endemik Onosma bornmuelleri Hausskn.’nın morfolojisi, anatomisi ve ekolojisi üzerine bir araştırma. Ecology 13(51): 13-19. (in Turkish) Akçin, Ö.E. 2007. Nutlets micromorphology of some Onosma L. (Boraginaceae) species from Turkey. Biologia 62(6): 684-689. Akçin, Ö.E. and Engin, A. 2001. Onosma isauricum Boiss. & Heldr. and O. stenolobum Hausskn. ex H. Riedl türleri üzerinde karşılaştırmalı morfolojik ve anatomik bir araştırma. The Herb Journal of Systematic Botany 8: 75-95. (in Turkish) Akçin, Ö.E. and Engin, A. 2005. The morphological, anatomical and ecological properties of endemic Onosma bracteosum Hausskn. & Bornm. (Boraginaceae) species. Turk. J. Bot. 29: 317-325. Azizian, D., Khatamsaz, M. and Kasaian, J. 2000. The taxonomic significance of leaf anatomy in the genus Onosma L. (Boraginaceae) in Iran. Iran. Journ. Bot. 8(2): 167-180. Barthlott, W. 1984. Microstructural features of seed surfaces. In: Heywood, V.H. and Moore, D.M. (eds), Current Concept in Plant Taxonomy. Academic Press, London, pp. 95-105. 164 AKÇIN Binzet, R. and Akçin, Ö.E. 2009. Nutlet size, shape and surface ornamentation in 14 Onosma species (Boraginaceae). Acta Bot. Croatica 68(1): 117-126. Binzet, R. and Orcan, N. 2007. A new species of Onosma L. (Boraginaceae) From Southern Turkey. Novon, A Journal for Botanical Nomenculature 17(1): 8-10. Davis, P.H., Mill, R.R. and Tan, K. 1988. Flora of Turkey and the East Aegean Islands. Vol 10, Edinburgh University Press, Edinburgh, pp. 1-590. Khajuria, R.K. and Jain, S.M. 1993. Two new naphthoquinones from the roots of Onosma hispidum. Indian Journal of Chemistry 32: 390-391. Metcalfe, C.R. and Chalk, L. 1979. Anatomy of Dicotyledons. Vol. I. Oxford University Press, London, pp. 1-276. Ozgen, U., Maksut, C., Kazaz, C. and Secen, H. 2004. Naphthoquinones from the roots of Onosma argentatum Hub.-Mor. (Boraginaceae). Turk. J. Chem. 28: 451-454. Özcan, T. 2002. SEM observations on petals and fruits of some Turkish endemic Bupleurum L. (Umbelliferae) species. Botanical Journal of the Linnean Society 138: 441-449. Öztürk, M. and Özçelik, H. 1991. Doğu Anadolu’nun Faydalı Bitkileri. SİSKAV, Ankara, pp. 1-196. (in Turkish) Reule, H. 1937. Vergleichendanatomische Untersuchungen in der Gattung Mesembryanthemum L. Flora 31: 24-400. (in German) Riedl, H. 1978. Onosma. In: Davis, P.H. (ed.), Flora of Turkey and the East Aegean Islands. Vol. 6. Edinburgh University Press, Edinburgh, pp. 326-376. Riedl, H., Bınzet, R. and Orcan, N. 2004. A new species of Onosma (Boraginaceae-Lithospermeae) from Southern Turkey. Edinburgh Journal of Botany 61: 127-130. Stace, C.A. 1984. The taxonomic importance of the leaf surface. In: Heywood, V.H. and Moore D.M. (eds), Current Concepts in Plant Taxonomy. Academic Press, London, pp. 67-94. Stearn, W.T. 1973. Botanical Latin. David & Charles, Newton, Abbot, London, pp. 1-566. Teppner, H. 1981. Karyosystematik von Onosma stellulatum, O. pygmaeum und O. leptanthum (Boraginaceae). Bot. Jahrb. Syst. 102: 297-306. Teppner, H. 1988. Onosma kaheirei spec. nova und O. erectum (Boraginaceae) aus Griechenland. Phyton (Austria). 28: 115-131. Vardar, Y. 1987. Botanikte Preparasyon Tekniği. Ege Üniversitesi, Izmir, pp.1-66. (in Turkish) (Manuscript received on 24 September 2008; revised on 1 July 2009) Akçin, Ö.E. 2007. Nutlets micromorphology of some Onosma L.