Bull 349 BULLETIN OF THE IRAQ NATURAL HISTORY MUSEUM Hassan and Hamdy Bull. Iraq nat. Hist. Mus. (2023) 17 (3): 349-373. https://doi.org/10.26842/binhm.7.2023.17.3.0349 ORIGINAL ARTICLE COMPARATIVE STUDY ON TRICHOMES TYPES OF WILD SPECIES OF SOLANUM L., 1753 (SOLANALES, SOLANACEAE) IN EGYPT AND ITS TAXONOMIC SIGNIFICANCE Rania A. Hassan* and Rim Hamdy **♦ *Botany and Microbiology Department, Faculty of Science, Cairo University, Egypt. **Department of Botany, Faculty of Science, The Herbarium, Cairo University, Giza, Egypt. ♦ Corresponding author: rhamdy@sci.cu.edu.eg Recived Date: 03 November 2022, Accepted Date 09 January 2023, Published Date:20 June 2023 This work is licensed under a Creative Commons Attribution 4.0 International License ABSTRACT Trichomes are extensions of the epidermis, frequently used as diagnostic traits for determining plant species. Solanum L., 1753 is a widespread and taxonomically complex genus. Although the genus Solanum has been the subject of numerous types of research, little attention has been given to the trichomes of the wild species found in Egypt. Therefore, the objective of the current study was to examine trichome types in ten wild Solanum species and assess their taxonomic importance. Using light, scanning electron microscopy and line drawings, indumentum characteristics on the abaxial leaf surface are investigated. The results showed a wide range of variation in trichome density on a 1mm 2 area of leaf blade (sparse, moderate, and dense), nature (glandular or non-glandular, simple or stellate), and structure (number of composing cells in simple non-glandular and glandular stalk and head; the number of radiating rays in stellate hairs). SEM revealed the existence of unique wax structures, including warty granules in addition to flakes. Our observations are consistent with the general characteristics of the subgenus Leptostemonum and the subgenus Solanum. This work provides strong evidence for the separation and interspecific delimitation of the investigated Solanum species using trichome morphology as a significant taxonomic trait. Keywords: Glandular, Non-glandular, Scanning Electron Microscopy, Solanum, Trichomes INTRODUCTION Almost all plant species possess some kind of hair-like epidermal structures; these structures are commonly referred to as trichomes when found on a plant's aerial parts. Trichomes are extensions of the epidermis and are not a part of the plant's vascular system. (Wagner et al., 2004). They have a remarkably wide range of shapes, sizes, and densities within each species. As a result, they are frequently used as diagnostic traits to identify different plant species (Seithe and Sullivan, 1990; van Dam et al., 1999; Reis et al., 2002; Adedeji et al., 2007; Kang et al., 2010; Nurit-Silva and Fatima Agra, 2011; Glas et al., 2012; Munien et al., 2015; Talebi et al., 2018). BULLETIN OF THE IRAQ NATURAL HISTORY MUSEUM Iraq Natural History Research Center & Museum, University of Baghdad https://jnhm.uobaghdad.edu.iq/index.php/BINHM/Home Copyright © Bulletin of the Iraq Natural History Museum Online ISSN: 2311-9799-Print ISSN: 1017-8678 https://doi.org/10.26842/binhm.7.2023.17.3.0349 https://orcid.org/0000-0003-0253-0972 https://orcid.org/0000-0001-7777-693X mailto:rhamdy@sci.cu.edu.eg https://creativecommons.org/licenses/by/4.0/ https://jnhm.uobaghdad.edu.iq/index.php/BINHM/Home 350 BULLETIN OF THE IRAQ NATURAL HISTORY MUSEUM Comparative study on trichomes types Trichomes and epidermal features are the main foliar adaptations in response to specific environments (Li et al., 2011). Generally, trichomes are classified into glandular and non- glandular (Werker, 2000). Both types have been well-documented to protect plants from abiotic pressures like UV radiation, dehydration, extreme temperatures, and herbivore damage (Li et al., 2018; Oksanen, 2018; Kaur and Kariyat, 2020 a, b; Watts and Kariyat, 2021), either by the chemical products in their glandular heads or by their sturdy structure (Karabourniotis et al., 2019; Tang et al., 2020). Trichomes can also decrease leaf wettability and keep the epidermis dry for better gas exchange (Hess and Falk, 1990; Brewer and Smith, 1997; Brewer and Nuñez, 2007; Huangfu et al., 2009). Hayat et al. (2009) and Dipa and Daniel (2011) revealed how foliar trichomes in Acanthaceae and Asteraceae have taxonomic importance. Celep et al. (2011) revealed the importance of Lamium (L., 1753) species' trichome micromorphology. The Family Solanaceae (Juss., 1789) includes 90 genera with about 3000-4000 species distributed in warm and temperate parts of the globe (Knapp et al., 2004). It contains a variety of economically significant vegetable species that are also employed as biological model systems. Solanum (L., 1753) is the largest and most complex genus in the family, with around 1235 species according to POWO (2020), found in tropical and subtropical parts of the Americas, Africa, and Australia (Bohs, 2005; Eskandari et al., 2019). Among the angiosperms, the diversity of Solanum is highly displayed by the morphological plasticity of its vegetative organs (Roe, 1972; Frodin, 2004). This morphological plasticity with the high species number has resulted in a very complex taxonomy of the genus, being a challenge for many taxonomists (Weese and Bohs, 2007). D'Arcy (1972, 1991) divided genus Solanum into seven subgenera: Archaesolanum, Bassovia, Brevantherum, Leptostemonum, Lyciosolanum, Solanum and Petota, with numerous sections and series. Lester et al. (2011) modified D'Arcy’s system of classifying species growing in Africa and divided Solanum into five subgenera: Lyciosolanum, Solanum, Petota, Brevantherum and Leptostemonum. The previous divisions were mainly based on the morphological characters. The trichomes morphology of Solanum species was originally described by Luckwill (1943) and revised later by Channarayappa et al. (1992) then Simmons and Gurr (2005). Eight different types of trichomes were distinguished based on their length, number of stalk cells and basal cells, and the absence or presence of glands. Many studies have used the great diversity of trichomes in Solanum as diagnostic characters for the systematics of the genus, and for specific and infrageneric delimitation (Peiffer et al., 2009; Weinhold and Baldwin, 2011; Burrows et al., 2013; Sampaio et al., 2014; Kariyat et al., 2018). According to Boulos (2002) Solanum species are herbs, shrubs, climbers without tendrils, or small trees. Leaves are alternate, often paired, entire or irregularly toothed or divided. Calyx is campanulate or rotate, with five segments. Corolla is usually rotate, with five lobes. Filaments are very short. Stamens are five in number. Anthers are with apical pore. Ovary 2-loculled, with numerous ovules. Fruit is spherical variously-colored berry, with numerous compressed seeds. 351 BULLETIN OF THE IRAQ NATURAL HISTORY MUSEUM Hassan and Hamdy In Egypt, nine wild Solanum species are present (Boulos, 2009), belong to two subgenera. Subgenus Leptostemonum with six species, namely: S. coagulans (Forssk., 1775), S. elaeagnifolium (Cav., 1795), S. forskalii (Dunal, 1813), S. incanum (L.,1753), S. schimperianum (Hochst., 1841), and S. virginianum (L., 1753). Subgenus Solanum with three species, namely: S. nigrum (L., 1753), S. sinaicum (Boiss., 1849), S. villosum (Mill., 1768). Shaheen et al. (2004) has recorded Solanum diphyllum (L., 1753) as a new species for the Egyptian flora. The later species also belongs to subgenus Solanum. Despite the many studies interested in the micromorphological features of the genus Solanum, little attention was paid to the trichomes of wild species in Egypt. Therefore, the present study aimed to evaluate different trichome types in wild Solanum species and their taxonomic significance. MATERIALS AND METHODS Collection of plant material: Leaf samples for ten studied taxa were chosen from revised authenticated voucher specimens collected from their natural habitats of different localities, or from fresh samples newly collected, preserved and kept in Cairo University Herbarium (CAI). The examined representative species are recorded in Table (1), with the collector, date of collection and their distribution according to the phytogeographical territories of Egypt proposed by El Hadidi (2000). The nomenclature and identification were made according to Linnaeus (1753), Miller (1768), Forsskål (1775), Cavanilles (1795), Dunal (1813), Hochstetter (1841) and Boissier (1849). Preparation of leaves for Light Microscopy (LM): The leaf samples were examined with a Light microscope model number AmScope M150C-I at magnification 40X-1000X. Preparation of leaves for Scanning Electron Microscope (SEM): The samples were examined with a dissecting microscope under diffuse light and then prepared for Scanning Electron Microscope (SEM) studies. The adaxial surfaces of the leaf were fixed using double- sided adhesive tape and then attached to the labelled stubs. Each sample was coated with gold/ palladium in a vacuum evaporator and examined by JEOL-JSM 5500 LV scanning electron microscopy accelerated by a voltage of 20 kV in the SEM Unit at the Regional Center of Mycology, and Biotechnology, Al Azhar University, Cairo, and JEOL JSM 5400 LV scanning electron microscopy accelerated by a voltage of 15 kV at the Electron Microscopy Unit (EMU) in Assiut University, Egypt. Morphological examination: The general characteristics of trichomes were investigated and summarized in Table (2). The trichome density on a 1 mm2 area of leaf blade was determined as sparse (< 300), moderate (300-600), or dense (> 600). Nature (glandular or non-glandular, simple or stellate) and structure (the number of composing cells in simple non-glandular trichomes and glandular stalk and head; the number of radiating rays in stellate hairs) were determined. Length of various trichome types was measured depending on the length of spikes from base to apex in non-glandular trichomes; length of trichome from base to head apex in glandular trichomes; length of lateral rays till the center of central ray in stellate trichomes. Standard deviation was calculated for all measurements. Line drawings were made by the author to clear fine details that are not visible in SEM photos. 352 BULLETIN OF THE IRAQ NATURAL HISTORY MUSEUM Comparative study on trichomes types Terminology: In this work, the terminology of Knapp et al. (2017), and Watts and Kariyat (2021) for trichomes were adopted. Table (1): List of the studied Solanum species examined in the present study along with voucher specimens and fresh collecting materials. No. Species Voucher specimens 1 S. coagulans Forsk. R: Mersa Halaib, 21.1.1929; Gunnar Täckholm s.n. (CAI). 2 S. diphyllum L. Nv: Giza, Research institute of vegetables and aromatic plants, Dokki, 20.4.2017; M. Mahdy s.n. (CAI). 3 S. elaeagnifolium Cav. M: El-Arish, near Garada railway station, 11 km north, 29.41955, L. Boulos s.n. (CAI). 4 S. forskalii Dunal Ge: 23-27.1.1929, collected during the excursion of the Botanical Department of the Egyptian University, M. T. Hefnawy & G. Täckholm s.n. (CAI); Wadi Aak. 27.1.1962, V. Täckholm, M. Kassas, H. Fawzy, F. Shalaby, M. Samy, M.A. Zahran (CAI). 5 S. incanum L. Nn: Kom Ombo, near the temple, 21.1.1927, G. Täckholm s.n. (CAI); Ge: 1932, M. Drar s.n. (CAI). 6 S. nigrum L. Nv: Tal El- Ruba, 18 Km north of Senbellawin, 21-24.7.1977; A. El- Gazzar s.n. (CAI); Cairo University garden, 14.8.2022; R. Hamdy s.n. (CAI). 7 S. schimperianum Hochst. Sudan: Ekwit, Red Sea hills, Gebl Sila, 6.2.1938, M. Drar 371 (CAI). 8 S. sinaicum Boiss. S: Gebel El Deir near the Monastery of St Catherine, 11.5.1956, V. Täckholm s.n. (CAI). 9 S. villosum Mill. Nn: Silwa Bahri, between Kom Ombo and Edfu, 29.6.1967, M.N.El Hadidi & S.I.Ghabbour s.n. (CAI); Nv: Giza: Faculty of Pharmacy Farm, 4. 2014, M. Mahdy s.n. (CAI); Cairo University garden, 24.10.2022; R. Hamdy s.n. (CAI). 10 S. virginianum L. Sudan: Kordofan, Melbeis, 1875; J.-H. Zarb 404 (CAI). RESULTS AND DISCUSSION Trichomes play an important role in plant defense against various biotic and abiotic stresses (Radcliffe, 1982; Radcliffe and Ragsdale, 2002; Pompon et al., 2010). Many studies have represented the trichomes features on epidermal surfaces as being important classification criteria (Rollins and Shaw, 1973; Adedeji et al., 2007), and have long been used in delimiting species, genera, or families (Cantino, 1990; Benitez and Ferrartto, 2009; Hayat et al., 2009; Shaheen et al., 2009; Ajmal and Al Hemaid, 2011; Saheed and Illoh, 2010; Kemka and Nwachukwu, 2011; Adedeji, 2012; Al Sheef et al., 2013; Khosroshahi and Salmaki, 2019). The trichomes were employed by Rao and Ramayya (1977) to distinguish the two Malvastrum (A. Gray, 1849) species in India. Similarly, the structure, ontogeny, and taxonomic importance of trichomes in the family Cucurbitaceae were described by Inamdar et al. (1990). Moreover, the species of Leucas (R. Br., 1810) from Asia and Africa were divided by Mannethody and Purayidathkandy (2018) by using the differences in capitate trichomes. 353 BULLETIN OF THE IRAQ NATURAL HISTORY MUSEUM Hassan and Hamdy The morphology of the trichomes in Solanum has taxonomic significance at both the generic and specific levels (Seithe, 1962, 1979; Roe, 1972; Mosaferi et al., 2021; Kumar et al., 2017; Watts and Kariyat, 2021). The different types of trichomes formerly described by Luckwill (1943) and revised by Channarayappa et al. (1992) aimed mainly to limit the diversity of trichomes to glandular and non-glandular types. Although, this fundamental classification is unable to account for the vast differences between subtypes of glandular and non-glandular trichomes (Watts and Kariyat, 2021). In this work, the trichome morphology on the abaxial surface of ten wild Solanum species in Egypt has been well characterized using a scanning Electron microscope (SEM). The micromorphological investigation of the studied species showed a wide range of variations in trichome density, nature, and structure (Tab. 2). Both non-glandular and glandular trichomes were evidenced in the studied species. The non-glandular trichomes were simple or stellate with a varied number of rays, while the number of cells in the stalk and head of the glandular trichomes varied. The genus Solanum and other Solanaceae members are characterized by the presence of glandular trichomes except for Nicotiana glauca (Graham, 1828) and Solandra nitida (Sw., 1787) as reported by Maiti et al. (2002). Among the studied species, the non-glandular stellate trichomes were found in S. coagulans (Pl. 1A, 1B), S. elaeagnifolium (Pl. 1G, 1H), S. forskalii (Pl. 1J, 1K), S. incanum (Pl. 2A), S. schimperianum (Pl. 2J) and S. virginianum (Pl. 4D, 4E), while absent in S. diphyllum, S. nigrum, S. sinaicum and S. villosum. These results agree with the general characteristics of subgenus Leptostemonum (Dunal) Bitt. (S. coagulans; S. elaeagnifolium; S. forskalii; S. incanum; S. schimperianum; S. virginianum) which characterizes by the presence of stellate hairs and those of subgenus Solanum (L.) Seithe (S. diphyllum, S. nigrum, S. sinaicum, and S. villosum) which characterizes by the absence of stellate hairs (Edmonds, 1982; Seithe and Anderson, 1982; Bohs, 1994). However, the density, number, and nature of radiating rays exhibit significant variations among these taxa (Tab. 2). The stellate trichomes appear dense forming mat-like covering over the leaf surface in S. coagulans (Pl. 1B), S. elaeagnifolium (Pl. 1G), S. forskalii (Pl. 1J) and S. incanum (Pl. 2A), moderate in S. virginianum (Pl. 4C), while sparse in S. schimperianum (Pl. 2J). The dense mat of stellate trichomes acts as a bio-shield against the stresses (Wagner et al., 2004). 354 BULLETIN OF THE IRAQ NATURAL HISTORY MUSEUM Comparative study on trichomes types Table (2): Detailed micromorphological characterization of trichomes on the abaxial leaf surface of the studied Solanum species. Species Trichome types Line Drawing Trichome density (avg. number / cm2)* Trichome Length (μm) ± st. deviation S. coagulans (Pl. 1A-C) 1. Non-glandular, porrect-stellate, multiradiate, sessile/ stalked, with 6-8 (9) subulate rays and short central ray. dense 50-205 ± 50.04 2. Glandular with unicellular stalk and unicellular globular head. moderate no data 3. Glandular with unicellular stalk and bicellular globular head. moderate no data 4. Glandular with unicellular stalk and multicellular globular head. moderate no data S. diphyllum (Pl. 1D-F) 1. Glandular with unicellular stalk and unicellular globular head. sparse no data 2. Glandular with unicellular stalk and large multicellular doliform head. sparse 19-68 ± 24.41 3. Non-glandular, simple multicellular, with obtuse apex. sparse 75-85 ± 7.07 355 BULLETIN OF THE IRAQ NATURAL HISTORY MUSEUM Hassan and Hamdy S. elaeagnifolium (Pl. 1G-I) 1. Non-glandular, porrect-stellate, multiradiate, multiangulate, lepidote, sessile/ stalked, with 13- 16 subulate rays and short central ray. dense 100-284 ± 58.69 S. forskalii (Pl. 1J-L) 1. Non-glandular, porrect-stellate, multiradiate, sessile/ stalked, with 4-8 subulate rays and long-very long central ray. dense 175-425 ± 92.52 2. Non-glandular, simple unicellular with acute apex. sparse no data 3. Glandular with unicellular stalk and multicellular globular head. sparse no data S. incanum (Pl. 2A-B) 1. Non-glandular, porrect-stellate, multiradiate, multiangulate, sessile/ stalked, with 8 subulate rays and a long central ray. dense 180-400 ± 73.28 S. nigrum (Pl. 2C-I) 1. Non-glandular, simple unicellular with acute apex. sparse no data 2. Non-glandular, simple bicellular, with large basal cell and shrivelled apical one. moderate 113-138 ± 17.68 3. Non-glandular, simple multicellular (3-4- celled), commonly falcate with acute apex. dense 163-188 ± 17.67 356 BULLETIN OF THE IRAQ NATURAL HISTORY MUSEUM Comparative study on trichomes types 4. Non-glandular, simple multicellular (3-4- celled) with hooked apex. moderate 88-94 ± 4.24 5. Non-glandular, simple multicellular (3-4- celled) with obtuse apex. dense 138-150 ± 8.48 6. Glandular with unicellular stalk and large unicellular globular striated head. moderate 57-64 ± 5.05 7. Glandular with unicellular stalk and large bicellular globular head. moderate 35-39 ± 2.73 8. Glandular with unicellular stalk and large multicellular globular head. sparse 55-69 ± 9.89 S. schimperianum (Pl. 2J-L, Pl. 3A-C) 1. Non-glandular, porrect-stellate, multiradiate, sessile with 5-6 subulate rays and short central ray. sparse 100-163 ± 25.92 2. Glandular with bicellular stalk and unicellular globular head. moderate 70-75 ± 3.53 3. Glandular with bicellular stalk and tetracellular globular head. sparse 77-88 ± 7.78 357 BULLETIN OF THE IRAQ NATURAL HISTORY MUSEUM Hassan and Hamdy 4. Glandular with bicellular stalk and multicellular clavate head. moderate 65-112 ± 33.25 5. Glandular with no stalk and unicellular clavate head. sparse 37-44 ± 4.95 S. sinaicum (Pl. 3D-G) 1. Non-glandular, simple, multicellular (3-5- celled), commonly falcate with acute apex. sparse no data 2. Glandular with unicellular stalk and multicellular clavate head. sparse no data 3. Glandular with multicellular [(3)4-5-celled] stalk and small unicellular clavate head. dense 60-550 ± 190.54 4. Glandular with multicellular bifurcated stalk and small unicellular globular head. moderate no data S. villosum (Pl. 3H-L, Pl. 4A-B) 1. Non-glandular simple, with multicellular stalk (3-4-celled) and acute apex. moderate 150-415 ± 90.13 2. Non-glandular simple, with multicellular stalk (3-4-celled) and hooked apex. sparse 180-200 ± 14.14 3. Non-glandular simple, with multicellular stalk (3-4-celled) and obtuse apex. moderate 165-200 ± 24.74 358 BULLETIN OF THE IRAQ NATURAL HISTORY MUSEUM Comparative study on trichomes types 4. Glandular with unicellular stalk and unicellular globular head. sparse no data 5. Glandular with unicellular stalk and multicellular clavate head. sparse 40-57 ± 7.59 6. Glandular with multicellular (3-6- celled) stalk and small unicellular clavate head. moderate 40-315 ± 131.05 S. virginianum (Pl. 4C-I) 1. Non-glandular, porrect-stellate, multiradiate, multiangulate, sessile/ stalked, with 6-8 subulate rays and short central ray. dense 50-150 ± 33.07 2. Glandular with unicellular stalk and unicellular globular head. sparse 38-55 ± 12.37 3. Glandular with unicellular stalk and tetracellular globular head. sparse 63-88 ± 17.67 4. Glandular with unicellular stalk and multicellular clavate head. sparse 35-40 ± 3.53 * < 300= sparse; 300-600: moderate; > 600: dense; ‘no data’ means difficulty of measuring length. The number of radiating rays ranges from 5 in S. schimperianum up to 16 in S. elaeagnifolium (Tab. 2). The shape of radiating rays is subulate in all the previous species, however, they appear slender in S. coagulans (Pl. 1A), S. elaeagnifolium (Pl. 1G), S. forskalii (Pl. 1J), and S. incanum (Pl. 2A), and wide in S. schimperianum (Pl. 2J) and S. virginianum 359 BULLETIN OF THE IRAQ NATURAL HISTORY MUSEUM Hassan and Hamdy (Pl. 4D, 4E). Solanum elaeagnifolium is characterized by the lepidote shape of stellate trichomes (Pl. 1H) in which the lateral rays appear fused at the base. This is the same result as Knapp et al. (2017). The longest radiating rays are in S. forskalii and S. incanum, while the shortest is in S. virginianum (Tab. 2). Solanum forskalii and S. incanum are characterized by having long central ray (Pl. 1J, 2A) which appears short in the other species. Wax orientations patterns are seen on the trichomes in SEM, characterized by their irregular, mostly isodiametric, rounded warty granules described as verrucate sculptures on all the studied species (Pl. 1C, I, L; Pl. 2B, F; Pl. 3G; Pl. 4B, F), except S. schimperianum which is found to be distinct from the rest of the species by having a striate sculpture of central ray (Pl. 2 K). The distribution of these granules varied from moderate in most of the studied species to sparse in S. forskalii, S. sinaicum and S. villosum. These granules were mixed with flakes in S. elaeagnifolium (Pl. 1I). The latter was confirmed by Burrows et al. (2013). The simple non-glandular unicellular trichomes are traced in S. nigrum, and S. forskalii (Tab. 2). However, S. nigrum is distinct by the presence of non-glandular bicellular type (Pl. 2I; Tab. 2). Mohamed and El-Gohary (2007) and Ewas and Ghaly (2019) support our results. The simple non-glandular multicellular trichomes with acute apex and verrucate sculpture are found in S. nigrum (Pl. 2E), S. sinaicum, and S. villosum (Pl. 3I). These findings agree with Mohamed and El-Gohary (2007). While the multicellular type with hooked or obtuse apexes is found in S. nigrum (Pl. 2C) and S. villosum only (Pl. 3J; Tab. 2). The study of Mohamed and El- Gohary (2007) have traced hooked trichomes in S. villosum only. Rebora et al. (2020) reported the important role of hooked non-glandular trichomes in the entrapment of pests as in Phaseolus vulgaris (L. 1753). The glandular trichomes in the studied Solanum species are found in S. coagulans (Pl. 1A), S. diphyllum (Pl. 1D, E), S. forskalii (Tab. 2), S. nigrum (Pl. 2G, H), S. schimperianum (Pl. 2L; Pl. 3A, B, C), S. sinaicum (Pl. 3E, F), S. villosum (Pl. 3L, Pl. 4A) and S. virginianum (Pl. 4G, H, I). This result agrees with Edmonds (1982), Adedeji et al. (2007), Mohamed and El- Gohary (2007), Hamada et al. (2010), Bello et al. (2017) and Ogundola et al. (2017). The glandular trichomes are dense in S. sinaicum (Pl. 3A), while sparse to moderately distribute in the other species (Tab. 2). Previous studies reported the function of leaf trichome density as a defensive trait against herbivory among solanaceous species (van Dam and Hare, 1998). The glandular unicellular type is found in all the above species except S. schimperianum which has either a bicellular stalk or no stalk (Tab. 2) as found by Mohamed and El-Gohary (2007). The glandular multicellular type is found in Solanum sinaicum (Pl. 3D, E) and S. villosum (Pl. 4A). Mohamed and El-Gohary (2007) support our findings. An additional spot character is the presence of a glandular multicellular bifurcated type in S. sinaicum but absent in all the studied species (Tab. 2). The number of cells and shape of the glandular head vary among the studied species. The unicellular globular head with smooth sculpture is found in S. coagulans (Pl. 1A), S. 360 BULLETIN OF THE IRAQ NATURAL HISTORY MUSEUM Comparative study on trichomes types diphyllum (Pl. 1D), S. schimperianum (Pl. 2L), S. villosum (Pl. 3K) and S. virginianum (Pl. 4G; Tab. 2). While the unicellular globular head appears in S. nigrum with striated sculpture (Pl. 2G; Tab. 2). On the other hand, the unicellular clavate head is found in S. schimperianum (Pl. 3C), S. sinaicum (Pl. 3F), and S. villosum (Pl. 4A). Solanum coagulans and S. nigrum are distinguished by the presence of large bicellular globular head which is absent in the other species (Tab. 2). Adedeji et al. (2007) and Mohamed and El-Gohary (2007) agree with this result in S. nigrum. Additionally, S. schimperianum, and S. virginianum show the presence of a tetracellular globular head (Tab. 2), while the multicellular head is traced in all the above species as reported by Mohamed and El-Gohary (2007). Although, it appears globular in S. coagulans, S. forskalii and S. nigrum, clavate in S. schimperianum, S. sinaicum, S. villosum, and S. virginianum, while appears doliform in S. diphyllum (Tab. 2). 361 BULLETIN OF THE IRAQ NATURAL HISTORY MUSEUM Hassan and Hamdy Plate (1): Scanning Electron Micrographs showing trichomes on the abaxial leaf surface of the studied Solanum species; (A-C) S. coagulans: (A, B) non-glandular porrect- stellate multiradiate hairs with 6-8 subulate rays and short central ray, (A) showing small glandular hairs with uni-, bi-, and multicellular heads, (C) magnified part showing verrucate sculpture of central ray; (D-F) S. diphyllum: (D) glandular hair with unicellular stalk and unicellular head, (E) glandular hair with unicellular stalk and large multicellular doliform head, (F) non-glandular multicellular uniseriate hair; (G-I) S. elaeagnifolium: (G) non-glandular porrect-stellate multiradiate lepidote hairs with 13-16 subulate rays and short central ray, (H) lepidote hair with lateral rays fused at the base, (I) magnified part showing verrucate sculpture of central ray; (J-L) S. forskalii: (J, K) non-glandular porrect-stellate multiradiate hairs with 4-7 subulate rays and long central ray, (L) magnified part showing verrucate sculpture of central ray. 362 BULLETIN OF THE IRAQ NATURAL HISTORY MUSEUM Comparative study on trichomes types Plate (2): Scanning Electron Micrographs showing trichomes on abaxial leaf surface of the studied Solanum species; (A-B) S. incanum: non-glandular porrect-stellate multiradiate hairs with 8 subulate rays and long central ray, (B) magnified part showing verrucate sculpture of central ray; (C-I) S. nigrum: (C) simple multicellular non-glandular hairs with acute, hooked and obtuse apex, (D) simple multicellular non-glandular hairs with normal base cell and shriveled middle cell, (E) simple multicellular non-glandular hairs with acute or obtuse apex, (F) magnified part showing verrucate sculpture, (G) glandular hairs with unicellular stalk and unicellular striated and multicellular smooth globular heads, (H) glandular hairs with unicellular stalk and uni-, bi- and multicellular smooth head, (I) simple bicellular non-glandular hairs with large normal base cell; (J-L) S. schimperianum: (J) porrect-stellate multiradiate non-glandular hairs with 5-6 subulate rays and short central ray, (K) magnified part showing striate sculpture of central ray, (L) glandular hair with bicellular stalk and unicellular head. 363 BULLETIN OF THE IRAQ NATURAL HISTORY MUSEUM Hassan and Hamdy Plate (3): Scanning Electron Micrographs showing trichomes on abaxial leaf surface of the studied Solanum species; (A-C) S. schimperianum: (A) glandular hair with bicellular stalk and tetracellular clavate head, (B) glandular hair with bicellular stalk and multicellular clavate head,(C) glandular hair with no stalk and unicellular clavate head; (D-G) S. sinaicum: (D) unicellular and multicellular glandular hairs, (E) small glandular hairs with unicellular stalk and multicellular heads, (F) multicellular glandular hair with small unicellular clavate head, (G) magnified part showing verrucate sculpture; (H-L) S. villosum: (H) small glandular unicellular and long non-glandular multicellular hairs, (I) simple non-glandular multicellular hair with acute apex, (J) simple non-glandular multicellular hairs with hooked and obtuse apex, (K) small glandular hair with unicellular stalk and unicellular head, (L) small glandular hair with unicellular stalk and multicellular shriveled head. 364 BULLETIN OF THE IRAQ NATURAL HISTORY MUSEUM Comparative study on trichomes types Plate (4): Scanning Electron Micrographs showing trichomes on abaxial leaf surface of the studied Solanum species; (A-B) S. villosum: (A) multicellular glandular hair with small unicellular clavate head, (B) magnified part showing verrucate sculpture; (C- I) S. virginianum: (C-E) porrect-stellate multiradiate non-glandular hairs with 6-8 subulate rays and short central ray along with small glandular hairs, (F) magnified part showing verrucate sculpture of central ray, (G) glandular hair with unicellular stalk and unicellular globular head, (L) glandular hair with unicellular stalk and tetracellular head, (I) glandular hair with unicellular stalk and multicellular head. CONCLUSIONS Despite some overlapping trichomes characters, which reflect the relative closeness of the species in this genus, this work highlights the general characters that specify the studied species and greatly supports the use of trichome morphology as valuable taxonomic features for the separation and interspecific delimitation of the studied Solanum species. CONFLICT OF INTEREST STATEMENT The authors have no conflicts of interest to declare. LITERATURE CITED Adedeji, O. 2012. Systematic significance of trichomes and foliar epidermal morphology in the species of Stachytarpheta Vahl (Verbenaceae) from Nigeria. Thaiszia Journal of Botany, 22(1): 1-31. [Click here ] https://www.upjs.sk/public/media/7803/001-031-adedeji-upr.pdf 365 BULLETIN OF THE IRAQ NATURAL HISTORY MUSEUM Hassan and Hamdy Adedeji, O., Ajuwon, O. Y. and Babawale, O. 2007. Foliar epidermal studies, organographic distribution and taxonomic importance of trichomes in the family Solanaceae. 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Solanum L., 1773 جنس البرية من في األنواع ألنواع الشعيراتدراسة مقارنة (Solanalis, Solanaceae في مصر وأهميتها )التصنيفية رانيا حسن* و ريم حمدي** ، كلية العلوم، جامعة القاهرة، مصر.املجهرية* قسم النبات واألحياء ، جامعة القاهرة، الجيزة، مصر.النباتي م النبات، كلية العلوم، املعشب** قس 20/6/2023، تأريخ النشر: 9/1/2023القبول: ، تأريخ 3/11/2022تأريخ االستالم: الخالصة الشعيرات هي امتداد لخاليا البشرة وغالًبا ما تستخدم كخصائص تشخيصية لتحديد األنواع ، الفصيلة الباذنجانية Solanaceaeرتبة الباذنجانيات Solanum L., 1753 . جنسالنباتية Solanoideae هذا على الرغم من أن ؛معقد من الناحية التصنيفية هو جنس واسع االنتشار و كان موضو جنسال ً للعديد من األبحاث ، فقد تم إيالء القليل من االهتمام لترايخومات عا صر. لذلك ، كان الهدف من الدراسة الحالية هو فحص أنواعاألنواع البرية املوجودة في م تقييم أهميتها التصنيفية بإستخدام املجهر و Solanumفي عشرة أنواع برية لجنس الشعيرات مسح تم ؛اإللكتروني الخفيف واملسح الضوئي والتحليل اإلحصائي والرسومات الخطية أظهرت النتائج حورية لألنواع املدروسة.الخصائص التعويضية الدقيقة على سطح الورقة امل م لم 1مدى واسع من التباين في كثافة الشعر الثالثي على مساحة 2 من نصل األوراق )متناثر ، ، كثيف(، الطبيعة )غدية أو غير غدية، بسيطة أو نجمية( والبنية )عدد الخاليا متوسط رأس الشعيرات الغدية؛ عدد األشعة و فى ساق و -الغدية املكونة في الشعيرات البسيطة وغير عن وجود تراكيب شمعية فريدة من نوعها، بما في SEM املشعة في الشعر النجمي(. كشفت ذلك الحبيبات التؤلولية باإلضافة إلى الرقائق. تتوافق مالحظاتنا مع الخصائص العامة لجنيس كل كبير استخدام خصائص هذا العمل بش . يدعمSolanumوجنيس الـ Leptostemonum ال .الشعيرات كميزات تصنيفية قّيمة للفصل بين األنواع املدروسة وترسيم حدودها بين األنواع