Turkish Journal of Botany Turk J Bot (2020) 44: 178-191 http://journals.tubitak.gov.tr/botany/ © TÜBİTAK Research Article doi:10.3906/bot-1907-20

Trichome micromorphology and its significance in the systematics ofConvolvulus L. ()

1 1, 2 3 Elham ROUDI , Hamed KHODAYARI *, Valiollah MOZAFFARIAN , Shahin ZARRE  1 Department of Biology, Faculty of Science, Lorestan University, Khorramabad, Iran 2 Department of Botany, Research Institute of Forests and Rangelands, Agricultural Research Education and Extension Organization, Tehran, Iran 3 Center of Excellence in Phylogeny of Living Organisms and Department of Science, School of Biology, College of Science, University of Tehran, Tehran, Iran

Received: 11.07.2019 Accepted/Published Online: 31.01.2020 Final Version: 17.03.2020

Abstract: Trichomes of 35 species of the Convolovulus and one species of the genus Calystegia (C. sepium) were investigated using light and scanning electron microscopy. The trichomes show a great variation, which provides valuable data for sections and species delimitation in Convolvulus. Trichomes of Convolvulus are nonglandular, simple, and basifixed or rarely asymmetrically medifixed. Characters of taxonomic interest were the degree of curviness (straight to spiral), orientation relative to the epidermal surface (appressed to erect), and presence of papillae on trichome surface. The trichomes are divided into two basic types: cylindrical and flattened ribbon-like. Our data provide the additional evidence to include Calystegia in Convolvulus; the former is characterized by glabrous shoots supporting its inclusion in the Convolvulus sect. Convolvulus. Using the evolutionary framework provided by recent molecular phylogenetic investigations, the following trends can be proposed in Convolvulus: long cylindrical trichomes are advanced against the flattened ribbon-like ones, densely papillate trichomes are derived against the nonpapillate or loosely papillate ones, long trichomes are advanced against the short ones, and appressed trichomes are primitive compared with the erect ones. In most investigated species of Convolvulus, a mixture of various kinds of trichomes has been detected, and the level of advancement should be determined by a collective approach.

Key words: Convolvulus, epidermis, indumentum, Iran, phylogenetics,

1. Introduction ovary and capsule. He divided the genus into 10 unranked Convolvulaceae are a large family, including 59 genera (indicated as “§”) groups. Rechinger (1963), treated and 1950 species (Staples 2018). They occur in both Convolvulus distinct from Calystegia, mainly followed tropical and temperate regions and exhibit a rich Boissier (1875), and divided the genus into nine series. This diversity of morphological characteristics. Convolvulus classification was not followed by Sáad (1967), who revised L. (Convolvuleae, Convolvulaceae) comprises 190–200 the genus in the Mediterranean area and western Asia and species following its most recent circumscription (William classified its species in three sections: C. sect. Acanthocladi, et al., 2014; Wood et al., 2015). The genus includes annual, C. sect. Inermes and C. sect. Convolvulus. She also perennial herbs, subshrubs and shrubs that are widely recognized 12 subsections in the genus. Wood et al. (2015) distributed in dry, sandy and stony and gravelly habitats presented the most updated monograph of Convolvulus of temperate biomes. Several centers of diversity have based on the phylogenetic framework published by been recognized for the genus in both the Northern and William et al. (2014) and assigned these species to seven Southern hemispheres. Although the genus is almost morphological and geographical units. They hesitated to absent from East Asia, it is most diverse in the Irano- present a formal supra-specific classification of the genus Turanian region (Wood et al., 2015). given the nature of the morphological variation and high In terms of subgeneric classification, Boissier (1875) level of homoplasy. based his system on differences in the habit (shrubby, The family Convolvulaceae has been the subject of cushion, annual to perennial herbs and prostrate or erect several molecular phylogenetic studies. The monophyly of stems, trailing or twinning), spine presence, hairiness of the family has been confirmed within using several * Correspondence: [email protected] 178

This work is licensed under a Creative Commons Attribution 4.0 International License. ROUDI et al. / Turk J Bot molecular markers including, all three plant genomes peltate glandular trichomes in the genera Evolvulus L., (Stefanović et al., 2002). Referring to this established well- Jacquemontia Choisy and Merremia Dennst. ex Endl.), resolved framework, several monophyletic groups were respectively (Buril et al., 2012; Aron et al., 2013; Ketjarun et detected supporting the traditional tribal classification of al., 2016 ). Ezazi et al. (2019) provided the trichome-based the family, and five well-supported clades were also added, identification key of five species of sect.Acanthocladi . which match with the tribal concept (Stefanović et al., 2002). None of the previous studies dealt with the systematic All these findings have led to lessening the incompatibility importance of trichome characters in Convolvulaceae of traditional taxonomic classification systems, which sufficiently, despite the potential value known for such have used homoplasious characters as criteria. Moreover, structures in other dicot families (e.g., Metcalfe and Chalk, two groups previously considered to represent separate 1950; El-Gazzar and Watson, 1970; Abu-Asab and Cantino, families, viz. genus Cuscuta and tribe Dichondreae, were 1987; Cantino, 1990). shown to be nested within Convolvulaceae (Stefanović et The present study aims at documenting the trichome al., 2003). micromorphology of Convolvulus spp. to evaluate their Micromorphology and ultrastructural data have systematic significance and discuss them on the background provided useful information on the evolution and of both molecular and traditional classifications. We classification of different genera of seed and might are going to test the trichome micromorphology in the play a significant role in modern synthetic classification delimitation of subgeneric taxa or known clades in the systems. Trichome micromorphology could provide genus. Besides, the informative characters which might further evidence to create more natural classifications, be useful in determining and distinguishing the species/ particularly at generic and subgeneric levels. Sáad (1967), subspecies in Convolvulus, which were primarily based on who presented the most comprehensive monograph Iranian taxa, will be explained. of Convolvulus, described some features of trichomes, including the shape and length of apical cells (ranging 2. Materials and methods from 0.2 to 5 mm), but she did not use the trichome In the present study, trichomes of 35 species of Convolvulus types for species delimitation. Aykurt and Sümbül (2014) (including Convolvulus sepium L. = Calystegia sepium (L.) presented a revision of genus Convolvulus in Turkey, in R.Br.) were investigated. We used mainly fresh materials which they used the indumentum type as a diagnostic collected in 2015–2018 from natural populations. character at the species level. According to Wood et al. Otherwise, in some cases, the materials were removed (2015), six groups can be distinguished based on trichome from the specimens deposited mainly in the herbarium of size and density on leaves and stems. There are several Research Institute of Forest and Rangelands, Iran (TARI), descriptive studies on single or few species of the genus, the central herbarium of the University of Tehran (TUH) without any comprehensive implication. Khokhar et al. and herbarium of the Iranian Research Institute of Plant (2012) examined six species of the genus Convolvulus and Protection (IRAN). A list of voucher specimens examined distinguished the papillate ornamentations on trichomes is provided in Table 1. of C. psuedocantabrica to represent pneumatophores. Trichomes were obtained from the vegetative parts Trichome density appears to exhibit phenotypic plasticity (stems and leaves) and calyces and investigated with in drought conditions in C. chilensis (Gianoli and González- stereo-, light, and scanning electron microscope (SEM). Teuber, 2005). The genus Ipomea L. shows greater variability For scanning electron microscopy, small dried pieces (2 × in trichomes of vegetative organs; Paiva and Martins (2011) 2 mm) of stem, leaves, and calyces were fixed on aluminum detected specialized calycinal (peltate, shortly stalked, and stubs using a double-sided adhesive, which was coated secretory) trichomes located on the calyces of I. carica subsequently with gold. The SEM micrographs were taken (L.) Sweet, which had been neglected before and showed with a TESCAN FE-SEM scanning microscope at Lorestan the function and structure analogous to colleters. Khan University. For measurements, we used an ocular linear et al. (2013) studied the diversity of trichomes of foliar applied in the stereomicroscope. Digimizer software1 was epidermis corresponding to 40 genera and 20 families, used to measure the exact length of trichomes. The types including some members of Convolvulaceae in the tropical of trichomes were described and classified according to part of Pakistan, recognizing two main types of trichomes terminology provided by Payne (1978) as well as Navarro in the family, i.e. attenuate and peltate. Furthermore, and El Oualidi (2000). Ashfaq et al. (2019) studied the foliar micromorphology of Convolvulaceous taxa, gathered from arid parts of 3. Results Northern Punjab Pakistan to estimate the hypothesis that The main types of trichomes and their distribution among glandular trichomes density decreases with high aridity. 35 studied species are described in detail below and Other studies in the family detected stellate, capitate, and summarized in Table 2. Selected SEM micrographs of the 1 https://www.digimizer.com

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Table 1. Collection data of Convolvulus spp. distributed in Iran and adjacent countries examined in the present study for trichome characters. Sectional and subsectional concept follows Sáad (1967).

Species Section/subsection Collection data and herbarium

Prov. Bushehr, Khurmuj, H. Khodayari & E. Roudi 2019200 C. acanthocladus Boiss. & Kotschy Acanthocladi/Acantocladi (HSBU) Afghanistan, between Alizaiee and Habibkalla, Kurrama C. aitchsonii C.B.Clarke Acanthocladi/Acantocladi valley, 1000-2000m. J. Aitchison 35719 (TARI) C. ammannii Desr. Inermes/Inermes Prov. Krasnojrask, Chakassia, V. Reverdatto 3764 (TARI) Prov. Semnan, Ray Abad to Hossein Abad Kalpoosh, 1356m, C. arvensis L. Convolvulus/Convolvulus E. Roudi et al. 2019202 (HSBU) C. betonicifolius Mill. Convolvulus/Convolvulus Prov. Ilam, Eivan, E. Roudi & M. Arabameri 2019203 (HSBU) Prov. Semnan, Hossein Abad Kalpoosh to Till Abad, E. Roudi C. calvertii Boiss. Inermes/Lanuginosi et al. 2019204 (HSBU) Prov. Semnan, Between Rezvan and Hossein Abad Kalpoosh, C. cantabrica L. Inermes/Oleifolii E. Roudi et al. 201920 (HSBU) Prov. Bushehr, Khurmuj, H. Kodayari & E. Roudi 2019205 C. cephalopodus Boiss. Inermes/pannosi (HSBU) Prov. Lorestan, Lorestan University Campus, H. Khodayari & C. chondrilloides Boiss. Inermes/Inermes E. Roudi 2019207 (HSBU) Prov. West Azarbayjan, Urmia, Shahriar, in the road to Anhar C. commutatus Boiss. Inermes/Lanuginosi village, Sh. Bahadori & M. Arab Ameri 2019209 (HSBU) Prov. Khorasan, Shirvan to Kopedagh, M. Arab Ameri et al. C. dorycnium L. Inermes/Inermes 2019211 (HSBU) C. elymaiticus Mozaff. Prov. Ilam, Kaver to Zarrin Abad, E. Roudi & M. Arab Ameri Inermes/Lanuginosi 2019212 (HSBU) Prov. Semnan, Mayami to Biarjemand, E. Roudi et al. 2019214 C. eremophilus Boiss. & Buhse Inermes/Inermes (HSBU) Prov. Isfahan to Shahreza, 5 km to Shahreza, Nik Abad, E. C. fruticosus Pall. Acanthocladi/Acantocladi Roudi et al. 2019215 (HSBU) Prov. Khuzestan, Behbahan to Borazjan, H. Khodayri & E. C. gonocladus Boiss. Inermes/Pannosi Roudi 2019216 (HSBU) Prov. Hormozgan, Bandar Abbas, 21 km on road of Bandar C. glomeratus Choisy Inermes/Diffusi Lengeh to Bandar Khamir, V. Mozzafarian 63593 (TARI) Prov. Hormozgan, Bandar Abbas, 21 km from Bandar Charak C. kotschyanus Boiss. Inermes/Pannosi to Gavbandi, M. Iranshahr & F. Termeh 13159 (IRAN) Prov. Kurdistan, Kamyaran, H. Khodayari & E. Roudi, C. lineatus L. Inermes/Pannosi 2019217 (HSBU) Prov. Bushehr, Kangan to Taheri, H. Khodayari & E. Roudi C. leiocalycinus Boiss. Acanthocladi/Acantocladi 2019218 (HSBU) Prov. Ilam, Saleh Abad, Sarney, E. Roudi & M. Arab Ameri C. oxyphyllus Boiss. Acanthocladi/Spinescentes 2019219 (HSBU) Prov. Kerman, Jiroft, Dam Area of Halilroud, 1202 m, V. C. oxysepalus Boiss. Acanthocladi/Serospinescentes Mozaffarian 88568 (TARI) Prov. East Azarbyjan, After Eskanlou deviation, 5 km to C. pilosellifolius Desr. Inermes/Diffusi Kaleibar, E. Roudi et al. 2019220 (HSBU)

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Table 1. (Continued).

Prov. Hormozgan, Charak, Kish Iland, F. Termeh & M. C. prostratus Frossk. Inermes/Diffusi Karavar 25899 (IRAN) Prov. Semnan, Abr Forest, Ghatri Mount., E Roudi et al. C. pseudocantabrica Schrenk Inermes/Inermes 2019223 (HSBU) Afghanistan, 35 km NW Urgun, 2200-2400m, K. H. C. rectangularis Rech.f. Inermes/Inermes Recshinger 35902 (TARI) Prov. Ilam, SalehAbad, Sarney, E.Roudi & M. Arab ameri, C. reticulatus Choisy Inermes/Pannosi 2019222 (HSBU) Prov. Kerman, 40km Baft, South of Gugher, A. Ghahraman et C. schirazianus Boiss. Inermes/Lanuginosi al. 28591 (TUH) Prov. Baluchestan, Rask, Pishin village, A.H. Pahlavani et al. C. spinosus Forssk. Acanthocladi/Acantocladi 47517 (IRAN) Prov. Lorestan, Lorestan University sight, E. Roudi & H. C. stachydifolius Choisy Convolvulus/Convolvulus Khodayari 2019221 (HSBU) Prov. Fars, Shiraz, Baramshur, 750m, A. Dehbozorgi 32683 C. stapfii Rech.f. Inermes/Pannosi (TARI) Prov. Sistan and Baluchestan, Bazman, 1366m., M. Ranjbar et C. turrillianus Parsa Acanthocladi/Serospinescentes al. 37437.(Bu Alisina University herbarium) Prov. Lorestan, Azna, Tyan village, 2700-3300m, M. Iranshahr C. urosepalus Pau Acanthocladi/Spinescentes 13332 (IRAN) Prov. Baluchestan, Sareh, 1000 m, A. Ghahraman et al. 21578 C. virgatus Boiss. Acanthocladi/Serospinescentes (TUH) Prov. Guilan, Rasht, Imamzade Hashem region, E. Roudi C. sepium L. Convolvulus/Convolvulus 2019224 (HSBU) common types of trichomes are presented in Figures 1–3. basal epidermal cell and an elongated apical cell slightly The trichomes in all examined species were nonglandular, folded at base (Figures1a–1c), 2) hooked: erect trichomes simple or bifurcate (medifixed), and unicellular. Among abruptly curved or bent at tip (Figure 1e), 3) falcate: evenly several analyzed criteria of trichomes, characters of curved trichomes (Figure 2e), and 4) spiral: trichomes taxonomic importance were the size of trichome, surface folding along their entire length, being erect or appressed of trichome (smooth, papillate or articulate), orientation of (Figure 2i). Flattened ribbon-like trichomes ranged from trichome (erect, subappressed, or appressed), attachment erect (Figure 1l) to appressed (Figure 3i) and from smooth of trichome to the surface (basifixed or medifixed), and to articulate on the surface (Figure 3c). These trichomes the curviness of trichomes (hooked, bent, or twisted). might be divided into basifixed or medifixed subtypes. The Based on the solidness of epidermal cells, two types of basifixed subulate trichomes (Figures 3b and 3c) tapered trichomes were recognized, viz. cylindrical and flattened, from a thick base to a sharp point, while the medifixed as the basic trichome types in the investigated species trichomes (Figure 3i) were shortly stalked and split into which can be subdivided into six groups (four subtypes two lateral opposite halves forming equal to unequal arms. in cylindrical type and two subtypes in flattened type, The density of trichomes varied among the examined see below) based on variations observed. The cylindrical species and different parts of a certain species (Table 2). trichomes included short to extremely long hairs attached Acicular trichomes occur in almost all species but vary to a rounded epidermal cell, and might be appressed in density among various species. In some species, both or slightly erect, smooth, or papillate on the surface. main types of trichomes (simple and medifixed) could Based on the variation observed in terms of level of simultaneously occur. Indumentum is not distributed curviness, cylindrical trichomes could be subdivided uniformly on all parts of the plants, for example, the into four subtypes: 1) acicular: needle-shaped trichomes, cylindrical trichomes in Convolvulus chondrilloides covered subappressed or appressed trichomes with rounded the calyx densely, while they were sparsely distributed

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Table 2. Trichome characteristics of examined Convolvulus spp. Abbreviations used: C= calyx, L= leaf, ‘S= stem; all measurements in µm.

Species/Section Density Surface Size Cylindrical Flattened ribbon-like

Sect. Acanthocladi Acicular Falcate Hooked Spiral Medifixed Basifixed

S, + S, - S, - S, - S, - S, + C. acanthocladus Dense Smooth 900/657-(1260/38)-1661/57 L, + L, - L, - L, - L, - L, - C, + C, - C, - C, - C, - C, - S, + S, - S, - S, - S, - S, - C. fruticosus Dense Papillate 615/45-(803/65)-919/62 L, + L, - L, - L, - L, - L, - C, + C, - C, - C, - C, - C, + S, + S, - S, - S, - S, - S, - C. leiocalycinus Dense Smooth 758/86-(906/07)-1054/62 L, + L, - L, - L, - L, - L, - C, - C, - C, - C, - C, - C, - S, + S, - S, - S, - S, - S, + C. oxyphyllus Dense Papillate 448/065-(554/8)-761/465 L, + L, - L, - L, - L, - L, - C, + C, - C, - C, - C, - C, - S, + S, - S, - S, - S, - S, - C. oxysepalus Dense Smooth 314/14-(475/549)-620/126 L, + L, - L, - L, - L, - L, - C, + C, - C, - C, - C, - C, - S, + S, - S, - S, - S, - S, - C. spinosus Sparse Smooth 106/98-(150/81)-173/96 L, + L, - L, - L, - L, - L, - C, + C, - C, - C, - C, - C, - S, + S, - S, - S, - S, - S, + C. turrilianus Dense Smooth 435/60-(683/55)-931/77 L, + L, - L, - L, - L, - L, - C, + C, - C, - C, - C, - C, - S, + S, - S, - S, - S, - S, - C. urosepalus Sparse Smooth 366/595-(610/77)-730/644 L, + L, - L, - L, - L, - L, - C, + C, - C, - C, - C, - C, - S, + S, - S, - S, - S, - S, - C. virgatus Sparse Papillate 545/62-(753/55)-962/87 L, + L, - L, - L, - L, - L, - C, + C, - C, - C, - C, - C, - Sect. Inermes S, + S, - S, - S, - S, - S, - C. aitchisonii Dense Smooth 515/35-(703/55)-819/52 L, + L, - L, - L, - L, - L, - C, + C, - C, - C, - C, - C, - S, + S, - S, - S, - S, - S, - C. ammani Dense Smooth 110/320-(160/324)-219/326 L, + L, - L, - L, - L, - L, - C, - C, - C, C, - C, - C, + S, + S, + S, - S, + S, - S, - Very C. cephalopodus Smooth 394/98-(526)-868/58 L, + L, - L, - L, + L, - L, - dense C, + C, + C, - C, - C, - C, - S, + S, - S, - S, - S, - S, - C. calvertii Dense Smooth 123/639-(405/166)754/217 L, + L, - L, - L, - L, - L, - C, + C, - C, - C,- C, - C, + S, + S, - S, - S, - S, - S, - C. cantabrica Dense Smooth 96/152-(325/54)-475/93 L, + L, - L, - L, - L, - L, - C, + C, - C, - C, - C, - C, -

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Table 2. (Continued).

S, + S, - S, - S, - S, - S, - C. chondrilloides Dense Smooth 100/764-(339/332)-762/625 L, + L, - L, - L, - L, - L, - C, + C, - C, - C, - C, - C, - S, + S, - S, - S, - S, - S, - C. commutatus Dense Smooth 58/43-(435/41)-993/55 L, + L, - L, - L, - L, - L, - C, + C, - C, - C, - C, - C, + S, - S, - S, - S, - S, + S, + C. dorycnium Dense Smooth 128/06-(204/05)-281/69 L, - L, - L, - L, - L, - L, - C, + C, - C, - C, - C, - C, + S, + S, - S, - S, - S, - S, - Very C. elymaiticus Smooth 764/62-(1159/38)-1246/67 L, + L, - L, - L, - L, - L, - dense C, + C, - C, - C, - C, - C, - S, + S, - S, - S, - S, - S, + C. eremophilus Dense Papillate 402/977-(588/68)-751/561 L, + L, - L, - L, - L, - L, - C, + C, - C, - C, - C, - C, + S, + S, - S, + S, - S, - S, - C. glomeratus Sparse Papillate 317/297-(440/392)-522/198 L, + L, - L, - L, - L, - L, - C, + C, - C, - C, - C, - C, - S, + S, + S, - S, + S, - S, - C. gonocladus Dense Smooth 504/98-(726)-1068/58 L, + L, - L, - L, - L, - L, - C, + C, - C, - C, - C, - C, - S, + S, + S, - S, - S, - S, - C. kotschyanus Dense Smooth 313/61-(352/9)-380/90 L,+ L, - L, - L, - L, - L, - C, + C, - C, - C, - C, - C, - S, + S, - S, - S, - S, - S, - C. lineatus Dense Smooth 291/52-(333/15)-378/731 L, + L, - L, - L, - L, - L, - C, + C, - C, - C, - C, - C, - S, + S, + S, - S, - S, - S, - C. pilosellifolius Dense Smooth 237/58-(298/76)-361/284 L, + L, + L, - L, - L, - L, - C, + C, + C, - C, - C, - C, - S, + S, - S, - S, - S, - S, - C. prostratus Dense Smooth 800/006-(1159/38)-1561/75 L, + L, - L, - L, - L, - L, - C, + C, - C, - C, - C, - C, - S, - S, - S, - S, - S, + S, + C. pseudocantabrica Dense Smooth 98/06-(145/29)-181/69 L, + L, - L, - L, - L, - L, - C, - C, - C, - C, - C, - C, - S, + S, - S, - S, - S, - S, - C. rectangularis Dense Smooth 327/85-(394/76)-461/328 L, + L, - L, - L, - L, - L, - C, - C, - C, - C, - C, - C, - S, + S, - S, - S, - S, - S, - Very C. reticulatus Smooth 484/95-(1655/76)-2999/87 L, + L, - L, - L, - L, - L, - dense C, + C, - C, - C, - C, - C, - S, + S, - S, - S, - S, - S, - C. schirazianus Dense Papillate 578/86-(686/07)-854/62 L, + L, - L, - L, - L, - L, - C, + C, - C, - C, - C, - C, - + S, S, - S, - S, - S, - S, - C. stapfii Dense Smooth 321/152-(449/05)-578/451 L, + L, - L, - L, - L, - L, - C, + C, - C, - C, - C, - C, -

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Table 2. (Continued).

Sect. Convolvulus S, + S, - S, - S, - S, - S, - C. arvensis Sparse Smooth 212/621-(338/53)-465/77 L, + L, - L, - L, - L, - L, - C, - C, - C, - C, - C, - C, - S, + S, - S, - S, - S, - S, - C. betonicifolius Sparse Smooth 312/549-(598/127)-993/552 L, + L, - L, - L, - L, - L, - C, + C, - C, - C, - C, - C, - S, + S, - S, - S, - S, - S, - C. stachydifolius Sparse Smooth 145/31-(257/21)-369/11 L, + L, - L, - L, - L, - L, - C, - C, - C, - C, - C, - C, - C. sepium S, - S, - S, - S, - S, - S, - Very (= Calystegia Smooth L, - L, - L, - L, - L, - L, - sparse sepium) C, - C, - C, - C, - C, - C, - on the adaxial and abaxial sides of leaves. The medifixed in Convolvulaceae discussing their taxonomic value trichomes show high variability among the examined in recognition of tribes and genera in this family. species, for example, two species of C. sect. Inermes, i.e. According to Austin (1973), different types of trichomes C. psuedocantabrica (Figure 3i) and C. dorycnium L., were might be indicative at generic rank, but the intrageneric covered densely by medifixed trichomes. The density of variation of trichomes in the genus Convolvulus has not indumentum on calyx varies extensively from very sparse been sufficiently addressed. Following previous studies to very dense. The calyx shows also considerable variability (Austin, 1973; Gianoli and González-Teuber, 2005; Paiva in trichome types (Table 2). The density and types of and Martins, 2011; Khokhar et al., 2012; Ashfaq et al., trichomes in C. sect. Inermes show higher variability than 2019), our results showed that Convolvulus spp. lack any the two other sections studied here. Convolvulus sepium branched (except for the medifixed ribbon-like ones) is nearly glabrous and lacks any trichome that could be and glandular trichomes. On the contrary, other genera correlated to any other studied species. proposed to be related to Convolvulus, for example, Evolvulus, Jacquemontia and Merremia are covered partly 4. Discussion by branched trichomes. Members of the genera Ipomea and This study presents the first comprehensive investigation Maripa Aubl. differ from Convolvulus by having glandular of trichome micromorphology in the genus Convolvulus trichomes derived from the simple peltate scales located and reveals significant interspecific variation in trichome on the leaf apex (Austin, 1973). Based on the available characteristics that provide a valuable source of data data (Austin, 1973; Stefanović et al., 2002, 2003), it seems potentially informative for natural grouping in the genus. that tribe Convolvuleae including Calystegia, Convolvulus, It seems that the observed variation is most useful to and Polymeria RBr. is characterized by nonglandular distinguish the species of the genus, but some characters trichomes, while various kinds of trichomes including the are also section or subsection specific. Without paying glandular and nonglandular (in some species combined detailed attention to trichome characteristics, some and present together in one individual) ones could be general features of indumentum, have been used in detected in tribe Ipomeeae. previous studies to discriminate the species of Convolvulus The previous molecular phylogenetic studies provided (Sáad, 1967; Nowroozi, 2000), for example, pubescent a framework allowing mapping of the trichome characters ovary against the glabrous one was mentioned as a and indicating their patterns of evolution (Stefanović et diagnostic feature to separate C. chondrilloides (with al., 2002, 2003; William et al., 2014). Mapping of trichome hairy ovary) from C. leptocladus (with glabrous ovary). characters on these phylogenetic trees indicates that the Since the trichome characters have successfully been these characters are too homoplasious to allow determining used in indicating the evolutionary trends in some other certain trends in their evolution in Convolvulus, as it is families, such as Lamiaceae (Navarro & El Qualidi,1999; the case for indicating clear evolutionary transformation Salmaki et al., 2009; Xiang et al., 2010; Eiji and Salmaki, series corresponding to plant habit (William et al., 2014). 2015), the observed variability in Convolvulus might Thus, the proposed evolutionary trends, suggesting short also be linked with the phylogenetic patterns known in flattened ribbon-like trichomes to be primitive against the the genus (Stefanivic et al., 2002, 2003). Austin (1973) long cylindrical ones (Austin, 1973), are not corroborated presented a comprehensive description of trichomes by the available data.

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Figure 1. Selected SEM micrographs of Convolvulus spp. (a, b, c) acicular trichome in C. chondrilloides; (d) dense indumentum in C. chondrilloides; (e, f) hooked trichome in C. glomeratus; (g) acicular trichome in C. urosepalus; (h) nonpapillate trichome in C. cephalopodus; (i) calyx indumentum in C. prostrates; (j, k) acicular and basifixed trichomes inC. calvertii; (l) acicular and flattened trichomes on calyx ofC. oxysepalus.

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Figure 2. Selected SEM micrographs of Convolvulus spp. (a) dense indumentum in C. oxysepalus; (b) basifixed trichomes in C. acanthocladous; (c) long basifixed trichomes inC. elymaiticus; (d, e) falcate trichomes in C. betonicifolius; (f, g) falcate trichomes in C. cephalopodus; (h, i) spiral trichomes in C. gonocladous; (j, k, l) calyx indumentum in C. reticulatus.

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Figure 3. Selected micrographs of Convolvulus spp. (a, b, c) erect basifixed trichomes inC. ammani; (d, e) basifixed papillate trichomes in C. fruiticosus; (f) flattened basifixed trichomes in C. acanthocladus; (g) glabrous surface of calyx in C. leiocalycinus; (h, i) medifixed trichomes in stem ofC. psuedocantabrica; (j, k, l) glabrous surface of leave, shoot and calyx in C. sepium.

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Several previous efforts using trichome characteristics The foliar indumentum density might have differed as to address the infrageneric classification ofConvolvulus an ecophysiological response to aridity, and has been used (formally or informally) applied rather general groupings often to define infraspecific taxa (see, e.g., Gianoli and based on indumentum type. Wood et al. (2015) presented González-Teuber, 2005). Recently, based on examining the a grouping of Convolvulus spp. based on indumentum foliar micromorphology of 18 species of Convolvulaceae features of the stem and leaves, defining six informal in arid habitats of Pakistan, Ashfaq et al. (2019) indicated groups without praising detailed features of individual that the density of glandular trichomes dramatically trichomes: 1- velvety-tomentose, 2- densely sericeous/ decreased due to physiological compatibility to drought, canescent, 3- very finely sericeous and often somewhat while the density and size of nonglandular trichomes glabrescent, 4- villous-tomentose, 5- glabrous or nearly particularly in Convolvulus spp. was at highest among the so, and 6- sepal indumentum strikingly different from investigated genera. It seems that trichome density and that of stem and leaves. Although the mentioned trichome type are more strongly affected by the ecological factors classification does not support the traditional subgeneric than the geographic patterns. Generally, the densely hairy classification of the genus based on morphological features plants are expected to be found in arid areas, while the (Sáad, 1967), the villous-tomentose group (group 4) glabrous or less densely hairy ones in humid habitats (for characterized by long trichomes matches well with C. sect. example in C. prostratus, Ashfaq et al., 2019). However, we Inermes as circumscribed by Sáad (1967), predominantly observed some exceptional cases where the densely hairy consisting of perennial plants. This finding is partly also populations of C. pilosellifolius were distributed in North Iran (Prov. Ardebil, Kaleibar), but the loosely covered in line with our results (for details see below under C. populations were found in the South West (Prov. Ilam, sect. Inermes). Besides, ‘group 5’ as defined by Wood et al. Dareshahr). (2015) is compatible with C. sect. Convolvulus, as defined Trichome micromorphology can potentially provide by Sáad (1967) and also matches well with our results in a basis for evaluating the challenging infrageneric this section. classification of Convolvulus as well as some unresolved Grouping of species in the genus Convolvulus based phylogenetic issues in the genus, but it is known to be very on indumentum features may be explained by the homoplastic at the same time (Austin, 1998b; Manos et geographical distribution patterns (Mitchel et al., 2016). al., 2001; Carine and Scotland, 2002). As the next scope Wood et al. (2015) indicated that nearly all species of C. of the present research, we are going to test the efficiency sect. Acanthocladi and some members of C. sect. Inermes, of trichome characters in the subgeneric classification which are distributed widely in the Mediterranean region of Convolvulus. We will also address the traditional and the Middle-East, are covered by densely sericeous classification systems based on morphological characters indumentum and can be classified in the same group (Boissier, 1875; Rechinger, 1963; Saad, 1967), even if this based on indumentum type. Although in the large country traditional concept of sections have not been supported by of Iran which, is occupied by four distinct geographical the recent phylogenetic studies (Williams et al., 2014). phytochoria (Zohary, 1973), the trichome features cannot 4.1. C. sect Acanthocladi be correlated to the biogeographical patterns known in The species of this section are characterized by shrubby the country. As an example, in the northern parts of Iran or subshrubby habit, with branches either ending into representing the Hyrcanian region, Convolvulus sepium (= spines and upper sterile peduncles or peduncles with Calystegia sepium), which is related to the members of C. falling flowers (Sáad, 1967). This section has been sect. Convolvulus is frequently distributed, while the other divided into three subsections by Sáad (1967): C. subsect. three species of this section in Iran are predominantly Acanthocladi Boiss., C. subsect. Spinescentes Boiss. and C. distributed in Southwest Iran. A group of closely related subsect. Serospinescentes Sáad. Most species of C. subsect. species known from North East Iran (Semnan to Khorasan), Acanthocladi have densely pilose calyx and sericeous viz. C. dorycnium, C. eremophilus and C. pseudocantabrica, leaves, except C. leiocalycinus with glabrous calyx (Figure are morphologically similar, but the cylindrical trichomes 3g). According to Wood et al. (2015) the indumentum are lacking in C. dorycnium and C. pseudocantabrica and density could be useful in distinguishing C. acanthocladus frequent in C. eremophilus. Other members of this section, from C. iranicus, the latter being less densely hairy. Ezazi et which are distributed in South Iran, are covered mainly by al. (2019) also used the density and size of leaf trichomes in cylindrical trichomes. The indumentum coverage among discrimination of five species ofC. subsect. Acanthocladi. Convolvulus spp. distributed in South Iran was dense, Both main types of cylindrical and flattened appressed while the species of Convolvulus, growing in North Iran, trichomes are present in most species of this subsection, show less indumentum density. Furthermore, the longest while C. fruticosus is merely covered by short basifixed and trichomes were found in those species of C. sect. Inermes medifixed flattened trichomes, sparsely papillate on the distributed in Southern parts of the Country. surface of all parts of the plants (Figures 3d).

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Convolvulus leiocalycinus is well-characterized by commutatus, C. glomeratus, C. rectangularis, C. reticulatis, petiolate leaves and also glabrous calyx suggesting its are covered by cylindrical trichomes. Although other isolated position in the section as deduced according members of C. sect. Inermes are covered by cylindrical to the molecular phylogenetic findings (William et al., trichomes at least on the calyx, C. dorycnium and 2014). Convolvulus oxyphyllus and C. urosepalus (two C. psuedocantabrica lack spreading cylindrical long representatives of C. subsect. Spinescentes) are characterized trichomes on the shoots. Moreover, C. psuedocantabrica by cylindrical (acicular) trichomes sparsely papillate on the has a cylindrical calyx, which is glabrous. In general, surface. Other members of this subsection are, however, our results indicate that the trichome type could be characterized by long cylindrical trichomes smooth on the informative to allow characterizing the subsections (sensu surface mixed with short, flattened semiappressed ones. Sáad, 1967). In this section C. commutatus and C. calvertii These two main types of the nonglandular trichomes are which were included in C. subsect. Lanuginosi by Sáad observed together and in densely appressed arrangement (1967) are morphologically very similar while they could on the calyx, but the leaves and shoots are covered by be distinguished by orientation of the acicular trichomes, the uniform trichomes consisting of one of either type which are erect in the latter while appressed in the former. of trichomes. Two endemic species in South Iran, C. Wood et al. (2015) suggested a close relationship between turrillianus, and C. oxysepalus could be discriminated C. calvertii, C. commutatus, and C. elymaiticus Mozaff. Long based on leaf and shoot trichomes. Greyish sericeous cylindrical trichomes densely covering the whole plant is indumentum is characteristic for C. turrillianus, but both a characteristic feature that supports discriminating the species are semiappressed hairy on the calyx with long newly described C. elymaiticus (Mozaff, 2010) from other trichomes up to 2 mm. Phylogenetically, C. turrillianus is mentioned species of this species complex. Although there placed in the Old World clade (William et al., 2014; Mitchel are many significant morphological differences between C. et al., 2016) together with other species characterized by reticulatus (e.g. prostrate habit) and other members of C. sericeous leaves and shoots. Consequently, we believe that commutatus alliance (which are erect subshrubs), they have C. oxysepalus belongs to the same clade, which needs to be been placed in C. sect. Inermes by Sáad (1967). In a recent confirmed yet. phylogenetic study (William et al., 2014), C. reticulatus was not retrieved in the same clade as the members of the C. 4.2. C. sect. Inermes commutatus alliance. Trichome size and density provide The species of this section are characterized by erect and additional evidence on separating C. reticulatus from the rigid or prostrate shoots covered densely by long trichomes members of C. commutatus alliance, as the shoots in the almost uniformly distributed throughout the plants. The former are covered densely by long spreading trichomes members of C. sect. Inermes were divided into seven (Table 2 and Figures 2j–2l), while they are acicular and subsections, in which representatives of five subsections appressed in other members of C. commutatus alliance. were examined in our study: C. subsect. Diffusi Boiss., C. Convolvulus gonocladus and C. kotschyanus seem to subsect. Inermes Boiss., C. subsect. Lanuginosi Peter, C. be very similar, through scorpioid cymes, spathulate basal subsect Oleifolii Peter, and C. subsect. Pannosi Boiss. (Sáad, leaves and also very long cylindrical trichomes, covering 1967). These subsections could be considered equivalent the whole plant. Recently, C. gonocladus was treated as a to informal groups in Boissier’s (1875) system, which were synonym of C. kotcshyanus (Wood et al., 2015). Trichome defined based on the presence or absence of trichomes characteristics examined here confirm this treatment on the ovary or elsewhere. Seventeen species of this because representatives of both species have the unique section were included in our study consisting of the most falcate type of trichomes, which is not reported in any taxonomically problematic species, C. eremophilus, with other species of Convolvulus. As another example, C. more than 10 species names considered as its synonyms bushiricus had been reduced to subspecific rank under due to overlapping morphological characters (Wood et C. cephalopodus by Wood et al. (2015). Although the al., 2015). The presence of trichome on the ovary could be indumentum in both taxa is mainly of the same type partly informative for its discrimination from C. erinaceus (consisting of long cylindrical trichomes), the calyx in which is characterized by a glabrous ovary (Sáad, 1967). C. cephalopodus is less hairy than that in C. bushiricus, According to Wood et al. (2015), shoot indumentum also confirming the recent (Wood et al., 2015) taxonomic reveals some diagnostic characters of taxonomic interests. treatment in this group. Convolvulus glomeratus, a Saharo- As an example, the species of C. sect Inermes based on the Sindian element, is less densely hairy compared with other shoot trichome type might be divided into two groups. species of C. sect. Inermes. Two types of trichomes were Flattened basifixed trichomes covered the shoots ofC. observed in the species of this section, of which the acicular dorycnium, C. eremophils, and C. psuedocantabrica, which type is distributed uniformly on all parts of the plants in all might be informative in discriminating the subspecies. studied species, while the hooked trichomes are common However, most other members of C. sect. Inermes, viz. in the C. subsect. Diffusi. Based on a recent phylogenetic C. bushiricus, C. cephalopodus, C. chondrolloides, C. investigation (William et al., 2014), C. glomeratus is placed

189 ROUDI et al. / Turk J Bot in a different clade isolated from all other species ofC. sect. delimitation of species. Some possible evolutionary trends Inermes. The trichomes in C. glomeratus are appressed and can be recognized corresponding to trichome features: distinctly shorter than the other members of the section long cylindrical trichome is advanced against the flattened corroborating its isolate placement in the phylogeny. ribbon-like ones, densely papillate trichomes are derived 4.3. C. sect. Convolvulus from the nonpapillate or loosely papillate ones, long The members of this section are characterized by twinning trichomes are advanced against the short ones and the branches or twinning shoots (Sáad, 1967). The trichomes appressed trichomes are primitive compared with the in this section are acicular and not papillate on the surface, erect ones. There are some clear examples of the genus loosely arranged, uniform and soft. The calyx varies in Convolvulus in dryer habitats, contradicting the ecological density among the species of the section ranging from pattern of trichomes expected to be cylindrical, long, and glabrous (C. arvensis) to densely hairy. The indumentum erect. Our results support the inclusion of Calystegia in density seems to be taxonomically informative in this section Convolvulus and its placement close to the members of C. and can provide a useful tool in recognition of the species. sect. Convolvulus. The presence of pubescent indumentum versus the villous A diagnostic key to distinguish the sections and one could be taxonomically valuable in discriminating two subsections in the genus Convolvulus: members of this section, C. stachydifolius var. stachydifolius 1a. Glabrous plants or nearly glabrous plants sparsely and C. stachydifolius var. villosus Hallier f. Thus, this covered by cylindrical trichomes ...... C. sect. Convolvulus character is useful in the delimitation of subspecific rank. 1b. Hairy plants covered uniformly or randomly by The members of theC. sect. Convolvulus phylogenetically trichomes on one part or all parts of the plant ...... 2 form a subclade in a larger clade consisting of all the Euro- 2a. Plants covered by cylindrical trichomes or both Siberian species of the genus (William et al., 2014). Most cylindrical and flattened ribbon-like trichomes ...... 3 of the species representing this section in our study are 2b. Plants covered just by flattened ribbon-like glabrous (except C. betonicifolius, which is covered by trichomes ...... 5 spreading trichomes, particularly on the calyx). 3a. Plants with sericeous indumentum, simultaneously 4.4. Calystegia sepium covered by cylindrical and ribbon-like trichomes ...... In the most recent molecular studies of Convolvulus ...... C. sect Acanthocladi (Stefanović et al., 2002; Carine et al., 2004; William 3b. Plants with certain type of cylindrical trichomes .... 4 et al., 2014), Calystegia nested within the same clade 4a. Plants densely covered by erect cylindrical as the representatives of C. sect. Convolvulus. From trichomes ...... C. subsect Pannosi a micromorphological point of view, most members 4b. Plants densely covered by appressed cylindrical of this clade at least on leaves and stems are glabrous. trichomes ...... C. subsect. Lanuginisi Calystegia sepium, as the only representative of the genus, 5a. Plants uniformly covered by flattened ribbon-like is glabrous, corroborating its close relationship with C. trichomes on the whole plant ...... 6 sect. Convolvulus. Among the species of this section, some 5b. Plant randomly covered by flattened ribbon-like species such as C. scammonia are also glabrous and similar trichomes ...... 7 to Calystegia, but morphologically have yellow corolla 6a. Plants covered densely by flattened ribbon-like and smaller bracts enveloping the calyx. Thus, inclusion appressed trichomes ...... C. subsect. Oleifolii of Calystegia in the genus Convolvulus is supported by trichome micromorphology and other morphological 6b. Plants sparsely covered by flattened ribbon-like characters. appressed trichomes ...... C. subsect. Acanthocladi 7a. Plants sparsely covered by flattened ribbon-like 5. Conclusion trichomes on the shoot; calyx glabrous ...... The diversity of trichomes in the genus Convolvulus is quite ...... C. subsect. Inermes low, because of the absence of the glandular and branched 7b. Plants sparsely covered by flattened ribbon-like trichomes. Two basic types of trichomes are recognized trichomes on the calyx; shoots nearly glabrous ...... in the genus: the flattened ribbon-like and the cylindrical ...... C. subsect. Diffusi ones. Both kinds of trichome show variation to some extent, allowing their application for various taxonomical Acknowledgment purposes. The present study indicates the importance of We appreciate the three reviewers, who helped us to trichome micromorphology in the taxonomy of the genus improve the text considerably both linguistically and Convolvulus, especially in discriminating the sections scientifically. This study is part of the PhD thesis by E. and subsections. In a few cases, the type of trichomes Roudi at University of Lorestan. We kindly appreciate the and their density provide characteristic features in the support from Lorestan University.

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