OPCE-STR.vp Acta Bot. Croat. 69 (1), 93–105, 2010 CODEN: ABCRA 25 ISSN 0365–0588 Trichome micromorphology in drupe of Amygdalus L. (Rosaceae) from Iran MAHNAZ VAFADAR1*, FARIDEH ATTAR1, HOSEIN MAROOFI2 1 Central Herbarium of University of Tehran, School of Biology, Faculty College of Science, University of Tehran, Po. Box: 14155-6455, Tehran, Iran. 2 Research Center of Agriculture and Natural Resources, Kurdistan Province, Po. Box: 66169-36311-714, Sanandaj, Iran. For delimitation of species and systematic resolution, pericarp indumentum in drupes of 17 species and two hybrids of the genus Amygdalus L., representing two subgenera and two sections distributed in Iran, were studied using scanning electron microscopy (SEM) in order to assess whether in this genus, pericarp micromorphological characters are of taxonomic value. The pericarp indumentum type is velutinous with different density of trichomes. Glabrous pericarp was observed solely in A. reticulata Runemark ex Kha- tamsaz. All trichomes are simple. Two basic types of trichomes were distinguished on the surface of the pericarp: tubular and flattened. Among these, tubular trichomes are more frequent than other trichomes in most species except for A. kotschyi Boiss. et Hohen., A. eburnea Spach, A. spinosissima Bge. subsp. spinosissima and A. lycioides Spach var. lycioides. Density of trichomes was variable among the studied taxa. In the first subgenus (subgen. Amygdalus) with two sections, there was enough difference between sections. While density of trichomes in sect. Spartioides Spach was very low, most of species in the another section, sect. Amygdalus showed dense pericarp indumentum. Regarding density, the second subgenus, subgen. Dodecandra (Spach) Browicz showed dense indumentum. Two hybrids studied, A.´keredjensis Browicz and A.´kamiaranensis Khatamsaz et Assadi showed different pericarp indumenta, dense and sparse respectively. In conclusion, micromorphological investigation of pericarp indumentum in drupes is a useful tool for distinguishing taxa in some cases, especially those of the two sections in the first subgenus in Amygdalus. Key words: Amygdalus, pericarp, drupe, indumentum, micromorphology Introduction The genus Amygdalus L. with approximately 40–45 species in the world is distributed mainly in southwest Asia, central Asia and Middle East, although a few species in this ge- nus are distributed in the east of Asia (China and Mongolia) as well as southeast Europe (BROWICZ and ZOHARY 1996). The main phytogeographical region for Amygdalus distribu- tion is the Irano-Touranian region. The genus Amygdalus is classified in the tribe Amyg- ACTA BOT. CROAT. 69 (1), 2010 93 * Corresponding author, e-mail: vafa@khayam.ut.ac.ir U:\ACTA BOTANICA\Acta-Botan 1-10\Vafadar.vp 9. travanj 2010 13:14:23 Color profile: Disabled Composite 150 lpi at 45 degrees daleae, subfamily Spiraeoideae, former subfamily Amygdaloideae (CRONQUIST 1981, TAKHTAJAN 1997), in family Rosaceae (POTTER et al. 2007). Classification of Amygdalus has changed over the course of time. In most classic classifications, Amygdalus was consid- ered as a subgenus or as a section in the genus Prunus. For example, REHDER (1940) consid- ered five subgenera in Prunus: Prunus, Amygdalus, Cerasus, Laurocerasus and Padus (LEE and WEN 2001). This treatment is the most acceptable classifications in the world. Phylogenetic classifications treated a new state for this genus. According to phylogeny and classification of Rosaceae (POTTER et al 2007), Amygdalus has been inserted within the ge- nus Prunus with Armeniaca, Cerasus, Laurocerasus, Padus, Pygeum and Maddenia in the tribe Amygdaleae, subfamily Spiraeoideae. In the Flora of Iran, in Persian, Amygdalus is treated as a single genus in the subfamily Prunoideae. We say that there are sufficient mor- phological differences between Amygdalus and Prunus for them to be considered different genera. According to the study of BROWICZ (1969), there are 15 species and two hybrids of Amygdalus in Iran. However, according to studies of KHATAMSAZ (1992), in Persian, 21 species and six hybrids of this genus occur in Iran. Among those, seven species, one variety and all the hybrids are endemic elements for the flora of Iran (KHATAMSAZ 1992). This ge- nus includes two subgenera, subgen. Amygdalus and subgen. Dodecandra (BROWICZ 1969, KHATAMSAZ 1992). The former subgenus includes 15 species as trees or shrubs in two sec- tions, sect. Amygdalus and sect. Spartioides Spach. The second subgenus includes six spe- cies (KHATAMSAZ 1992). Regarding vegetative features, two sections of the former subge- nus are different from each other as follows. The main morphological feature of sect. Amygdalus is the presence of brachyblast (short shoots) whereas species in sect. Spartio- ides lack brachyblast and exhibit junciform feature (these species include shoots that show them as Juncus-like form). The second subgenus, subgen. Dodecandra, is completely dif- ferent from the first, the species in this subgenus being spiny and shrubby with thick spines (BROWICZ 1969, KHATAMSAZ 1992). In fact, this genus is one of the most important ele- ments of the Elburz and Zagros mountains, steppes, rocky places and semi-arid habitats in Iran. Amygdalus is one of the most problematic genera of the family Rosaceae. This genus involves numerous taxonomic problems including a high degree of morphological varia- tion even in different populations of one species and interspecific hybridization; so bound- aries between species are not clear and delimitation of species in this genus is not possible based on morphological characters alone. In addition, we need more evidence including micromorphological, anatomical, molecular and phytochemical information to elucidate the taxonomic complexity in this problematic genus. Micromorphological studies are useful in resolving taxonomic problems because of high efficiency and reliability as well as the detailed data they provide. Plant hairs (tri- chomes) are of great interest to descriptive and experimental botanists and data on these and indumenta are routinely included in many types of studies (JURI[I] GRUBE[I] et al. 2007). Scanning electron microscopy (SEM) provides useful data on surface indumentum ultrastructure of seed, fruit, leaf and stem. Several researchers have focused on hair micromorphology of different families and genera including Eugenia L., Myrtaceae (FONTENELLE et al. 1994), Ranunculus L., Ranunculaceae (XUHAN and VAN-LAMMEREN 1994), Cordia L. and Onosma L., Boraginaceae (RAPISARDA et al. 1997, AKCIN 2007), Rosaceae and Sanguisorba L. (DOWIDAR et al. 2003, LATIF 2004), Astragalus L. and Arbus Adanson, Fabaceae (ZARRE 2003, AGBAGWA and OKOLI 2006), Verbascum L., Scrophula- 94 ACTA BOT. CROAT. 69 (1), 2010 VAFADAR M., ATTAR F., MAROOFI H. U:\ACTA BOTANICA\Acta-Botan 1-10\Vafadar.vp 9. travanj 2010 13:14:23 Color profile: Disabled Composite 150 lpi at 45 degrees riaceae (ATTAR et al. 2007), Teucrium L. and Nepeta L., Lamiaceae (JURI[I] GRUBE[I] et al. 2007, KAYA et al. 2007) and Isatis L., Brassicaceae (MOAZZENI et al. 2007). So far, micromorphology of pericarp indumentum in the drupe of Amygdalus has not been studied and this study was conducted to investigate the pericarp indumentum of Iranian species of Amygdalus. Regarding the drupe, among allied genera in the tribe Amygdaleae, subfamily Spiraeoideae, or as formerly classified in the subfamily Amygdaloideae, Amygdalus has a unique feature as its mesocarp is thin and completely dried after fruit maturation and to- gether with pericarp is separated from the endocarp, which is stony with various surface or- namentations. Generally, the surface of the pericarp is hairy in Amygdalus. The main aims of this study are to document a pericarp micromorphology of Iranian species of Amygdalus and then to use this feature for evaluating taxonomic relationships in this genus. Material and methods Matured, dried and clean drupes of 17 species and two hybrids of Iranian species of Amygdalus were selected and their pericarp was removed. The specimens are deposited in the Central Herbarium of the University of Tehran (TUH) and the voucher specimens are presented in table 1. A piece of pericarp was mounted on a 12.5 mm diameter aluminium stub with double sided adhesive and then was coated in a sputter coater with approximately 25 nm of Gold-Palladium at an accelerating voltage of 10–15 kv. The specimens were ex- amined and photographed with Leo SEM-440I and Tscan SEM-Vega mostly at magnifica- tions of 300–400´. The terminology for indumentum description follows that of HARRIS and HARRIS (1994). Results The main features of pericarp indumentum of the studied species of Iranian Amygdalus are presented in table 2 and SEM micrographs in plates 1–3 (figs. 1–23). The pericarp indumentum type is velutinous. Except for A. reticulata Runemark ex Khatamsaz with gla- brous pericarp (Fig. 11), all other examined taxa were hairy. The trichomes could be stud- ied with respect to different aspects including density, shape and length. Regarding density, trichomes were subdivided into four subtypes: dense, dense-sparse, sparse and very sparse. All trichomes are simple but two basic types of shape were found in the pericarp: tubular and flattened. Trichome length differs among the studied species. The length of tubular tri- chomes showed a diverse range from approximately 100–200 mm in A. communis L. and A. carduchorum Bornm. to more than 1000 mm in A. korshinskyi (Hand.-Mazz.) Bornm., A. haussknechtii (C. K. Schneider) Bornm. var. pubescens Bornm., A. lycioides Spach var. horrrida (Spach) Browicz and A. ´kamiaranensis Khatamsaz et Assadi. The length of flat- tened trichomes was in the range of 100–150 mm in A. ´kamiaranensis to an approximately 800–900 mm or more in A. kotschyi Boiss. et Hohen., A. lycioides Spach var. lycioides and then followed by A. arabica Spach, A. spinosissima Bge. subsp. spinosissima. Tubular tri- chomes were more frequent than other trichome in most species except for A. kotschyi (subgen. Amygdalus) and the three studied taxa of subgen. Dodecandra (Spach) Browicz including A. eburnea Spach, A. spinosissima Bge. subsp. spinosissima and A. lycioides var. lycioides (Figs. 8, 17, 19, 21). ACTA BOT. CROAT. 69 (1), 2010 95 TRICHOME MICROMORPHOLOGY IN DRUPE OF AMYGDALUS U:\ACTA BOTANICA\Acta-Botan 1-10\Vafadar.vp 9. travanj 2010 13:14:23 Color profile: Disabled Composite 150 lpi at 45 degrees 96 A C T A B O T .C R O A T .69 (1),2010 V A F A D A R M .,A T T A R F .,M A R O O F IH . Tab. 1. Voucher specimens of Iranian species of Amygdalus used in the drupe pericarp indumentum study Collectors Collection data Species Attar, Maroofi & Zamani Iran, Kurdistan: Ca. 30 km to Ghorveh, 36323-TUH A. arabica Olivier Attar, Maroofi & Zamani Iran, Kurdistan: Kamiaran to Marivan, Takht-zangi village, 36333-TUH A. communis L. Maroofi & Naseri Iran, Kurdistan: Marivan, Dezli, 6285-kurdistan Herbarium A. carduchorum Bornm. Mobayen Iran, Fars: Road of Nourabad, 8621-TUH A. eburnea Spach Attar & Zamani Iran, Fars: Pass after Dasht-e Ardzan, 36286-TUH A. elaeagnifolia Spach subsp. elaeagnifolia Attar & Zamani Iran, East Azerbayjan: After Kaleibar, 37212-TUH A. fenzliana (Fritsch) Lipsky Attar & Zamani Iran, Fras: Kotal Pir-e Zan, 36299-TUH A. glauca Browicz Attar, Maroofi & Zamani Iran, Kurdistan: Ca.15 km to Kamiaran, Morvarid pass, 36330-TUH A. haussknechtii (C. K. Schneider) Bornm. var. pubescens Bornm. Attar, Maroofi & Zamani Iran, Kurdistan: Dezli pass, 36343-TUH A. korshinskyi (Hand.-Mazz.) Bornm. Attar, Maroofi & Zamani Iran, Kurdistan: Ca. 30 km from Saqqez to Baneh, Nakarouz mountain, 363673-TUH A. kotschyi Boiss. et Hohen. Mobayen Iran, Tehran: Kiasman, Fasham mountain, 19425-TUH A. lycioides Spach var. horrida (Spach) Browicz Attar & Zamani Iran, Esfahan: Fereidoonshahr, Vahdatabad village, Pishkooh mountain, 36319-TUH A. lycioides Spach var.lycioides Attar & Zamani Iran, East Azerbayjan: After Ahar to Tabriz, 37219-TUH A. nairica Fed. et Takht. Attar, Khatamsaz & Sheikh Iran, Fars: Shiraz, Bamou National Park, 20390-TUH A. reticulata Runemark ex Khatamsaz Attar & Zamani Iran, Fars: Dasht-e Ardzan, 36285-TUH A. scoparia Spach Ghahreman, Attar, Okhovvat & Mehdigholi Iran, Khorasan: Mashhad to Torbat-e Heidariyeh, Robat-e Sang, 27289-TUH A. spinosissima Bge. subsp. spinosissima Attar, Maroofi & Zamani Iran, Kurdistan: Takht-zangi village, 36331-TUH A. trichamygdalus (Hand.-Mazz.) Woronow Mirtadzadini Iran, Kerman: Bam, Mij, 37820-TUH A. wendelboi Freitag Attar, Maroofi & Zamani Iran, Kurdistan: Ca. 35 km from Sanandaj to Kamiaran, 36322-TUH A. ´ kamiaranensis Khatamsaz et Assadi Rieben Iran, Tehran: Karaj, Koohdashteh, 8618-TUH A. ´ keredjensis Browicz U : \ A C T A B O T A N I C A \ A c t a - B o t a n 1 - 1 0 \ V a f a d a r . v p 9 . t r a v a n j 2 0 1 0 1 3 : 1 4 : 2 3 C o l o r p r o f i l e : D i s a b l e d C o m p o s i t e 1 5 0 l p i a t 4 5 d e g r e e s Amygdalus haussknechtii var. pubescens contained only tubular hairs (Fig. 7). In three studied taxa including A. kotschyi, A. arabica and A. lycioides var. lycioides, flattened tri- chomes were folded (Figs. 8, 12, 13, 21). Most studied species of sect. Amygdalus (subgen. ACTA BOT. CROAT. 69 (1), 2010 97 TRICHOME MICROMORPHOLOGY IN DRUPE OF AMYGDALUS Plate 1. SEM micrographs of drupe pericarp indumentum of Iranian species of Amygdalus. 1, 2 – A. communis, 3 – A. trichamygdalus, 4 – A. wendelboi, 5 – A. korshinskyi, 6 – A. fenzliana, 7 – A. haussknechtii var. pubescens, dense tubular trichomes, 8 – A. kotschyi, frequent flattened trichomes. U:\ACTA BOTANICA\Acta-Botan 1-10\Vafadar.vp 9. travanj 2010 13:14:28 Color profile: Disabled Composite 150 lpi at 45 degrees Amygdalus) except for A. reticulata contained indumentum with dense trichomes includ- ing A. communis L., A. trichamygdalus (Hand.-Mazz.) Woronow, A. wendelboi Freitag, A. korshinskyi, A. fenzliana, A. haussknechtii var. pubescens, A. kotschyi and A. elaeagnifolia Spach subsp. elaeagnifolia (Figs. 1, 3, 4, 5, 6, 7, 8, 10) but in A. carduchorum, indumentum was dense-sparse (Fig. 9). In contrast to the former section, three species of sect. Spar- tioides Spach showed very sparse indumentum with tubular and flattened trichomes (Figs. 12, 15, 16). The density of trichomes was very low and trichomes were very sparse. Exam- ined species of subgen. Dodecandra including A. spinosissima subsp. spinosissima, A. 98 ACTA BOT. CROAT. 69 (1), 2010 VAFADAR M., ATTAR F., MAROOFI H. Tab. 2. Features of pericarp indumentum of Iranian species of Amygdalus. Abbreviations: F. T. – flattened trichomes; T. T. – tubular trichomes. Species Trichome density Tubular trichomes Flattened trichomes Dominance of trichomes subgen. Amygdalus sect. Amygdalus A. communis Dense + + T. T. A. trichamygdalus Dense + + T. T. A. wendelboi Dense + + T. T. A. korshinskyi Dense + + T. T. A. fenzliana Dense + + T. T. and F. T. A. haussknechtii var. pubescens Dense + – T. T. A. kotschyi Dense + + F. T. A. carduchorum Dense-sparse + + T. T. A. elaeagnifolia subsp. elaeagnifolia Dense + + T. T. A. reticulata Glabrous – – – sect. Spartioides A. arabica Very sparse + + Both rare A. glauca Very sparse + + Both rare A. scoparia Very sparse + + Both rare subgen. Dodecandra A. spinosissima subsp. spinosissima Dense + + F. T. A. eburnea Dense + + F. T. A. nairica Dense + + T. T. and F. T. A. lycioides var. horrida Dense + + T. T. and F. T. A. lycioides var. lycioides Dense + + F. T. Hybrids A. ´keredjensis Dense + + T. T. A. ´kamiaranensis Sparse + + Both few Abbreviations: F. T.: Flattened Trichomes; T. T.: Tubular Trichomes. U:\ACTA BOTANICA\Acta-Botan 1-10\Vafadar.vp 9. travanj 2010 13:14:28 Color profile: Disabled Composite 150 lpi at 45 degrees eburnea, A. nairica and A. lycioides (both varieties) showed dense indumentum (Figs. 17, 18, 19, 20, 21). Two varieties of A. lycioides showed different portions of trichomes as fol- lows: in A. lycioides var. horrida, both tubular and flattened trichomes were frequent while in another variety, var. lycioides, flattened trichomes were more frequent (Figs. 20, 21) ACTA BOT. CROAT. 69 (1), 2010 99 TRICHOME MICROMORPHOLOGY IN DRUPE OF AMYGDALUS Plate 2. SEM micrographs of drupe pericarp indumentum of Iranian species of Amygdalus. 9 – A. carduchorum, 10 – A. elaeagnifolia subsp. elaeagnifolia, 11 – A. reticulata, showing the gla- brous pericarp, 12–14 – A. arabica, 15 – A. glauca, 16 – A. scoparia. U:\ACTA BOTANICA\Acta-Botan 1-10\Vafadar.vp 9. travanj 2010 13:14:33 Color profile: Disabled Composite 150 lpi at 45 degrees (Tab. 2). Two studied hybrids, A.´keredjensis and A.´kamiaranensis showed different indumentum types, dense and sparse respectively (Figs. 22, 23). Worthy of note, these two hybrids showed different details of trichomes, as well (Tab. 2). 100 ACTA BOT. CROAT. 69 (1), 2010 VAFADAR M., ATTAR F., MAROOFI H. Plate 3. SEM micrographs of drupe pericarp indumentum of Iranian species and hybrids of Amyg- dalus. 17 – A. eburnea, 18 – A. nairica, 19 – A. spinosissima subsp. spinosissima, 20 – A. lycioides var. horrid, 21 – A. lycioides var. lycioides, 22 – A. ´keredjensis, 23 – A.´kamia- ranensis. U:\ACTA BOTANICA\Acta-Botan 1-10\Vafadar.vp 9. travanj 2010 13:14:38 Color profile: Disabled Composite 150 lpi at 45 degrees Discussion In the present study, we studied pericarp indumentun in the drupe of Iranian Amyg- dalus. Trichome micromorphology has been the subject of several studies for taxonomic goals in different plant families which include trichomes in various parts especially leaf, stem, and seed-fruit coat (FONTENELLE et al. 1994, XUHAN and VAN-LAMMEREN 1994, ZARRE 2003, AGBAGWA and OKOLI 2006, AKCIN 2007, ATTAR et al. 2007, JURI[I] GRUBE[I] et al. 2007, KAYA et al. 2007, MOAZZENI et al. 2007). Reports that have assessed hair micromorphology of the family Rosaceae are rare. These studies deal with surface of seed and achene coat that is mostly glabrous and possesses different seed coat pattern including reticulate, faviulariate, ruminate, coolleculate, honey-combed, different cell wall features and different shapes of epidermal cells (DOWIDAR et al. 2003, LATIF 2004). In the following sections, we will summarize the pericarp indumentum of the drupe of Iranian taxa of Amygdalus. Subgen. Amygdalus A. sect. Amygdalus In this section, there are two vegetative groups regarding habit, tree (three species) and shrub (nine species). Tree species are: A. communis, A. trichamygdalus and A. wendelboi (KHATAMSAZ 1992). The first two species are distributed in the west and northwest of Iran but the third, A. wendelboi, an endemic species for the flora of Iran (KHATAMSAZ 1992), has a distribution range far from the two former localities and is found in the south of Iran. A. communis also has been found in some other areas including Turkey (BROWICZ 1972), Rus- sia (SHISHKIN and YUZEPCHUK 1941) and China (LU and BARTHOLOMEW 2003). Amygdalus trichamygdalus is also distributed in Turkey (BROWICZ 1972). Regarding pericarp indu- mentum micromorphology, except the length of tubular trichomes, longer in A. tricham- ygdalus than in the two closely related species, these three species show similarities and homogeneity in pericarp trichomes including dense indumentum and frequent tubular tri- chomes (Figs. 1, 3, 4). It seems that in this subgroup, different ecological conditions includ- ing semi-humid to semi-arid environments in the west and northwest Iran in Zagros region and arid environments in the south Iran do not affect the indumentum density of the pericarp. This finding is in contrast to findings concerning the indumentum of other plant parts including leaf or stem showing that their trichomes are dependent on habitat condi- tions; in arid environments, the indumentum is dense for adaptation to severe conditions (ZARRINKAMAR 1993, ZARRINKAMAR and DINARVAND 2006). Nine shrubby species are included in sect. Amygdalus (KHATAMSAZ 1992). Among them, seven species were investigated for pericarp indumentum study including A. kor- shinskyi (west and northwest Iran), A. fenzliana (northwest Iran), A. haussknehtii var. pubescens (west and central Iran), A. kotschyi (west and northwest Iran), A. carduchorum (west and northwest Iran), A. elaeagnifolia subsp. elaeagnifolia (central and south Iran) and A. reticulata (south Iran) (BROWICZ 1969, KHATAMSAZ 1992). Among those, three spe- cies including A. haussknechtii, A. elaeagnifolia and A. reticulata, are endemic species for the flora of Iran (BROWICZ 1969, KHATAMSAZ 1992). Some species of this subgroup are found in neighboring countries especially in Turkey (BROWICZ 1972). Regarding pericarp indumentum, this shrubby subgroup is the most heterogeneous group with emphasis on indumentum type, density and portion of trichomes (Tab. 2). Except for A. reticulata from ACTA BOT. CROAT. 69 (1), 2010 101 TRICHOME MICROMORPHOLOGY IN DRUPE OF AMYGDALUS U:\ACTA BOTANICA\Acta-Botan 1-10\Vafadar.vp 9. travanj 2010 13:14:38 Color profile: Disabled Composite 150 lpi at 45 degrees the south of Iran with glabrous pericarp (Fig. 11), other species have dense or dense-sparse indumentum (Figs. 5, 6, 7, 8, 9, 10). A. haussknechtii var. pubescens and A. korshinskyi possessed the longest tubular trichomes among the studied species of this subgroup (Figs. 5, 7) and A. kotschyi possessed the longest flattened trichomes (Fig. 8). In A. korshinskyi and A. fenzliana, two related species, we observed a number of differences (Tab. 2, Figs. 5, 6). Also, two closely related species (according to morphological evidence) including A. kotschyi and A. carduchorum exhibit extreme difference regarding to density and portion of trichomes as follows: as against most of the species, in A. kotschyi with dense indu- mentum, the flattened hairs were long and more frequent (Fig. 8), while in A. carduchorum, the tubular trichomes were short and more frequent (Fig. 9). It is worthy of mention that pericarp indumentum in this species is dense-sparse. Pericarp indumentum heterogeneity is observed in the last closely related species of this subgroup including A. elaeagnifolia and A. reticulata. In A.reticulata, the pericarp was completely glabrous, a unique feature among the studied species (Fig. 11) but in A. elaeagnifolia subsp. elaeagnifolia, it is dense (Fig. 10). Worthy of note, like the findings in former subgroup, in this subgroup, different ecological conditions could not affect the pericarp indumentum and as seen above, most species from the west and northwest Iran and south Iran exhibit dense indumentum except for the A. reticulata. As discussed above, as against the first subgroup in subgen. Amyg- dalus, our findings of pericarp indumentum show considerable variation in this shrubby subgroup even between closely related species. It is interesting that this subgroup is the most problematic subgroup in the genus Amygdalus from a morphological point of view. A. sect. Spartioides This section includes three junciform species: A. arabica, A. glauca and A. scoparia. The main morphological feature of this section is the absence of brachyblast (short shoots) (BROWICZ 1969, KHATAMSAZ 1992). Among those, A. glauca is an endemic element for the flora of Iran (BROWICZ 1969, KHATAMSAZ 1992). Amygdalus arabica is mainly distributed in the west of Iran as well as Turkey (BROWICZ 1972). Amygdalus scoparia is distributed in many different localities in Iran except for the west and northwest and is one of the most widespread species of Amygdalus in Iran. It is found in Russia as well (SHISHKIN and YUZEPCHUK 1941). Amygdalus glauca is found in a limited region in the south of Iran in Fars province (BROWICZ 1969, KHATAMSAZ 1992). Regarding pericarp indumentum, there was significant difference between this and the former section. In contrast to sect. Amyg- dalus with dense indumentum in most studied species, all species in sect. Spartioides ex- hibited very sparse indumentum with more or fewer similarities (Figs. 12, 15, 16). Subgen. Dodecandra This subgenus is completely different from the former regarding its habit feature, be- cause in this subgenus there are six shrubby species with thick spiny shoots (BROWICZ 1969, KHATAMSAZ 1992). Species in this subgenus are found in different ecological condi- tions in the west, northwest, east, northeast, central, north and south Iran. Some of them are found in the neighboring countries (SHISHKIN and YUZEPCHUK 1941, BROWICZ 1969, 1972). From six species in this subgenus, we studied four species. Among them, A. lycioides is widely distributed in Iran. In all studied species, the pericarp indumentum was dense (Figs. 17, 18, 19, 20, 21). Studied species in this subgenus show differences in pericarp trichomes in shape and trichome portions (Tab. 2). Two varieties of A. lycioides exhibit significant difference. A. lycioides var. lycioides possessed the longest flattened trichomes and A. 102 ACTA BOT. CROAT. 69 (1), 2010 VAFADAR M., ATTAR F., MAROOFI H. U:\ACTA BOTANICA\Acta-Botan 1-10\Vafadar.vp 9. travanj 2010 13:14:38 Color profile: Disabled Composite 150 lpi at 45 degrees lycioides var. horrida the longest tubular trichomes (Figs. 20, 21). While in A. lycioides var. horrida, an endemic variety for the flora of Iran (KHATAMSAZ 1992), both tubular and flat- tened trichomes were frequent (Fig. 20), in another variety, var. lycioides, flattened tri- chomes were more frequent and they were folded as well (Fig. 21). According to results in this subgenus, the density of trichomes in the pericarp is independent of ecological condi- tions. Hybrids Among Amygdalus hybrids, two hybrids were examined for pericarp indumentum study. Both hybrids are endemic elements for the flora of Iran (KHATAMSAZ 1992). These two hybrids show different features regarding to pericarp trichomes (Tab. 2). Amygdalus ´keredjensis from the north of Iran showed dense indumentum. Tubular hairs were more frequent (Fig. 22). Amygdalus ´kamiaranensis, a hybrid from the west of Iran, showed sparse indumentum (Fig. 23). Also, Amygdalus ´kamiaranensis, together with a few other species, possessed the longest tubular trichomes. Amygdalus ´ keredjensis is a hybrid re- sulting from a hybridization process between A. scoparia and A. lycioides (BROWICZ 1969, KHATAMSAZ 1992). Comparison of pericarp features between this hybrid and its parents showed that regarding pericarp indumentum, A. ´ keredjensis was related to A. lycioides (Figs. 20, 22). Also according to Khatamsaz (1992), A. ´ kamiaranensis is a hybrid be- tween A. haussknectii and A. scoparia, but based on our studies on Iranian Amygdalus, two other species are its parents: A. arabica and A. lycioides, because A. ´ kamiaranensis is a hybrid that found in the west of Iran but A. scoparia is found in different localities in Iran except for the west and northwest. The presence of thin spiny shoots in this hybrid shows that one of its parents is a spiny species from the second subgenus as well; so A. haussknechtii could not be another parent. Khatamsaz’ hypothesis is based on morphologi- cal evidence as is the hypothesis presented in this paper. Unfortunately, she did not intro- duce the exact parents because she did not consider the distribution of parent species and morphological features exactly, whereas evidence for the present hypothesis was shown above. We have collected numerous specimens of this hybrid from the distribution locali- ties in the west Iran. Amygdalus scoparia is not distributed in the west of Iran and based on presence of thin spiny shoots in this hybrid, one spiny species should be another parent. Unfortunately there are no crossing studies about these hybrids in Iran. A molecular phylo- genetic study on Iranian species and hybrids of Amygdalus is currently being undertaken. Perhaps this investigation will be able to throw light on the real parents of A. ´ kamiara- nensis. A comparison of pericarp results only showed some similarities to A. lycioides (Figs. 20, 23). Conclusion With an emphasis on pericarp indumentum micromorphological findings, it is clear that in some cases, these results confirm classic classifications in the genus Amygdalus. For ex- ample, two sections of subgen. Amygdalus were easily distinguished from each other. But two subgenera were not separated according to pericarp indumentum results. Within sect. Amygdalus there was enough variation even between two closely related species in the shrubby subgroub such as A. elaeagnifolia and A. reticulata. Regarding our findings in this study, it is clear that the density of trichomes in pericarp is not dependent on habitat condi- ACTA BOT. CROAT. 69 (1), 2010 103 TRICHOME MICROMORPHOLOGY IN DRUPE OF AMYGDALUS U:\ACTA BOTANICA\Acta-Botan 1-10\Vafadar.vp 9. travanj 2010 13:14:39 Color profile: Disabled Composite 150 lpi at 45 degrees tions. 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