The Apiaceae Lindl. family contains around 460 genera and 3700 species distributed worldwide, with Turkey being one of the richest countries in southwest Asia in terms of number of species. The country has 105 genera and approximately 495 species of Apiaceae followed in richness by Iran, Georgia, Syria, Azerbaijan, and Iraq. There are 60 genera endemic to Asia, of which 45 are monotypic (Sales & Hedge 2013Sales F. & Hedge I.C. 2013. Generic endemism in South-West Asia: an overview. Rostaniha 14: 22-35.). Genera Chamaesciadium C.A.Mey., Cymbocarpum DC. ex C.A.Mey., Diplotaenia Boiss., Exoacantha Labill., Fuernrohria K.Koch, Froriepia K.Koch, Gongylosciadium Rech.f., Lisaea Boiss., Oliveria Vent., Ormosciadium Boiss., Petroedmondia Tamamsch., Rhabdosciadium Boiss., Szovitsia Fisch. & C.A.Mey, Thecocarpus Boiss. and Trigonosciadium Boiss. have small geographic ranges and are endemic to Turkey, Iran, and Iraq. Genera Aegokeras Raf., Crenosciadium Boiss. & Heldr., Postiella Kljuykov, Ekimia H.Duman & M.F.Watson are only endemic to Turkey.
Oliveria decumbens Vent. is scatteredly distributed in small areas in Iran, Iraq, Syria, and Turkey. The genus Oliveria was established by Ventenat (1801)Ventenat E.P. 1800‒1803. Description des Plantes Nouvelles et peu connues, cultivées dans le jardin de J. M. Cels. De L’Imprimerie de Crapelet, Paris.. Oliveria aucheri Jaub. & Spach, O. bruguieri Jaub. & Spach, and O. orientalis DC. were then published as new species and are currently regarded as synonyms of O. decumbens. Oliveria was placed into tribe Smyrneae by de Candolle (1830)Candolle A.P. 1830. Umbelliferae. In Candolle A.P (ed.), Prodromus systematis naturalis regni vegetabilis 4: 55-250. Treüttel & Würtz, Paris. and then transferred into tribe Ammineae by Bentham (1867)Bentham G. 1867. Umbelliferae. In Bentham G. & Hooker J.D. (eds.), Genera plantarum 1: 859-931. Reeve, London. followed by Boissier (1872)Boissier, E. 1872. Oliveria Hoffm. In Boissier E. (ed.), Flora orientalis 2: 894. Geneva et Basileae.. Afterwards, Oliveria was placed in tribe Apieae by Rechinger & Hedge (1987)Rechinger K.H. & Hedge I.C. (eds.) 1987. Flora Iranica 162. Akademische Druck und Verlagsanstalt, Graz.. These traditional Apiaceae classification systems were largely based on fruit anatomy and morphology. Apiaceae is undergoing a major taxonomic rearrangement within the angiosperms given that current systematic knowledge has changed in light of molecular phylogenetics (e.g., Jiménez-Mejías & Vargas 2015Jiménez-Mejías P. & Vargas P. 2015. Taxonomy of the tribe Apieae (Apiaceae) revisited as revealed by molecular phylogenies and morphological characters. Phytotaxa 212: 57-79.). A comprehensive molecular phylogenetic analysis of tribal classification of Apiaceae, based on DNA sequences, showed that Oliveria is sister to Trachyspermum within Pyramidoptereae (Mousavi et al. 2020Mousavi S., Mozaffarian V., Mummenhoff K., Downie S.R. & Zarre S. 2020. An updated lineage-based tribal classification of Apiaceae subfamily Apioideae with special focus on Iranian genera. Systematics and Biodiversity 19: 89‒109. ).
Plants from the Apiaceae family are commonly used for food, flavoring, fragrance, and medicines. They are also known for their uses as household remedies for centuries. Many recent experimental and biological investigations have been conducted to validate the ethnomedicinal claims of the plants belonging to this family (Ahmad & al. 2018Ahmad B.S., Talou T., Saad Z., Hijazi A., Cerny M., Kanaan H., Chokr A. & Merah O. 2018. Fennel oil and by-products seed characterization and their potential applications. Industrial Crops & Products 111: 92‒98. ). In traditional medicine, Oliveria has been used for indigestion, diarrhea, abdominal pain, fever, and skin wounds since ancient times (Amin & al. 2005Amin G, Sourmaghi M.S., Zahedi M., Khanavi M. & Samadi N. 2005. Essential oil composition and antimicrobial activity of Oliveria decumbens. Fitoterapia 76: 704‒707.; Mahboubi & al. 2016Mahboubi M., Feizabadi M.M., Khamechian T., Kazempour N., Razavi Zadeh M., Sasani F. & Bekhradi M. 2016. The effect of Oliveria decumbens and Pelargonium graveolens on healing of infected skin wounds in mice. World Journal of Plastic Surgery 5: 259‒264.; Alizadeh-Behbahani & al. 2018Alizadeh-Behbahani B., Tabatabaei-Yazdi F., Vasiee A. & Mortazavi S.A. 2018. Oliveria decumbens essential oil: chemical compositions and antimicrobial activity against the growth of some clinical and standard strains causing infection. Microbial Pathogenesis 114: 449‒452.). There are many studies on the antioxidant, antihemolytic, anticancer, and anti-inflammatory properties of Oliveria. However, there are no detailed morphological, anatomical, and palynological studies about this genus (Sajjadi & Hoseini 2002Sajjadi S.E. & Hoseini S.A. 2002. Essential oil constituents of Oliveria decumbens Vent. Journal of Essential Oil Research 14: 220‒21. ; Amin & al. 2005Amin G, Sourmaghi M.S., Zahedi M., Khanavi M. & Samadi N. 2005. Essential oil composition and antimicrobial activity of Oliveria decumbens. Fitoterapia 76: 704‒707.; Mahboubi & al. 2016Mahboubi M., Feizabadi M.M., Khamechian T., Kazempour N., Razavi Zadeh M., Sasani F. & Bekhradi M. 2016. The effect of Oliveria decumbens and Pelargonium graveolens on healing of infected skin wounds in mice. World Journal of Plastic Surgery 5: 259‒264.; Eftekhari & al. 2019Eftekhari M., Ardekani M.R.S., Amin M., Attar F., Akbarzadeh T., Safavi M., Elahe Karimpour-Razkenari, Amini M., Isman M. & Khanavi M. 2019. Oliveria decumbens, a bioactive essential oil: chemical composition and biological activities. Iranian Journal of Pharmaceutical Research 18: 412-421.). For this reason, the aim of this study was to investigate the morphological, carpological, and palynological characteristics of O. decumbens and to evaluate their significance in Apiaceae taxonomy.
Updated morphological description
⌅Oliveria decumbens Vent., Descr. Pl. Nouv., pl. 21 (1801). Type: cultivated in Hort. Cels, s.d., E.P. Ventenat s.n. (lectotype designated by Callmander & al. 2017: G 00341532, image!Callmander M.W., Durbin O.D., Lack H.W., Bungener P., Martin P., Gautier L. 2017. Etienne-Pierre Ventenat (1757-1808) and the gardens of Cels and Empress Joséphine. Candollea 72: 87-132.). Fig. 1-2.
Ascending to erect or rarely decumbent, aromatic, annual herbs. Stem (13-)20-45(-75) cm tall, rigid, whitish, ± much branched, glabrous or rarely hirsute, solid, terete, 2-4 mm in diameter at base. Basal leaves soon withering; 3-10 cm long (inc. petiole), lamina oblong in outline, ± glabrous, 1-pinnate with 4-5 pairs of segments; each segment divided into smaller, decurrent lobes; ultimate segments lanceolate, ± toothed; petioles 0.6-2.5 cm long with sheathing base. Lower cauline leaves similar to basal leaves; middle and upper cauline leaves ovate, subsessile or sessile, pilose, pinnatisect. Umbels 1.5-2.5 cm in diameter, ± condensed, (2-)3-5(-7) rayed; rays (2-)3-10 mm long, slightly thickened, hairy, ± equal. Bracts 3-5, 3-8 mm long, obovate, dissected, densely pilose. Flowers 15-35(45), hermaphrodite, condensed, pedicellate. Pedicels 0.5-2 mm long, slightly thickened, rounded, hairy. Bracteoles 6-8, 2.5-5 mm long, dissected, obovate, densely pilose. Sepals 5, 0.5-0.75 mm, distinct, persistent, ovate-triangular, acute, hairy. Petals 5, 1-1.6 × (0.6-)0.8-1.1 mm, white or pink, ± oblong-obovate, emarginate, with narrow tip bent inward, hairy on abaxial surface. Ovary hairy. Stamens enrolled; filaments whitish, c. 1.5 mm long; anthers 0.4-0.9 mm, sub-globular, dorsally inserted. Fruits 2.0-3.6 × 1-1.6 mm, oblong; mericarps densely hirsute, laterally compressed; ribs filiform, obscured by hair; stylopodium ± conical; style 1.0-1.8 mm, slender, erect; vittae large, oblong, vallecular vitta 1; commissural vittae 2.
Distribution and phenology.-Oliveira decumbens is distributed along the northwest-southeast transect of a narrow area in the western and southern region of Iran and the northern regions of Iraq (Fig. 3; Appendix 1) at elevations between 150 and 1700 m. In Turkey, the species is only known from the Ceylanpınar region near the border with Syria. It grows in steppes and flowers in May and July.
Fruit anatomy and micromorphology.-The fruit of Oliveira decumbens is oblong-elliptic in the transverse section. Mericarps are homomorphic, nearly circular, and have five projecting ribs. The exocarp is a single layer and consists of rectangular-like cells near the distal ends of the marginal ribs. Their walls are slightly thickened and the outer walls are covered with a smooth cuticle layer and simple unicellular trichomes, which originate from the epidermal cells. The mesocarp is multilayered with thin-walled parenchymatous cells. They are irregularly shaped and polygonal. Vascular bundles are located under the ribs and are surrounded by mesocarp cells. The vittae are large and oblong-elliptic or nearly orbicular. They are lined with thin-walled epithelial cells. There is one vitta per vallecula and two commissural vittae. The endocarp is single layer and consists of thin-walled cells. Endosperm cells are irregular, polygonal in shape, and are filled with granular contents (Fig. 4). The fruit of O. decumbens is covered with dense, long, hirsute hairs that have a papillose surface (Fig. 6).
Palynology.-Pollen materials were taken from herbarium specimen. Light microscopy (LM) observations were carried out on acetolyzed pollen and prepared according to Erdtman (1952)Erdtman G. 1952. Pollen morphology and Plant taxonomy I. Angiosperms. Almqvist & Wikshell, Stockholm. . Measurements, based on 50 samples from one population, were taken with a Leica microscope. For SEM analyses, the acetolyzed pollen grains were mounted on stub and coated with gold, using a Polaron SC7620 sputter coater. Microphotographs were taken using an incorporated Zeiss LS-10 camera. The terminologies of Erdtman (1952)Erdtman G. 1952. Pollen morphology and Plant taxonomy I. Angiosperms. Almqvist & Wikshell, Stockholm. and Faegri & Iversen (1975) were used for the micromorphological features. The pollen grains of Oliveria decumbens are monad, isopolar, radially symmetric, and tricolporate (Fig. 5). The polar axis (P) ranges from 28.30 to 35.55 µm and the equatorial axis (E) ranges from 11.39 to 16.58 µm. The mean length of the polar axis (P) is 30.05 ± 2.30 μm, and the mean of the equatorial diameter (E) is 12.68 ± 1.74 μm. P/E averages 2.29 ± 0.16, making the pollen grain shape perprolate. In polar view, the pollen grains are nearly triangular with obtuse angles. In an equatorial view, the grains are narrowly oblong with slightly equatorial constriction and obtuse polar caps. The colpus extends nearly to the poles. The pore area is slightly protruding and located in the middle of colpus. The sculpturing pattern is striate or psilate at the polar area and irregularly rugulate at the equatorial area, but sometimes striate at the polar area and psilate-foveolate toward the polar area. The fruit of O. decumbens is covered with dense, long, hirsute hairs that have a papillose surface (Fig. 6).
Comments.-Oliveria is very isolated from other members of Apiaceae and its morphological characteristic is rather distinctive and apparently does not closely resemble other genera in tribe Apieae. Oliveria is characterized by a much-branched and bright whitish stem; conspicuous and persistent sepals; densely hairy and divided bracts and bracteoles; dorsally hairy and white or pink petals; and slightly laterally compressed, densely hairy, and ovoid-oblong fruits.
Although our description corresponds to that in Flora of Turkey (Matthews 1972Matthews V.A. 1972. Oliveria. In Davis P.H. (ed.) Flora of The Turkey and the East Aegean Islands 4: 425-426. Edinburgh University Press, Edinburgh. ), there are several differences as follows: the stem is (13)20-45(60) cm (not 20-40 cm), basal leaves 3-10 cm long (not determined), the rays are (2-)3-5(-7) (not 3-5) in number and 3-5(-10) mm long (not 5-10 mm long), bracts are 3-5 (not determined) in number, 3-8 mm long (not determined), sepals are 0.5-0.75 mm long (not determined), petals are 1-1.6 x (0.6-) 0.8-1.1 mm in size (not determined).
One of main characteristics of Oliveria is its shiny white and glabrous stem. Similar stem structure is also seen in Ergocarpon C.C.Towns., Eryngium L., and Schumannia Kuntze. Amiri & al. (2011)Amiri H., Lari Yazdı H., Dosti B. & Samsamnia F. 2011. Essential oil composition and anatomical study of Oliveria decembens. Iranian Journal of Medicinal and Aromatic Plants 26: 513‒520. have studied the anatomical characteristics of the leaf and stem of Oliveria. Their studies have shown that the surface of leaves is covered by non-glandular hairs, while the cross section of the stems show secretory canals in the cortex region. In the present study, we examined the anatomy and morphology of the fruit. According to our findings, the fruit of O. decumbens is oblong, laterally compressed, and densely hirsute. The bracts of Oliveria are divided and resemble those of Ammi L., Artedia L., Cuminum L., Daucus L., Eremodaucus Bunge, Kalakia Alava, Lagoecia L., Ormosciadium Boiss., Scandix L., and Trachyspermum Link.
According to Erdtman (1952)Erdtman G. 1952. Pollen morphology and Plant taxonomy I. Angiosperms. Almqvist & Wikshell, Stockholm. , Umbelliferae species are stenopalynous. Observations by Perveen & Qaiser (2006)Perveen A, Qaiser M. 2006. Pollen Flora of Pakistan-XLVIII. Umbelliferae. Pakistan Journal of Botany 38: 1‒14. have indicated that the pollen grains of Apiaceae are usually radially symmetrical, isopolar, and prolate to perprolate and tricolporate (rarely 4-colporate). The tectal surface is commonly striate-rugulate, rugulate-striate, or simple striate. Our result confirms the stenopalynous characteristic of the family Apiaceae, and the palynological observations reveal that the pollen grains are perprolate in shape and irregularly rugulate in the equatorial area.
Our study provides a detailed account of the morphology, palynology, and micromorphology of Oliveria, increasing our botanical knowledge of a species that has been traditionally used since ancient times.