Use of Leaf Anatomy for Identification of Quercus L. Species Native to Kurdistan-Iraq
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ISSN: 2410-7549 Journal University of Zakho, Vol. 3(A) , No.2, Pp 222-232, 2015 USE OF LEAF ANATOMY FOR IDENTIFICATION OF QUERCUS L. SPECIES NATIVE TO KURDISTAN-IRAQ Saleem Esmael Shahbaz¹, Shamiran Salih Abdulrahman², Haliz Arif Abdulrahman² ¹ Plant taxonomy, Faculty of Agriculture, University of Duhok, Kurdistan region – Iraq. ² Department of Biology, faculty of Science, University of Zakho, Kurdistan region – Iraq. (Accepted for publication: August 27, 2015) Abstract: Anatomical features of the leaves of Quercus L. species are presented in this study for the first time. Leaves are bifacial and the palisade parenchyma of Q. aegilops and Q. libani is stratified into two layers, of nearly equal width, while that of Q. infectoria and Q.macranthera composed of only one layer. The cortex of both midrib and petiole is well developed with collenchyma starting just beneath the epidermis. The collenchyma of Q. aegilops is extremly thick compared with that of other species. Vascular bundles of the midrib and petiole are completely enclosed by the two pericycle layers of fibers and sclerenchyma. While the number of vascular bundles and sclerenchyma groups cupping them is 3 and 2 for midribs of Q. aegilops and Q. libani respectively, the number turns into 2 vascular elements of different appearance in their petioles. Petiole secondary vascular bundles are well developed and their sclerenchyma groups more lignified in Q. infectoria but less developed and reduced in Q. macranthera. From the results, it is concluded that the leaf blade and petiole anatomical features can provide diagnostic characters for distinguishing Quercus species of Iraq. Results also strongly support placing Q. aegilops and Q. libani in the section Cerris but Q. infectoria is more reliable in the section Mesobalanus. Key words: Quercus aegilops; Quercus libani; Quercus infectoria; Quercus macranthera; Collenchyma; Sclerenchyma; Bifacial. Introduction sea level up to 4000 m. in the Himalaya Mountains (Wang, 1961; Menitsky, 2005). uercus species occur in the northern Based on molecular analysis, the genus Qhemisphere in North America, Europe, Quercus is estimated to have separated from Asia, and Africa (Axelrod, 1983), down to the Castanea about 60 million years ago (Hogan, Equator. Depending on the author’s report, there 2012). are between 300 (Lawrence, 1951; Elias, 1971) Because of the great number of Quercus taxa and 600 (Soepadmo, 1972) oak species in the and its wide distribution and the frequent world. Recent counting of Quercus genus in hybridization between members of the genus, America, Asia, and Europe amount to 320 to 354 taxonomists did not always agree for the method species for the subgenus Euquercus and 76 and characters used for classification of this species for the subgenus Cyclobalanopsis genus (De Candolle, 1868; Nixon, 1993). (Valencia, 2004; Menitsky, 2005; and Schwarz, Disagreements concentrate on the sub-genera 1964). According to Menitsky (2005), Quercus and sections adopted, and species delineation. in western Asia grow in Iran and Iraq in the Moreover, due to the huge variation within mountains of Zagros (Q. brantii, Q. libani) and species, Burger (1975) and Van Valen (1976) Elbruz mountains in north Iran and southern has suspected the concept of species in this coast of the Caspian Sea (Q. castaneifolia, Q. genus. macranthera). European species namely Q. Using numerical taxonomy, Peng et al. petraea, Q. robur and Q. pubescens extend in (2007) classified oak genus in China into Caucasus where they meet western Asian different sections based only on qualitative and species mainly Q. macranthera, and Q. quantitative characters namely Quercus infectoria. Lebanon and Palestine are regarded aegilops, Brachylepides, Engleriana and as the extreme Asian edge of the distribution of Echinolepides. the widespread Iraqi species Q. aegilops and Q. Mostly based on foliar and fruit infectoria. characteristics, Camus (1936-1954) classified Quercus grows in diverse habitats ranging the genus Quercus (sensu lato) into two from damp to relatively dry or desert, or from subgenera: subgenus Euquercus (Quercus sensu cool wet winter to hot dry summer, and from the stricto) and subgenus Cyclobalanopsis, which exist only in South Asia. Moreover, Camus 222 Journal University of Zakho, Vol. 3(A) , No.2, Pp 222-232, 2015 (1936-1954) further divided the subgenus petioles. The cross sections samples were stained Euquercus (Quercus sensu stricto) into 6 with Safranin and fast green (Al-Mukhtar, et al. different sections. 1982). Histological observations and Recently, the genus Quercus is classified into micrographs were performed with Olympus subgenera Quercus and Cyclobalanopsis and the CX2. Suitable images were photographed using subgenus Quercus into5 sections (Quercus, Sony 18.2 mega pixel. Mesobalanus, Cerris, Protobalanus, Lobatae) on the basis of style length, acorns maturation Results and Discussion period, acorn taste whether sweet or bitter, and Leaf blade Anatomy the acorn inside shell whether hairy or glabrous. According to the later sub-division, species Q. The range of leaf lamina thickness is 114.8- brantii Lindl.-Persian oak (Synonym to Q. 187.5 µm with the thickest in Q. aegilops and aegilops L. var. brantii), Q. infectoria Oliv.- the thinnest in Q. infectoria (Table 1). The Aleppo oak, and Q. libana Oliv. Lebanon oak internal leaf structure of our native Quercus belongs to the section Cerris, while Q. species shows both epidermises consist of single macranthera Fisch. et Mey. ex Hohen.- cell layer. As a mean value, the cuticle and the Caucasian oak to the section Mesobalanus epidermal layer cells on the adaxial face is much (David,1987) thicker than the corresponding abaxial characters Four oak species in Kurdistan region-Iraq: (Figure 1). The cuticle covering epidermis is Quercus aegilops, Quercus libani, Quercus relatively thick, especially on the adaxial face, infectoria, and Quercus macranthera. For but differences between species are insignificant Zohary (1973) the first 3 ones, are endemic to from the stand point of taxonomic application. Kurdo-Zagrozian Mountains for these species Leaves are bifacial with the mesophyll tissue exhibit large variability and extensive natural clearly differentiated into palisade parenchyma distribution in Kurdo zagros region while cells and spongy parenchyma cells. avoiding real Mediterranean climate. In Q. aegilops and Q. libani, the palisade Keys employed to separate between Quercus parenchyma is stratified in to two layers, and species using merely morphological characters contains many more chloroplasts than the has not been satisfactory and in some instances spongy cells (Figure 1-A, B), while in there is misidentification. Therefore, this study Q.infectoria and Q.acranthera it consists of only was planned to gain knowledge of the one palisade layer (Figure 1-C, D). The first anatomical characteristics of Quercus leaf and layer is longitudinal shape and in direct contact use them in support of the morphological with the adaxial epidermal layer , arranged characters for identifying the Iraqi representative perpendicular to it, the second layer comes oak species. directly below the first one. While the first layer Little is known about the anatomy of the oak cells are densely packed leaving no or very few leaf in Iraq. With the exception of the air spaces between cells, mainly because stomata contribution of Shahbaz (1993) who investigated are only confined to the abaxial epidermis the leaf cuticular structure but not the leaf blade, (Shahbaz, 2010), the second layer cells are midrib, and petiole cross section anatomy, no shorter and poorly arranged with more air spaces major contribution is to be observed as yet. compared with the first one. The palisade parenchyma (both layers) of Q. aegilops and Q. Material and Methods libani are nearly equally thick (the ratio of approximately 1:1) and forming nearly half of The anatomical observations were based and the blade thickness (48.53, 49.03% respectively). carried out on 20 mature leaves from each The difference between species is mainly species, collected from the Duhok and Erbil showed as a result of a thicker palisade provinces during May 2015. Herbarium parenchyma layer due to an additional second specimens made from trees used for anatomy layer of cells. The spongy tissue is made of cells investigation were deposited in the herbarium of which are round, isodimetric, or irregular in the Faculty of Agriculture/University of Duhok shape, some are elongated and poorly arranged (DPUH). The vegetal material was fixed in FAA in 3-5 layers, with very wide lacunae or air (formalin: glacial acetic acid: alcohol 5:5:90). spaces which increase rapidly towards the For the anatomical study, free-hand sections abaxial epidermis. Spongy layer width greatly were made on the central parts of leaf blades and differs between species, but the differences are 223 Journal University of Zakho, Vol. 3(A) , No.2, Pp 222-232, 2015 insignificant in taxa delimitation because of high the center of the midrib, running parallel to the degree of data overlapping (Table 1). Using the adaxial and abaxial strips of primary vascular average value for all species, the spongy bundles. The only difference between them is in parenchyma tissues are found to occupy a range the number of separate bundles and their of 31.91-36.98% of the total width of the leaf Sclerenchyma, which are 3 in Q. aegilops and 2 blade. in Q. libani (Figure 2-A, B). On the other hand, The secondary vein vascular bundles are the secondary vascular tissue produced by Q. interspersed in the mesophyl tissue, enclosed by infectoria and Q. macranthera is quite different bundle sheaths with their mechanical tissue of from vascular tissue of Q. aegilops and Q. libani collenchyatic nature located under both in structure, shape and arrangement. In Q. epidermises. infectoria the secondary vascular tissue is The measurements presented in this study are unique; its xylem is produced in direct contact to comparable with those of Nikolić, et al. (2005) the xylem of the corresponding primary vascular on Q.