The Triticeae is one of the most important tribes of the family Poaceae. It contains wheat (Triticum L.), barley (Hordeum L.) and rye (Secale L.) which are economically the most important cereals. Although the tribe has been the focus of several systematic studies there has not been a universally accepted taxonomic treatment for the tribe. This research study aiming to revise the tribe Triticeae Dumort. (Poaceae) in Turkey has been carried out by means of collecting specimens from all the localities in Turkey as well as examining the material collected over the years by the other researchers either from Turkey or abroad for a 4 year period starting from June 1th, 2006. All the specimens belonging the tribe were analysed by means of using standart taxonomic methods. This thesis is divided into four main chapters. In the first and second chapters, an introduction and general information about the tribe Triticeae and the material and methods used in the study are given. In the introduction part different taxonomic treatments on the tribe are explained briefly and the recent studies on the genera included in the tribe such as taxonomical, morphological and cytological are explained breifly. In the third chapter of the thesis, the significance of the morphological, micromorphological and ecological data which were used as diagnostic features in the taxonomy of the tribe are explained. Especially, SEM surveys of the glumes and lemma parts found to have great taxonomic values for the systematics of tribe. Distribution and habitat preferences of the tribe are discussed and IUCN threat categories of the taxa are reevaluated along with the types of threats so as to guarantee their sustainability of the rare taxa in Turkey. The fourth chapter covers the revision of the Tribe Triticeae in Turkey. A key for the genera is given. Synonymy, updated descriptions, flowering time, habitat, type citation, general distribution in Turkey, phytogeographical elements, specimen citations on a grid basis and general distribution outside Turkey, are given for each species. Along with general descriptions, keys to species and infraspecific categories are where necessary. In Tribe Triticeae, 18 genera, 79 species, 27 subspecies and 37 varieties have been recognized including 1 new species (Psathyrostachys narmanica Cabi &amp / Dogan sp. nov.), 3 new subspecies (Psathyrostachys fragilis (Boiss.) Nevski subsp. artvinense Cabi &amp / Dogan subsp. nov. / P. daghestanica (Alex.) Nevski subsp erzurumica Cabi&amp / Dogan subsp. nov. / Aegilops triuncialis L. subsp bozdagensis Cabi&amp / Dogan subsp nov.) and 4 new varieties (Agropyron cristatum (L.) subsp. pectinatum (Bieb.) Tzvelev var. mucranatum var. nov. / Eremopyrum bonaepartis (Sprengel) Nevski. var. aristatum Cabi &amp / Dogan / Thinopyrum pycnanthum (Godr.) Barkworth var. aristatum Cabi &amp / Dogan var. nov. / Hordeum spontaneum C. Koch var. anatolicum Cabi &amp / Dogan var. nov. In addition to the taxa new for science, Aegilops juvenalis (Thell.) Eig. and Hordeum spontaneum var. proskowetzii N&aacute / b

The genus Quercus L. is represented with more than 400 species in the world and 18 of these species are found naturally in Turkey. Although its taxonomical, phytogeographical and dendrological importance, the genus Quercus is still taxonomically one of the most problematical woody genus in Turkish flora. In this study, multivariate morphometric approach was used to analyze oak specimens collected from an isolated forest (Beynam Forest, Ankara) where Quercus pubescens Willd., Q. infectoria Olivier subsp. boissieri (Reuter) O. Schwarz and Q. macranthera Fisch. &amp / C. A. Mey. ex Hohen. subsp. syspirensis (C.Koch) Menitsky taxa are belonging to section Quercus sensu stricto (s.s.) are found. Additional oak specimens were included in the analysis for comparison. Morphometric study was based on 52 leaf characters such as, distance, angle, and area as well as counted, descriptive and calculated variables. Morphometric variables were calculated automatically by use of landmark and outline data. Random forest classification method was used to select discriminating variables and predict unidentified specimens by use of pre-identified training group. The results of the random forest variable selection procedure and the principal component analysis (PCA) showed that the morphometric variables could distinguish the specimens of Q. pubescens and Q. macranthera subsp. syspirensis mostly based on the overall leaf size and number of intercalary veins while the specimens of Q. infectoria subsp. boissieri were separated from others based on lobe and lamina base shape. Finally, micromorphological observations of abaxial lamina surface have been performed by scanning electron microscope (SEM) on selected specimens which were found useful to differentiate, particularly the specimens of Q. macranthera subsp. syspirensis and its putative hybrids from other taxa.