Taxonomic Studies of Some Species of the Family Cucurbitaceae in Saudi Arabia

Abstract

This thesis includes taxonomic studies of some of genera from the family Cucurbitaceae in the Kingdom of Saudi Arabia. The study included 11 species belonging to 8 genera, representing 70% of the species registered in the flora of Saudi Arabia. Each of the genera was described in detail based on specific morphological characteristics and their geographical distribution that shown on a distribution map. The study also presented a list of the samples that were studied. Each of Kedrostis, Cucumis, and Momordica include two species while the other genera (Corallocarpus, Zehneria, Citrullus, Coccinia and Blastania) include only one for each. This study focuses on the characteristics of trichomes on the leaves, stems, and flowers that were available as well as the characteristics of seeds and stomata. Throughout this study, the trichomes were divided into six groups: simple filiform trichomes, conical trichomes, macroform conical trichomes, flagellate macroform conical trichomes, wavy macroform trichomes and finally cylindrical trichomes and each group contains a number of trichomes. The Kedrostis foetidissima is characterized by the presence of Uniseriate flagellate macroform conical hair whereas the Kedrostis gijef is characterized by the presence of Uniseriate conical capitat hair. Momordica and Coccinia are distinguished by a variety of Uniseriate cylindrical hair. Additionaly, the genera Blastania and Citrullus contain Uniseriate conical hair and Uniseriate macroform conical hair. The genera of Corallocarpus, Zehneria, and Cucumis were distinguished by a wide variety of Uniseriate simple filiform hair, Uniseriate conical hair, Uniseriate macroform conical hair and Uniseriate wavy macroform curved hair. The study showed that the morphological character of the seeds (the surface of the seed) is a distinguishing feature of two groups of the genera in the family. The results showed that Kedrostis, Corallocarpus, Blastania, Zehneria, Cucumis and Citrullus are genera having seeds with smooth surfaces while Momordica and Coccinia are genera with roughes surface seed. Moreover, seeds shapes varied between pyriform, oblong, ovoid and elliptic. The current study showed that there are four types of stomata in the family. These are: anomocytic, anisocytic, paracytic and finally diacytic, which are considered as taxonomic characteristics because of their presence in the upper and lower surfaces, or both, and through the guard cells as well. Coccinia, Citrullus, Momordica, Blastania , and Cucumis contain two types of stomata, which are: the diacytic and paracytic whereas Kedrostis includes anisocytic and paracytic. In addition, Corallocarpus has only one type, which is paracytic. Similarly, the Zehneria contains only one type, which is anomocytic. Statistical analysis for some morphological characteristics of the species was performed using Mega program.