The patterns of water content and reserve allocation in the bulb parts of red squill (Urginea maritima (L.) Baker) and the plant's adaptive strategy to Mediterranean climate (Crete, Greece) were investigated. The different bulb parts serve varying ecological functions in terms of their resources and their importance for these functions. The basal plate is the active centre, developing one or two apical meristems and roots in autumn, as well as the flowering bud in late summer. The middle of the bulb (approximately the third bulb scale) stores the resources and the tunics (the outer covering structures) that provide mechanical defense. The water content and reserve allocation patterns synchronize the plant's phenological development with the seasonality of the Mediterranean climate. The adaptive strategies are based on the development of a deciduous semisubterranean life form primarily for the avoidance of drought, herbivores, and other environmental hazards, as well as nutrient shortage. The presence of cells containing lipids, polysaccharides, raphides, water, mucilage, bufadienolides, the presence of sclerenchyma, the tightly packed epidermis, and the presence of the tunics facilitate this.Résumé : Les auteurs ont examiné les patrons de teneur en eau et l'allocation des réserves dans les parties du bulbe du Urginea maritima (L.) Baker, ainsi que les stratégies d'adaptation de la plante au climat méditerranéen (Crête, Grèce). Les différentes parties du bulbe servent différentes fonctions écologiques, en termes de ressource et de leur importance pour ces fonctions. La plaque basale constitue le centre d'activité, développant à l'automne un ou deux méristèmes et des racines, ainsi que le bourgeon floral à la fin de l'été. Le milieu du bulbe (environ la troisième écaille du bulbe) emmagasine les ressources, et les tuniques (structures enveloppantes externes) servent à la défense. La teneur en eau et les patrons d'allocation des réserves synchronisent le développement phénologique de la plante selon le caractère saisonnier du climat méditerranéen. Les stratégies d'adaptation reposent sur le développement d'une forme vitale décidue semi-souterraine, surtout pour éviter la sécheresse, les herbivores et les autres aléas environnementaux, ainsi que l'emmagasinage des nutriments. Ceci est facilité par la présence de cellules contenant des lipides, polysaccharides, raphides, eau, mucilage, bufadienolides, la présence de sclérenchymes, l'épiderme bien serré et la présence de tuniques.

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The morphology, anatomy, and ultrastructure of the floral nectary of Urginea maritima (L.) Baker were investigated at three stages of nectary development. The plant possesses a typical gynopleural (septal) nectary with secondary presentation. The nectary consists of one layer of epithelium secretory cells and one to four layers of subsidiary cells subtended by two to six layers of parenchyma (subnectary) cells. The nectary releases the nectar at a point two-thirds towards the summit of the ovary by means of carpellary sutures. Nectar secretion appears to depend largely on the hydrolysis of starch grains stored in amyloplasts at the intermediate stage. The hydrolysis process most likely commences in the epithelium layer followed by the subsidiary tissue and then the parenchyma cells of the ovary wall. A symplastic transfer of the secreted nectar occurs by plasmodesmata connecting the subsidiary cells to the parenchyma and the epithelial secretory cells. However, microchannels in the cell wall of the epithelial cells may facilitate the apoplastic transfer of the nectar into the nectary cavity. The old stage of nectary development is characterized by a crystallized form of nectar, collapse of the parenchyma cells, complete starch hydrolysis, and disappearance of the amyloplasts and endoplasmic reticulum.Résumé : Les auteurs ont étudié la morphologie, l'anatomie et l'ultrastructure des nectaires floraux de l'Urginea maritima (L.) Baker, à trois stades du développement des nectaires. La plante possède un nectaire (septé) gynopleural typique avec présentation secondaire. Le nectaire comporte une couche épithéliale de cellules sécrétrices et 1-4 couches de cellules subsidiaires sous-tendues par 2-6 couches de cellules de parenchyme (sous-nectaire). Les nectaires relâchent le nectar à un point situé aux deux tiers vers le sommet de l'ovaire, au moyen de structures carpellaires. La sécrétion du nectar semble dépendre de l'hydrolyse de grains d'amidon en réserve dans des amyloplastes au stade intermédiaire. Le processus d'hydrolyse commence vraisemblablement dans la couche épithéliale, suivi du tissu subsidiaire et par après des cellules de parenchyme de la paroi ovarienne. On observe un transfert symplastique du nectar sécrété par des plasmodesmes reliant les cellules subsidiaires au parenchyme et aux cellules épithéliales. Cependant, des microcanaux dans la paroi cellulaire des cellules épithéliales pourraient faciliter le transfert apoplastique du nectar dans la cavité à nectar. Le dernier stade du déve-loppement des nectaires se caractérise par une forme cristalline de nectar, un affaissement des cellules de parenchyme, une hydrolyse complète de l'amidon et une disparition des amyloplastes et du réticulum endoplasmique.

The thanks I owe for this PhD are rather as many as the words that it consists of, probably equally important and definitely harder to express. I would, nevertheless, like to express my gratitude to everyone, who was, as meant to be, present or absent. I would like to express my deep gratitude to my supervisor Prof. Stylianos Delivopoulos for many things, most of which are difficult to express in words. I thank him for his continuous assistance, guidance, encouragement and friendship during the time I have spent at AUTH, Greece. Moreover, I would like to express my deep gratitude for his kindness and hospitality, for his quantity of enthusiasm and quality of interest. But most of all I thank him for having been both a teacher and a 'father' to me. I would also like to express my gratitude to Dr. Thomas Sawidis for helping me in the subject and scientifical revision of my work. I thank him for his kind heart which has boosted up my enthusiasm and emotions. I will never forget his assistance, discussions and joke especially about the "noble price". I also thank Dr. Barbara-Evelin Diannelidis for her endless assistance and encouragement. I am deeply grateful to the following botanical staff; Prof. Ioannes Tsekos who gave me the opportunity to elaborate my Ph.D at the Aristotle University of Thessaloniki before his retirement. In addition, I would like to express my very deep gratitude for his assistance and critical suggestions that he has made on my research. I also thank Dr. George Nikolaidis, Maria Moustaka and Michael Moustakas for their help and technical support especially in the use of their microscopes. Thanks are also due to Dr. Stylianos Kokkini, Artemios Bosabalidis and Eleftherios Eleftheriou for their moral support and encouragement. I am deep grateful to Dr Emmanuel-Nicholas Panderis for his friendship, jokes and some scientific assistance. Finally, I would like to thank everybody in the Department of Botany for the joyful atmosphere created in the lab during my research work. I also thank the SEM technician Mr. Stavros Oikonomidis for his help in carrying out the SEM protocol. I would like to express my deep gratitude to Mr. Tasos Makrantonakis and Thanasis Nikodimos for their help, moral support and lovely atmosphere created in Sharaf Al-Tardeh Prolegomena vii the TEM laboratory. I also thank Mrs. Soula Sapountzoglou (mama tou kosmou), Pavlos Gaithatzis and the secretary of the Department Mrs Arete Dimopoulou.I express my sincere thanks to my colleagues who, with their behaviour, gave a unique meaning of the concept "team work" and academic ethics. Those folks are Ioannes Akdamakis, Spyros Gelis, Natasa Tsirika, Giorgos Kofidis, Katerina Aligizaki, and Kalopesa Eleni for their constant encouragement and making a friendly atmosphere in the lab. They made sure not let a day pass without joking, smiling and drinking as well.