الفهرس | Only 14 pages are availabe for public view |
Abstract Calcium oxalate (CaOx) crystal formation in plants is ubiquitous and it is under full genetic control and regulation. The ubiquity of CaOx crystals in higher plant families and the observation that they can account for a large amount of the total calcium in a plant demonstrates that CaOx crystal formation is a basic and important process and indicates its important physiological role within the plant kingdom. The biological function of CaOx crystals in plants is not sufficiently understood. The study presented in this thesis was conducted as an extension of the previous studies on CaOx crystal formation in plants. It is a contribution to other research efforts made toward understanding the biological significance of this important mineralization process in plants. Investigation of some features of this process in three new model plant species was the aim of this study. The present work was carried out to explore the relationships between CaOx crystal formation in three plant species, namely, Corchorus olitorius, Malva Parviflora and Portulaca oleracea and of some factors in the environment in which plants forming these crystals were growing. These factors by which plants were treated show dynamic variation in calcium levels in the plant growth medium, heavy metals presence in the growth media, exogenous application of plant hormones and exposure of plants to cycles of heat shocks. Occurrence and description of crystals and crystal cell were also part of the aim of this study. Results using light, scanning and transmission electron microscopic examination of CaOx crystal formation in the three plants revealed presence of crystalline deposits. This crystalline deposit was of prismatic type in case of C. olitorius and of druse type in cases of M. parviflora and P. oleracea. Ultrastructurally, some differences could be observed between crystal idioplast and non crystal cells. Results encountered in the study presented herein this thesis proved existence of a strong relationship between crystal formation and calcium level in the growth media in which experimental plants were grown. Generally, presence of the four heavy metals tested in this study led to reduction in crystal formation in leaf tissues of the three plant species used. None of any of these metals could be detected in the crystal material. The effects of hormone on crystal formation were variable from plant species to another. Also, response of this process in the same plant species was dependent on the hormone identity. Effect of heat shock on crystal formation process in each of the three plants used in this study was negatively effect. |