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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.