Читать книгу Diatom Morphogenesis - Группа авторов - Страница 25

Morphogenesis has been characterized as a system of detached movement of ensembles of cells in animals in contrast to lack of detached movement via ensembles of cells in plants. That is, locomotion is one way to associate a specific kind of symmetry to motile organisms in contrast to sessile organisms which may exhibit another kind of symmetry [2.59]. Modes of growth contribute to the recognition of specific types of symmetry. Branching growth exhibits continuous symmetry decrease and increase in size during growth [2.47]. Stepwise growth and size reduction are modes of discrete growth where size increases or decreases over time. Growth changes are concomitant with symmetry changes as potential indicators of stress associated with development, morphogenesis, cytogenesis, epigenesis [2.154], and embryogenesis [2.43, 2.149], depending on evolutionary or ecological conditions. Levels of environmental or teratological stress are said to influence fitness and adaptability of an organism, although this connection has not been quantitatively or definitively formalized [2.53, 2.54, 2.35, 2.68].

Developmental instability has been associated with fluctuating asymmetry which is generally considered as small random deviations from perfect reflective (bilateral) symmetry [2.7, 2.53, 2.60, 2.87, 2.94, 2.128, 2.152]. Instability is presumed to be associated with either side of an organism and developmental processes, and genetics or environmental conditions may influence the size of the fluctuations in asymmetry [2.53]. No explicit or quantitative relation has been given connecting fluctuating asymmetry with instability as a measure of stress. Assessment using fluctuating asymmetry characterizations have been made on a population (species) level and has not been carried out with individuals or at interspecific or higher taxonomic levels [2.53, 2.54].