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AN ULTRASTRUCTURAL AND STEREOLOGICAL ANALYSIS OF POLLEN GRAINS OF HYOSCYAMUS NIGER DURING NORMAL ONTOGENY AND INDUCED EMBRYOGENIC DEVELOPMENT
Author(s) -
Reynolds Thomas L.
Publication year - 1984
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1984.tb12534.x
Subject(s) - biology , pollen , botany , plastid , nucleoplasm , ultrastructure , cytoplasm , nucleolus , microbiology and biotechnology , tapetum , stamen , microspore , chloroplast , biochemistry , gene
Selected nuclear and cytoplasmic changes of pollen grains of Hyoscyamus niger during normal gametophytic development and embryogenic development, induced by anther culture, were analyzed and compared ultrastructurally using stereological methods. Potentially embryogenic, uninucleate pollen could be identified within 6 hr of culture by an increased ratio of the volume density of the nucleolar granular zone to the volume density of the fibrillar zone and an increased ratio of dispersed to condensed chromatin in the nucleoplasm. Nonembryogenic pollen in vitro and in vivo possessed prominent nucleolar fibrillar zones and low ratios of dispersed to condensed chromatin. These differences may reflect changes in nuclear activity in potentially embryogenic pollen grains during early stages of culture. Following the first haploid mitosis, in potentially embryogenic pollen the generative cell maintained its large granular nucleolus and high ratio of dispersed to condensed chromatin through its first division to form a proembryoid. The volume fraction of the cytoplasm occupied by mitochondria and plastids and the area fraction occupied by RER and Golgi cisternae differed in the generative cells of potentially embryogenic and nonembryogenic pollen. Those changes only detected in generative cells of potentially embryogenic pollen include: increased area and complexity of cytoplasmic membranes, increased mitochondrial volume, and the presence of plastids at all stages of development. These results support the idea that embryogenic induction of H. niger takes place at the uninucleate stage of development and that subsequent nuclear and cytoplasmic changes are essential for continued sporophytic development.

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