Subcellular Organization of Developing Embryos of Bidens cernua

Anatomical and submicroscopical changes in the cotyledons and radicles of Bidens cernua L. have been studied at five developmental stages. In the subcellular structure, these two plant organs are relatively similar but each developmental stage is characterized by a distinct fine structure. Protein bodies, which occupy the bulk of the cell in dormant embryos, develop as filling products of vacuoles. Ribosomes are seen abundantly at this stage, both in the nucleus and the plasma strands. Small vesicles which are the initials of globoids can be detected in the vacuoles even of rather young cells. They later associate at the periphery of protein masses secreted in the vacuoles. Many light globoids are seen in the protein bodies of mature cells. Some amyloplasts are present in the early developmental stages but not in the dormant cells. The endoplasmic reticulum becomes filled with osmiophilic storage fat, and later many spherosomes are seen between the protein bodies. Some osmiophilic material is also found in the intercellular spaces.