Scanning electron microscopy was used to observe the morphology and structure of protein bodies in dormant and imbibed sunflower cotyledons and to document the morphological changes in protein bodies during germination and seedling growth. In order to clearly visualize dormant seed structure, anhydrous fixation techniques were employed. Definite differences in cellular structure are seen in comparisons of dry and imbibed seed tissues. As germination proceeds, protein bodies lose their smooth spherical shape and become indented and pitted. Protein body coalescence and fusion precedes the formation of a central protein vacuole. As protein is hydrolyzed, protein vacuole density decreases, and its surface becomes granular, then fibrous, in appearance. Removal of protein from the protein vacuole appears to proceed more rapidly in cells closest to the embryonic axis. The protein vacuole becomes the main cell vacuole as remaining storage protein is hydrolyzed. The cotyledon cells undergo a gradual change in function from a quiescent storage stage, through a major exporting phase and to their final function of photosynthesis.
Allen, R. D. and Arnott, H. J.
"Protein Bodies in Dormant, Imbibed and Germinated Sunflower Cotyledons,"
1, Article 7.
Available at: http://digitalcommons.usu.edu/foodmicrostructure/vol1/iss1/7