Submitted to: Journal of Japanese Society of Horticultural Science
Publication Type: Abstract Only
Publication Acceptance Date: September 1, 1996
Publication Date: N/A
Technical Abstract: Chloroplasts of senescing broccoli inflorescence were studied with a scanning electron microscope to better understand the ultrastructural changes of chloroplasts during degradation. Broccoli florets were placed individually in a 100 ml vial and stored at 1C and one floret was transferred daily to 20C. When several stages of senescence were available, sepals were prepared for analysis. Sepals were fixed in Osmium oxide, rinsed in phosphate buffer, washed in ethanol, frozen in liquid nitrogen and fractured. They were then thawed and rehydrated back and prepared for analysis with scanning electron microscope. Initially, the stroma thylakoids were parallel to the long axis of chloroplast and the grana thylakoids were stacked compactly. With senescence of inflorescence, the thylakoid membrane became disorganized and grana stacks had collapsed and formed globules. Vesicles developed in chlorplasts as well as from vesicles and, with age, they appeared in clusters. These results indicate that during the degradation of chloroplasts, different structural changes occur and further studies are needed to understand the meaning of these ultrastructural changes.