Submitted to: Journal of Japanese Society of Horticultural Science
Publication Type: Abstract Only
Publication Acceptance Date: June 10, 1997
Publication Date: N/A
Technical Abstract: Ultrastructural changes of broccoli chloroplasts during storage were determined with florets that were heat-treated prior to storage. Florets were heat treated at 50C for 0, 1, 2, or 3 hours (0h, 1h, 2h, and 3h, respectively) and stored in perforated film bag for 5 days at 20C. Florets were removed periodically from storage and sepals were prepared for analysis with a scanning electron microscope. Florets with 0h treatment (control) were full-yellow on day 3; 1h treatment were half-yellow on day 3-4; 2h treatment were slightly-yellow on day 4, and 3h treatment were slightly-yellow on day 5. Stroma thylakoids of controls were oriented in parallel at the beginning of storage. By day 3, disintegration of grana thylakoids and formation of globules were noted. Many globules and vesicles were in the cytosol on day 5. With 1h treatment, changes were noted with stroma thylakoids similar to controls, but the rate of change was not as great as that noted with control samples. With 2h treatment, stroma thylakoids were distorted on day 1 and a few vesicles were noted in the stroma thylakoid area on day 5. With 3h treatment, the degree of distortion in stroma thylakoids was more severe than that of 2h treated samples, and stroma thylakoids became separated on day 3. Many vesicles were noted in the vicinity of stroma thylakoids on day 5. Results indicate that alteration of grana thylakoids to globules were inhibited with heat treatment but the formation of vesicles occurred eventually. However, it is not clear if the mechanism of vesicle formation in heat treated sample was the same as that of controls (0h).