Green fruits of normal ripening type of tomatoes (Lycopersicon esculentum Mill) were picked 13-39 days after anthesis and stored at 20°C. Although more days were required for the ripening of the fruits if the stage of picking was earlier, all fruits became red and soft during storage. This result shows that considerably immature fruits have the ability of ripening. Green tomato fruits at three stages (18. 29 and 38 days after anthesis) were treated with ethylene for one day. The activity of ethylene forming enzyme (EFE) and the conversion of applied 1-aminocyclopropane-1-carboxylic acid (ACC) to N-malonyl-ACC (MACC) in the three stages of tomato fruits were accelerated by exogenous ethylene, though endogenous ethylene production was hardly observed. When the green tomato fruits (31-34 days after anthesis) were treated with ethylene for one day and then transferred to air. the activity of EFE and the conversion of applied ACC to MACC were depressed. The activity of ACC synthase was not accelerated by ethylene treatment of only one day, but was accelerated by a longer term treatment, followed by increased ethylene production and the onset of ripening.
Hirofumi Terai, Hironobu Tsuchida, and Masashi Mizuno
Hirofumi Terai, Hironobu Tsuchida, Masashi Mizuno, and Noriyoshi Matsui
Tomato fruit were given a short-term (24 h) high CO2 (80%) or N2 (100%) treatment and then transferred to air storage at 20 °C. The CO2 treatment stimulated ACC oxidase activity and ethylene production, whereas the N2 treatment increased ACC content but did not increase ethylene production. Both CO2, and N2 treatments delayed ripening for one day, but fruit ripened normally. Although short-term 80% CO2, had a stimulating effect, and 100 % N2 had no effect on ethylene production, ripening was delayed slightly by both treatments. Chemical name used: 1-aminocyclopropane-1-carboxylic acid (ACC).
Hirofumi Terai, Hironobu Tsuchida, Masashi Mizuno, and Yumi Fukui
Green broccoli (Brassica oleracea L. Italica Group) flower heads were stored in perforated polyethylene bags at 20C. Green color of sepals in broccoli flower buds changed to yellow and individual flower buds wilted gradually during storage. Chlorophyllase activity in flower buds tended to increase and chlorophyll content decreased during senescence. Optical and scanning electron microscopic observations were conducted to elucidate the structural changes of chloroplasts in sepals of broccoli flower buds through the senescence. The chloroplasts observed with optical microscope were fine and green when the stage of broccoli flower buds was all green. However, at half-yellow stage, the shapes of chloroplasts obscured and the green color faded. After this stage, colored small particles appeared in the cells and the number of particles tended to increase as yellowing of the flower buds progressed through the senescence. Scanning electron micrographs indicated that the small particles were formed in the chloroplasts and come out from them with senescence followed by aggregation with each other.
Hirofumi Terai, Alley E. Watada, Charles A. Murphy, and William P. Wergin
Structural changes in chloroplasts of broccoli (Brassica oleracea L., Italica group) florets during senescence were examined using light microscopy, scanning electron microscopy (SEM) with freeze-fracture technique, and transmission electron microscopy (TEM) to better understand the process of chloroplast degradation, particularly at the advanced stage of senescence. Light microscopy revealed that chloroplasts, which initially were intact and green, became obscure in shape, and their color faded during senescence. Small, colored particles appeared in cells as the florets approached the final stage of senescence and became full- to dark-yellow in color. Scanning electron microscopy showed that stroma thylakoids in the chloroplast initially were parallel to each other and grana thylakoids were tightly stacked. As senescence advanced, the grana thylakoids degenerated and formed globules. The globules became larger by aggregation as senescence progressed, and the large globules, called “thylakoid plexus,” formed numerous vesicles. The vesicles ultimately were expelled into the cytosol, and the light microscope revealed many colored particles in the senescent cells. These results indicate that the degradation of chloroplasts in broccoli florets progresses systematically, with the final product being colored particles, which are visible in yellow broccoli sepal cells.