Electron microscope studies on the morphogenesis of plastids. XI. Ultrastructural changes of the chloroplasts in tomato leaves treated with ethylene and kinetin.

Abstract

Ultrastructural changes of the chloroplasts in the mesophyll cells of tomato plants which were exposed continuously to 2.0ppm ethylene up to 120hr were observed through the time course. At the same time, the effects of kinetin on the fine structure of chloroplasts were also examined. In the chloroplasts exposed to ethylene over 48hr, most of the normal membrane systems were decomposed and transformed into the macrograna. The chloroplasts exposed to ethylene for 48hr and then followed by 8 days water treatment had also macrograna in the stroma. However, the chloroplasts in the leaves undergoing natural senescence collapsed without the formation of macrograna. On the other hand, in the chloroplasts exposed to ethylene for 48hr and then followed by the incubation in kinetin solution (10mg/l) for 8 days, there were no formmtion of macrograna, and the thylakoid systems were kept with a little senescent symptom. To sum up, the ethylene exposure to tomato plants induces the formation of macrograna, plastoglobules and phytoferritin aggregates in the chloroplasts which are the significant characteristics of the chloroplast senescence. The kinetin treatment delays temporarily the chloro-plast senescence caused by ethylene exposure.