Gerontoplast

Gerontoplasten ( from Ancient Greek γέρον Géron " old man " and ancient Greek πλαστός plastos "formed" ), the plastids of autumn foliage. You are responsible for the yellowing of the leaves in autumn.

They arise in contrast to chromoplasts exclusively from the breakdown of the green chlorophyll in the chloroplasts. Furthermore, they differ from the chromoplasts by the fact that there is no de novo synthesis of carotenoids and no cell division in them. Both chromoplasts and Gerontoplasten can develop into chloroplasts again.

The transition from chloroplast to Gerontoplast is triggered by the iron-containing oxygenase enzyme Pheide a oxygenase ( PaO ). This enzyme is found only in Gerontoplasten. A Gerontoplast is smaller than a chloroplast. During the transition, many thylakoids and particles are lost in the stroma, but take the plastoglobules both in number and in density. The membrane of the Gerontoplasten intact.