Gerontoplast

Gerontoplasts (from ancient Greek γέρον géron , German 'old man' and ancient Greek πλαστός plastós , German 'formed' ) are the plastids of autumn leaves . They are responsible for the yellowing of the leaves in autumn.

In contrast to the chromoplasts, they arise exclusively from the breakdown of the green chlorophyll in the chloroplasts . Furthermore, they differ from chromoplasts in that there is no new synthesis of carotenoids and no cell division. Both chromoplasts and gerontoplasts can develop back into chloroplasts.

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

Individual evidence

^ Zavaleta-Mancera HA, Thomas BJ, Thomas H, Scott IM: Regreening of senescent Nicotiana leaves. II. Redifferentiation of plastids . In: Journal of Experimental Botany . 50, 1999, pp. 1683-1689.
↑ Pružinská, Adriana; Tanner, Gaby; Anders, Iwona; Roca, Maria; Hörtensteiner, Stefan: Chlorophyll breakdown: Pheophorbide a oxygenase is a Rieske-type iron-sulfur protein, encoded by the accelerated cell death 1 gene . In: Proceedings of the National Academy of Sciences . 100, No. 25, 2003, pp. 15259-15264. doi : 10.1073 / pnas.2036571100 .

[1] Zavaleta-Mancera HA, Thomas BJ, Thomas H, Scott IM: Regreening of senescent Nicotiana leaves. II. Redifferentiation of plastids . In: Journal of Experimental Botany . 50, 1999, pp. 1683-1689.

[2] Pružinská, Adriana; Tanner, Gaby; Anders, Iwona; Roca, Maria; Hörtensteiner, Stefan: Chlorophyll breakdown: Pheophorbide a oxygenase is a Rieske-type iron-sulfur protein, encoded by the accelerated cell death 1 gene . In: Proceedings of the National Academy of Sciences . 100, No. 25, 2003, pp. 15259-15264. doi : 10.1073 / pnas.2036571100 .