A gerontoplast is a plastid found in formerly green tissues that are currently senescing. A gerontoplast is a chloroplast that has re-purposed through a process of developmental senescence.
Transformation of chloroplasts to gerontoplasts
The term gerontoplast was first introduced by Sitte (1977) to define the unique features of the plastid formed during leaf senescence. The process of senescence brings about regulated dismantling of cellular organelles. The possible temporal pattern of degradation of different organelles of a green plant cell is shown in Fig. 58. Chloroplast shows the first sign of senescence induced degradation and is the last organelle to survive when other organelles are completely disorganized. The formation of gerontoplast from chloroplast during senescence involves extensive structural modifications of thylakoid membrane with the concomitant formation of a large number of plastoglobuli with lipophilic materials. The envelope of the plastid, however, remains intact.