Epigenetics deals mainly with changes that come about as a result of changes in the gene expression including gene products. These changes do not occur as a result of changes in the genetic code. It mainly studies modifications made to gene expression. These include DNA methylation: addition of a methyl group to a region on the DNA molecule preventing some genes from being expressed. Another is Histone modifications: Acetylation, methylation, phosporylation, etc
All these either help in activating transcription or deactivate transcription.
Since chloroplast use energy to make food for plant cells (Photosynthesis) I could compare it to lunch money, and how you have to keep refilling up, and up, just to use it again for food, for yourself.
