During vegetative phase change plants transition from juvenile to adult vegetative growth. In Arabidopsis thaliana, vegetative phase change is signified by an increase in abaxial trichomes and a decrease in leaf angle. This transition is mediated by the microRNA miR156 and its targets in SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SBP/SPL) transcription factors. As a plant ages, a decrease in the expression of miR156 allows for an increase in SPL gene expression, which leads to morphological and physiological changes in the leaves. The cause of the temporal change in miR156 is unknown. To determine what genes mediate the temporal decline in miR156, we used natural accessions to discover new mechanisms of vegetative phase change. One candidate gene that may have a role in vegetative phase change is PSAE-1, a gene that encodes for subunit E of Photosystem I. If the SNPs in PSAE-I have a role in delaying vegetative phase change then we expect to null mutations to delay vegetative phase change and for the natural accessions with SNPs in PSAE-I to have delayed vegetative and to have lower values of maximum quantum yield of PSII (Fv/Fm). Null mutations of PSAE-1 delay the timing of vegetative phase and SNPs in PSAE-I are associated with delayed timing of vegetative phase change. Mutations in PSAE-I are also known to have lower values of Fv/Fm. We measured the timing of vegetative phase change by the appearance of abaxial trichomes and found that trichomes appear significantly later in the natural accessions Galdo-1, Bur-0, and Cal-0 than in Col-0. We performed Sanger sequencing on various natural accessions of Arabidopsis thaliana to confirm the annotated SNPs from http://signal.salk.edu/. Sequencing determined that there is a pattern of SNPs in the Galdo-1, Bur-0, and Cal-0 which were not in Col-0, Xan-1, and Sha. In addition, we found novel deletions in the PSAE-I gene of Galdo-1, Bur-0, and Cal-0 which were not in Col-0, Xan-1, and Sha. This indicates that the SNPs and deletions in PSAE-I are associated with later vegetative phase change. All the natural accessions had lower Fv/Fm values than Col-0, but only one natural accession had a significant difference. This indicates that photosystem I might be less efficient in these accessions compared to Col-0. To discover more about the role of PSAE-I in vegetative phase change, we will do genetic analysis and RT-qPCR of PSAE-I and miR156 in this group of natural accessions. This will determine if PSAE-1 transcript abundance is associated with changes in the timing of vegetative phase change. If the natural accessions with SNPs in PSAE-I have lower expression of PSAE-I and slower decrease in miR156, then it would be possible that sugars are a signal for miR156 decline.