| Past research has proven that several hormones play a role in different stages of development, dormancy, and the germination of seeds. Ethylene, a gaseous plant hormone, is involved throughout many plant processes including the development and germination of seeds, though the action of ethylene is not completely understood with respect to seeds. The goal of this research was to take a more detailed look at ethylene's role in Petunia x hybrida seed development and germination.; It was observed in transgenic petunias (44568 CaMV35S::etr1-1 ) reduced in ethylene sensitivity that ethylene primarily acts by stimulating the developmental time-course and thereby increasing germination rates. The full time-course of seed development was delayed in homozygous 44568 seeds by approximately five days compared to wild-type Mitchell Diploid (MD) seeds. Also, when the two lines were reciprocally crossed, only seeds produced on the 44568 maternal plants displayed the phenotype of delayed seed development. When germination was assayed, both hemizygous and homozygous seeds carrying the etr1-1 transgene had reduced germination, but both were able to recover to MD germination levels after six months of cold storage. All seeds carrying the etr1-1 transgene were also more sensitive than wild-type to exogenously applied ABA during an additional germination assay.; Differences in gene expression between 44568 and MD were observed through microarray analysis. The results of the microarray experiments and the observation of a color difference of freshly harvested seeds altered in ethylene perception led to further analysis of proanthocyanidins, or condensed tannins. Expression analysis of genes involved in condensed tannin synthesis did not exhibit any major differences between the genotypes carrying the etr1-1 transgene versus MD. Overall, the primary findings of this research were that the ethylene sensitivity of the maternal parent had a significant role in the developmental timing of seeds. Conversely, the overall decreased sensitivity of the zygotic tissue to ethylene determined the stronger dormancy induction and heightened ABA germination sensitivity observed in all seeds carrying the etr1-1 transgene. |
