 Only plant cells that have successfully integrated the gene cassette as shown above will be able to express the antibiotic resistance selectable marker and therefore grow normally on agar plates containing antibiotics.Plant tissue that do not grow normally will have a bleached appearance as the spectinomycin antibiotic inhibits the ribosomes in the plastids of the plant cell, thereby preventing maintenance of the chloroplast However, as heteroplasmic population of chloroplasts may still be able to grow on agar plates effectively, many rounds of antibiotic selection and regrowth are required to cultivate a plant tissue that is homoplasmic and stable.Generation of homoplasmic plant tissue is considered to be a major difficulty in transplastomics and incredibly time consuming.