In Helianthus annuus NMUmutagenesis of the seeds resulted in the establishment of a collection of viable photosynthetically defective mutants of the en:chlorina type, inherited maternally. Based on their morphological and physiological characteristics (ultrastructure alterations, photosynthetic deficiencies), it was suggested that the mutations were located in the chloroplast DNA [8, 9, 10], but this has not been proved to date.