Plastid analysis of pigmented undifferentiated cells of marigold Tagetes erecta L. by transmission electron microscopy - Vanegas-Espinoza, Pablo Emilio; Ramos-Viveros, Verónica; Jiménez-Aparicio, Antonio Ruperto; López-Villegas, Oliver; Heredia-Mira, Francisco José; Meléndez-Martínez, Antonio Jesús; Quintero-Gutiérrez, Adrián Guillermo; Paredes-López, Octavio; Del Villar-Martínez, Alma Angélica