meristeemides esinev arengu algusjärgus olev pigmentideta plastiid, mis võib arengu käigus muutuda spetsialiseerunud plastiidiks nagu kloroplast, kromoplast ja amüloplast, A proplastids is an undifferentiated plastid which occurs in a meristem. During development a proplastid can differentiate into a chloroplast, chromoplast and amyloplast.