Ultrastructural Aspects of the Glandular Cells from the Secretory Trichomes and from the Cell Suspension Cultures of Achillea millefolium L. ssp. millefolium

The ultrastructure of the glandular cells of the floret secretorytrichomes from Achillea millefolium L. ssp. millefolium (yarrow)was examined before and after anthesis and compared with theultrastructure of the cells from the cell suspension culturesobtained from the same plant. The profuse tubular structuresobserved in the plastids of the glandular cells of the trichomesduring the pre-secretory stage were much reduced in the secretorystage and showed an osmiophilic content. Some endoplasmic reticulumprofiles could be seen adjacent to the plastids. Later in thesecretory stage, the secretion appeared in the periplasmic spacebetween the cells of the upper tiers and in the sub-cuticularspace. Finally the secretion was released by rupture of thecuticle. At the lag phase, the cells from the cell suspensioncultures of yarrow were characterized by the presence or plastidswith tubular structures, similar to those observed in the plastidsof the trichomes in the pre-secretory stage. By the end of thelag phase accumulations of starch were observed inside the plastids.At the beginning of the exponential phase, the tubular structuresof the plastids started to show an osmiophilic content and theaccumulations of starch were still present. At the end of thisphase starch disappeared from the plastids and only osmiophilictubular structures were observed. Rough endoplasmic reticulumas well as smooth endoplasmic reticulum profiles were frequentlyin close association with plastids and mitochondria. At thestationary phase a very large vacuole filled the cells, andin the remaining cytoplasm some endoplasmic reticulum profilesand osmiophilic droplets were observed.Copyright 1994, 1999Academic Press Achillea millefolium L. spp. millefolium, yarrow, ultrastructure, trichomes, glandular cells, plant cell suspension cultures