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 secretory trichomes from Achillea millefolium L. ssp. millefolium (yarrow) was examined before and after anthesis and compared with the ultrastructure of the cells from the cell suspension cultures obtained from the same plant. The profuse tubular structures observed in the plastids of the glandular cells of the trichomes during the pre-secretory stage were much reduced in the secretory stage and showed an osmiophilic content. Some endoplasmic reticulum profiles could be seen adjacent to the plastids. Later in the secretory stage, the secretion appeared in the periplasmic space between the cells of the upper tiers and in the subcuticular space. Finally the secretion was released by rupture of the cuticle. At the lag phase, the cells from the cell suspension cultures of yarrow were characterized by the presence of plastids with tubular structures, similar to those observed in the plastids of the trichomes in the pre-secretory stage. By the end of the lag phase accumulations of starch were observed inside the plastids. At the beginning of the exponential phase, the tubular structures of the plastids started to show an osmiophilic content and the accumulations of starch were still present. At the end of this phase starch disappeared from the plastids and only osmiophilic tubular structures were observed. Rough endoplasmic reticulum as well as smooth endoplasmic reticulum profiles were frequently in close association with plastids and mitochondria. At the stationary phase a very large vacuole filled the cells, and in the remaining cytoplasm some endoplasmic reticulum profiles and osmiophilic droplets were observed.