ULTRASTRUCTURAL ASPECTS OF THE GLANDULAR CELLS FROM THE SECRETORY TRICHOMES AND FROM THE CELL-SUSPENSION CULTURES OF ACHILLEA-MILLEFOLIUM LSSP MILLEFOLIUM

The ultrastructure of the glandular cells of the floret secretory tric homes from Achillea millefolium L. ssp. millefolium (yarrow) was exami ned before and after anthesis and compared with the ultrastructure of the cells from the cell suspension cultures obtained from the same pla nt. The profuse tubular structures observed in the plastids of the gla ndular cells of the trichomes during the pre-secretory stage were much reduced in the secretory stage and showed an osmiophilic content. Som e endoplasmic reticulum profiles could be seen adjacent to the plastid s. Later in the secretory stage, the secretion appeared in the peripla smic space between the cells of the upper tiers and in the subcuticula r space. Finally the secretion was released by rupture of the cuticle. At the lag phase, the cells from the cell suspension cultures of yarr ow were characterized by the presence of plastids with tubular structu res, similar to those observed in the plastids of the trichomes in the pre-secretory stage. By the end of the lag phase accumulations of sta rch were observed inside the plastids. At the beginning of the exponen tial 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 on ly osmiophilic tubular structures were observed. Rough endoplasmic ret iculum as well as smooth endoplasmic reticulum profiles were frequentl y in close association with plastids and mitochondria. At the stationa ry phase a very large vacuole filled the cells, and in the remaining c ytoplasm some endoplasmic reticulum profiles and osmiophilic droplets were observed.