| Abstrakt: |
The ultrastructure of foliar secretory cavities of Porophyllum lanceolatumDC. was studied at three developmental phases, and shows to have the basic characteristics of terpene-secreting glands. The ability to secrete is already present in young, differentiating cavities. In the epithelial cells, dark osmiophilic material occurs in plastids, mitochondria, the nuclear envelope, the endoplasmic reticulum (ER) and dictyosomes, indicating the participation, in some way, of such structures in the secretory process. The ER is seen to be associated with plastids (periplastidal ER), mitochondria and the nuclear envelope, seeming to play a role in transporting the secretory material from these organelles to the plasmalemma. The granulocrine mechanism, involving portions of ER, and independently, vesicles derived from dictyosomes, is considered to be the main process for the elimination of secretory material from the protoplast. Multivesicular, multilamellar and mixed bodies were also observed, as well as microbodies (associated with ER in some cases), in the epithelial cells. In the cells of the gland sheath the walls are thicker than those of the epithelial cells; starch is often present in their plastids |
Full Text from ScienceDirect