Fine structure and development of laticifers inGnetum gnemon L.

Summary Articulated laticifers are a regular component of stem cortex and pith ofGnetum gnemon L. Differentiation of laticifers starts very early and is completed within the very first centimeters adjacent to the apical meristem.Ultrastructurally, young laticifers ofGnetum can be distinguished from surrounding cells by the presence of characteristic cytoplasmic inclusions, called spherule complexes and composed of 40–70 nm light spherules and up to 0.5 by 1.0 m large particles. While there is no record on their first beginnings, a connection between rER and the large particles can be demonstrated during many steps of laticifer differentiation which includes an increase in spherule complex areas. On account of positive Sudan staining and responses to EM fixations and in comparison to other laticifers it is concluded that the spherule complexes are terpenoid-containing. A transition from spherules to larger particles (orvice versa) is discussed, but could not be documented.Relative to the formation of the spherule complexes the other changes during laticifer maturation are inferior. The vacuolar system, in close connection to an extensive ER system, does largely expand and finally takes over the almost entire cell lumina. Nuclei do persist for an extended period, even after breakdown of the end walls and during disorganization of the cytoplasm. Plastids in all stages of laticifer ontogeny are very rarely encountered.Supplemented part of an investigation presented in 1976 by S. H. to the Fakultät für Biologie der Universität Heidelberg in partial fulfilment of the requirements for the degree of a Diplom-Biologe.