XVI International Botanical Congess

The studying of protoderm cell form during a first leaf initiation carryed out on example of one monocotyledon plant - Dactylorhiza baltica (Orchidaceae) by using of scanning electron microscopy. It shown the appearance of especial cell patterns which connected with general morphogenesis of shoot apex structures. The site of primordium summit can predict long before its protrusion as soon as larger-celled sector appears in peripheral zone of shoot apex. On a side shoot apex opposite to larger-celled sector it can see the sector compound by the oblong to perpendicular of protocorm longitudinal axe cells. The larger-celled sector as a site of future primordium is a zone of local intensifyed growth and may be a zone of higher concentration of auxin. The later may be connected either 1) with disruption of auxin flow (Sachs, 1991) or 2) with intensifyed auxin synthesis in this region of shoot apex. The form and growth direction cells of periclinal" sector, and as well as its interdependent arrangement are bound with morphogenesis of shoot apex in general. This sector forms as a result of common deformation of dome frame. The laws of cytomechanic as the process of polar transport of morphogenic substance may be responsible for protoderm cell pattern of shoot apex.