THE INTRUSIVE GROWTH OF INITIAL CELLS IN RE-ARRANGEMENT OF CELLS IN CAMBIUM OF TILIA-CORDATA MILL

In the cambium of linden producing wood with short period of grain inc lination change (2-4 years), the intensive reorientation of cells take s place. This is possible mainly through an intrusive growth of cell e nds from one radial file entering space between tangential walls of ne ighboring file and through unequal periclinal divisions that occur in the ''initial surface''. The intrusive growth is located on the longit udinal edge of a fusiform cell close to the end, and causes deviation of cell ends in a neighbouring file from the initial surface. Unequal periclinal division divides a cell with a deviated end into two deriva tives, unequal in size. The one of them, which inherits the deviated e nd, leaves the initial surface becoming a xylem or phloem mother cell. This means that the old end is eliminated. The intensity of intrusive growth and unequal periclinal divisions is decisive for the velocity of cambial cell reorientation. The oriented intrusive growth occurs on ly in the initial cells. For that reason, changes in cell-ends positio n do not occur within one packet of cells but are distinct between nei ghbouring packets.