Cytological analysis of early microspore divisions leading to gametic embryo formation in Quercus suber L. anther cultures

The cor re la tion be tween the phenologic stage of the in flo res - cence and the microspore de vel op ment stage was stud ied. Cyto log i cal ex am i na tions of the de vel op ment of micro spores dur - ing in vi tro an ther cul ture of cork oak (Quercus suber L.), were car ried out dur ing the first four weeks of cul ture. To ob serve the di vi sion oc cur ring in the micro spores, an thers were taken ran domly from the cultures after heat shock treatment and were stained with DAPI. Most of the an thers re spond ing to a heat stress treat ment con tained 91 % vacuolated micro spores, in di cat ing that this de vel op men tal stage is re spon sive to embryo genesis in duc tion in cork-oak micro spores. Af ter the heat shock treat ment some cork-oak micro spores were in duced and ini ti ated the embryogenic path way with the oc cur rence of nu mer ous sym met ric mi to sis, pro duc ing struc tures with two to ten or more nu clei. These lead to the for ma tion of high num - bers of multicellular cork-oak micro spores (pro-em bryos). Twenty-forty days af ter in duc tion, small white glob u lar and cotyledonal em bryos were ob served, which fur ther de vel oped root and shoot, re gen er at ing plantlets.