ROLE OF MICROTUBULES IN THE MOVEMENT OF THE VEGETATIVE NUCLEUS AND GENERATIVE CELL IN TOBACCO POLLEN TUBES

The germination and growth of pollen grains of Nicotiana tabacum and N . alata with the anti-microtubule drug oryzalin retarded significantly the movement of the vegetative nucleus (VN) and the generative cell ( GC) from the grain to the tube apex but had no effect on pollen tube e longation. In N. tabacum, only 11% and 48% of the pollen tubes treated with oryzalin for 6 h and 12 h, respectively, had the VN and GC in th e tube mainly in its middle part. In corresponding control materials, 79% and 99% of pollen tubes contained the VN and GC close to the apex. Indirect immunofluorescence microscopy and related studies of the tub es grown in the presence of oryzalin revealed complete absence of micr otubules (MTs) but apparently intact microfilaments (MFs). These resul ts suggested that the movement of VN and GC from the grain into the tu be is possible when no MTs but only MFs are present, but the movement is then slow. In control tubes, the parallel orientation of MT bundles and extensions of VN were interpreted to represent the structural org anization needed for the MT-dependent movement of VN.