Fig. 4

Mannitol induces changes in MT orientation and length in embryogenic microspores. A1-A6 Late uni-nucleate microspore. Fragmented and disorganized MT in the (A1, A3) cortical and subcortical cytoplasm. A2, A3 Multiple and short EMT bundles around the nucleus (N). A4-A6 3D model of the subcellular volume of the same structure. Only scarce and very short CMT and a very dense network of EMT around the nucleus are visible. A4 Superior visualisation axis model presenting MT tightly associated with the nucleus (N). Volumetric ortho-slicer view from the forward (A5) and opposite site of the microspore model (A6). B1-B3 Bi-nucleate pollen-like structure resembling the product of asymmetric gametophytic mitosis with the vegetative-like nucleus (VLN) and generative-like nucleus (GLN). B1 Scarce and dot-like CMT. B2-B3 A slightly denser network of scant EMT around the GLN. C1-C3 Bi-nucleate structure with similar nuclei (N). C1 Single and mainly short CMT oriented with a preference. C1-C3 Some long and longitudinal cortical CMT, subcortical MT and EMT around both nuclei forming a basket-like structure. Short and wavy EMT located away from the nuclei and the opposite pole to the operculum (O). Cortex F - CMT; z-series projected as a maximum intensity projection from cortex optical sections collected from the front side (F) of microspore. Middle - optical section at the middle of the z-series. Middle+Cortex B – Endoplasmic and cortical MT; z-series projected as a maximum intensity projection from middle and cortical optical sections collected from the back side (B) of microspore. Inserts on the upper-right corner in the first panels show a corresponding image in the differential interference contrast (DIC). The dashed line indicates the axis between the operculum (O) and the opposite pole. Prj – z-series projected as a maximum intensity from the front side (Prj F) or from the back side (Prj B) of microspore. Green fluorescence (Alexa 488) shows α-tubulin. Red fluorescence of nuclei is caused by PI staining. Red autofluorescence of exine. Scales =20 μm