Ultrastructural Aspects of Unilateral Interspecific Incompatibility between Lycopersicum Peruvianum and L. Esculentum

SUMMARYObservations have been made, at the electron microscope, of the pollen tubes present in the styles of Lycopersicum esculentum and L. peruvianum after reciprocal crosses between the two species.The unilateral incompatibility barrier which isolates the two species when L. peruvianum is used as pistillate parent was then compared to the processes of pollen tube rejection which have been recently analysed (J. Cell Sci., 1972) after self-pollination in this self-incompatible species. Such a comparison, which was also carried out by means of fluorescence techniques, has permitted to find out that for both types of incompatibility the rejection process was characterised by a progressive disappearance of the callose-rich inner wall of the pollen tube and by an accumulation of bi-partite particles in the tube cytoplasm.In the case of unilateral incompatibility, however, the tube outer wall is gradually disaggregated while the callosic inner wall remains quite thick at the tube apex, becoming thinner and fin..