1970 Volume 39 Issue 2 Pages 149-156
To elucidate the mechanisms of cross-incompatibility in interspecific hybridization in the genus Cucumis, pollen tube growth, fertilization and embryogenesis in the earlier stage of post-fertilization, were studied in the incompatible crossings, C. dipsaceus (_??_)×C. figarei (_??_) and C. dipsaceus (_??_) ×C. melo (_??_).
1. In both the incompatible crossings, the rate of pollen tube growth in the style was slower and the occurence of the entrance of pollen tube into ovules was less frequent than in selfing of maternal plant.
2. When the parental species were selfed, fertilization took place during 24-48 hours after pollination and the primary nuclear division of endosperm occurred immediately after fertilization. The cell division of the zygotes began after 84 hours or later of pollination when endosperms had already grown including 8-16 nuclei. In the most advanced ovule sampled six days after pollination, the embryo which was surrounded with the well developed endosperm became already globular. No specific differnce was found in the process of embryogenesis as mentioned above.
3. In both incompatible crossings fertilization took place in a part of ovules and the endosperms slightly developed in such fertilized ovules. However, the cell division of the zygotes never occurred even after few days following pollination and the endo sperms could not continue their growth and aborted later. Fertilization and division of the endosperm nucleus did not occur in some of the ovules into which pollen tubes entered.
It is assumed that fertilization rarely occurred owing to the abnormal behaviors of pollen tubes.