High temperature injuries in tomato. V. Fertilization and development of embryo with special reference to the abnormalities caused by high temperature

In the previous paper~6~ it was reported that flowers of one to three days after anthesis, were especially sensitive to high temperature and almost all flowers failed to set fruits. However, the more advanced the stages of flowers at the high temperature treatment, the more resistant to high temperature were the flowers. And the plot treated 5-8 days after anthesis resulted in good fruit set. It is well known that the germination of pollen grains and the elongation of pollen were affected by high temperature~2'10~. Therefore, one of the causes of the poor fruit set may be attributed to the remarkable susceptibilities of pollen germination and pollen tube elongation to high temperature. But it remains unknown whether the development of proembryo and endosperm is affected by high temperature. For the solution of the problems the detailed information of whole processes from pollination to fertilization must be obtained. On the elongation of pollen tubes of tomato there are two reports by Fuji(2) and SMITH and COCHRAN~10~. JUDKINS~7~ reported thatt considerable numbers of pollen grains passed through style within 24 hours after pollination. While, concerning the fertilization and embryogenesis of tomato, there is only one report by SMITH (9) in which he informed that it took about 48 hours from pollination to fertilization. However, the definition of fertilization and the temperature during the experiments which may greatly influence the results~3,4,7~ are not clear in his study. Moreover, there are no inves. tigations on the abnormalities of the developing proembryo and endosperm caused by high temperature. In the present investigation the flowers of the first cluster on the tomato plants grown in the greenhouse maintained 20t constantly, were emasculated and hand-pollinated. With definite intervals the flowers and young fruits were sampled and the fertilization processes andd development of proembryo and endosperm were observed. Another lot of flowers was treated with high temperature at various time intervals after hand-pollination, and the resulted abnormalities of ovules were observed.