Studies on the Fertilization and the Seed Formation of the Tea Plant

Abstract

Double fertilization : The pollen tubes entered into the embryosac and the mail gametes were situated close to the egg cell or the pollar nuclei in about 2-5 days after pollination. The male nucleus came into contact with the egg cell and on the other hand, the triple fusion was comleted in about 5-8 days. The male and egg nuclei were situated confronting each other within the egg cell, and the first division of the primary endosperm nucleus took place in about 8-13 days. The male nucleus in the egg cell grew as large as the egg nucleus and four endosperm nuclei were formed by the second division in about 13 days. The male nucleus in the egg cell was seen as the fused nucleus, and nuclear division was repeated more than three times in about 20 days. It was 35 days after pollination that, the first mitosis occurred in the fertilized egg cell.The maximum percentage of fertilization was seen in 8 days after pollination, and the percentage of normal ovules amounted to 50-60% in each reciprocal crossing of Yabukita and Sayamamidori. The process of collapse of auxiliary cells varied according to individuals, so, to know the success of fertilization it was thought to be desirable to judge it from the conditions of egg cell and pollar nuclei.Formation of seeds in-the fruit : One ovary involved about 12 ovules, but the average numder of seeds in one fruit was three in common varieties. This was due both to the low fertilization percentage and to the occurrence of many abortive seeds which was seen 13 days after pollination. The definite causes that the number of seeds in a fruit varied among varieties were thought to be either the failure of fertilization or the degeneration of fertilized ovules.Fruit drop : The fertilization percentage was very high in every variety, so the cause of fruit drop was thought to be scarcely due to fertilization' failure. The fruit drop rate till March was comparatively low. Early stage of fruit growth in April and May corresponded just to the first growth period of tea shoots, and fruit drop in this period fairly increased in every variety. But after this time, the percentage of fruit drop was very different among varieties. In common varieties, the fruit drop continued up to the autumn, but in well seed setting varieties it seldom occurred when the flowers were open pollinated; the fruit drop habit was observed to be similar to that of non-pollinated fruits, so it was considered that the low percentage of fruit setting in open pollinated plant was largely due to the fertilization failure.