Petunia violaceaノ受精力ニ關スル生理學的研究XI

自家不和合性ニ對スル温度ノ影響

抄録

Temperature is an important factor for self fertilization. Extreme coldness is, of course, unfavourable for fertilization. But in general, cool weather is likely more favourable than hot weather for self fertilization in some plants.
In order to study the effect of temperature upon self fertilization, the following experiments with Petunia violacea were made by the author.
1. Intra-self pollination (strictly self pollination) was carried on with some self incompatible plants in 1931. As the flower season advanced from the beginning of August toward the end of September, the percentage of seed setting was observed to have gradually increased. But it is not evident that whether this increase in percentage is due to the effect of cool weather or of the so-called “end-season fertility.”
2. So, the author divided these materials into two groups, one of which was kept in a hot glass house (27°C-40°C) and the other in a cool glass house kept between 18°C-32°C. After that, they were intra-self pollinated. The results showed exactly that cool weather was more favourable for seed bearing than hot weather.
3. However, it is by no means certain that whether these seeds were produced through self fertilization or through parthenogenesis. In order to see which of these is really responsible, about 30 flowers in each group were left unpollinated, with the result that there was no phenomenon of parthenogenesis observed. Thus, it becomes clear that the increase in seed bearing ability in cool weather must be due to the increase in the fertility.
4. Does cool weather act on the character of the pistil or on the activity of the pollen? This is a question. So, the author smeared the pistils with the pollen from another plant of the same vegetative line kept under medium condition. In this experiment a similar pollen was applied on to the pistils in each group. Nevertheless, the fertilizing percentage under cool condition was higher than those obtained in hot weather.
5. Thus, it becomes clear that cool weather affects the character of pistils making it favourable for self fertilization. Again, the high seed bearing percentage must be due to the changed character of pistils and not to the increase in the fertility on the part of eggs. For, the author observed that the cross fertilization was easier in hot weather than under cool condition.
6. The author took notes of the life-duration of each flower, which was intra-self pollinated immediately after the opening of its anthers. The life-duration was about 10-20% longer during cool weather, say, in October, than during hot weather, say, in August. This may suggest that the longer duration gives to the tubes of the selfed pollen an opportunity to reach the ovules. But the tubes of selfed pollen could penetrated into only onefifth part of the length of the style during flower life in summer, as was reported in the author's foregoing papers. Therefore, such a slight increase in life-duration can not be taken as the cause of self fertilization in cool weather.
7. The author gathered the flower buds which were to bloom about three days hence, and placed them in two glass bottles containing some amount of water. Each bottle was placed either in a thermostat regulated at 30°C, or in that kept at 22°C. When the flowers opened, their pistils were smeared with the pollen of the same line. After the application of pollen, all bottles were placed in the cooler thermostat. Two days after this pollination, the pistils of these flowers were gathered and fixed, and the length of the pollen tubes penetrated was measured. The results showed that the tube-growth was inhibited more strikingly in the pistiles of the flowers which had been placed, during their bud stages, in a hotter thermostat.