2020 年 64 巻 4 号 p. 171-177
Passion fruit flowers were pollinated at various temperatures range from 28–42°C, and the fruit set and the number of seeds were recorded to determine the critical high temperature which negatively affected to the fruit set. Other flowers which were detached just before anthesis were incubated and pollinated also at various temperatures. The germination of the obtained pollen was tested on agar medium, and pollen-tube growth in pistil was observed anatomically to determine the thermal response of pistil receptivity. Fruit set was more than 90% when daytime temperatures were regulated at 28–34°C. Fruit set decreased at temperatures ≥38°C. Flowers did not set fruit at 42°C. The number of seeds reduced at temperatures ≥36°C. Pollen tubes reaching the embryo sac were observed within 24 h after pollination in all detached flowers which were incubated at 28–32°C. Whereas at incubation temperatures ≥34°C, pistil morphological disorder was observed in all detached flowers, and pollen tubes did not reach the embryo sac within 24 h. Pollen germinated on the stigma without elongation into the style, even 24 h after pollination at 40°C. Germination percentages of the pollen, which was obtained from detached flowers incubated at 28–40°C, did not vary on agar medium. Although pistils on a detached flower were damaged by high temperatures ≥34°C, those growing under orchard condition did not show any symptom of damages at 36°C.
