2017 Volume 99 Issue 4 Pages 150-155
Seeking measures to address pollinosis caused by pollen from the Japanese cypress, we searched for a sterile staminate individual. We discovered an individual with staminate flowers that did not release pollen, in a Japanese cypress forest in Kanagawa Prefecture. To check whether pollen is released, after bagging the branch with staminate flowers and pouring water in, we found that the microsporangia did not open and no pollen was released at all, even after the typical release period. An optical microscope revealed particles larger and smaller than normal pollen inside the microsporangia. An electron microscope revealed orbicules inside the microsporangia on the pollen surface, similar to normal pollen, although normal pollen was not found. When investigating seed fertility, cones were found to be small in size and abnormally shaped. The rooting rate of cuttings was 70%, and clonal growth succeeded. No pollen was released from the staminate flowers of the cloned tree, showing that sterility traits were reproducible in the cloned individual. There were 22 chromosomes for both the selected individual and normal individual. From observation of the pollen tetrad period, it was hypothesized that the staminate sterility traits were caused by unequal division at the time of meiosis. Based on the condition of staminate flowers and cones, it was concluded that sterility had been confirmed in both the staminate and pistillate flowers.
