Effects of High Temperature Period on Seed and Embryo Development in Seedless Citrus

摘要

The effects of high temperature on seed and embryo development in the Mukaku Kishu-type seedless cultivar, ' Southern Yellow' , grown in the field and greenhouse were investigated in comparison with the results of our previous study. In the field, 'Southern Yellow' was completely seedless, forming small and eatable seed (type A seeds) with an immature seed coat. In the previous study, greenhouse grown plants produced perfect mature seeds with a hard seed coat. In the present study, however, greenhouse-grown plants produced type A seeds with an immature seed coat. At 18 weeks after pollination (WAP) , the embryos in the field were arrested at the zygote or proembryo stage. In the previous study, greenhouse-grown plants produced embryos that developed to the cotyledon-shaped stage. In the present study, however, most embryos remained at the proembryo stage, while some embryos reached to the cotyledon- and torpedo-shaped stage. In the field, the average temperature from 0 to 4 WAP was less than 20°C. In our previous study, mean greenhouse temperature was more than 251, but it was 20°Cin the present study. After 4 WAP, there was no difference in the average temperature between field and greenhouse. These observations indicate that embryo development is promoted by high temperature during 0 to 4 WAP in the Mukaku Kishu-type seedless cultivar.