Characteristics of Sex Expression in Monoecious Persimmons

A persimmon (Diospyros kaki) tree may manifest three types of flowers; female, male, and perfect (hermaphrodite). Most cultivars bear only female flowers but others have both female and male and sometimes perfect flowers as well. In monoecious or polygamous cultivars, sex expression has been observed to be modified by the previous year's fruit load and the nutri-tional status of the tree. Our results demonstrate that presence of a flower type in one sea-son's branch affects the following year's flower type.1. Using monoecious cvs. Fujiwara-gosho, Zenji-maru, Toh-hachi, and Hana-gosho, the in-fluence of flower types in a branch on the flower types occurring on the new shoots arising from this branch was determined for 3 successive years. In 'Fujiwara-gosho' and 'Zenji-maru', male flowers were predominantly formed on the shoots from a branch that had borne male flowers, whereas female flowers differentiated on shoots from a branch that had borne fe-male flowers. Male flowers in 'Fujiwara-gosho' were formed only on the shoots from a branch that had borne male flowers. Such a tendency was also observed with 'Toh-hachi' and 'Hana-gosho'. However, new shoots arising from upper buds on a branch that had borne male flow-ers tend to form female flowers, especially with 'Hana-gosho'.2. When the relationship between the length or diameter of a nonflowering branch and flow-er types occurring on shoots from the branch were examined with 'Toh-hachi', 'Hana-gosho', and 'Zenji-maru', there was no obvious correlation between the branch length and the flow-er type that differentiated on the new shoots. With respect to branch diameters, 'Zenji-maru' and 'Toh-hachi' formed male flowers on shoots from thinner branches and conversely, there was weak positive correlations between large branch diameter and the occurrence of female flowers. These relationships did not hold for 'Hana-gosho'.These results suggest that the previous year's flower types and bud positions from which new shoots arise are more influential in determinig sex expression than in branch size that has often been used as a criterion of the nutritional status of a tree.