Changes in carbohydrate and water content with ovule growth of Ginkgo biloba L.

The carbohydrate and water contents of the ovule of Ginkgo biloba L. (ginkg o) were evaluated during its development. The ovule grew rapidly (stage I) after pollination in early May, temporarily stopped growing, in mid-July (s tage II), and resumed growth slowly (stage III) from mid-August until matur ation. The water content in the endosperm and outer integument were highest in June, and decreased thereafter, accompanied by ovule development. In th e endosperm, the sugar content decreased rapidly during stage I, followed b y a rapid increase in the starch content which is high level in early Septe mber. In the outer integument, the sugar content increased in early June, a nd remained nearly constant until early August. Then it transiently decreas ed in mid-August, when meso-integument hardening was completed, followed by a rapid increase. The starch content in the outer integument was low, but peaked in mid-August, when the sugar content was lowest. Although ginkgo nu ts are usually harvested in October, we recommend early harvest in late Aug ust when starch accumulation in the endosperm, an important factor influenc ing the taste of ginkgo nuts, is at a high level.