Development of the Female Gametophyte and the Embryogeny of Ginkgo biloba

Abstract

Trees of Ginkgo biloba are large, long-lived, deciduous, and dioecious. They have pale green young leaves in the spring; the leaves turn to clear yellow in the autumn. Female trees produce many edible seeds every autumn. These beautiful and valuable plants have been cultivated for more than a thousand years in China and Japan. The long-lived trees are especially well preserved in the precincts of Buddhist temples or shrines in Japan. Now they have been cultivated all over the world, but wild trees are found only in China [1], The ovuliferous structure develops in the axil of a scale or a leaf of the short shoot of the female tree. Two to six ovuliferous structures exist in one short shoot [2]. Usually ovuliferous structures consist of a stalk and two sessile ovules on the top. More than two ovules on a stalk, or ovules on a branched stalk, were observed in certain trees [2–9] (Fig. 1). Ovuliferous structures more or less different from the usual type were found in 40% of old trees and in 25% of young trees [2]. These values mean unusual structures are not exceptional. Unusual structures were observed in the axil of a scale in 58% of old trees and in 50% of young trees, while those formed in the axil of a leaf were seen in 26% of old trees and 6% of young trees. Therefore, unusual ovuliferous structures arise much more in the axil of a scale than in that of a leaf [2].