关键词: 叶籽银杏, 叶生胚珠, 正常胚珠, 授粉期, 形态结构

Abstract: Comparative analysis and observation on morphological structure of the epiphyllous ovule
and normal ovule during pollination period in Ginkgo biloba L. var. epiphylla using the resin semi-thin
section and scanning electron microscopy（SEM）was taken in order to reveal the mechanism of
morphogenesis of the former. The results showed that：Normal ovule organizations had already
differentiated completely before pollination，and the integument grew rapidly，then drew together in apex
of the nucellus gradually in normal ovule. Meanwhile，there were no differentiation in collar and nucellus，
but with some ridge gibbosities in epiphyllous ovule which obtained the nutrition from the vascular bundle
in gibbosities. Then the palisade tissue and spongy tissue differentiated along with the development of
gibbosities. In pollination period，there was pollination drop secreted by the nucellus and then the pollen
chamber formed by the programmed cell death of the nucellus in normal ovule. While there was no
pollination drop in epiphyllous ovule，besides the collar and nucellus had already differentiated with the
rostrate micropyle，the extended micropylar canal. But no pollen chamber was formed because there was
no cell degradation in the bottom of micropylar canal in epiphyllous ovule. Then epiphyllous ovuleand ovulewere into free nuclei stage of female gametophyte after pollination period. In addition，
epiphyllous ovule developed asymmetrically and was obviously smaller from appearance than the normal
ovule.

Key words: Ginkgo biloba L. var. epiphylla, epiphyllous ovule, normal ovule, pollination period, morphological structure