A Primary Investigation On Fertilization And Embryology Of Castanopsis Fissa And Lithocarpus Dealbatus(Fagaceae)

Fagaceae widely distributs in warm temperate forests in the Northern Hemisphere and are the keystone family in the ecosystems.It contains eight to ten genera and about 1000 species.Genera Lithocarpus and Castanopsis with restrictive distribution in Asian subtropics are dominant trees in tropical-subtropical evergreen broadleaved forests(EBLFs)and have important ecosystem functions and signficant economic values.However,there are a limited studies on fertilization and flower development of the two genera.In this study,the embryonic development and fertilization rhythm of Castanopsis fissa and Lithocarpus dealbatus were studied.By comprehensively compared and analyzed the flower anatomical traits,fertilization and embryological traits of the two genera with other genera in Fagaceae and Fagales,the evolution trends of these traits in Fagaceae were investigated in contrast to the well-resolved phylogenetic relationships inferred by previous molecular phylogeny.The key results obtained in this study were summarized below:1.The pistillate flowers of Castanopsis fissa and Lithocarpus dealbatus have three ovary loculi.Of each locule,there are two anatropous ovules with two integuments.The endosperm is free-nuclear type.The embryo sac is Polygonum-type.Both the inner and outer integuments form the micropyle.The o uter integument in Castanopsis fissa develops early than the inner integument.When the outer integument forms the micropyle,the inner integument remains at meristem stage,until the megaspore mother cell appears.At this stage,both the inner and outer integuments form the micropyle.The outer integument of Lithocarpus dealbatus develops early or the two interguments develop simultaneously.2.The flowering period of Castanopsis fissa is from April to May.After fast germination of pollen gains on the stigma,the pollen tubes grow from the stigma to basal part of the style,then stop growing for 1-2 months.At the end of June,pollen tubes resume to grow to the micropyle,then go into the embryo sac to fertilize.The flowering period of Lithocarpus dealbatus is from July to October.The pollen gains germinate quickly on the stimage and pollen tubes grow through the stylar canal to basal part of the style,then stop growing for 8-9 months.In Next May,the pollen tubes resume growth and move toward the micropyle into the embryo sac to fertilize.During the dormancy period,no ovule primordia are established in the ovules of Castanopsis fissa and Lithocarpus dealbatus.After resuming growth,the ovule primordia developes rapidly.The inner and outer integuments establish very fast.The mature of the acorns of Castanopsis fissa takes 7-8 months,but about 16 month for Lithocarpus dealbatus.3.Based on the phylogenetic tree approches,five flower developmental and fertilization traits were subjected to the evolutionary pattern analysis.The study implicated four traits,incl.1)locule without trichomes,2)ovule with long placenta,3)ratio of volume on ovary locule to style and 4)pollen dormancy place inside the pistillate flower are plesiomorphy.The delay time of fertilization is parallel evolutionary trait.