Study on micropyle closure in Platycladus orientalis and its evolutionary significance
[Objective]In order to enrich the data for the study of micropyle closure in gymnosperms and to provide a reference for the phylogenetic study of gymnosperms,micropyle closure of Platycladus oriental-is Franco was investigated.[Methods]Female cones of P.orientalis were sampled and examined using morphological techniques,including paraffin section and scanning electron microscopy.In addition,cluster analysis of the mode of micropyle closure was conducted for Bennettitales.[Results](1)After pollen en-ters the ovule,the innermost two cell layers of the integument began to grow radially inward until the mi-cropyle was completely closed.(2)During the micropyle closure,the innermost cells of the integument were elongated and became conical in shape,with the cell layers typically increased to 4 to 6 layers.(3)The micropyle closure of gymnosperms could be divided into four clades:One for Cycas and Ginkgo,one for Pinus and Podocarpaceae,a separate group for Bennettitales,and a cluster of P.orientalis and other species.[Conclusion]The micropyle closure of P.orientalis differs from Ginkgo and cycads,which is similar to Pinus and Bennettitales.This study suggests that there is an evolutionary relationship in micro-pyle closure between Bennettitales and existing conifers,providing novel morphological evidence for the understanding of evolution of the reproductive systems of gymnosperms.
万方数据
维普
