Histological, hormonal and transcriptomic reveal the changes upon gibberellin-induced parthenocarpy in pear fruit

Phytohormones play crucial roles in fruit set regulation and development.Here,gibberellins(GA4+7),but not GA3,induced pear parthenocarpy.To systematically investigate the changes upon GA4+7 induced pear parthenocarpy,dynamic changes in histology,hormone and transcript levels were observed and identified in unpollinated,pollinated and GA4+7-treated ovaries.Mesocarp cells continued developing in both GA4+7-treated and pollinated ovaries.In unpollinated ovaries,mesocarp cells stopped developing 14 days after anthesis.During fruit set process,GA4+7,but not GA1+3,increased after pollination.Abscisic acid(ABA)accumulation was significantly repressed by GA4+7 or pollination,but under unpollinated conditions,ABA was produced in large quantities.Moreover,indole-3-acetic acid biosynthesis was not induced by GA4+7 or pollination treatments.Details of this GA–auxin–ABA cross-linked gene network were determined by a comparative transcriptome analysis.The indole-3-acetic acid transport-related genes,mainly auxin efflux carrier component genes,were induced in both GA4+7-treated and pollinated ovaries.ABA biosynthetic genes of the 9-cis-epoxycarotenoid dioxygenase family were repressed by GA4+7 and pollination.Moreover,directly related genes in the downstream parthenocarpy network involved in cell division and expansion(upregulated),and MADS-box family genes(downregulated),were also identified.Thus,a model of GA-induced hormonal balance and its effects on parthenocarpy were established.

Hole Injection Enhancement of MoO3/NPB/Al Composite Anode

An ultra-thin molybdenum(VI)oxide(MoO3)modification layer can significantly improve hole injection from an electrode even though the MoO3 layer does not contact the electrode.We find that as the thickness of the organic layer between MoO3 and the electrode increases,the hole injection first increases and it then decreases.The optimum thickness of 5 nm corresponds to the best current improvement 70%,higher than that in the device where MoO3 directly contacts the Al electrode.According to the 4,4-bis[N-(1-naphthyl)-N-phenyl-amino]biphenyl(NPB)/MoO3 interface charge transfer mechanism and the present experimental results,we propose a mechanism that mobile carriers generated at the interface and accumulated inside the device change the distribution of electric field inside the device,resulting in an increase of the probability of hole tunneling through the injection barrier from the electrode,which also explains the phenomenon of hole injection enhanced by MoO3/NPB/Al composite anode.Based on this mechanism,different organic materials other than NPB were applied to form the composite electrode with MoO3.Similar current enhancement effects are also observed.