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A fluorenone-based polycatenar consisting of a central 2,7-bis­((5-phenyl­thiophen-2-yl)­ethynyl)-9-fluorenone core and −OCH2– linked 3,4,5-tris­(dodecyloxy)­benzoate unit at both sides (FTQ) has been synthesized by using Sonogashira coupling reactions as key steps. FTQ molecule exhibits columnar liquid crystalline phase. The molecular self-assembled behavior at the solid/liquid interface is investigated by scanning tunneling microscopy (STM). With the decrease of solution concentration, three nanostructures (parallelogram, wave-like, and double-S patterns) are formed at the 1-phenyloctane/HOPG interface. More importantly, the molecular cis–trans isomerization is observed, resulting from different packing fashions of the side chains. The dimers are the basic building units due to the similar C­(sp2)–H···OC hydrogen bonds formed between the hydrogen atom in the thiophene group and the oxygen atom in the carbonyl group. Density functional theory (DFT) results show that the isomerized structure constructing by the S-shaped conformation is more stable. We speculate that the double-S structure might be in accordance with the molecular conformation in liquid crystalline phase. Our work is of significance to further explore molecular packing mechanism and stability of fluorenone-based polycatenars with liquid crystal property.

Paeonia ludlowii (Stern & Taylor) D.Y.Hong, an endangered species, is indigenous to Tibet, China and propagated only by seed under natural conditions. Its natural reproduction is constrained by low fecundity. Excess seed abortion is a key factor restricting its natural reproduction, cultivation, introduction, and protection. Understanding the specific origin and occurrence of aborted ovules is important for the protection of offspring. Using serial sectioning analysis, we studied the process of pollination and fertilization of P. ludlowii and examined the characteristics of aborted ovules, developmental differences after flowering of normal and aborted ovules, and their ratios at different positions in P. ludlowii ovaries. During pollination, fertilization, and seed development, ovule abortion was frequent, with a random abortion position. There were three types of abortion, namely, abnormal pistil, sterile ovules, and embryo and endosperm abortions. Of these, embryo and endosperm abortions could be divided into early abortion and middle abortion. The early aborted ovules stopped growing on day 12, the endoblast and endosperm in the embryo sac aborted gradually. Furthermore, the shape of the embryo sac cavity changed. The volume of aborted ovules was significantly different from that of fertile ovules. At ripening, the external morphology of different types of aborted seeds was significantly different. The possible reasons for the abortion of the ovules are also discussed.

Background Paeonia ludlowii (Stern & G. Taylor D.Y. Hong) belongs to the peony group of the genus Paeonia in the Paeoniaceae family and is now classified as a “critically endangered species” in China. Reproduction is important for this species, and its low fruiting rate has become a critical factor limiting both the expansion of its wild population and its domestic cultivation. Results In this study, we investigated possible causes of the low fruiting rate and ovule abortion in Paeonia ludlowii. We clarified the characteristics of ovule abortion and the specific time of abortion in Paeonia ludlowii, and used transcriptome sequencing to investigate the mechanism of abortion of ovules in Paeonia ludlowii. Conclusions In this paper, the ovule abortion characteristics of Paeonia ludlowii were systematically studied for the first time and provide a theoretical basis for the optimal breeding and future cultivation of Paeonia ludlowii.