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A small semiartificial pond, revealing high species richness with respect to the aquatic macrophytes, was studied in the Aomori Prefecture, Japan. The pond had been completely formed ca. 10 years previously after excavation into a wet bog. To identify and evaluate its aquatic macrophyte flora during 2017–2018, we listed the species of aquatic vascular plants and charophytes in the pond and compared this list with those from the natural Japanese lakes using a database of aquatic flora in Japan. Two species were identified by molecular analyses because they lacked any reproductive organs, which were necessary for identifying the species level. We found a total of 57 taxa of aquatic macrophytes including 15 Red List species in Japan or Aomori Prefecture. Comparing the flora list with those from the 66 natural Japanese lakes surveyed since 2001, the pond was ranked fourth in the order of diversity (based on species richness) and rarity (based on numbers of Red List species). Therefore, the pond is an important aquatic environment in terms of aquatic macrophyte conservation in Japan. Interestingly, for a pond with such high species diversity, it is relatively small (0.14 km2), semiartificial, and relatively recently formed.

The conformation of a photoresponsive polymer bearing azo units in the main chain, poly(propionaldehyde azine) (PrAz), in tetrahydrofuran was investigated by viscosity measurements before and after trans-to-cis photoisomerization and also by the rotational isomeric state (RIS) model. Before photoisomerization (i.e., in the case of trans-pPrAz), viscosity data indicated that pPrAz took a more extended conformation than did a diene polymer analog poly(butadiene). The RIS model analysis revealed that the extended conformation of pPrAz arose mainly from the difficulty of gauche conformation around the carbon-carbon bond in the main chain. After trans-to-cis photoisomerization (i.e., in the case of pPrAz consisting of trans and cis units), viscosity data indicated that the photoisomerization led to a slight extension of the pPrAz chain. The RIS model analysis explained that the photoisomerization formed preferentially the anti-cis isomer, resulting in a larger characteristic ratio to avoid severe steric hindrance between the ethyl groups on neighboring main-chain carbon atoms.