Hilde Vinje

There is growing evidence that plastic particles can accumulate microorganisms that are pathogenic to humans or animals. In the current study, the composition of the plastispheres that accumulated on polypropylene (PP), polyvinyl chloride (PVC), and high‐density polyethylene (HDPE) pieces submerged in a river in the southeast Norway was characterized by 16S rRNA amplicon sequencing. Seasonal and geographical effects on the bacterial composition of the plastisphere were identified, in addition to the detection of potential foodborne pathogenic bacteria and viruses as part of the plastisphere. The diversity and taxonomic composition of the plastispheres were influenced by the number of weeks in the river, the season, and the location. The bacterial diversity differed significantly in the plastisphere from June and September, with a generally higher diversity in June. Also, the community composition of the plastisphere was significantly influenced by the geographical location, while the type of plastic had less impact. Plastics submerged in river water assembled a variety of microorganisms including potentially pathogenic bacteria and viruses (noro‐ and adenovirus) detected by qPCR. Cultivation methods detected viable bacteria such as Escherichia coli and Listeria monocytogenes . The results highlight the need for additional research on the risk of contaminating food with plastic particles colonized with human pathogens through irrigation water.

Conservative flowering behaviours, such as flowering during long days in summer or late flowering at a high leaf number, are often proposed to protect against variable winter and spring temperatures which lead to frost damage if premature flowering occurs. Yet, due the many factors in natural environments relative to the number of individuals compared, assessing which climate characteristics drive these flowering traits has been difficult. We applied a multidisciplinary approach to 10 winter‐annual Arabidopsis thaliana populations from a wide climactic gradient in Norway. We used a variable reduction strategy to assess which of 100 climate descriptors from their home sites correlated most to their flowering behaviours when tested for responsiveness to photoperiod after saturation of vernalization; then, assessed sequence variation of 19 known environmental‐response flowering genes. Photoperiod responsiveness inversely correlated with interannual variation in timing of growing season onset. Time to flowering appeared driven by growing season length, curtailed by cold fall temperatures. The distribution of FLM , TFL2 and HOS1 haplotypes, genes involved in ambient temperature response, correlated with growing‐season climate. We show that long‐day responsiveness and late flowering may be driven not by risk of spring frosts, but by growing season temperature and length, perhaps to opportunistically maximize growth.