Despite the importance of secondary dormancy for plant life cycle timing and survival, there is insufficient knowledge about the (epigenetic) regulation of this trait at the molecular level. Our aim was to determine the role of (epi)genetic processes in the regulation of secondary seed dormancy using natural genotypes of the widely distributed Capsella bursa-pastoris. Seeds of nine ecotypes were exposed to control conditions or histone deacetylase inhibitors [trichostatin A (TSA), valproic acid] during imbibition to study the effects of hyper-acetylation on secondary seed dormancy induction and germination. Valproic acid increased secondary dormancy and both compounds caused a delay of t50 for germination (radicle emergence) but not of t50 for testa rupture, demonstrating that they reduced speed of germination. Transcriptome analysis of one accession exposed to valproic acid versus water showed mixed regulation of ABA, negative regulation of GAs, BRs and auxins, as well as up-regulation of SNL genes, which might explain the observed delay in germination and increase in secondary dormancy. In addition, two accessions differing in secondary dormancy depth (deep vs non-deep) were studied using RNA-seq to reveal the potential regulatory processes underlying this trait. Phytohormone synthesis or signalling was generally up-regulated for ABA (e.g. NCED6, NCED2, ABCG40, ABI3) and down-regulated for GAs (GA20ox1, GA20ox2, bHLH93), ethylene (ACO1, ERF4-LIKE, ERF105, ERF109-LIKE), BRs (BIA1, CYP708A2-LIKE, probable WRKY46, BAK1, BEN1, BES1, BRI1) and auxin (GH3.3, GH3.6, ABCB19, TGG4, AUX1, PIN6, WAT1). Epigenetic candidates for variation in secondary dormancy depth include SNL genes, histone deacetylases and associated genes (HDA14, HDA6-LIKE, HDA-LIKE, ING2, JMJ30), as well as sequences linked to histone acetyltransferases (bZIP11, ARID1A-LIKE), or to gene silencing through histone methylation (SUVH7, SUVH9, CLF). Together, these results show that phytohormones and epigenetic regulation play an important role in controlling differences in secondary dormancy depth between accessions.

Robert Heizer excavated Leonard Rockshelter (26Pe14) in western Nevada more than 70 years ago. He described stratified cultural deposits spanning the Holocene. He also reported obsidian flakes purportedly associated with late Pleistocene sediments, suggesting that human use extended even farther back in time. Because Heizer never produced a final report, Leonard Rockshelter faded into obscurity despite the possibility that it might contain a Clovis Era or older occupation. That possibility prompted our team of researchers from the University of Nevada, Reno and Desert Research Institute to return to the site in 2018 and 2019. We relocated the excavation block from which Heizer both recovered the flakes and obtained a late Pleistocene date on nearby sediments. We minimally excavated undisturbed deposits to rerecord and redate the strata. As an independent means of evaluating Heizer's findings, we also directly dated 12 organic artifacts housed at the Phoebe A. Hearst Museum of Anthropology. Our work demonstrates that people did not visit Leonard Rockshelter during the late Pleistocene. Rather, they first visited the site immediately following the Younger Dryas (12,900–11,700 cal BP) and sporadically used the shelter, mostly to store gear, throughout the Holocene.

Flint’s drinking water crisis has brought renewed⸺and needed⸺attention to the importance of safe drinking water in the United States. The Flint water crisis was the result of a confluence of factors operating at multiple scales in time and space. My aim is to draw out more explicitly the role of policy, and specifically rationalized policy, in incentivizing and allowing the mistakes and decisions that most proximately led to the Flint water crisis. I build on and extend existing analyses of the Flint water crisis, drawing on thirteen semi-structured interviews and publicly available reports, testimony, newspaper articles, and secondary data. My analysis brings to the fore the particular vulnerability to the marginalizing effects of rationalized policy and its implementation of poor and minority communities in the United States, and it reveals the stickiness and entrenchment of these rationalized policies. The response to the Flint water crisis, both in Michigan and nationally, has centered on renewed commitment to risk-based standards and rulemaking for safe drinking water protections, and maintains interventionist approaches to municipal financial distress. I discuss important alternatives that are emerging and indicate areas for future research on the politics of safe drinking water.

In summer, 2011, we investigated suspected glyphosate-resistant (GR) kochia in three chem-fallow fields (designated F1, F2, F3, each farmed by a different grower) in southern Alberta. This study characterizes glyphosate resistance in those populations, based on data from dose–response experiments. In a greenhouse experiment, the three populations exhibited a resistance factor ranging from 4 to 6 based on shoot biomass response (GR50 ratios), or 5 to 7 based on survival response (LD50 ratios). Similar results were found in a field dose–response experiment at Lethbridge, AB, in spring 2012 using the F2 kochia population. In fall 2011, we surveyed 46 fields within a 20-km radius of the three chem-fallow fields for GR kochia. In the greenhouse, populations were screened with glyphosate at 900 g ae ha−1. Seven populations were confirmed as GR, the farthest site located about 13 km from the three originally confirmed populations. An additional GR population more than 100 km away was later confirmed. Populations were screened for acetolactate synthase (ALS)–inhibitor (thifensulfuron : tribenuron) and dicamba resistance in the greenhouse, with molecular characterization of ALS-inhibitor resistance in the F1, F2, and F3 populations. All GR populations were resistant to the ALS-inhibiting herbicide, but susceptible to dicamba. ALS-inhibitor resistance in kochia was conferred by Pro197, Asp376, or Trp574 amino acid substitutions. Based upon a simple empirical model with a parameter for selection pressure, calculated from weed relative abundance and glyphosate efficacy, and a parameter for seedbank longevity, kochia, wild oat, and green foxtail were the top three weeds, respectively, predicted at risk of selection for glyphosate resistance in the semiarid Grassland region of the Canadian prairies; wild oat, green foxtail, and cleavers species were predicted at greatest risk in the subhumid Parkland region. This study confirms the first occurrence of a GR weed in western Canada. Future research on GR kochia will include monitoring, biology and ecology, fitness, mechanism of resistance, and best management practices.