SummaryThe actin cytoskeleton has been implicated in regulating plant gravitropism. However, its precise role in this process remains uncertain. We have shown previously that disruption of the actin cytoskeleton with Latrunculin B (Lat B) strongly promoted gravitropism in maize roots. These effects were most evident on a clinostat as curvature that would exceed 908 despite short periods of horizontal stimulation. To probe further the cellular mechanisms underlying these enhanced gravity responses, we extended our studies to roots of Arabidopsis. Similar to our observations in other plant species, Lat B enhanced the response of Arabidopsis roots to gravity. Lat B (100 nM) and a stimulation time of 5±10 min were suf®cient to induce enhanced bending responses during clinorotation. Lat B (100 nM) disrupted the ®ne actin ®lament network in different regions of the root and altered the dynamics of amyloplasts in the columella but did not inhibit the gravity-induced alkalinization of the columella cytoplasm. However, the duration of the alkalinization response during continuous gravistimulation was extended in Lat B-treated roots. Indirect visualization of auxin redistribution using the DR5:b-glucuronidase (DR5:GUS) auxin-responsive reporter showed that the enhanced curvature of Lat B-treated roots during clinorotation was accompanied by a persistent lateral auxin gradient. Blocking the gravity-induced alkalinization of the columella cytoplasm with caged protons reduced Lat B-induced curvature and the development of the lateral auxin gradient. Our data indicate that the actin cytoskeleton is unnecessary for the initial perception of gravity but likely acts to downregulate gravitropism by continuously resetting the gravitropic-signaling system.

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The current study explores interpersonal discussion following participation in a novel program of citizen engagement about nanotechnology. Participants answered closed- and open-ended questions about their discursive behavior in a postengagement survey. The study seeks to address whether organizers of citizen engagement can expect participants to extend the impacts of engagement beyond direct participants through interpersonal discussion. Respondents reported moderate levels of postengagement discussion and appeared to say positive things about both nanotechnology and the experts who contributed to the engagement program. Respondents also reported primarily talking about nanotechnology in terms of scientific progress while using a range of fairness and competence frames to discuss experts and the program.

This article presents early results from an opinion formation study based on a 76-member panel of U.S. citizens, with comparison data from a group of 177 nanotechnology experts. While initially similar to the expert group in terms of their perceptions of the risks, benefits, and need for regulation characterizing several forms of nanotechnology, the first follow-up survey indicates that the panel is beginning to diverge from the experts, particularly with respect to perceptions of the levels of various “societal” risks that nanotechnology might present. The data suggest that responding to public concerns may involve more than attention to physical risks in areas such as health and environment; concerns about other forms of risk actually appear more salient.

This article reports results from a three-year panel study of a nonrandom sample of 76 South Carolina citizens, recruited from a variety of walks of life, and their impressions of emerging nanotechnology. This discussion focuses on material from depth interviews conducted alongside a baseline opinion and awareness inventory at the beginning of the study, the most intensive data-gathering phase. These results are placed in the context of data from three additional surveys conducted at about equal intervals over the three years, plus exit interviews from 21 of the 34 individuals who completed the entire study. The results give insight into popular thinking about technology but little indication of strong emerging concerns, a trajectory of amplification of those concerns, or opinion polarization over time, despite some awareness of risks and potential ethical dimensions. Nanotechnology may stand out more as an example of risk attenuation than of risk amplification, consistent with most results from national surveys.