This thesis explores the relationship between journalism as a specific type of socio-cultural practice and the production of meaning in public discussion. Through a case study of newspaper coverage of the issue of genetic engineering in New Zealand (2001-2002), it specifically examines journalists' newsgathering methods, their use of sources and their story-telling frames, and analyses how the news media uses the norm of objectivity to shape public debate on contentious issues. The study argues that elements and structures of journalistic practice both determine a newspaper's ability to address events and issues in a meaningful way and define a newspaper's potential to create a space for public debate. Drawing on field theory, discourse studies and the sociology of journalism, the thesis develops a new operational framework for investigation of journalistic practice by looking at the ideal of objectivity as a method of news gathering, an account of representing reality, and an attitude towards the reality so constructed. This framework is applied in the case study of newspaper coverage of the GE issue where four components of journalistic practice are analysed: journalistic form, transparency of newsgathering, sources and frame. Using content analysis, discourse analysis, interviews and a survey, the thesis explores the relationship between journalistic norms around these elements of the practice and the discursive potential of the news text to represent, interpret and construct reality. The findings of this study highlight the tension between outmoded forms of practice and the complexity of issues in the public domain. The analysis reveals how the norm of objectivity, originally developed as a shield for the defence of the autonomy of the profession to mediate reality, became, in the case of media coverage of genetic engineering, an obstacle in extending journalism's potential to contribute to public debate. As a method, objectivity failed to provide a set of transparent protocols for the representation of the issue in the public arena; as an account, it reflected the impossibility of separating 'facts' from 'views' and positions of detachment from those of partisanship; and as an attitude, objectivity was endangered by the increasing power of economic imperatives in the production of news. Following this analysis, the thesis explores the influence of journalistic norms on public debate by looking at journalism as a text, as a discursive practice and as a field of cultural production. The GE issue, constructed in the New Zealand press as a key component of the 'knowledge economy', drew attention to the dynamics between the economic imperatives and professional standards of the journalistic field. The objectivity norm was reduced in news reports to reporting 'what people say' rather than what the issue or argument meant, which led to a simplification of the genetic engineering issue in the public domain. The study concludes with the call for a re-examination of the journalistic field in light of the press's incapacity to challenge the status quo and map the social world for its readers.